Search

New heterocyclic diradicaloids (i.e., boron and nitrogen-doped polycyclic systems with open-shell ground-states) are obtained based on concomitant structural and quinoidal extensions, allowing thus to merge the best of both design strategies. The combination of experimental characterization and theoretical calculations have helped to disclose their electronic structure, as well as to rationalize their associated magnetic and photophysical properties, spanning the chemical space of available molecular templates for cutting-edge applications in organic electronics and spintronics. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant n° F.4534.21 (MIS-IMAGINE). J.-C. S.-G. acknowledges funding from the "Ministerio de Ciencia e Innovación" through the PID2019-106114GB-I00 project.

The importance of intermediate triplet states and the nature of excited states has gained interest in recent years for the thermally activated delayed fluorescence (TADF) mechanism. It is widely accepted that simple conversion between charge transfer (CT) triplet and singlet excited states is too crude, and a more complex route involving higher-lying locally excited triplet excited states has to be invoked to witness the magnitude of the rate of reverse inter-system crossing (RISC) rates. The increased complexity has challenged the reliability of computational methods to accurately predict the relative energy between excited states as well as their nature. Here, we compare the results of widely used density functional theory (DFT) functionals, CAM-B3LYP, LC-ωPBE, LC-ω*PBE, LC-ω*HPBE, B3LYP, PBE0, and M06-2X, against a wavefunction-based reference method, Spin-Component Scaling second-order approximate Coupled Cluster (SCS-CC2), in 14 known TADF emitters possessing a diversity of chemical structures. Overall, the use of the Tamm–Dancoff Approximation (TDA) together with CAM-B3LYP, M06-2X, and the two ω-tuned range-separated functionals LC-ω*PBE and LC-ω*HPBE demonstrated the best agreement with SCS-CC2 calculations in predicting the absolute energy of the singlet S1, and triplet T1 and T2 excited states and their energy differences. However, consistently across the series and irrespective of the functional or the use of TDA, the nature of T1 and T2 is not as accurately captured as compared to S1. We also investigated the impact of the optimization of S1 and T1 excited states on ΔEST and the nature of these states for three different functionals (PBE0, CAM-B3LYP, and M06-2X). We observed large changes in ΔEST using CAM-B3LYP and PBE0 functionals associated with a large stabilization of T1 with CAM-B3LYP and a large stabilization of S1 with PBE0, while ΔEST is much less affected considering the M06-2X functional. The nature of the S1 state barely evolves after geometry optimization essentially because this state is CT by nature for the three functionals tested. However, the prediction of the T1 nature is more problematic since these functionals for some compounds interpret the nature of T1 very differently. SCS-CC2 calculations on top of the TDA-DFT optimized geometries lead to a large variation in terms of ΔEST and the excited-state nature depending on the chosen functionals, further stressing the large dependence of the excited-state features on the excited-state geometries. The presented work highlights that despite good agreement of energies, the description of the exact nature of the triplet states should be undertaken with caution. The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) for financial support. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie–Bruxelles, infrastructure funded by the Walloon Region under the Grant Agreement n1117545. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant no. F.4534.21 (MIS-IMAGINE). D.B. is a FNRS Research Director. J.C.S.-G. acknowledges funding from the “Ministerio de Ciencia e Innovación” through the PID2019-106114GB-I00 project.

We theoretically study and characterize a set of rhombus-shaped nanographenes of increasing size, or n-rhombenes, where n = 2–6, displaying zigzag edges leading to an enhancement of the (poly)radicaloid nature and the appearance of intrinsic magnetism as a function of n. Due to that system-dependent radicaloid nature, we employ spin-flip methods able to capture the challenging physics of the problem, thus providing accurate energy differences between high- and low-spin solutions. The theoretical predictions agree with the experimentally available magnetic exchange coupling for the recently synthesized 5-rhombene, as well as with the size at which the transition from a closed-shell to an open-shell ground-state solution occurs. We also investigate if standard DFT methods are able to reproduce the trend disclosed by spin-flip methods and if the results are highly dependent on the functional choice and/or the intrinsic spin contamination. This work is supported by projects PID2019-106114GB-I00 (“Ministerio de Ciencia e Innovación”), AICO/2021/093 and PROMETEO/2021/017 (“Generalitat Valenciana”).

Linear and cyclic acenes are polycyclic aromatic hydrocarbons that can be viewed as building blocks of graphene nanoribbons and carbon nanotubes, respectively. While short linear acenes demonstrated remarkable efficiency in several optoelectronic applications, the longer members are unstable and difficult to synthesize as their cyclic counterparts. Recent progress in on-surface synthesis, a powerful tool to prepare highly reactive species, opens promising perspectives and motivates the computational investigations of these potentially functional molecules. Owing to their di- and poly-radical character, low-lying excited states dominated by doubly excited configurations are expected to become more important for longer members of both linear and cyclic molecules. In this work, we investigate the lowest-lying La and the doubly excited (DE) state of linear acenes and cyclacenes, with different computational approaches, to assess the influence of the di-/poly-radical characters (increasing with the molecular dimensions) on their relative order. We show that DFT/MRCI calculations correctly reproduce the crossing of the two states for longer linear acenes, while TDUDFT calculations fail to predict the correct excitation energy trend of the DE state. The study suggests a similarity in the excited electronic state pattern of long linear and cyclic acenes leading ultimately to a lowest lying dark DE state for both.

A family of non-empirical double-hybrid (DH) density functionals, such as Perdew–Burke–Ernzerhof (PBE)0-DH, PBE-QIDH, and their range-separated exchange (RSX) versions RSX-0DH and RSX-QIDH, all using Perdew-Burke-Ernzerhof(PBE) exchange and correlationfunctionals, is applied here to calculate the excitation energies for increasingly longer linear and cyclic acenes as part of their intense benchmarking for excited states of all types. The energies for the two lowest-lying singlet 1La and 1Lb states of linear oligoacenes as well as the triplet 3La and 3Lb states, are calculated and compared with experimental results. These functionals clearly outperform the results obtained from hybrid functionals and favorably compare with other double-hybrid expressions also tested here, such as B2-PLYP, B2GP-PLYP, ωB2-PLYP, and ωB2GP-PLYP. The study is complemented by the computation of adiabatic S0–T1 singlet-triplet energy difference for linear acenes as well as the extension of the study to strained cyclic oligomers, showing how the family of non-empirical expressions robustly leads to competitive results. The work in Alicante was supported by Project No. PID2019-106114GB-I00 (“Ministerio de Ciencia e Innovación”). E.B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l’Investissement d’Avenir) for their financial support of this work through Labex SEAM (Science and Engineering for Advanced Materials and devices), Grant Nos. ANR-10-LABX-096, ANR-18-IDEX-0001, and ANR-21-CE29-0003. The authors thank the GENCI-CINES for HPC resources (Project No. A0100810359).

ilustraciones, graficas La Organización Mundial de la Salud estima que hay cerca de 50 millones de personas que padecen demencia en el mundo, casos de los cuales del 60% al 70% se trata de la enfermedad de Alzheimer (EA). Entre las características más importantes de su patología se encuentra la agregación de péptidos ß-amiloide (Aβ) a nivel cerebral, la desregulación de iones metálicos y el estrés oxidativo. Particularmente, ha sido demostrado que los complejos formados por el Aβ y el cobre extraneuronal son capaces de catalizar la producción de especies reactivas de oxígeno que pueden desencadenar la muerte neuronal. En este trabajo se estudió la potencial aplicación de 109 ligandos quelantes de cobre como posibles agentes multifuncionales en el marco de la EA, distribuidos en tres conjuntos de estructuras diversas: ligandos con átomos donadores de N, O y S, ligandos tipo pinza y ligandos tipo salen. La evaluación de su potencial farmacológico se realizó empleando herramientas bioinformáticas y de estructura electrónica siguiendo cuatro criterios clave: el cumplimiento de las reglas de cinco de Lipinski, la permeación de la barrera hematoencefálica, el potencial estándar de reducción y las afinidades por los iones de cobre. Como resultado se redujo el conjunto inicial de 109 candidatos identificando 8 ligandos como prometedores agentes antioxidantes y 8 ligandos como prometedores agentes redistribuidores en el marco de la EA. Adicionalmente, se propone un mecanismo multifuncional novedoso denominado mecanismo supresor para el cual se identificaron 3 candidatos prometedores. De esta forma, se proponen en total 19 moléculas para dar el paso a una caracterización farmacológica en el marco de la EA de manera experimental. (Texto tomado de la fuente) The World Health Organization estimates that about 50 million people suffer from dementia worldwide, cases of which 60% to 70% are due to Alzheimer’s disease (AD). Among the most important characteristics of its pathology are the β-amyloid peptide (Aβ) aggregation in the brain, the metallic ion dysregulation, and oxidative stress. In particular, it has been shown that the complexes formed by Aβ and extraneuronal copper are capable of catalyzing the production of reactive oxygen species that can lead to neuronal death. In this work, the potential application of 109 copper chelating ligands as multifunctional agents in the framework of AD was studied, distributed in three sets of diverse structures: ligands with N, O and S donor atoms, pincer-type ligands, and salen-type ligands. Its pharmacological potential evaluation was carried out using bioinformatic and electronic structure tools following four key criteria: compliance with Lipinski’s rules of five, blood-brain barrier permeation, standard reduction potential, and affinities towards copper ions. As a result, the initial set of 109 candidates was narrowed down, identifying 8 ligands as promising antioxidant agents and 8 ligands as promising distributor agents in AD’s framework. Additionally, a novel multifunctional mechanism called suppressor mechanism is proposed for which 3 promising candidates were identified. In this way, a total of 19 molecules are proposed to initiate their experimental pharmacological characterization in AD’s framework. Maestría

We investigate the relationships between electron-density and electronic-energy errors produced by modern exchange-correlation density-functional approximations belonging to all of the rungs of Perdew’s ladder. To this aim, a panel of relevant (semi)local properties evaluated at critical points of the electron-density field (as defined within the framework of Bader’s atoms-in-molecules theory) are computed on a large selection of molecular systems involved in thermodynamic, kinetic, and noncovalent interaction chemical databases using density functionals developed in a nonempirical and minimally and highly parametrized fashion. The comparison of their density- and energy-based performance, also discussed in terms of density-driven errors, casts light on the strengths and weaknesses of the most recent and efficient density-functional approximations. E.B. and V.T. gratefully acknowledge GDR 3333 RFCT CNRS for their financial support through the call for proposals “Soutien á des collaborations scientifiques”. E.B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat á l’Investissement d’Avenir) for their financial support of this work through Labex SEAM (Science and Engineering for Advanced Materials and devices) ANR-10-LABX-096 and ANR-18-IDEX-0001. V.T. and L.J. thank the Labex SynOrg (ANR-11-2ABX-0029) for funding. The authors acknowledge the GENCI-CINES and the CRIANN centers for HPC resources (Projects A0080810359 and A0100810359) just like the local P3MB HPC platform of Université de Paris (ANR-18-IDEX-0001).

The inversion of the lowest singlet and triplet excited state energy gap, in fully organic triangle-based compounds, can give rise to a new exergonic pathway to enhance the Organic Light Emitting Diodes (OLEDs) performance, going beyond the novel yet promising Thermally Activated Delayed Fluorescence (TADF) mechanism. If, on one hand, the origin of this inversion, arising from the interplay between exchange and electron correlation effects, has been extensively investigated in last years, identifying the wavefunction methods as key to predict the excited-state inversion, on the other hand a proper picture of the structure-property relationships characterizing these systems is still missing. In this work, we thus assess the effect of different symmetry point groups (D3h, C2v, C3h and C3v) on the orbital localization to shed light on the role that the symmetry has in determining the optical features of the triangulene systems (on both S1-T1 inversion and oscillator strengths). The presence of the C_2 axis and the σ_v plane (as it happens for the D3h, C2v and C3v groups) turned out to be critical for ensuring the proper orbital localization aimed at minimizing the exchange interaction and therefore favouring the inversion. In particular, adopting a C2v (and its subgroups) symmetry, either through the proper doping pattern, by introducing substituents, or by merging two triangulene cores, is the only way to conciliate a negative ΔEST and a non-zero oscillator strength. Finally, we gathered the lessons learnt from this analysis to establish a series of design rules, aimed at helping the identification of inverted singlet-triplet (INVEST) emitters for applications in the next generation of OLEDs. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant n° F.4534.21 (MIS-IMAGINE). G. R. acknowledges a grant from the ‘‘Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture’’ (FRIA) of the FRS-FNRS. Computational resources were also provided by the ‘‘Consortium des Équipements de Calcul Intensif’’ (CÉCI), funded by the ‘‘Fonds de la Recherche Scientifiques de Belgique’’ (FRS-FNRS) under Grant No. 2.5020.11. The work in Alicante is supported by the Ministry of Science and Innovation of Spain (project PID2019-106114GB-I00).

The St Andrews team would like to thank the Leverhulme Trust (RPG-2016-047) for financial support. E. Z.-C. is a Royal Society Leverhulme Trust Senior Research fellow (SRF\R1\201089). Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11, as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement n1117545. G.R. acknowledges a grant from the “Fonds pour la formation à la Recherche dans l’Industrie et dans l’Agriculture” (F.R.I.A.) of the F.R.S.-F.N.R.S. Y.O. acknowledges funding by the Fonds de la Recherche Scientifique-FNRS under Grant n° F.4534.21 (MIS-IMAGINE). D.B. is a FNRS Research Director. J.C.S.G. acknowledges “Ministerio de Ciecia e Innovación” of Spain (PID2019-106114GB-I00). With the surge of interest in multiresonant thermally activated delayed fluorescent (MR-TADF) materials, it is important that there exist computational methods to accurately model their excited states. Here, building on our previous work, we demonstrate how the spin-component scaling second-order approximate coupled-cluster (SCS-CC2), a wavefunction-based method, is robust at predicting the ΔEST (i.e., the energy difference between the lowest singlet S1 and triplet T1 excited states) of a large number of MR-TADF materials, with a mean average deviation (MAD) of 0.04 eV compared to experimental data. Time-dependent density functional theory calculations with the most common DFT functionals as well as the consideration of the Tamm-Dancoff approximation (TDA) consistently predict a much larger ΔEST as a result of a poorer account of Coulomb correlation as compared to SCS-CC2. Very interestingly, the use of a metric to assess the importance of higher order excitations in the SCS-CC2 wavefunctions shows that Coulomb correlation effects are substantially larger in the lowest singlet compared to the corresponding triplet and need to be accounted for a balanced description of the relevant electronic excited states. This is further highlighted with coupled cluster singles-only calculations, which predict very different S1 energies as compared to SCS-CC2 while T1 energies remain similar, leading to very large ΔEST, in complete disagreement with the experiments. We compared our SCS-CC2/cc-pVDZ with other wavefunction approaches, namely, CC2/cc-pVDZ and SOS-CC2/cc-pVDZ leading to similar performances. Using SCS-CC2, we investigate the excited-state properties of MR-TADF emitters showcasing large ΔET2T1 for the majority of emitters, while π-electron extension emerges as the best strategy to minimize ΔEST. We also employed SCS-CC2 to evaluate donor–acceptor systems that contain a MR-TADF moiety acting as the acceptor and show that the broad emission observed for some of these compounds arises from the solvent-promoted stabilization of a higher-lying charge-transfer singlet state (S2). This work highlights the importance of using wavefunction methods in relation to MR-TADF emitter design and associated photophysics. Postprint

gráficas, ilustraciones, tablas El desarrollo de modelos y metodologías destinadas a entender las peculiaridades de ciertas estructuras moleculares confinantes, como clatratos, endofullerenos y nanogotas, tiene consecuencias directas en el campo de las ciencias moleculares. Estos sistemas constituyen 'nanolaboratorios' extraordinarios en los que las moléculas encapsuladas se comportan como rotores cuánticos, y en donde los niveles traslacionales y rotacionales se encuentran mezclados por el confinamiento, generando una rica estructura de niveles energéticos. Además, estos complejos han sido teorizados como materiales promisorios, con aplicaciones en el almacenamiento de energía, secuestro de gases de efecto invernadero, computación cuántica, etc. Sin embargo, el costo computacional prohibitivo que implican los cálculos teóricos ha derivado en simplificaciones de la dimensionalidad de los sistemas, o en el empleo de tratamientos clásicos que son incapaces de explotar la riqueza de los efectos cuánticos inherentes. En este trabajo se presenta la metodologı́a desarrollada en nuestro grupo para tratar moléculas triatómicas nanoconfinadas a través del método computacional Multi Configuration Time Dependent Hartree (MCTDH), con el fin de incluir cálculos de alta precisión de los niveles vibracionales y traslacionales de las moléculas enclaustradas. Se estudió la estructura de niveles energéticos de los fullerenos endohedrales H2O@C60 y H2O@C70 como casos particulares, y se exploraron dos modelos teóricos plausibles para explicar la ruptura de simetría observada en el primer sistema. Como una consecuencia directa de lo anterior, se realizó un estudio de estructura electrónica para el complejo H2O@C60, considerando la interacción de la molécula encapsulada con las estructuras de carbono básicas que constituyen al fullereno, con el objeto de obtener una descripción razonablemente precisa de la superficie de energía potencial (PES) intermolecular que incluya las interacciones entre muchos cuerpos a partir de técnicas DFT/DFT-D. Finalmente, se presenta un modelo termodinámico para el sistema H2O@C60, que reproduce algunas de las características inusuales que se observan en la concentración de isómeros de espín ortho y para del H2O a bajas temperaturas. (Texto tomado de la fuente) The development of models and methodologies aiming to understand the features of certain confining molecular structures, as clathrates, fullerenes and nanodroplets, has direct consequences on the fields of the fundamental and applied physics, as such systems constitutes astonishing 'nanolaboratories', where encapsulated molecules behave as quantum rotors. The translational and rotational levels are mixed due to the confinement, giving rise to a rich energetic level structure. Also, these compounds has been proposed as promising materials with applications in energy storage, greenhouse gases capture, quantum computation, etc. Nonetheless, until recently the rather high computational cost of the quantum simulations has limited the theoretical efforts to reduced dimensional simplifications, or classical treatments, that were not able to explore properly the richness of the inherent quantum effects. In this work we present the methodology developed in our group to treat triatomic nanoconfined molecules through the Multi Configuration Time Dependent Hartree (MCTDH) framework. In this way, we performed "exact" full-dimensional quantum calculations, coupling all degrees of freedom, and accurate values on vibrational, rotational and translational states of the trapped molecule were reported. In particular, the energetics and levels structure of the H2O@C60 and H2O@C70 endohedral fullerenes were investigated, and two plausible theoretical physical models to explain the observed symmetry breaking in the former system were proposed and explored. As a direct consequence, a quantum chemistry electronic structure study of the H2O@C60 was performed. Given the size of the system, we first considered the encapsulated molecule’s interaction with the fundamental unit structures, such as C5 and C6 from the C60 cavity, with the purpose to assess the performance of different DFT/DFT-D approaches in describing the underlying many-body intermolecular potential energy surface (PES). Finally, a thermodynamic model for the H2O@C60 system was developed, which can reproduce some of the unusual features observed in the ortho and para H2O spin isomers' concentration at low temperatures. Doctorado Doctor en Ciencias - Física Física molecular Química computacional

In this study, a set of 10 positional indolocarbazole (ICz) isomers substituted with dicyanomethylene groups connected via para or meta positions are computationally investigated with the aim of exploring the efficiency of structural isomerism and substitution position in controlling their optical and electronic properties. Unrestricted density functional theory (DFT), a spin-flip time-dependent DFT approach, and the multireference CASSCF/NEVPT2 method have been applied to correlate the diradical character with the energetic trends (i.e., singlet–triplet energy gaps). In addition, the nucleus-independent chemical shift together with ACID plots and Raman intensity calculations were used to strengthen the relationship between the diradical character and (anti)aromaticity. Our study reveals that the substitution pattern and structural isomerism represent a very effective way to tune the diradical properties in ICz-based systems with meta-substituted systems with a V-shaped structure displaying the largest diradical character. Thus, this work contributes to the elucidation of the challenging chemical reactivity and physical properties of diradicaloid systems, guiding experimental chemists to produce new molecules with desirable properties. Funding for open access charge: Univesidad de Málaga/CBUA. The work at the University of Málaga was funded by the MICINN (PID2019-110305GB-I00) and Junta de Andalucía (UMA18-FEDERJA-080, P09FQM-4708, and P18-FR-4559) projects. The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the SCBI (Supercomputing and Bioinformatics) centre of the University of Málaga. The work at the University of Alicante was supported by the MICINN (PID2019-106114GB-I00). The work at the University of Bologna was supported by University of Bologna (RFO) funds.

The so-called protobranching phenomenon, that is the greater stability of branched alkanes with respect to their linear isomers, represents an interesting challenge for approaches based on density functional theory (DFT), since it requires a balanced description of several electronic effects, including (intramolecular) dispersion forces. Here, we investigate this problem using a protocol recently developed based on double-hybrid functionals and a small basis set, DH-SVPD, suited for noncovalent interactions. The energies of bond separation reactions (BSR), defined on the basis of an isodesmic principle, are taken as reference properties for the evaluation of 15 DFT approaches. The obtained results show that error lower than the so-called “chemical accuracy” (

We investigate the performance of a set of recently introduced range‐separated double‐hybrid functionals, namely ωB2‐PLYP, ωB2GP‐PLYP, RSX‐0DH, and RSX‐QIDH models for hard‐to‐calculate excitation energies. We compare with the parent (B2‐PLYP, B2GP‐PLYP, PBE0‐DH, and PBE‐QIDH) and other (DSD‐PBEP86) double‐hybrid models as well as with some of the most widely employed hybrid functionals (B3LYP, PBE0, M06‐2X, and ωB97X). For this purpose, we select a number of medium‐sized intra‐ and inter‐molecular charge‐transfer excitations, which are known to be challenging to calculate using time‐dependent density‐functional theory (TD‐DFT) and for which accurate reference values are available. We assess whether the high accuracy shown by the newest double‐hybrid models is also confirmed for those cases too. We find that asymptotically corrected double‐hybrid models yield a superior performance, especially for the inter‐molecular charge‐transfer excitation energies, as compared to standard double‐hybrid models. Overall, the PBE‐QIDH and its corresponding range‐separated RSX‐QIDH functional are recommended for general‐purpose TD‐DFT applications, depending on whether long‐range effects are expected to play a significant role. The work in Alicante is supported by project PID2019-106114GB-I00 (“Ministerio de Ciencia e Innovación”). E.B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l'Investissement d'Avenir) for their financial support to this work through Labex SEAM (Science and Engineering for Advanced Materials and devices), Grant Nos. ANR-10-LABX-096 and ANR-18-IDEX-0001. I.C. gratefully acknowledge support from the European Research Council (ERC) for grant agreement No. 648558 (STRIGES CoG). The authors thank the GENCI-CINES for HPC resources (Project Nos. A0060810359 and A0080810359).

This work describes the synthesis and properties of a dicyanomethylene‐substituted indolo[3,2‐b]carbazole diradical ICz‐CN. This quinoidal system dimerises almost completely to (ICz‐CN)2, which contains two long C(sp3)−C(sp3) σ‐bonds between the dicyanomethylene units. The minor open‐shell ICz‐CN component in the solid‐state mixture was identified by EPR spectroscopy. Cyclic voltammetry and UV–visible spectroelectrochemical data, as well as comparison with reference monomer ICz‐Br reveal that the nature of the one‐electron oxidation of (ICz‐CN)2 at ambient temperature and ICz‐CN at elevated temperature is very similar in all these compounds due to the prevailing localization of their HOMO on the ICz backbone. The peculiar cathodic behaviour reflects the co‐existence of (ICz‐CN)2 and ICz‐CN. The involvement of the dicyanomethylene groups stabilizes the close‐lying LUMO and LUMO+1 of (ICz‐CN)2 and especially ICz‐CN compared to ICz‐Br, resulting in a distinctive cathodic response at low overpotentials. Differently from neutral ICz‐CN, its radical anion and dianion are remarkably stable under ambient conditions. The UV/Vis(–NIR) electronic transitions in parent (ICz‐CN)2 and ICz‐CN and their different redox forms have been assigned convincingly with the aid of TD‐DFT calculations. The σ‐bond in neutral (ICz‐CN)2 is cleaved in solution and in the solid‐state upon soft external stimuli (temperature, pressure), showing a strong chromism from light yellow to blue–green. Notably, in the solid state, the monomeric diradical species is predominantly formed under high hydrostatic pressure (>1 GPa). The work at the University of Málaga was funded by the MICINN (PID2019-110305GB-I00, PID2019-104293GB-I00 and PCI2019-111825-2), Instituto de Salud Carlos III (ISCIII) (RETIC ARADYAL, RD16/0006/0012) and Junta de Andalucía (UMAFEDERJA-080, UMA-FEDERJA-007 and P09FQM-4708) projects. S.R.G. also thanks the Ayuda para la incorporación de doctores of the University of Malaga. The work at the University of Alicante was supported by the MICINN (PID2019-106114GB-I00) and Generalitat Valenciana (AICO/2018/175) projects. The work at SIOC was supported by National Natural Science Foundation of China (grants no. 21875279 and 21790362). The authors thankfully acknowledge the computer resources, technical expertise, and assistance provided by the SCBI (Supercomputing and Bioinformatics) center of the University of Malaga. The spectro-electrochemical studies (R.N.) were fully funded by Spectroelectrochemistry Reading (a spinout company of the University of Reading). M.P.-A. would like to acknowledge the support of the European Research Council (ERC) Grant “Hecate”, reference no. 695527, held by Prof. Graeme Ackland. This work has been also supported by MCIU/MINECO through the projects CTQ2013-48252-P, CTQ2015-67755-C02-01-R and PGC2018-094814-B-C21.

We calculate the relative energy between the cumulene and polyyne structures of a set of C4k+2 (k=4-7) rings (C18, C22, C26, and C30 prompted by the recent synthesis of the cyclo[18]carbon (or simply C18) compounds. Reference results were obtained by a costly Quantum Monte-Carlo (QMC) approach, providing thus very accurate values allowing to systematically compare the performance of a varierty of wavefunction methods [(i.e., MP2, SCS-MP2, SOS-MP2, DLPNO-CCSD, and DLPNO-CCSD(T)] as well as DFT approaches, applying for the latter a diversity of density functionals covering global and range-separated hybrid and double-hybrid models. The influence of the use of a range-separation scheme for density functionals, for both hybrid and double-hybrid expressions, is discussed according to its key role. Overall, range-separated double-hybrid functionals (e.g., RSX-QIDH) behave very accurately and provide competitive results, compared with DLPNO-CCSD(T), at a more reasonable computational cost. The work in Alicante is supported by project PID2019-106114GB-I00 (“Ministerio de Ciencia e Innovación”). E.B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l'Investissement d'Avenir) for their financial support to this work through Labex SEAM (Science and Engineering for Advanced Materials and devices), Grant Nos. ANR-10-LABX-096 and ANR-18-IDEX-0001. The authors acknowledge the GENCI-CINES for HPC resources (Projects A0080810359 and A0100810359).

We study the emergence of magnetism and its interplay with structural properties in a two-dimensional molecular crystal of cyclacenes, using density functional theory (DFT). Isolated cyclacenes with an even number of fused benzenes host two unpaired electrons in two topological protected zero modes, at the top and bottom carbon rings that form the molecule. We show that, in the gas phase, electron repulsion promotes an open-shell singlet with strong intramolecular antiferromagnetic exchange. We consider a closed packing triangular lattice crystal phase and we find a strong dependence of the band structure and magnetic interactions on the rotation angle of the cyclacenes with respect to the crystal lattice vectors. The orientational ground state maximizes the intermolecular hybridization, yet local moments survive. Intermolecular exchange is computed to be antiferromagnetic, and DFT predicts a broken symmetry 120∘ spin phase reflecting the frustration of the intermolecular spin coupling. Thus, the cyclacene crystal realizes a bilayer of two antiferromagnetically coupled S = 1/2 triangular lattices. Our results provide a bottom-up route towards carbon based strongly correlated platforms in two dimensions. We acknowledge funding support from Ministry of Science and Innovation of Spain (Grants No. PID2019-106114GB-I00 and No. PID2019-109539GB), Generalitat Valenciana and Fondo Social Europeo (Grant No. ACIF/2018/175), Generalitat Valenciana (Grant No. Prometeo2017/139), and FEDER/Junta de Andalucía Consejería de Transformación Económica, Industria, Conocimiento y Universidades, Grant No. PY18-4834.

The lowest-energy singlet (S1) and triplet (T1) excited states of organic conjugated chromophores are known to be accurately calculated by modern wavefunction and Time-Dependent Density Functional Theory (TD-DFT) methods, with the accuracy of the latter heavily relying on the exchange-correlation functional employed. However, there are challenging cases for which this cannot be the case, due to the fact that those excited states are not exclusively formed by single excitations and/or are affected by marked correlation effects, and thus TD-DFT might fall short. We will tackle here a set of molecules belonging to the azaphenalene family, for which research recently documented an inversion of the relative energy of S1 and T1 excited states giving rise to a negative energy difference (ΔEST) between them and, thereby, contrary to most of the systems thus far treated by TD-DFT. Since methods going beyond standard TD-DFT are not extensively applied to excited-state calculations and considering how challenging this case is for the molecules investigated, we will prospectively employ here a set of non-standard methods (Multi-Configurational Pair Density Functional Theory or MC-PDFT) and correlation functionals (i.e., Lie–Clementi and Colle–Salvetti) relying not only on the electronic density but also on some modifications considering the intricate electronic structure of these systems. This research was funded by “Ministerio de Ciencia e Innovación” of Spain grant number PID2019-106114GB-I00.

El desarrollo progresivo y constante de nuevas tecnologías ha impactado en la sociedad de forma importante y, en ocasiones, de manera desapercibida. Se trata, sin duda, de un importante agente y motor para cualquier cambio social como constatamos al analizar su incidencia en aspectos tan variados como la productividad en la empresa e industria, o el sector productivo en general, los canales y medios de comunicación, las relaciones sociales y, decididamente, en la calidad de vida percibida por los ciudadanos/as. Para encuadrar adecuadamente el impacto de este desarrollo tecnológico es conveniente que lo contextualicemos con el fenómeno de la globalización, junto con los hitos propios de las tecnologías emergentes, y con el desarrollo paralelo de la Sociedad de la Información, analizándolo atendiendo no solo a los resultados deseables que produce en la sociedad, sino también resaltando aquellas consecuencias no tan deseables que produce en las actuales sociedades contemporáneas. Con este encuadre esperamos alcanzaremos una perspectiva correcta de nuestro objeto de estudio. The progressive and constant deployment of new technologies has remarkably impacted on the society, even inadvertently. It constitutes, without any doubt, a timely agent and force for any social change, as we can evidence analyzing its incidence in diverse aspects such as companies and industries, or the productive sector generally speaking, the communication channels and mass media, the social relationships, and markedly on the citizenship quality of life. To adequately framework the last impact of this technological development, it is convenient to not forget its imbrication within the globalization phenomena, aligned with the milestones of the emerging technologies, and with the parallel growth of the information society. This would allow its analysis not only looking at the tangible results for the society, but also underlining those undesired consequences for the contemporaty societies. We hope to achieve with this approach a correct perspective for the subject of our research. Este trabajo se ha realizado en el marco del Proyecto de Investigación “Estudio teórico-computacional de las propiedades y perspectivas de aplicación de nanoformas orgánicas (poli-)radicalarias”, financiado por el Ministerio de Ciencia e Innovación, Programa Estatal de Generación de conocimiento y Fortalecimiento Científico y Tecnológico del Sistema.

The energy difference (ΔEST) between the lowest singlet (S1) and triplet (T1) excited state of a set of azaphenalene compounds, which is theoretically and experimentally known to violate Hund's rule giving rise to the inversion of the order of those states, is calculated here with a family of double-hybrid density functionals. That excited-state inversion is known to be very challenging to reproduce for TD-DFT employing common functionals, e.g. hybrid or range-separated expressions, but not for wavefunction methods due to the inclusion of higher-than-single excitations. Therefore, we explore here if the last developed family of density functional expressions (i.e., double-hybrid models) is able to provide not only the right excited-state energy order but also accurate ΔEST values, thanks to the approximate inclusion of double excitations within these models. We herein employ standard double-hybrid (B2-PLYP, PBE-QIDH, and PBE0-2), range-separated (B2-PLYP ωand RSX-QIDH), spin-scaled (SCS/SOS-B2PLYP21, SCS-PBE-QIDH, andSOS-PBE-QIDH), and range-separated spin-scaled (SCS/SOS-B2-PLYP, SCS-RSX-QIDH, and SOS-RSX-QIDH) expressions, to systematically assess the influence of the ingredients entering into the formulation while concomitantly providing insights for their accuracy. The work in Alicante is supported by the “Ministerio de Ciencia e Innovación” of Spain (Grant No. PID2019-106114GB-I00). Y.O. acknowledges funding by the “Fonds de la Recherche Scientifique-FNRS” under Grant n. F.4534.21 (MIS-IMAGINE). E.B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l’Investissement d’Avenir) for their financial support to this work through Labex SEAM (Science and Engineering for Advanced Materials and devices), Grant Nos. ANR-10-LABX-096 and ANR-18-IDEX-0001. G.R. acknowledges a grant from the “Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture” (F.R.I.A.) of the F.R.S.-F.N.R.S.

ilustraciones, graficas This thesis presents theoretical developments, computational implementations, and numerical applications of multicomponent methodologies that describe positron-molecule interactions. The theoretical developments combine wavefunction methodologies, such as the any particle molecular orbital propagator theory, with density functional theory (DFT) approaches for electrons and positrons. The projector operator embedding scheme of Manby et al. [J. Chem. Theory Comput., 8, 2564 (2012)] has been extended to a multicomponent formulation. The extended wavefunction embedded in DFT scheme reduces the computational cost of positron binding energy predictions obtained with third-order propagator theory at the complete basis set limit without affecting their quality. The stability of novel positron bound states with alkoxide and carboxylate anions is predicted with the extended embedding scheme. This thesis also reports the development of a new positron-electron correlation functional inspired by the Colle-Salvetti formulation of electron correlation. The proposed functional is parameterized to reproduce the annihilation rate and the energy of a positronium atom with a single parameter. DFT positron and positronium binding energies obtained with the new functional display good correlation with results reported employing wavefunction methodologies. In addition, this thesis contains a computational study of positron dihalide molecules, e+[X-Y-] with X,Y=F,Cl,Br, in which the positron binds two repelling halide anions. The covalent positron bonds between halide anions present similar features to one-electron bonds in dialkali cations with isoelectronic atomic cores. This study reveals that positron covalent bonding is not restricted to the e+[H-H-] molecule, previously reported. Esta tesis presenta el desarrollo teórico, la implementación computacional y aplicaciones numéricas de metodologías multicomponente que describen interacciones positrón-molécula. Los desarrollos teóricos combinan metodologías de función de onda, como la teoría del propagador para orbitales moleculares de cualquier partícula, con procedimientos de la teoría del funcional de la densidad (DFT) para electrones y positrones. El esquema de embebido empleando operadores de proyección de Manby et al. [J. Chem. Theory Comput., 8, 2564 (2012)] se ha extendido a una formulación multicomponente. El esquema extendido de función de onda embebida en DFT reduce el costo computacional de las predicciones de energías de enlace de positrón obtenidas con la teoría del propagador de tercer orden en el límite de conjunto de base completo sin afectar su calidad. La estabilidad de nuevos estados ligados de positrones con aniones alcóxido y carboxilato es predicha con el esquema extendido de embebido. Esta tesis también contiene el desarrollo de un nuevo funcional de correlación positrón-electrón inspirado en la formulación de correlación electrónica de Colle-Salvetti. El funcional propuesto está parametrizado para reproducir la tasa de aniquilación y la energía de un átomo de positronio con un solo parámetro. Las energías de unión de positrón y positronio obtenidas con el nuevo funcional muestran una buena correlación con resultados reportados con metodologías de función de onda. Además, esta tesis contiene un estudio computacional de moléculas de dihaluro de positrón, e+[X-Y-] con X,Y=F,Cl,Br, en las que el positrón une dos aniones haluro que se repelen entre sí. Los enlaces covalentes de positrón entre los aniones haluro muestran características similares a los enlaces de un electrón en los cationes dialcalinos con núcleos atómicos isoelectrónicos. Este estudio revela que el enlace covalente positrónico no está restringido a la molécula e+[H-H-] previamente reportada. (Texto tomado de la fuente) Doctorado Doctor en Ciencias - Química

The development of universal and accurate approximations for electronic structure calculations lies at the central core of (past and modern) research in theoretical and computational chemistry. For that purpose, any reliable method needs to treat in a balanced way exchange and correlation effects arising from the intricate structure of matter at the nanoscopic level. Following this principle, we have developed a set of non-empirical (double-hybrid) density functional expressions, minimizing the parameterization and also widely applicable even for systems of considerable size, while being accurate enough to compete with wavefunction methods or even matching experimental information. The underlying expressions are now implemented in many available codes worldwide, then allowing the access to the whole set of key properties needed for addressing chemical structure, reactivity, and bonding, at all nanostructured levels and/or states of matter. Additionally, the recent extension to excited states through a time-dependent (linear-response) formalism also allows one to deal with photochemistry, photophysical, and related properties. Therefore, this family of methods can now be successfully applied to organic, inorganic, or biomolecular compounds, or any other complex system, within an affordable computational effort. The work in Alicante is supported by Project PID2019-106114GB-I00 (‘Ministerio de Ciencia e Innovación’). EB thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l’Investissement d’Avenir) for their financial support to this work through Labex SEAM (Science and Engineering for Advanced Materials and devices), Grant Nos. ANR-10-LABX-096, ANR-18-IDEX-0001 and ANR-21-CE29-0003. IC gratefully acknowledge support from the European Research Council (ERC) for Grant Agreement No. 648558 (STRIGES CoG). The authors thank the GENCI-CINES for HPC resources (Project No. A0100810359).

A computational protocol making use of double hybrid functionals in conjunction with a recently developed basis set tailored to reproduce noncovalent interactions (hereafter named DH-SVPD) is here applied and tested for the evaluation of the properties of C60 fullerenes, namely intermolecular interactions in the weakly bound C60 dimer and relative stabilities of C60 isomers (as described by the C60ISO and iso-C60 data sets). The obtained results suggest that the DH-SVPD performance is very close to that obtained with empirical corrections and larger quadruple-ζ basis for the C60 dimer. In contrast, both approaches (tailored basis set and larger basis with empirical potential) do not reach the envisaged accuracy for the relative stabilities of C60 isomers. Nevertheless, this test well underlined how the DH-SVPD basis set is able to recover the performance obtained by coupling the DH functionals with empirical dispersion corrections and larger basis set, significantly reducing the computational effort for double hybrids and thus enabling expansion of their application domain to larger molecular systems. This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No 648558). E.B. gratefully acknowledges the GENCI-CINES for HPC resources (Projects AP010810360 and A0040810359). ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l’Investissement d’Avenir) are gratefully acknowledged for their financial support of this work through Labex SEAM (Science and Engineering for Advanced Materials and devices) ANR 11 LABX 086 and ANR 11 IDEX 05 02.

P-postmodified polyaniline was obtained by reacting phosphorus trichloride (PCl3) and chlorodiphenylphosphine (PPh2Cl) and polyaniline (PANI), under mild conditions. The reaction was found to be very selective, as only the imine groups were involved in the P-functionalization, and efficient as well, affording a P-loading of 3 at.% and 5 at.% for PPh2Cl and PCl3, respectively. All the polymers were characterized by different techniques and the results were endorsed by theoretical calculations. Experimental and Density Functional Theory results proved that the reaction occurs through the imine groups and the phosphorus atoms, generating NP bonds. The electrochemical properties of the NP modified materials were evaluated and the catalytic activity towards oxygen reduction reaction was measured. It was found that a high concentration of phenyl groups from PPh2Cl (about 3 at.%) affected negatively the activity of the catalyst since they prevented the access of the oxygen molecules to the catalytic active sites. However, a lower amount of PPh2 groups (1 at.%) or the use of PCl3 avoided this hindrance and resulted in an improved catalytic activity with respect to pristine PANI. The authors thank MINECO, MICIUNIN, FIS2015-64222-C2-2-P and FEDER (RTI2018-095291-B-I00 and MAT2016-76595-R) for the financial support.

We have recently demonstrated that carbazole-based biradicaloids are promising building blocks in dynamic covalent chemistry. To elucidate their intriguing dynamic covalent chemical properties, it is necessary to understand the physical origin of their biradical nature. To this end, here we focus on two quinoid carbazole systems substituted with dicyanomethylene (DCM) groups via para (p-Cz-alkyl) or meta positions (m-Cz-ph), which are able to form cyclophane macrocycles by the formation of long C–C bonds between the bridgehead carbon atoms linked to the DCM groups. We aim at exploring the following questions: (i) How is the biradicaloid character of a quinoid carbazole affected by the substitution position of the DCM groups? (ii) How is the stability of the resulted cyclophane aggregate attained? (iii) How is the dynamic interconversion between the carbazole-based monomers and cyclophane aggregates affected by this subtle change in the substitution pattern position? Density functional theory-based calculations reveal that both p-Cz-alkyl and m-Cz-ph are open-shell biradicals in the ground electronic state, with the DCM substitution in the meta position resulting in a more pronounced biradical character. In contrast, the derivatization via the nitrogen of the carbazole unit is not predicted to affect the biradicaloid character. The spontaneous nature of the cyclophane-based macrocycle formation (i.e., the cyclic tetramer in p-Cz-alkyl and the cyclic trimer and the tetramer in m-Cz-ph) is supported by the negative relative Gibbs free energies calculated at 298 K. Interestingly, cyclic oligomers in which the DCM groups are inserted in the meta position tend to adopt folded conformations with attractive π–π interactions resulting in more stable aggregates; in contrast, note that an extended ring-shaped conformation is acquired for (p-Cz-alkyl)4. In addition, the larger spin density on the bridgehead carbon atom in the meta-substituted system strengthens the bridging C–C bond in the aggregate forms, hampering its dissociation. In fact, the C–C bond dissociation of (m-Cz-ph)4 and (m-Cz-ph)3 was suppressed in solution state, although it was achieved in solid state in response to soft external stimuli (i.e., temperature and grinding). In summary, we report a very comprehensive study aiming at elucidating the challenging chemical properties of carbazole-based biradicaloid systems. The work at the University of Málaga was funded by the MINECO (CTQ2015-66897) and Junta de Andalucía (P09-FQM-4708) projects. The work at the University of Alicante was supported by the MINECO (CTQ2014-55073) and Generalitat Valenciana (AICO/2018/175) projects.

Unlike conventional thermally activated delayed fluorescence chromophores, boron-centered azatriangulene-like molecules combine a small excited-state singlet-triplet energy gap with high oscillator strengths and minor reorganization energies. Here, using highly correlated quantum-chemical calculations, we report this is driven by short-range reorganization of the electron density taking place upon electronic excitation of these multi-resonant structures. Based on this finding, we design a series of π-extended boron- and nitrogen-doped nanographenes as promising candidates for efficient thermally activated delayed fluorescence emitters with concomitantly decreased singlet-triplet energy gaps, improved oscillator strengths and core rigidity compared to previously reported structures, permitting both emission color purity and tunability across the visible spectrum., Thermally activated delayed fluorescence is a mechanism for enhancing the efficiency of organic light emitting diodes by harvesting triplet excitons, but there is still a need to design more efficient materials. Here, the authors rationally design and characterize a series of π-extended boron- and nitrogen-doped nanographenes as promising candidates.

We systematically investigate the relationships between structural and electronic effects of finite size zigzag or armchair carbon nanotubes of various diameters and lengths, starting from a molecular template of varying shape and diameter, i.e. cyclic oligoacene or oligophenacene molecules, and disclosing how adding layers and/or end-caps (i.e. hemifullerenes) can modify their (poly)radicaloid nature. We mostly used tight-binding and finite-temperature density-based methods, the former providing a simple but intuitive picture about their electronic structure, and the latter dealing effectively with strong correlation effects by relying on a fractional occupation number weighted electron density (ρFOD), with additional RAS-SF calculations backing up the latter results. We also explore how minor structural modifications of nanotube end-caps might influence the results, showing that topology, together with the chemical nature of the systems, is pivotal for the understanding of the electronic properties of these and other related systems. A. J. P. J. and J. C. S. G acknowledge the project CTQ2014-55073-P from the Spanish Government (MINECO/FEDER) and the project AICO/2018/175 from the Regional Government (GVA/FSE). J. F. R. acknowledges the projects MAT2016-78625 from the Spanish Government (MINECO/FEDER) and projects No. PTDC/FIS-NAN/4662/2014 and No. PTDC/FIS-NAN/3668/2014 from the Portuguese Government (Fundaçao para a Ciencia e Tecnologia). D. C. is thankful to projects IT588-13 (Eusko Jaurlaritza) and CTQ2016-80955 from the Spanish Government (MINECO/FEDER). M. E. S.-S. acknowledges CONACyT-México for a PhD fellowship (ref. 591700). R. O. C. acknowledges “Generalitat Valenciana” and “Fondo Social Europeo” for a PhD fellowship (ACIF/2018/198).

We have investigated the origin of the S1-T1 energy levels inversion for heptazine, and other N-doped π-conjugated hydrocarbons, leading thus to an unusually negative singlet-triplet energy gap (DEST < 0). Since this inversion might rely on substantial doubly-excited configurations to the S1 and/or T1 wavefunctions, we have systematically applied multi-configurational SA-CASSCF and SC-NEVPT2 methods, SCS-corrected CC2 and ADC(2) approaches, and linear-response TD-DFT, to analyse if the latter method could also face this challenging issue. We have also extended the study to B-doped π-conjugated systems, to see the effect of chemical composition on the results. For all the systems studied, an intricate interplay between the singlet-triplet exchange interaction, the influence of doubly-excited configurations, and the impact of dynamic correlation effects, serves to explain the DEST < 0 values found for most of the compounds, which is not predicted by TD-DFT. The work in Alicante is supported by “Ministerio de Ciencia e Innovación” of Spain (Grant No. PID2019-106114GB–I00). Computational resources in Namur are provided by the “Consortium des Équipements de Calcul Intensif” (CÉCI), funded by the “Fonds de la Recherche Scientifiques de Belgique” (F.R.S.-F.N.R.S.) under Grant No. 2.5020.11. G.R. acknowledges a grant from the “Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture” (F.R.I.A.) of the F.R.S.-F.N.R.S.

ilustraciones, gráficas, tablas La acumulación de agregados de péptidos y proteínas es una de las marcas patológicas de alrededor de 50 enfermedades. Estudios experimentales revelan una relación de dependencia entre la secuencia de aminoácidos de una proteína y el proceso de formación de agregados, además de la existencia de regiones específicas que son más propensas a agregarse que otras. En este trabajo, se estudió el proceso de agregación de péptidos considerando que es posible predecir su tendencia intrínseca a agregarse en función de la energía de interacción entre dos unidades peptídicas. Se propuso que esta energía de interacción puede aproximarse como la suma de interacciones individuales de los pares de aminoácidos que componen los pépti dos. La energía de interacción entre pares de aminoácidos se obtuvo mediante cálculos de estructura electrónica bajo el esquema ONIOM (DFT/AM1). La energía de interacción se separó en dos contribuciones: la energía de distorsión de la cadena principal y la energía de interacción de la cadena lateral. Los resultados muestran que estas contribuciones se relacionan con características químicas y estructurales de los aminoácidos. La aproximación propuesta permite estimar energías de interacción de hexapéptidos de manera rápida y con un error de 0.76 kcal/mol por aminoácido en comparación con cálculos a nivel DFT. Con estos resultados se diseñó una herramienta que permite estimar la energía de interacción de dos hexapéptidos con un bajo costo computacional comparado con cálculos en DFT. (Texto tomado de la fuente). Protein aggregation is one of the pathological hallmarks of about 50 diseases. Experimental studies have shown a relationship between the amino acid sequence and the aggregation pro cess, in addition to the existence of specific regions more prone to aggregate than others. In this work, peptide aggregation process was studied by considering that the intrinsic aggrega tion propensity can be predicted as a function of the interaction energy between two peptide units. An approach was proposed in which the interaction energy is expressed as the sum of amino acid pair interactions comprising the hexapeptides. For this purpose, electronic structure calculations were carried out using ONIOM (DFT/AM1) scheme. The interaction energy was separated into two contributions: the peptide backbone distortion energy and the side chain interaction energy. Results revealed that the interaction energy is related to chemical and structural features of amino acids. The approach enables estimating hexapep tide interaction energies with an error of 0.76 kcal/mol per amino acid compared with DFT calculations. These results were consequently used to design a computational tool that cal culates hexapeptide interaction energies with a low computational cost compared to DFT calculations. Incluye anexos Maestría Magíster en Ciencias - Química Química computacional

Numerous theoretical and experimental studies have attempted to determine the mechanisms of bacterial potassium channel selectivity (KcsA). However, there are still different aspects that remain uncovered. In this paper, we have built a model based on a selective filter (SF) for the KcsA, taking into account its structure and calculating the system interaction energy (cation–water–SF-fragment), using both sodium and potassium as cations. The results tell us which aspects could be responsible for the higher selectivity of the channel. All this reveals that there are two most important aspects: the dehydration of potassium in relation to sodium, and the environment where such dehydration occurs, in the entrance of the SF. Both semi-empirical and ab initio methods are applied to analyse and quantify the change of the interactions that take place when the cation K+ or Na+ crosses the SF. Financial support by the Spanish “Ministerio de Economia y Competitividad MINECO” (Grants FIS2015-64222-C2-2-P and PID2019-106114GB-I00) and the Universidad de Alicante, is gratefully acknowledged.

The search of compounds emitting in the near-infrared (NIR) has been accelerated owing to their use in biomedical and telecommunications applications. In this regard, nanographenes (NGs) are attractive materials adequate for integration with other technologies, which have recently demonstrated amplified spontaneous emission (ASE) and lasing across the visible spectrum. Here, the optical and ASE properties of four-zigzag edged NGs of the [m,n]peri-acenoacene family are reported, whose size is increased through conjugation extension by varying n (from 3 to 5) while keeping m = 2. Results show that such 1D conjugation extension method is more efficient in terms of shifting the photoluminescence (PL) to the infrared (PL at 710 nm in the larger compound, PP-Ar) than through 2D conjugation extension as in previously reported NGs (PL at 676 nm with the largest compound FZ3, with n = 3 and m = 4). Additionally, PP-Ar shows dual-ASE (at 726 and 787 nm), whose origin is elucidated through Raman and transient absorption spectroscopies. These compounds’ potential for red and NIR lasing is demonstrated through the fabrication of distributed feedback lasers with top-layer resonators. This study paves the way towards the development of stable low-cost all-plastic NIR lasers. The authors acknowledge financial support from the “Ministerio de Ciencia, Innovación y Universidades” of Spain, European Regional Development Fund and European Social Funds (MAT2015-66586-R, PDI2019-106114GB-I00, BES-2016-077681, PGC2018-098533-B-100 and RED2018-102815-T). J.C. thanks the Junta de Andalucía of Spain (UMA18FEDERJA057). The authors also thank the Research Central Services (SCAI) of the University of Málaga. F.G. acknowledges the Spanish Government for an FPI grant. G.M.P. thanks Fondazione Cariplo (grant no 2018-0979) for the financial support. J.W. acknowledges the “Agency for Science, Technology and Research of Singapore” for financial support from A*STAR AME grant (A20E5c0089). A.M.R. and F.S. have received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. [816313]).

Electrochemical functionalization of Single-Walled Carbon Nanotubes and Herringbone Carbon Nanotubes (SWCNTs and hCNTs, respectively) has been successfully performed with aminophenylphosphonic acid isomers by potentiodynamic treatment in oxidative conditions. Exceptional selectivity and control of the functional species embedded into the Carbon Nanotubes (CNTs) have been achieved by carefully optimizing the electrochemical conditions in the functionalization. X-ray photoelectron spectroscopy (XPS) analysis determined a maximum heteroatom incorporation of ca. 2.3-2.6 at. % N and 1.4-1.6 at. % P when 2-aminophenylphosphonic acid (2APPA) is used with both carbon materials, probably because of the linear polymeric growth comparable to that of oligomers derived from aniline (ANI). However, the polymeric product obtained with 4-aminophenylphosphonic acid (4APPA) is much more limited, giving rise to a branched structure. In addition, electrochemical characterization, Raman spectroscopy and electron microscopy suggest that SWCNTs structure facilitates the oligomerization of longer but less stable chains through π-π interactions with the walls of CNTs, while hCNTs promote a more stable attachment according to their heterogeneity and higher reactivity. Computational calculations have confirmed the experimental results obtained, which allow us to shed more light on the mechanisms of the electrochemical functionalization of CNT with phosphorus and nitrogen-containing polymers. B.M.-S. thanks the Ministry of Science, Innovation and Universities of Spain for the FPU grant (FPU18/05127). The authors would like to thank MICINN and FEDER (projects PID2019-105923RB-100 and RTI2018-095291-B-I00) for the financial support.

La estrategia de aprendizaje en la que se ha centrado este trabajo es el método POGIL (Process Oriented Guided Inquiry Learning), el cual está orientado a mejorar el trabajo del alumnado en grupo haciendo uso de diferentes roles participativos. Este método de carácter cooperativo se aplicó en diferentes asignaturas impartidas en la Facultad de Ciencias, tanto de grado como de postgrado, obteniendo resultados que reflejan la aceptación del método POGIL por parte del alumnado y una mejora en la adquisición de los conceptos en comparación con las clases tradicionales. En esta experiencia se ha planteado el desafío de implementar este método en clases en formato no presencial (online), ya que la situación sanitaria acaecida ha limitado la asistencia del alumnado. A partir de las encuestas realizadas por el alumnado y comparando con los resultados de las encuestas de años anteriores, se puede afirmar que este método se ha aplicado de manera satisfactoria tanto en clases presenciales como en clases online. Adicionalmente, se observó que el contraste entre clases POGIL online y las clases expositivas clásicas es aún mayor que en años anteriores cuando se aplicaba el método POGIL en clases presenciales.

Con el constante aumento del uso de dispositivos electrónicos equipados con pantallas, la sostenibilidad y el consumo energético adquieren una mayor importancia. Así, los dispositivos OLED (diodos orgánicos emisores de luz) basados en la fluorescencia retardada térmicamente activada (TADF) permiten la producción de avanzados dispositivos de emisión de luz con bajo consumo energético y libre de metales pesados. Entre las posibles moléculas emisoras, los nanotriangulenos heterodopados ofrecen una prometedora alternativa, siempre que la diferencia energética entre sus estados excitados singulete y triplete sea lo suficientemente baja. Esta propiedad se puede estudiar de forma precisa con sofisticados métodos químico-cuánticos como CASSCF, NEVPT2 o SCS-CC2, en lugar de TD-DFT, para los sistemas aquí abordados. With the increasing trend in the use of electronic devices equipped with screens, the sustainability and power consumption become more important. Thus, OLED (Organic Light-Emitting Diodes) devices based on Thermally Activated Delayed Fluorescence (TADF) allow the production of advanced light emission devices with low energy consumption and (heavy) metal-free. Among the possible emitting molecules, heterodoped nanotriangulenes offer a promising alternative, provided the energy difference between their singlet and triplet excited states is low enough. This property can be accurately studied with sophisticated quantum-chemical methods such as CASSCF, NEVPT2 or SCS-CC2, instead of TD-DFT, for the systems tackled here. J. C. S. G. agradece el apoyo del Ministerio de Ciencia e Innovación a través del proyecto PID2019-106114GB-I00, así como a la Universidad de Alicante la ayuda concedida a J. S. R. en la modalidad de “Ayuda para Estudios de Master Oficial e Iniciación a la Investigación”.

A collection of five challenging datasets, including noncovalent interactions, reaction barriers and electronic rearrangements of medium-sized hydrocarbons, has been selected to verify the robustness of double-hybrid functionals used in conjunction with the small DH-SVPD basis set, especially developed for noncovalent interactions. The analysis is completed by other, more standard functionals, for a total of 17 models, including also empirical corrections for dispersion. The obtained results show that the chemical accuracy threshold, that is an error lower than 1.0 kcal mol−1, can be obtained by pairing the nonempirical PBE-QIDH functional with the DH-SVPD basis set, as well as by other semi-empirical functionals, such as DSD-PBEP86, using larger basis sets and empirical corrections. More in general, a significant improvement can be obtained using the DH-SVPD basis set with DHs, without resorting to any empirical corrections. This choice leads to a fast computational protocol that, avoiding any empirical potential, remains on a fully quantum ground. E. B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l'Investissement d'Avenir) for their financial support to this work through Labex SEAM (Science and Engineering for Advanced Materials and devices), Grant No. ANR-10-LABX-096 and ANR-18-IDEX-0001. H. L. acknowledges the financial support from the China Scholarship Council (grant no. 201908310062).

The energy difference between singlet and triplet excitons, or ΔEST, is a key magnitude for novel light-emission mechanisms (i.e., TADF or Thermally Activated Delayed Fluorescence) or other photoactivated processes. We have studied a set of conjugated molecules (peri-acenoacenes and their heteroatom-doped analogues) to observe the evolution of their excited-state properties upon increasing the system size without and with substitution with a pair of N atoms. Since these molecules exhibit a (ground-state) diradicaloid character, together with marked correlation effects influencing the excited-states formed, we have applied a variety of theoretical methods (FT-DFT, TD-DFT, CIS, CIS(D), SCS-CC2, SA-CASSCF, and SC-NEVPT2) to bracket the accuracy of the results while concomitantly providing electronic structure insights. The results show how this chemical strategy (N-doping) largely modifies not only the excited-state energies but also the oscillator strengths and the ΔEST values, constituting these molecules a versatile plattform for fine-tuned photophysical applications. The work in Alicante is supported by the “Ministerio de Ciencia e Innovación” of Spain (Grant No. PID2019-106114GB-I00). Computational resources were also provided by the “Consortium des Équipements de Calcul Intensif” (CÉCI), funded by the “Fonds de la Recherche Scientifiques de Belgique” (F.R.S.-FNRS) under Grant No. 2.5020.11. A.D. acknowledges the “Ministére de l’Enseignement Supérieur et de la Recherche Scientifique” of Algeria for a scholarship. G.R. acknowledges a grant from the “Fonds pour la formation a la Recherche dans l’Industrie et dans l’Agriculture” (F.R.I.A.) of the F.R.S.-F.N.R.S. Y.O. acknowledges funding by the “Fonds de la Recherche Scientifique-FNRS” under Grant n. F.4534.21 (MIS-IMAGINE).

In this communication, we assess a panel of 18 double-hybrid (DH) density functionals for the modeling of the thermochemistry and kinetics properties of an extended dataset of 449 organic chemistry reactions belonging to the BH9 database. We show that most of DHs provide a statistically robust performance to model barrier height and reaction energies in reaching the `chemical accuracy'. In particular, we show that nonempirical DHs like PBE0-DH and PBE-QIDH, or minimally parameterized alternatives like $\omega$B2PLYP and B2K-PLYP succeed to model accurately both properties in a balanced fashion. We demonstrate however that parameterized approaches like $\omega$B97X-2 or DSD-like DHs are more biased to only one of both properties. E.B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l’Investissement d’Avenir) for their financial support of this work through Labex SEAM (Science and Engineering for Advanced Materials and devices) ANR-10-LABX-096 and ANR-18-IDEX-0001. The authors acknowledge the GENCI-CINES for HPC resources (Projects A0100810359) just like the local P3MB HPC platform of Université de Paris (ANR-18-IDEX-0001). H.L. acknowledges the financial support from the China Scholarship Council (Grant 201908310062). A.J.P.J. and J.C.S.G. thank the Ministry of Science, Innovation, and Universities of Spain (PID2019-106114GB-I00).

DH‐SVPD is a tailored atomic basis set originally developed to enhance the domain of applicability of double‐hybrid density functionals to large molecular systems in weak interactions. In combination with any density functional belonging to this approximation, it provides an accurate estimate of noncovalent interaction energies at the cost of a double‐ζ basis set, without adding a posteriori an empirical dispersion correction. Here, we show that the accuracy/cost ratio observed previously for energy properties can be safely extended to the modeling of structural parameters of small‐ and medium‐sized organic molecules. In particular, we demonstrate that, in combination with the nonempirical PBE‐QIDH double hybrid, DH‐SVPD is competitive with very large quadruple‐ζ basis sets when modeling both covalent and noncovalent structural parameters. E. B. thanks ANR (Agence Nationale de la Recherche) and CGI (Commissariat à l'Investissement d'Avenir) for their financial support of this work through Labex SEAM (Science and Engineering for Advanced Materials and devices) ANR-10-LABX-096, ANR-18-IDEX-0001. The authors acknowledge the GENCI-CINES for HPC resources (Projects A0040810359 and A0060810359). C. A. and I. C. acknowledge ANR (grand E-Storic) for financial support.

We theoretically investigate here by means of DFT methods how the selective substitution in cyclic organic nanorings composed of pyrene units may promote semiconducting properties, analyzing the energy needed for a hole- or electron-transfer accommodation as a function of the substitution pattern and the system size (i.e., number of pyrene units). We choose to study both [3]Cyclo-2,7-pyrenylene ([3]CPY) and [4]Cyclo-2,7-pyrenylene ([4]CPY) compounds, the latter already synthesized, with substituents other than hydrogen acting in ipso and ortho positions, as well as the effect of the per-substitution. As substituents, we selected a set of electroactive halogen atoms (F, Cl, and Br) and groups (CN) to disclose structure–property relationships allowing thus to anticipate the use of these systems as organic molecular semiconductors. A.J.P.-J. and J.C.S.-G. acknowledge the project AICO/2018/175 from the Regional Government (GVA/FSE). M.M. acknowledges the E2TP-CYTEMA-SANTANDER program. A.N. acknowledges “Consejería de Economía y Conocimiento, Junta de Andalucía” (FQM-337) and “Acción 1-Plan 2017-18” (Universidad de Jaén, Spain).

Nanographenes with zigzag edges are predicted to manifest non-trivial pi-magnetism resulting from the interplay of hybridization of localized frontier states and Coulomb repulsion between valence electrons. This provides a chemically tunable platform to explore quantum magnetism at the nanoscale and opens avenues toward organic spintronics. The magnetic stability in nanographenes is thus far limited by the weak magnetic exchange coupling which remains below the room temperature thermal energy. Here, we report the synthesis of large rhombus-shaped nanographenes with zigzag periphery on gold and copper surfaces. Single-molecule scanning probe measurements unveil an emergent magnetic spin-singlet ground state with increasing nanographene size. The magnetic exchange coupling in the largest nanographene, determined by inelastic electron tunneling spectroscopy, exceeds 100 meV or 1160 K, which outclasses most inorganic nanomaterials and remarkably survives on a metal electrode., 4 figures plus supplementary information

We investigate here the lowest‐energy (spin‐conserving) excitation energies for the set of He‐Ne atoms, with the family of nonempirical PBE, PBE0, PBE0‐1/3, PBE0‐DH, PBE‐CIDH, PBE‐QIDH, and PBE0‐2 functionals, after employing a wide variety of basis sets systematically approaching the basis set limit: def2‐nVP(D), cc‐pVnZ, aug‐cc‐pVnZ, and d‐aug‐cc‐pVnZ. We find that an accuracy (ie, mean unsigned error) of 0.3 to 0.4 eV for time‐dependent density functional theory (DFT) atomic excitation energies can be robustly achieved with modern double‐hybrid methods, which are also stable with respect to the addition of a double set of diffuse functions, contrarily to hybrid versions, in agreement with recent findings employing sophisticated multiconfigurational DFT methods. L.H.M. acknowledges the “Instituto Universitario de Materiales (IUMA)” for a research internship. The work in Alicante is supported by the projects AICO/2018/175 from the Regional Government (GVA/FSE) and FIS2015-64222-C2-2-P from the “Ministerio de Ciencia, Innovación y Universidades”. E.B. thanks ANR (“Agence Nationale de la Recherche”) and CGI (“Commissariat à l'Investissement d'Avenir”) for financial support through Labex SEAM (Science and Engineering for Advanced Materials and devices) ANR 11 LABX 086, ANR 11 IDEX 05 02.

The synthesis of new carbon nanoforms with remarkable and fine‐tuned bulk properties still represents a formidable challenge, with cyclic organic nanorings emerging in recent years for the template‐driven design of this kind of systems. The design and engineering of these materials can be first controlled at the molecular scale, to further induce their specific self‐assembly toward tailored properties at the nanoscale. Theoretical studies have lately contributed to the understanding of the underlying physical effects, the development of synthetic strategies, and the rationalization of novel materials properties, employing a variety of methods ranging from accurate calculations of isolated molecules to atomistic molecular dynamics simulations of a large sample of molecules in realistic conditions, which will be reviewed here with a focus on the transition from single‐molecule to supramolecular properties. Computational resources were provided along the years by projects CTQ2014-55073-P and PID2019-106114GB-I00 (“Ministerio de Ciencia e Innovación”) and AICO/2018/175 (“Generalitat Valenciana”).

Recent advances in the synthesis of stable organic (open-shell) polyradicaloids have opened their application as active compounds for emerging technologies. These systems typically exhibit small energy differences between states with different spin multiplicities, which are intrinsically difficult to calculate by theoretical methods. We thus apply here some DFT-based variants (FT-DFT, SF-DFT, and SF-TDDFT) on a test set of large and real-world molecules, as test systems for which such energy differences are experimentally available, also comparing systematically with RAS-SF results to infer if shortcomings of previous DFT applications are corrected. Additionally, we explore the spin–spin contribution to the ZFS tensor, of high interest for EPR spectroscopy, and derive the spatial extent of the corresponding (photoexcited) triplet state. G.S. acknowledges the Erasmus+ program for a research internship. D.C. is thankful to projects PIBA19-0004 (Eusko Jaurlaritza) and CTQ2016-80955-P from the Spanish Government (MINECO/FEDER).

In this paper we describe the mechanism of light emission through thermally activated delayed fluorescence (TADF)—a process able to ideally achieve 100% quantum efficiencies upon fully harvesting the energy of triplet excitons, and thus minimizing the energy loss of common (i.e., fluorescence and phosphorescence) luminescence processes. If successful, this technology could be exploited for the manufacture of more efficient organic light-emitting diodes (OLEDs) made of only light elements for multiple daily applications, thus contributing to the rise of a sustainable electronic industry and energy savings worldwide. Computational and theoretical studies have fostered the design of these all-organic molecular emitters by disclosing helpful structure–property relationships and/or analyzing the physical origin of this mechanism. However, as the field advances further, some limitations have also appeared, particularly affecting TD-DFT calculations, which have prompted the use of a variety of methods at the molecular scale in recent years. Herein we try to provide a guide for beginners, after summarizing the current state-of-the-art of the most employed theoretical methods focusing on the singlet–triplet energy difference, with the additional aim of motivating complementary studies revealing the stronger and weaker aspects of computational modelling for this cutting-edge technology. Computational resources were provided by: (i) the University of Alicante under Grant No. VIGROB-108; and (ii) the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifiques de Belgique (F.R.S.-FNRS) under Grant No. 2.5020.11.

Las estrategias de aprendizaje tradicionales donde generalmente el profesor tiene el papel principal, podrían no alcanzar las necesidades educativas del alumnado (Guzmán, 2011), así como las competencias planteadas dentro del Espacio Europeo de Educación Superior (EEES). Desde este ámbito se pretenden realizar cambios en las metodologías de enseñanza-aprendizaje para que el alumnado adquiera un papel principal. En este sentido, el método POGIL (Process Oriented Guided Inquiry Learning) ha demostrado ser un método efectivo de enseñanza orientado a mejorar el trabajo del alumnado en el aula a partir de diferentes roles participativos. Este método de carácter cooperativo se aplicó en diferentes asignaturas impartidas en la Facultad de Ciencias, tanto de grado (Oceanografía Química u Operaciones Básicas de Laboratorio), como de postgrado (Polimeros Conductores en el Máster de Ciencia de Materiales). También se realizó una actividad POGIL en el Master en Profesorado de Educación Secundaria para ver el funcionamiento en grupos con mayor diversidad del alumnado. Las encuestas realizadas a los estudiantes reflejan una gran aceptación del método POGIL. Los resultados obtenidos de las pruebas escritas han mostrado que el método POGIL ayuda al alumnado a una mejor adquisición de los conceptos en comparación a los adquiridos en una clase magistral.

In this work, we have theoretically studied the electronic properties of a large series of 1,4-bis(phenylethynyl)benzene derivatives, with the chemical formula Y–C≡C–X–C≡C–Y, with X and Y being aromatic rings and chosen to act as donor and acceptor moieties. Employing state-of-the-art DFT calculations, we analyzed a set of relevant electronic properties related to the optoelectronic and semiconductor character of these systems, namely, molecular and energy levels, electron affinity, ionization potential, reorganization energy, and electronic coupling between neighboring molecules forming dimers, obtained after evaluation of binding energy landscapes. The latter energy magnitude is needed to disclose first the favored intermolecular interactions (i.e., the lowest binding energy) to concomitantly estimate next the charge transport rates. The systematic screening performed allowed us to anticipate the possible use of some of these derivatives as p-type, n-type, or even ambipolar organic molecular semiconductors. M.M. thanks the E2TP CYTEMA-SANTANDER program for financial support. Likewise, the authors are grateful for the project DIPUAB-16-GARZONRUIZ financed jointly by the “Diputación de Albacete” and the “Universidad de Castilla-La Mancha”.

Organic light emitting diodes (OLEDs) are current-driven devices that utilize light emission from excited states of molecules.(1) Operating OLEDs involves charge injection from the anode and the cathode into the adjacent organic layers, transport of injected charge carriers through the organic layers, and exothermic recombination of holes and electrons to generate electronically excited states of molecules. Subsequent deactivation of molecules produces electroluminescence (EL) that goes out of the device. Attaining high quantum efficiency for EL requires: (i) efficient charge injection from both electrodes into the adjacent organic layers at low drive voltage, (ii) charge balance, and (iii) confinement of charge carriers within the emitting layer to increase the probability of emissive recombination. The insertion of hole-acceptor and electron-acceptor layers between the electrodes and the emitting layer substantially increases efficiency. A multilayer structure of OLED’s consists of the emitting layer sandwiched between hole- and electron-acceptor layers that in turn are in contact with the metallic anode and cathode, respectively. Amorphous molecular materials have been proven to show several characteristics that qualify them as excellent materials to be used in OLED’s.(1) Their most remarkable feature is that, due to their homogeneous and isotropic properties, they form smooth thin films, allowing uniform contact with the metallic electrodes and between organic layers. An issue concerning nomenclature is here worthy of comment. As stated above, device operation involves three main processes, namely, charge injection, charge transport, and light emission. Although in this work we will only focus on the first, we shall also use the accepted terminology of hole- or electron-transporters, being aware of the fact that the correct one would be “acceptors” instead of ‘transporters” (investigating their transport performance(2) would require considering also carrier mobility). Hereafter both terminologies will be used indifferently., Financial support by the Spanish “Ministerio de Economía y Competitividad MINECO” and the European Union through FEDER funds (Grants FIS2012-35880, FIS2015-64222-C2-1-P, FIS2015-64222-C2-2-P, and MAT2015-66586-R) and the Universidad de Alicante, is gratefully acknowledged.

We study the orbital-dependence of three (parameter-free) double-hybrid density functionals, namely the PBE0-DH, the PBE-QIDH models, and the SOS1-PBE-QIDH spin-opposite-scaled variant of the latter. To do it, we feed all their energy terms with different sets of orbitals obtained previously from self-consistent density functional theory calculations using several exchange-correlation functionals (e.g., PBE, PBE0, PBEH&H), or directly with HF-PBE orbitals, to see their effect on selected datasets for atomization and reaction energies, the latter proned to marked self-interaction errors. We find that the PBE-QIDH double-hybrid model shows a great consistency, as the best results are always obtained for the set of orbitals corresponding to its hybrid scheme, which prompts us to recommend this model without any other fitting or reparameterization. Contract grant sponsors: “Ministerio de Economía y Competitividad” of Spain and the “European Regional Development Fund” through project CTQ2014-55073-P (to J.C.S.G. and A.J.P.J.).

Spin statistics greatly limits the efficiency of OLEDs, which might be largely improved upon conversion of triplet into singlet-excited (and thus light-emitting) states via a Thermally Activated Delayed Fluorescence (TADF) process. We theoretically investigate here the combination of some real-life donor (D) and acceptor (A) moieties with the connectivity D–A and D–A–D. We selected phenoxazine (PXZ) and phenylthiazine (PTZ) as electron-donating groups, and 2,5-diphenyl-1,3,4-oxadiazole (OXD), 3,4,5-triphenyl-4H-1,2,4-triazole (TAZ), and 2,5-diphenyl-1,3,4-thiadiazole (TDZ) as their electron-accepting partners. The systematic Tamm–Dancoff Approximation-Density Functional Theory calculations performed allowed us to calculate accurately not only the energy levels of low-lying singlet and triplet-excited states, but also to characterize their Charge-Transfer (CT) or Locally Excited (LE) nature, since the energy difference and the coupling between the 3CT, 3LE, and 1CT states become key to understanding the molecular mechanism involved in this process. We have also studied the role played by the conformational landscape, arising from the thermally accessible range of D–A(–D) torsion angles, in the singlet–triplet energy gap as well as its influence on oscillator strengths. Overall, we rationalize the origin of the higher efficiencies found in real devices for D–A–D molecules, disclosing the underlying structure–property relationships and thus anticipating successful design strategies. This work was partially supported by the Samsung Advanced Institute of Technology (SAIT)’s Global Research Outreach (GRO) Program. In addition, the research in Bordeaux has been funded by the French State grant ANR-10-LABX-0042-AMADEus managed by the French National Research Agency under the initiative of excellence IdEx Bordeaux program (reference ANR-10-IDEX-0003-02). The work in Mons was supported by the “Programme d’Excellence de la Région Wallonne” (OPTI2MAT project) and FNRS-FRFC. Computational resources have been provided by the Consortium des Équipements de Calcul Intensif (CÉCI), funded by the Fonds de la Recherche Scientifique de Belgique (F.R.S.-FNRS) under Grant no. 2.5020.11 as well as the Tier-1 supercomputer of the Fédération Wallonie-Bruxelles, infrastructure funded by the Walloon Region under the grant agreement no. 1117545. Mónica Moral thanks to the E2TP CYTEMA-Santander Program for their financial support.

The design of advanced N-doped carbon materials towards oxygen reduction reaction (ORR) catalysis is only possible if the nature of the active sites is fully understood. There is an important piece of research seeking to overcome this challenge through experimental or theoretical results. However, the combination of both approaches is necessary to deepen the knowledge about this subject. This work presents excellent agreement between experimental results and computational models, which provides evidence of the nature of the most active sites in N-doped carbon materials. N-doped carbon materials have been experimentally obtained through double stage treatment of polyaniline in distinct atmospheres (both oxygen-containing and inert atmospheres) at different temperatures (800–1200 °C). According to temperature programmed desorption (TPD), Raman spectroscopy, N2-adsorption isotherms at −196 °C and X-ray photoelectron spectroscopy (XPS), this synthesis method results in the selective formation of nitrogen species, without significant changes in structural order or porosity. ORR catalytic tests evidence the highly efficient catalysis, with platinum-like performance in terms of the current density and onset potential, of N-doped carbon materials selectively containing graphitic-type nitrogen species. Computational chemistry, through DFT calculations, shows that edge-type graphitic nitrogen is more effective towards ORR catalysis than pyridinic, pyrrolic, pyridonic, oxidized and basal-type graphitic nitrogen species. The authors thank Ministerio de Ciencia, Innovación y Universidades and FEDER for financial support (Project RTI2018-095291-B-I00, ENE2017-90932-REDT and FIS2015-64222-C2-2-P). MMF acknowledges support from the Portuguese Foundation for Science and Technology (FCT), under the projects IF/00894/2015, and FCT Ref. UID/CTM/50011/2019 for CICECO - Aveiro Institute of Materials.

The scalable production of homogeneous, uniform carbon nanomaterials represents a key synthetic challenge for contemporary organic synthesis as nearly all current fabrication methods provide heterogeneous mixtures of various carbonized products. For carbon nanotubes (CNTs) in particular, the inability to access structures with specific diameters or chiralities severely limits their potential applications. Here, we present a general approach to access solid-state CNT mimic structures via the self-assembly of fluorinated nanohoops, which can be synthesized in a scalable, size-selective fashion. X-ray crystallography reveals that these CNT mimics exhibit uniform channel diameters that are precisely defined by the diameter of their nanohoop constituents, which self-assemble in a tubular fashion via a combination of arene-pefluoroarene and C–H—F interactions. The nanotube-like assembly of these systems results in capabilities such as linear guest alignment and accessible channels, both of which are observed in CNTs but not in the analogous all-hydrocarbon nanohoop systems. Calculations suggest that the organofluorine interactions observed in the crystal structure are indeed critical in the self-assembly and robustness of the CNT mimic systems. This work establishes the self-assembly of carbon nanohoops via weak interactions as an attractive means to generate solid-state materials that mimic carbon nanotubes, importantly with the unparalleled tunability enabled by organic synthesis. The synthesis and structural analysis of 2 and 3 were supported by the National Science Foundation (NSF) under grant numbers CHE-1808791 and CHE-1800586. A.J.P.J. and J.C.S.G. acknowledge the project AICO/2018/175 from the Regional Government (GVA/FSE).