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The synthesis of a broad range of enantioenriched amines by the direct Fe-catalysed coupling of amines with alcohols through the borrowing hydrogen strategy, while at least one of these substrates is achiral is reported. When starting from α-chiral amines and achiral alcohols, a wide range of enantioenriched amine products, including N-heterocyclic moieties can be obtained with complete retention of stereochemistry and the power of this method is demonstrated in the one-step synthesis of known pharmaceuticals from commercially available, simple enantiopure primary amines and achiral alcohols. It was also found that the use of β-branched enantioenriched primary alcohols and achiral amines as reaction partners leads to a partial loss of stereochemical integrity in the final product, however, a systematic optimization enabled partial retention of enantiopurity and possible parameters effecting for racemization were identified.

Organic open-shell compounds are extraordinarily attractive materials for their use in molecular spintronics thanks to their long spin-relaxation times and structural flexibility. Porphyrins (Pors) have widely been used as molecular platforms to craft persistent open-shell structures through solution-based redox chemistry. However, very few examples of inherently open-shell Pors have been reported, which are typically obtained through the fusion of non-Kekulé polyaromatic hydrocarbon moieties to the Por core. The inherent instability and low solubility of these radical species, however, requires the use of bulky substituents and multistep synthetic approaches. On-surface synthesis has emerged as a powerful tool to overcome such limitations, giving access to structures that cannot be obtained through classical methods. Herein, we present a simple and straightforward method for the on-surface synthesis of phenalenyl-fused Pors using readily available molecular precursors. In a systematic study, we examine the structural and electronic properties of three surface-supported Pors, bearing zero, two (PorA2), and four (PorA4) meso-fused phenalenyl moieties. Through atomically resolved real-space imaging by scanning probe microscopy and high-resolution scanning tunneling spectroscopy combined with density functional theory calculations, we unambiguously demonstrate a triplet ground state for PorA2 and a charge-transfer-induced open-shell character for the intrinsically closed-shell PorA4., This work was supported by the Swiss National Science Foundation under Grant No. 200020_182015. Financial support from the Spanish MICINN (CTQ2017-85393-P) andthe ERA-NET/European Commission/MINECO (UNIQUE, SOLAR-ERA.NET Cofund 2 No. 008/PCI2019-111889-2) are acknowledged. IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV2016-0686). R.R. and N.L. are grateful for funding from the EU-FET Open H2020 Mechanics with Molecules project (grant 766864).

Porphyrin nanotapes (Por NTs) have attracted vast interest as potential molecular wires thanks to their exceptional electronic properties. Recently, Por NTs have been synthesized by solution-based methods, demonstrating high versatility and great potential for technological applications. However, their synthesis is tedious and their characterization limited by low solubility and stability. Here, we report the first example of meso-meso triply-fused Por NTs, which are prepared from a readily available Por precursor through a two-step synthesis on Au(111). The structural and electronic properties of individual Por NTs are addressed, both on Au(111) and on a thin insulating NaCl layer, by high-resolution scanning probe microscopy/spectroscopy complemented by density functional theory calculations. Remarkably, the triply-linked Por NTs carry one unpaired electron at each end, which leads to magnetic end states. Our study provides an alternative and versatile route to the fabrication of Por NTs and the atomic-scale characterizations of their structural and electronic properties.

Subphthalocyanines (SubPcs) are well-known cone-shaped chromophores consisting on three 1,3-diiminoisoindole units assembled around a boron atom. As a result of their 14 pi-electron aromatic core and their tetrahedral geometry, SubPcs exhibit outstanding physical and optoelectronic properties (e.g., strong dipole moment, excellent light absorption in the 550-650 nm, rich redox features, and excellent charge transport capabilities), that have been skilfully used in variety of applied fields, such as molecular photovoltaics, among others. SubPcs were used by us as non-fullerene acceptors in bulk heterojunctions (BHJ) solar cells. On the other hand as part of our systematic investigation in the preparation and study of novel SubPc-based D–A systems, we have used 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) as partner for SubPcs. Moreover, in the case of unsymmetrically substituted SubPcs (i.e., prepared by cyclotrimerization of a phthalonitrile with no C2v symmetry), they present inherent chirality and the corresponding couple of enantiomers can be isolated Columnar aggregates based on chiral SubPcs have been also prepared, giving rise to ferroelectric self-assembled molecular materials showing both rectifying and switchable conductivity. These chromophores have been incorporated in multicomponent systems showing a panchromatic response and allowing the tuning and controlling intramolecular FÖRSTER Resonance Energy Transfer for Singlet Fission.

Phthalocyanines (Pcs) have emerged as excellent light harvesting antennas for incorporation into D-A systems, mainly in connection with carbon nanostructures, like endohedral metallofullerenes, SWCNT and graphene, as acceptor or donor moieties, in which the Pc has been attached, covalently or through supramolecular interactions. They are among the few molecules that reveal an intense red and NIR absorption and therefore, constitute also promising dyes in molecular photovoltaics. Pcs have a great chemical versatility, which allows to modify their electronic character and their physicochemical properties by organic synthesis, by introducing substituents in the periphery or modifying the structure of the macrocycle. Most recently they have reached good efficiency values participating as hole transporting materials in Carbon-based Perovskite sensitized solar cells (PSSCs). Pcs are be appropriately designed to adapt well to the electronic levels of the different types of perovskites. Through a rational design, structure-property relationships will be established that will gradually improve the performance of the devices. On the other hand, on-surface synthesis offers a versatile approach to fabricate novel carbon-based nanostructures that cannot be obtained via conventional solution chemistry. Within the family of such nanomaterials, graphene nanoribbons (GNRs) hold a privileged position due to their high potential for different applications. One of the key issues for their application in molecular electronics lies in the fine-tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non-benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) represents a highly appealing strategy.

Tetracyanobuta-1,3-diene (TCBD) is a powerful and versatile electron-acceptor moiety widely used for the preparation of electroactive conjugates. While many reports addressing its electron-accepting capability have appeared in the literature, significantly scarcer are those dealing with its chemical modification, a relevant topic which allows to broaden the chemical space of this interesting functional unit. Here, we report on the first example of a high-yielding cyano-Diels-Alder (CDA) reaction between TCBD, that is, where a nitrile group acts as a dienophile, and an anthryl moiety, that is, acting as a diene. The resulting anthryl-fused-TCBD derivative, which structure was unambiguously identified by X-ray diffraction, shows high thermal stability, remarkable electron-accepting capability, and interesting electronic ground- and excited-state features, as characterized by a thorough theoretical, electrochemical, and photophysical investigation. Moreover, a detailed kinetic analysis of the intramolecular CDA reaction transforming the anthryl-TCBD-based reactant into the anthryl-fused-TCBD product was carried out at different temperatures.

On-surface synthesis has emerged as a powerful tool for the construction of large, planar, π-conjugated structures that are not accessible through standard solution chemistry. Among such solid-supported architectures, graphene nanoribbons (GNRs) hold a prime position for their implementation in nanoelectronics due to their manifold outstanding properties. Moreover, using appropriately designed molecular precursors, this approach allows the synthesis of functionalized GNRs, leading to nanostructured hybrids with superior physicochemical properties. Among the potential “partners” for GNRs, porphyrins (Pors) outstand due to their rich chemistry, robustness, and electronic richness, among others. However, the use of such π-conjugated macrocycles for the construction of GNR hybrids is challenging and examples are scarce. Herein, singly and doubly Por-capped GNR segments presenting a commensurate and triply-fused GNR–Por heterojunction are reported. The study of the electronic properties of such hybrid structures by high-resolution scanning tunneling microscopy, scanning tunneling spectroscopy, and DFT calculations reveals a weak hybridization of the electronic states of the GNR segment and the Por moieties despite their high degree of conjugation., Singly and doubly porphyrin-capped graphene nanoribbon segments are reported and their electronic properties are studied by high-resolution scanning tunneling microscopy and spectroscopy, and DFT calculations.

The recent development of organic polaritonic solar cells, in which sunlight absorbers and photon modes of a resonator are hybridized as a result of their strong coupling, has revealed the potential this interaction offers to control and enhance the performance of these devices. In this approach, the photovoltaic cell is built in such a way that it also behaves as an optical cavity supporting spectrally well-defined resonances, which match the broad absorption bands of the dyes employed. Herein we focus on the experimental and theoretical analysis of the specific spectral and angular optical absorption characteristics of a broadband light harvester, namely a subphthalocyanine, when operating in the ultrastrong coupling regime. We discuss the implications of having a broad distribution of oscillator strengths and demonstrate that rational design of the layered structure is needed to optimize both the spectral and the angular response of the sunlight harvester dye

Herein, we describe the first on-surface preparation of porphyrin nanotapes (Por NTs) on a gold surface. Structural and electronic characterization reveals that the Por NTs carry one unpaired electron at each end, which leads to magnetic end states. This study provides an alternative and versatile route to the fabrication of Por NTs and a detailed atomic-scale characterization of their structural and electronic properties., Porphyrin nanotapes (Por NTs) are promising structures for their use as molecular wires thanks to a high degree of π-conjugation, low HOMO—LUMO gaps, and exceptional conductance. Such structures have been prepared in solution, but their on-surface synthesis remains unreported. Here, meso–meso triply fused Por NTs have been prepared through a two-step synthesis on Au(111). The diradical character of the on-surface formed building block PorA2, a phenalenyl π-extended ZnIIPor, facilitates intermolecular homocoupling and allows for the formation of laterally π-extended tapes. The structural and electronic properties of individual Por NTs are addressed, both on Au(111) and on a thin insulating NaCl layer, by high-resolution scanning probe microscopy/spectroscopy complemented by DFT calculations. These Por NTs carry one unpaired electron at each end, which leads to magnetic end states. Our study provides a versatile route towards Por NTs and the atomic-scale characterization of such tapes., This work was supported by the Swiss National Science Foundation under Grant No. 200020_182015, the European Union's Horizon 2020 research and innovation programme under grant agreement number 785219 (Graphene Flagship Core 2), the Office of Naval Research (N00014-18-1-2708), MINECO, CTQ2017-85393-P (Phthalophoto, T.T.), and PID2020-116490GB-I00 (Porphyrinoids, T.T., G.B.). IMDEA Nanociencia also acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). R.R. and N.L. are grateful for funding from the EU-FET Open H2020 Mechanics with Molecules project (grant 766864).

Herein, we present a simple and straightforward method for the synthesis of phenalenyl-fused Pors (Por A0, PorA2 and PorA4) through readily available molecular precursors. While PorA0 was prepared by “wet” synthesis, the two- and four-fold phenalenyl-fused Por derivatives PorA2 and PorA4 were fabricated through a surface-assisted cyclodehydrogenation reaction from meso-2,6-dimethylphenyl(dmp) substituted precursors Por(dmp)2 and Por(dmp)4, respectively. In a systemat-ic way, we examined the structural and electronic properties of three surface-supported Pors.

We report the stereoisomerism and physicochemical properties of two novel electron donor–acceptor conjugates based on subphthalocyanines decorated at their peripheral, or peripheral/axial positions with multiple tetracyanobutadiene–aniline moieties., Two subphthalocyanines (SubPcs) decorated at their peripheral (SubPc 1) or peripheral and axial (SubPc 2) positions with tetracyanobuta-1,3-diene (TCBD)–aniline moieties have been prepared as novel electron donor–acceptor (D–A) conjugates. In 1 and 2, the multiple functionalization of C3-symmetric SubPcs by TCBD moieties, each of them having a chiral axis, results in the formation of several stereoisomers. Variable temperature 1H-NMR studies in chlorinated solvents suggest that these latter species, which are detected at low temperatures, rapidly interconvert – on the NMR timescale – into each other at room temperature. Beside their unique structural and stereochemical features, 1 and 2 present interesting physicochemical properties. Steady-state absorption and fluorescence, as well as electrochemical studies on 1 and 2 clearly point to an important degree of electronic communication between the SubPc, the TCBD and the aniline subunits. Moreover, in both derivatives, photoexcitation of the SubPc moiety yields charge transfer products involving the electron-rich SubPc moiety and the electron-withdrawing TCBD fragment. Interestingly, such polarized excited state species evolve in 1 and 2 in different ways. While in the former compound, it directly decays to the ground state, the fourth axial TCBD moiety in 2 leads to the formation of an intermediate fully charge separated state prior to the ground state deactivation.

We report here the synthesis of two novel subporphyrins (SubPs), in which the macrocycle has been functionalized at its meso (1) or axial (2) position with tetracyanobuta-1,3-diene (TCBD)–aniline. ...

The Front Cover Picture, designed by Anastasiia Afanasenko, illustrates the methodology for the synthesis of enantioenriched amines by the direct Fe-catalysed coupling of amines with alcohols through the borrowing hydrogen strategy, while at least one of these substrates is achiral. As in the well-known “The Tortoise and the Hare” fable by Aesop, tortoise – stands for chiral amine – won the race retaining the stereochemical integrity in the final product, whereas beta-branched enantioenriched primary alcohol – depicts by the hare – lost the competition due to its racemization that led to the partial loss of the chirality in the target amine. Details can be found in the Research Article by Katalin Barta and collaborators (G. Bottari, A. Afanasenko, A. A. Castillo-Garcia, B. L. Feringa, K. Barta, Adv. Synth. Catal. 2021, 363, 5436–5442; DOI: 10.1002/adsc.202100231).

Lignocellulose, the main component of agricultural and forestry waste, harbours tremendous potential as a renewable starting material for future biorefinery practices. However, this potential remains largely unexploited due to the lack of strategies that derive substantial value from its main constituents. Here, we present a catalytic strategy that is able to transform lignocellulose to a range of attractive products. At the centre of our approach is the flexible use of a non-precious metal catalyst in two distinct stages of a lignocellulose conversion process that enables integrated catalyst recycling through full conversion of all process residues. From the lignin, pharmaceutical and polymer building blocks are obtained. Notably, among these pathways are systematic chemo-catalytic methodologies to yield amines from lignin. The (hemi)cellulose-derived aliphatic alcohols are transformed to alkanes, achieving excellent total carbon utilization. This work will inspire the development of fully sustainable and economically viable biorefineries.

In this issue of Chem , Martin, Guldi, and colleagues describe the preparation and study of one of the first examples of near-infrared-absorbing donor-acceptor materials based on carbon nanotubes and graphene. These materials show charge-transfer interactions in both the ground and excited states.

In recent years, several tetracyanobuta-1,3-diene (TCBD) conjugates have been prepared by linking the tetracyano unit to various electroactive moieties. These push-pull conjugates, besides showing interesting physicochemical properties, are axially chiral, a feature arising from the restricted rotation around the central bond of the butadiene. Yet, only in a few cases, separation and isolation of the enantiomers have been successfully achieved, owing to the configurational lability of the corresponding enantiopure species. Herein, we report the first example of photo- and electroactive TCBD-based derivatives showing unprecedented configurational stability and a peculiar light-triggered enantiomer conversion mechanism enabled by triple-state photogeneration. These systems represent a nice addition to the fast-increasing arsenal of artificial, light-controllable molecular switches.

A rod-like cyclopenta[hi]aceanthrylene (CPA) derivative bearing three dodecyloxy chains at each of its two terminal positions was prepared. Spectroscopic (i.e., steady-state absorption and fluorescence) and electrochemical studies carried out with this polycyclic aromatic hydrocarbon (PAH) derivative showed an intense absorption through the entire UV-vis spectral range, weak fluorescence, small HOMO-LUMO gap, and excellent electron accepting capability. Transient absorption spectroscopy (TAS) revealed the formation of singlet and triplet excited states; the latter was, however, only observed in the presence of a triplet sensitizer. The exfoliation capability of this lipophilic CPA towards single-walled carbon nanotubes (SWCNTs) in THF was also investigated. On one hand, transmission electron microscopy (TEM) pointed to an efficient debundling of SWCNTs by the CPA derivative by means of non-covalent interactions. On the other hand, important differences in the ground and excited state features of the uncomplexed and SWCNT-complexed CPA were revealed by Raman and TAS, Financial support from the “Solar Energy goes Hybrid” Initiative of the Bavarian Ministry for Science, Culture and Education (SolTech), Comunidad de Madrid (FOTOCARBON), and Spanish MICINN (CTQ2017-85393-P) is acknowledged

This is the peer reviewed version of the following article: Angewandte Chemie - International Edition 59. 3 (2020): 1334-1339, which has been published in final form at https://doi.org/10.1002/anie.201913024. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions, On-surface synthesis offers a versatile approach to prepare novel carbon-based nanostructures that cannot be obtained by conventional solution chemistry. Graphene nanoribbons (GNRs) have potential for a variety of applications. A key issue for their application in molecular electronics is in the fine-tuning of their electronic properties through structural modifications, such as heteroatom doping or the incorporation of non-benzenoid rings. In this context, the covalent fusion of GNRs and porphyrins (Pors) is a highly appealing strategy. Herein we present the selective on-surface synthesis of a Por–GNR hybrid, which consists of two Pors connected by a short GNR segment. The atomically precise structure of the Por–GNR hybrid has been characterized by bond-resolved scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc-AFM). The electronic properties have been investigated by scanning tunneling spectroscopy (STS), in combination with DFT calculations, which reveals a low electronic gap of 0.4 eV, Financial support from Spanish MICINN (CTQ2017‐85393‐P) is acknowledged. IMDEA Nanociencia acknowledges support from the “Severo Ochoa” Programme for Centres of Excellence in R&D (MINECO, Grant SEV2016‐0686). This work was supported by the Swiss National Science Foundation (200020_182015, IZLCZ2_170184) and the NCCR MARVEL funded by the Swiss National Science Foundation (51NF40‐182892). Computational support from the Swiss Supercomputing Center (CSCS) under project ID s904 is gratefully acknowledged. Q.S. acknowledges the EMPAPOSTDOCS‐II programme under the Marie Sklodowska‐Curie grant agreement No 754364

We report here the synthesis and characterization of some novel Zn(II)phthalocyanine (Pc)-corannulene conjugates and their complexation ability towards a pyridyl-functionalized C[Formula: see text] fullerene through metal-ligand supramolecular interactions. Steady-state and time-resolved photophysical studies carried out on these electron donor–acceptor (D–A) Zn(II)Pc-corannulene/C[Formula: see text] ensembles indicate the formation of photogenerated charge-separated species. Interestingly, a stabilization of the photoinduced charge-separated state is observed in the case of the D–A supramolecular complexes comprising the corannulene-substituted Zn(II)Pcs when compared to their non-corannulene functionalized Zn(II)Pc analogues. We rationalize this stabilizing effect of the charge-separated state exerted by the corannulene as a result of the increased [Formula: see text]-extension and augmented hydrophobicity of the Zn(II)Pc core by the covalently-linked polyaromatic hydrocarbon (PAH) fragment.

Cyclopenta[hi]aceanthrylenes (CPAs) have been functionalized at two of the peripheral positions with electronically inert trimethylsilylethynyl (1), as well as with electron-donating 4-ethynyl-N,N-dimethylaniline (2), ethynyl ZnII phthalocyanine (3), and ethynyl ZnII porphyrin (4) units. Consistent with X-ray crystal structures of 2 and 4, analyses of absorption and fluorescence of 2-4 point to strong electronic communication between the CPA and the peripheral units, affording quadrupolar electron donor-acceptor-donor charge-transfer conjugates. By virtue of their quadrupolar/dipolar charge-transfer characters in the excited state, 2-4 exhibit fluoro-solvatochromism. Transient absorption spectroscopy confirmed delocalized quadrupolar ground states and formation of weakly solvent stabilized quadrupolar singlet excited states. The latter transform into strongly stabilized dipolar excited states before deactivating to the ground state in 2 and give rise to a fully charge separated state in 3 and 4.

Herein, both from the experimental and theoretical point of view, the optical absorption properties of a subphthalocyanine (SubPc), an organic macrocycle commonly used as a sunlight harvester, coupled to metallic optical cavities are analyzed. How different electronic transitions characteristic of this compound and specifically those that give rise to excitonic (Q band) and charge transfer (CT band) transitions couple to optical cavity modes is investigated. It is observed that whereas the CT band couples weakly to the cavity, the Q band transitions show evidence of hybridization with the photon eigenstates of the resonator, a distinctive trait of the strong coupling regime. As a result of the different coupling regimes of the two electronic transitions, very different spectral and directional light-harvesting features are observed, which for the weakly coupled CT transitions are mainly determined by the highly dispersive cavity modes and for the strongly coupled Q band by the less angle-dependent exciton-polariton bands. Modeling also allows discriminating parasitic from productive absorption in each case, enabling the estimation of the expected losses in a solar cell acting as an optical resonator.

The development of new chromophoric receptors able to bind curved carbon nanostructures is at the epicenter of the quest for fullerene-based organic photovoltaics with improved performances. Herein, a subphthalocyanine-based multicomponent ensemble consisting of two electron-rich SubPc-monomers rigidly attached to the convex surface of a electron-poor SubPc-dimer has been synthesized and characterized. Such a unique conformation, especialy in terms of the two SubPc-monomers, together with the overall stiffness of the tether endows the multicomponent system with a well-defined tweezer-like topology to efficiently embrace a fullerene in its inner cavity. On the other hand, the selective on-surface synthesis of a porphyrin-graphene nanoribbon hybrid has been accomplished. The atomically precise structure of the hybrid has been unambiguously characterized by bond-resolved scanning tunneling microscopy and noncontact atomic force microscopy. Finally, a novel electron donor-acceptor hybrid consisting of a NIR absorbing azulenocyanine as electron donor and few-layer graphene as electron acceptor was prepared. The extended aromatic core of azulenocyanine assist in the exfoliation of graphite and allows formation of a very high-quality few-layer graphene azulenocyanine hybrid system.

The direct conversion of ethanol to higher value 1-butanol is a catalytic transformation of great interest in light of the expected wide availability of bioethanol originating from the fermentation of renewable resources. In this contribution we describe several novel compositions of porous metal oxides (PMO) as highly active and selective catalysts for the Guerbet coupling of ethanol to 1-butanol in the temperature range 180-320 degrees C. The novel PMO catalysts that do not contain any noble metals are obtained by calcination of a series of hydrotalcite precursors synthesized through modular procedures. In particular, catalyst compositions simultaneously containing Cu and Ni dopants have shown excellent catalytic activities. Up to 22% 1-butanol yield at 56% ethanol conversion was reached in a batch mode; recycling and leaching tests showed excellent robustness of the new catalysts. An extensive characterization by means of several techniques such as powder XRD, SEM, TEM, BET, and NH3- and CO2-TPD was performed in order to understand structure-activity trends.

This review highlights the combined effort of the Torres and Guldi groups in the preparation and study of porphyrinoid-based photo- and electro-active systems. The perfect synergy between the deep knowledge on the chemistry of porphyrinoids and advanced carbon allotropes possessed by the Spanish team, and the profound expertise in the advanced photophysical characterization and photon- and charge-management held by the German group represents the real asset of this transnational collaboration. Along the last twenty years, the two groups have developed a plethora of electron donor–acceptor architectures based mainly on phthalocyanines and subphthalocyanines, but also porphyrins and other porphyrinoids, connected, either covalently or through supramolecular interactions, to several electroactive units such as advanced carbon allotropes, that is, fullerenes, carbon nanotubes, and graphene, among others. Important guidelines relating the structural and electronic features of such photo- and electro-active species with physical aspects such as the dynamics of charge separation, charge transport, charge shift, and charge recombination processes have been obtained. This knowledge has resulted crucial for the implementation of many of these systems into applied research fields such as optoelectronics, solar energy conversion, and biomedicine.

Herein, a novel electron donor-acceptor hybrid consisting of a NIR absorbing azulenocyanine as electron donor and few-layer graphene as electron acceptor was prepared. The extended aromatic core of azulenocyanine assist in the exfoliation of graphite and allows formation of a very high-quality few-layer graphene azulenocyanine hybrid system. The development of new chromophoric receptors able to bind curved carbon nanostructures is at the epicenter of the quest for fullerene-based organic photovoltaics with improved performances. Herein, a subphthalocyanine-based multicomponent ensemble consisting of two electron-rich SubPc-monomers rigidly attached to the convex surface of a electron-poor SubPc-dimer has been synthesized and characterized. Such a unique conformation, especialy in terms of the two SubPc-monomers, together with the overall stiffness of the tether endows the multicomponent system with a well-defined tweezer-like topology to efficiently embrace a fullerene in its inner cavity. The selective on-surface synthesis of a porphyrin-graphene nanoribbon hybrid has been accomplished. The atomically precise structure of the hybrid has been unambiguously characterized by bond-resolved scanning tunneling microscopy and noncontact atomic force microscopy.

We report on vapochromic films suitable for detecting volatile organic compounds (VOCs), based on polycarbonate (PC) doped with 4-(triphenylamino)phthalonitrile (TPAP), a fluorescent molecular rotor sensitive to solvent polarity and viscosity. PC films of variable thickness (from 20 up to 80 µm) and containing small amounts of TPAP (0.05 wt.%) were prepared and exposed to a saturated atmosphere of different VOCs. TPAP/PC films showed a gradual decrease and red-shift of the emission during the exposure to solvents with high polarity index and favourable interaction with the polymer matrix such as THF, CHCl3, and acetonitrile. In the case of the most interacting solvents (THF and CHCl3), TPAP/PC films also showed a fluorescence increase at longer exposure times, as a consequence of an irreversible, solvent-induced crystallization process of the polymeric matrix. The vapochromism of TPAP/PC films is rationalized on the basis of alterations of the rotor intramolecular motion upon solvent uptake by PC and polarity effects of the microenvironment. Interestingly, the fluorescence response of the TPAP/PC films shows a non-trivial, tuneable dependence on film thickness during the second solvent-exposure stage. The latter effect is attributed to a variable extent of the crystallization process occurring in the PC films. This observation promptly suggests, in turn, an effective procedure to modulate the spectroscopic response in such functionalized polymeric materials through the precise control of the film thickness.

To activate oxidative and/or reductive electron transfer reactions, N-pyridyl-substituted Sc3N@I(h)-C80 (4) and C60 (3) fulleropyrrolidines have been prepared and axially coordinated to electron-rich (1) or electron-deficient (2) Zn(II)phthalocyanines (Zn(II)Pcs) through zinc-pyridyl, metal-ligand coordination affording a full-fledged family of electron donor-acceptor ensembles. An arsenal of photophysical assays as they were carried out with, for example, 1/4 and 2/4 show unambiguously that a Zn(II)Pc-to-Sc3N@I(h)-C80 photoinduced electron transfer takes place in the former ensemble, whereas a Sc3N@I(h)-C80-to-Zn(II)Pc electron transfer occurs in the latter ensemble. To the best of our knowledge, this is the first time that a fullerene-based molecular building block shows an electron transfer dichotomy, namely acting both as electron-acceptor or electron-donor, and its outcome is simply governed by the electronic nature of its counterpart. In light of the latter, the present work, which involves the use of Sc3N@I(h)-C80, one of the most abundant and easy-to-purify endohedral metallofullerenes, is, on one hand, a paradigmatic change and, on the other hand, an important milestone en-route toward the construction of easy-to-prepare molecular materials featuring switchable electron transfer reactivity.

In this work, we report on the catalytic valorization of sugar fractions, obtained by aqueous phase extraction of fast pyrolysis oils, in supercritical methanol (scMeOH) and ethanol (scEtOH) over a copper doped porous metal oxide (Cu-PMO). The product mixtures obtained are, in principle, suitable for direct co-feeding in methanol to hydrocarbon (MTH) processes, as fuel additives, or can be further fractionated or transformed to useful bulk chemicals. The main components of the obtained product mixtures in scMeOH are aliphatic mono-alcohols (51%), diols (22%), esters (15%), ethers (9%) and furanics (3%). Similar product suite is obtained by converting concentrated, 15 wt% sugar fractions with added 50 bar H-2 in scEtOH. The extensive depolymerization of the sugar polymers and oligomers contained in the sugar fraction is verified by gel permeation chromatography (GPC) and product stability upon catalytic treatment is confirmed by thermogravimetric analysis (TGA). In addition, model compound studies, using levoglucosan and D-cellobiose allow for more specific insight into the chemical pathways taking place during these transformations. The catalyst is characterized by various techniques, including XRD, NH3-TPD, BET, and TEM. The stability of the catalyst using 5 wt% sugar fraction in scMeOH is also evaluated. (C) 2014 Elsevier B.V. All rights reserved.

Noble-metal-free copper-zinc nanoalloy (

Benzimidazoles and N-methylbenzimidazoles were synthesized by simply heating 1,2-diaminobenzenes in supercritical methanol over copper-doped porous metal oxides. These catalysts were derived from synthetic hydrotalcites that only contain earth-abundant starting materials. The carbon equivalents needed for the construction of the benzimidazole core originated from the solvent itself, which is known to undergo reforming to hydrogen and carbon monoxide through the formation of a formaldehyde intermediate. A variety of 1,2-diaminobenzenes were converted to the corresponding mixtures of benzimidazoles and N-methylated analogues in good yields. Interestingly, the more challenging, but readily available 2-nitroanilines, which require an additional reduction step prior to cyclization, could also be successfully converted to benzimidazoles in high selectivity. Furthermore, various other alcohols were applied besides methanol, to obtain 2-alkyl- and 1,2-dialkylbenzimidazoles. Preliminary mechanistic insights into the origins of N-alkylation as well as the reactivity of the nitro derivatives are discussed.

Two pairs of enantiomerically pure chiral bidentate nitrogen-donor ligands (N*-N) featuring one sp(3) and one sp(2) nitrogen atom have been applied to the CO/vinyl arene copolymerization reaction catalyzed by the corresponding monocationic palladium(11) complexes [Pd(CH3)(CH3CN)-(N*-N)][PF6]. The ligand frame containing the sp(2) nitrogen atom is a 2-pyridinyl or an 8-quinolinyl building block, while the chiral framework of the ligand derives from (S)-(+)-2.2'-(2-azapropane-1,3-diyl)-1,1'-binaphthalene or from trans-2.5-dimethylpyrrolidinyl. Ligands with the binaphthyl moiety generate catalysts showing a moderate activity, while ligands having the pyrrolidinyl fragment results in very low activity species. The stereochemistry of the synthesized polyketones depends of the sp(2) nitrogen-containing fragment: ligands with the 2-pyridinyl group lead to atactic copolymers, whereas those with the quinolinyl moiety give an isotactic polyketone. The effect of the nature of the quinone, added to the reaction mixture as oxidant, has been investigated MALDI-TOF analysis reveals the formation of several polymeric chains, differing in the presence of various end-groups.

Tunable and selective hydrogenation of the platform chemical 5-hydroxymethylfurfural into valuable C-6 building blocks and liquid fuel additives is achieved with copper-doped porous metal oxides in ethanol. A new catalyst composition with improved hydrogenation/hydrogenolysis activity is obtained by introducing small amounts of ruthenium dopant into the previously reported Cu0.59Mg2.34Al1.00 structure. At a mild reaction temperature (100 degrees C), 2,5-furandimethanol is obtained with excellent selectivity up to > 99%. Higher reaction temperatures (220 degrees C) favor selective deoxygenation to 2,5-dimethylfuran and minor product 2,5-dimethyltetrahydrofuran with a combined yield as high as 81 %. Notably, these high product yields are maintained at a substrate concentration up to 10 wt% and a low catalyst loading. The influence of different alcohol solvents on product selectivity is explored. Furthermore, reaction intermediates formed at different reaction temperatures are identified. The composition of these product mixtures provides mechanistic insight into the nature of the reduction pathways that influence product selectivity. The catalysts are characterized by elemental analysis, TEM, and BET techniques before and after the reaction. Catalyst recycling experiments are conducted in batch and in a continuous-flow setup.

A 1,1,4,4-tetracyanobuta-1,3-diene (TCBD)–aniline moiety has been introduced, for the first time, at the axial position of two subphthalocyanines (SubPcs) peripherally substituted with hydrogen (H12SubPc) or fluorine atoms (F12SubPc). Single-crystal X-ray analysis of both SubPc–TCBD–aniline systems showed that each conjugate is a racemic mixture of two atropisomers resulting from the almost orthogonal geometry adopted by the axial TCBD unit, which were separated by chiral high-performance liquid chromatography. Remarkably, the single-crystal X-ray structure of one atropisomer of each SubPc–TCBD–aniline conjugate has been solved, allowing to unambiguously assign the atropisomers’ absolute configuration, something, to the best of our knowledge, unprecedented in TCBD-based conjugates. Moreover, the physicochemical properties of both SubPc–TCBD–aniline racemates have been investigated using a wide range of electrochemical as well as steady-state and time-resolved spectroscopic techniques. Each of the two SubP...

Expanded porphyrins are large-cavity macrocycles with enormous potential in coordination chemistry, anion sensing, photodynamic therapy, and optoelectronics. In the last two decades, the surface science community has assessed the physicochemical properties of tetrapyrrolic-like macrocycles. However, to date, the sublimation, self-assembly and atomistic insights of expanded porphyrins on surfaces have remained elusive. Here, we show the self-assembly on Au(111) of an expanded aza-porphyrin, namely, an >expanded hemiporphyrazine>, through a unique growth mechanism based on long-range orientational self-assembly. Furthermore, a spatially controlled >writing> protocol on such self-assembled architecture is presented based on the STM tip-induced deprotonation of the inner protons of individual macrocycles. Finally, the capability of these surface-confined macrocycles to host lanthanide elements is assessed, introducing a novel off-centered coordination motif. The presented findings represent a milestone in the fields of porphyrinoid chemistry and surface science, revealing a great potential for novel surface patterning, opening new avenues for molecular level information storage, and boosting the emerging field of surface-confined coordination chemistry involving f-block elements., Work supported by the Spanish Ministerio de Economia y Competitividad (MINECO) (RYC-2012-11133, FIS 2013-40667-P, CTQ2014-52869-P, FIS 2015-67287-P), the Comunidad de Madrid (S2013/MIT-2841, NANOFRONTMAG, FOTOCARBON; S2013/MIT-3007, MAD2D), the European Union (FP7-PEOPLE-2011-COFUND AMAROUT II program), and the Russian Science Foundation (Project No. 14-23-00204-P).

A series of tri-tert-butyl zinc(II) phthalocyanines (Pcs) substituted with pyridyl, carboxyl, or picolinic acid anchoring groups on the periphery were prepared. Photovoltaic (PV) studies on these dyes were carried out revealing some interesting features. In the case of the pyridyl-substituted Pcs, the PV properties were found to depend strongly on the the pyridyl substitution pattern (meta or para) and the number of pyridyl units at the macrocycle's periphery (one or two). For these four pyridyl-substituted Pcs, higher photovoltaic efficiencies were obtained for 1) the para- versus the meta-substituted Pcs, and 2) the mono- versus the bis-functionalized dyes. In order to improve the poor adsorption of the pyridyl-substituted Pcs onto TiO2 , a new dye was tested bearing a picolinic acid unit. This moiety combines a carboxylic acid function, as a strong anchoring group for binding to TiO2 , with an electron-withdrawing nitrogen atom for better electron injection into the semiconductor's conduction band. For this latter system, an improvement in the PV efficiency up to 2.1 % was obtained.

Graphene-based materials (GBMs), with graphene, their most known member, at the head, constitute a large family of materials which has aroused the interest of scientists working in different research fields such as chemistry, physics, or materials science, to mention a few, arguably as no other material before. In this review, we offer a general overview on the most relevant synthetic approaches for the covalent and non-covalent functionalization and characterization of GBMs. Moreover, some representative examples of the incorporation into GBMs of electroactive units such as porphyrins, phthalocyanines, or ferrocene, among others, affording electron donor-acceptor (D-A) hybrids are presented. For the latter systems, the photophysical characterization of their ground- and excited-state features has also been included, paying particular attention to elucidate the fundamental dynamics of the energy transfer and charge separation processes of these hybrids. For some of the presented architectures, their application in solar energy conversion schemes and energy production has been also discussed.