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[Ln2L4]2− helicates easily undergo transmetalation. The lanthanide ionic radius difference (ΔEIR) strongly affects the kinetics of the dynamic process while the thermodynamics is independent and mainly entropy driven.

A series of Gd3+ complexes (Gd1-Gd3) with the general formula GdL3(EtOH)2, where L is a β-diketone ligand with polycyclic aromatic hydrocarbon substituents of increasing size (1-3), was studied by combining time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy and DFT calculations to rationalize the anomalous spectroscopic behavior of the bulkiest complex (Gd3) through the series. Its faint phosphorescence band is observed only at 80 K and it is strongly red-shifted (∼200 nm) from the intense fluorescence band. Moreover, the TR-EPR spectral analysis found that triplet levels of 3/Gd3 are effectively populated and have smaller |D| values than those of the other compounds. The combined use of zero-field splitting and spin density delocalization calculations, together with spin population analysis, allows us to explain both the large red shift and the low intensity of the phosphorescence band observed for Gd3. The large red shift is determined by the higher delocalization degree of the wavefunction, which implies a larger energy gap between the excited S1 and T1 states. The low intensity of the phosphorescence is due to the presence of C-H groups which favor non-radiative decay. These groups are present in all complexes; nevertheless, they have a relevant spin density only in Gd3. The spin population analysis on NaL models, in which Na+ is coordinated to a deprotonated ligand, mimicking the coordinative environment of the complex, confirms the outcomes on the free ligands.

The relative stability of trans-[(η5-C5H5)Fe(η1-CO)(μ-CO)]2 (trans-I) and cis-I tautomers in a vacuum and in solvents with different dielectric constants (e) has been investigated by exploiting density functional theory (DFT). Theoretical results indicate that, in agreement with experimental evidence, trans-I is more stable than cis-I in a vacuum (∼1.5 kcal mol−1; e = 1), while the opposite is true in media with e > 7. Differently from solution, DFT outcomes pertaining to the vapor-phase cis-I ⇆ trans-I equilibrium at T = 368 K, the temperature at which the Fe L2,3-edges and the C and O K-edge X-ray absorption spectroscopy (XAS) data of I have been recorded, ultimately indicate the trans-I predominance (∼93%). Compositions, oscillator strengths (f) and excitation energy (EE) values of cis-I transitions substantially mirror those of trans-I; nevertheless, the weighted cis-If(EE) distributions negligibly contribute to the diverse simulated XA spectra of I.

Surface alloying of Cu(001) by Sn deposition is a finely controllable method of tuning the degree of copper reactivity in order to drive the on-surface assembly and synthesis of metal-organic coordination networks. In this work we show that the (32×2)R45° reconstruction of the Sn/Cu(001) surface alloy acts as a weakly interacting substrate ideal for the assembly of rectangular metal-organic networks based on transition metals. As a demonstration, we have grown a two-dimensional coordination network formed by manganese and TCNQ (7,7,8,8-tetracyanoquinodimethane) with 1:1 stoichiometry. In contrast with the same structure grown on Au(111), the use of the Sn/Cu(001) substrate enables a commensurate structure with larger and more regular ordered domains. We show that the formation of a Cu-TCNQ coordination network and subsequent Mn-Cu transmetalation reactions are the key steps of the growth mechanism. Moreover, ab initio density-functional calculations indicate that the system studied in the present work is a unique example of a metal-organic coordination network weakly interacting with the substrate. Fil: Machain, Paloma. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fuhr, Javier Daniel. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro | Universidad Nacional de Cuyo. Instituto Balseiro. Archivo Histórico del Centro Atómico Bariloche e Instituto Balseiro; Argentina Fil: Schneider, S.. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Carlotto, Silvia. Università di Padova; Italia Fil: Casarin, M.. Università di Padova; Italia Fil: Cossaro, A.. No especifíca; Fil: Verdini, A.. No especifíca; Fil: Floreano, L.. No especifíca; Fil: Lingenfelder, Magalí Alejandra. École Polytechnique Fédérale de Lausanne; Suiza Fil: Gayone, Julio Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina Fil: Ascolani, Hugo del Lujan. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche | Comisión Nacional de Energía Atómica. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología. Unidad Ejecutora Instituto de Nanociencia y Nanotecnología - Nodo Bariloche; Argentina

Seven different [Ln2L4]2− (Ln = La, Nd, Eu, Tb, Er, Tm and Lu) lanthanide-based quadruple-stranded helicates are here reported and transmetalation among pre-assembled cages was studied. Combining two homonuclear helicates [LnA2L4]2− and [LnB2L4]2− leads to the formation of a mixture of homo- and heteronuclear systems due to ion exchange. This dynamic behaviour was studied by electrospray ionization mass spectrometry (ESI-MS) both qualitatively and quantitatively allowing to gain information on the thermodynamics as well as on the kinetics of the process. The rate of the Ln ion exchange is strongly dependent on the difference in lanthanide effective ionic radius (ΔEIR). Upon increasing ΔEIR, the kinetic constants grow exponentially: from the minimum to the maximum value of ΔEIR, the kinetic constants of the forward and backward reactions increase by three orders of magnitude. On the contrary, the equilibrium constant is the same for all the [LnA2L4]2−/[LnB2L4]2− couples, showing that the transmetalation is mainly entropy-driven towards a statistical mixture and not affected by ΔEIR.

The recently described monodimensional hybrid pseudo-perovskite ((CH3)3SO)PbI3 exhibits complete Pb2+/Bi3+ miscibility in the B site. Heterovalent substitution imposes that charge-compensating defects are introduced in the lattice as well. This paper reports the energetics of point defects and the interaction between charge-compensating defects that occur upon Bi3+ doping in ((CH3)3SO)PbI3. Periodic DFT simulations were employed to analyze the formation energy of Pb2+ vacancies, (CH3)3SO+ vacancies, iodide vacancies, or the insertion of interstitial iodide ions. Solid solutions with a large Bi3+ content were modeled considering different charge compensation defects (Pb2+ vacancies, (CH3)3SO+ vacancies, and interstitial iodide) to consider electrical neutrality. Both the formation energy evaluation and the structural parameters after relaxation are in very good agreement with available experimental data (both X-ray diffraction and absorption spectroscopy), confirming that Pb2+ vacancies are indeed the primary ionic charge-compensation mechanism leading to solid solutions described by the formula ((CH3)3SO)3Pb3xBi2(1-x)V(1-x)I9 (0 < x < 1), where V indicates a B site vacancy. As a consequence of the complete miscibility, the defect concentration at intermediate compositions is considerable, and it is probably responsible for various peculiar structural effects observed, e.g., in ((CH3)3SO)3Pb0.99Bi1.34I9, which are related to short-range order phenomena in the chain composition. Atomistic simulations were then carried out to estimate defect-defect interactions as a function of their respective positions inside the linear PbI6/BiI6 octahedral chains. The resulting bond energies for atom pairs and triads effectively explain the relative stability of defect clusters. This approach is expected to shed light on the short-range order in this class of doped materials, but it can be extended to other structures as well. The understanding of defect structures and control of structural and electronic properties have implications for the engineering of doped materials, which find vast applications in optoelectronic devices.

To drive the synthesis of metallo-supramolecular assemblies (MSAs) and to fully exploit their functional properties, robust computational tools are crucial. The capability to model and to rationalize different parameters that can influence the outcome is mandatory. Here, we report a computational insight on the factors that can determine the relative stability of the supramolecular isomers helicate and mesocate in lanthanide-based quadruple-stranded assemblies. The considered MSAs have the general formula [Ln2L4]2− and possess a cavity suitable to allocate guests. The analysis was focused on three different factors: the ligand rigidity and the steric hindrance, the presence of a guest inside the cavity, and the guest dimension. Three different quantum mechanical calculation set-ups (in vacuum, with the solvent, and with the solvent and the dispersion correction) were considered. Comparison between theoretical and experimental outcomes suggests that all calculations correctly estimated the most stable isomer, while the inclusion of the dispersion correction is mandatory to reproduce the geometrical parameters. General guidelines can be drawn: less rigid and less bulky is the ligand and less stable is the helicate, and the presence of a guest can strongly affect the isomerism leading to an inversion of the stability by increasing the guest size when the ligand is flexible.

Electron injection into electrode-supported metal complexes allows for charge redistribution within the molecule to be controlled. Here we show, for the first time, how the structural flexibility in electron-doped porphyrins is critical in defining charge localization by following the evolution of the spin state and charge distribution in the thermodynamically favored structure as a function of dopant dose and relaxation time. Two flexible transition metal-containing molecules are used as model systems, nickel and cobalt tetraphenylporphyrin, studied by combining a wide range of spectroscopic techniques with detailed DFT calculations.

The unoccupied electronic structures of three closed-shell, highly popular organoiron complexes ([Fe(CO)5], [(η5-C5H5)Fe(CO)(μ-CO)]2, and [(η5-C5H5)2Fe]; 0, I, and II, respectively) have been investigated both experimentally and theoretically by combining original gas-phase X-ray absorption spectroscopy (XAS) outcomes recorded at the C and O K-edge with results of scalar relativistic time-dependent density functional calculations carried out within the zeroth order regular approximation. Experimental evidence herein discussed complement the Fe L2,3-edges XAS ones we recently recorded, modeled, and assigned for the same complexes (Carlotto et al. Inorg. Chem. 2019, 58, 5844). The first-principle simulation of the C and O K-edge features allowed us to univocally identify the electronic states associated to the ligand-to-metal charge transfer (LMCT) transitions both in I and in II. At variance to that, LMCT transitions with sizable oscillator strengths do not play any role in determining neither the C nor the O K-edge spectral pattern of 0. The higher π-acceptor capability of the CO ligand, regardless of its terminal or bridging coordination, with respect to [(η5-C5H5)]- is herein ultimately confirmed.

A theoretical protocol combining density functional theory (DFT) and multireference (CAS) calculations is proposed for a Eu3+ complex. In the complex, electronic levels of the central Eu3+ ion are correctly calculated at the CASPT2 level of theory, and the effect of introducing different numbers of states in the configuration interaction matrices is highlighted as well as the shortcomings of DFT methods in the treatment of systems with high spin multiplicity and strong spin-orbit coupling effects. For the 5D0 state energy calculation, the inclusion of states with different multiplicity and the number of states considered for each multiplicity are crucial parameters, even if their relative weight is different. Indeed, the addition of triplet and singlets is important, while the number of states is relevant only for the quintets. The herein proposed protocol enables a rigorous, full ab initio treatment of Eu3+ complex, which can be easily extended to other Ln3+ ions.

We report on the synthesis and characterization of novel lead and bismuth hybrid (organic-inorganic) iodide and bromide pseudo-perovskites (ABX3) containing the trimethylsulfoxonium cation (CH3)3SO+ (TMSO) in the A site, Pb/Bi in the B site, and Br or I as X anions. All of these compounds are isomorphic and crystallize in the orthorhombic Pnma space group. Lead-based pseudo-perovskites consist of one-dimensional (1D) chains of face-sharing [PbX6] octahedra, while in the bismuth-based ones, the chains of [BiX6] are interrupted, with one vacancy every third site, leading to a zero-dimensional (0D) local structure based on separated [Bi2I9]3- dimers. Five solid solutions for the iodide with different Pb2+/Bi3+ ratios between (TMSO)PbI3 and (TMSO)3Bi2I9, and two for the bromide counterparts, were synthetized. Due to the charge compensation mechanism, these systems are best described by the (TMSO)3Pb3xBi2(1-x)I9 (x = 0.98, 0.92, 0.89, 0.56, and 0.33) and (TMSO)3Pb3xBi2(1-x)Br9 (x = 0.83 and 0.37) formulae. X-ray powder diffraction (XRPD) measurements were employed to determine the crystal structure of all studied species and further used to test the metal cation miscibility within monophasic samples not showing cation segregation. These systems can be described through an ionic defectivity on the pseudo-perovskite B site, where the Pb2+/Bi3+ replacement is compensated by one Pb2+ vacancy for every Bi3+ pair. This leads to a wide range of possible different (numerical and geometrical) chain configurations, leading to the unique features observed in XRPD patterns. The optical band gap of the iodide samples falls in the 2.11-2.74 eV range and decreases upon increasing the Bi3+ content. Interestingly, even a very low loading of Bi3+ (1%) is sufficient to reduce the band gap substantially from 2.74 to 2.25 eV. Periodic density functional theory (DFT) calculations were used to simulate the atomic and electronic structures of our samples, with predicted band gap trends in good agreement with the experimental ones. This work highlights the structural flexibility of such systems and accurately interprets the ionic defectivity of the different pseudo-perovskite structures.

Due to its unique magnetic properties offered by the open‐shell electronic structure of the central metal ion, and for being an effective catalyst in a wide variety of reactions, iron phthalocyanine has drawn significant interest from the scientific community. Nevertheless, upon surface deposition, the magnetic properties of the molecular layer can be significantly affected by the coupling occurring at the interface, and the more reactive the surface, the stronger is the impact on the spin state. Here, we show that on Cu(100), indeed, the strong hybridization between the Fe d‐states of FePc and the sp‐band of the copper substrate modifies the charge distribution in the molecule, significantly influencing the magnetic properties of the iron ion. The FeII ion is stabilized in the low singlet spin state (S=0), leading to the complete quenching of the molecule magnetic moment. By exploiting the FePc/Cu(100) interface, we demonstrate that NO2 dissociation can be used to gradually change the magnetic properties of the iron ion, by trimming the gas dosage. For lower doses, the FePc film is decoupled from the copper substrate, restoring the gas phase triplet spin state (S=1). A higher dose induces the transition from ferrous to ferric phthalocyanine, in its intermediate spin state, with enhanced magnetic moment due to the interaction with the atomic ligands. Remarkably, in this way, three different spin configurations have been observed within the same metalorganic/metal interface by exposing it to different doses of NO2 at room temperature., By exploiting the FePc/Cu(100) interface, the possibility to control, via nitrogen dioxide (NO2) dissociation at the interface, the magnetic properties of the chelated ion the FePc array is demonstrated. Three different spin configurations have been stabilized within the same metalorganic/metal interface.

A theoretical protocol combining density functional theory (DFT) and multireference (CAS) calculations is proposed for a Eu3+ complex. In the complex, electronic levels of the central Eu3+ ion are correctly calculated at the CASPT2 level of theory, and the effect of introducing different numbers of states in the configuration interaction matrices is highlighted as well as the shortcomings of DFT methods in the treatment of systems with high spin multiplicity and strong spin–orbit coupling effects. For the 5D0 state energy calculation, the inclusion of states with different multiplicity and the number of states considered for each multiplicity are crucial parameters, even if their relative weight is different. Indeed, the addition of triplet and singlets is important, while the number of states is relevant only for the quintets. The herein proposed protocol enables a rigorous, full ab initio treatment of Eu3+ complex, which can be easily extended to other Ln3+ ions., A theoretical protocol combining density functional theory and multireference calculations is proposed for a Eu3+ complex. For the 5D0 state energy calculation, the inclusion of states with different multiplicity and the number of states considered for each multiplicity are crucial parameters. The herein proposed protocol enables a rigorous, full ab initio treatment of Eu3+ complex, which can be easily extended to other Ln3+ ions.

Density functional theory-based methods have been exploited to look into the structural, vibrational and electronic properties of antenna ligands, all of them being crucial factors for the reliable design of customized luminescent lanthanide (Ln3+) complexes. The X-ray structures, UV-Vis absorption spectra and triplet (T1) energies of three novel β-diketone ligands with a thienyl group and naphthyl (L1), phenanthryl (L2), and pyrenyl (L3) polycyclic aromatic hydrocarbons as substituents have been modelled. Vibronic progressions provide a strong contribution to the L1 and L2 absorption spectra, while the L3 absorption spectrum needs the assumption of different conformational isomers in solution. T1 energies have been estimated either through the vertical- or the adiabatic-transition approach. The comparison with the phosphorescence spectra of Gd3+ complexes allowed us to infer that the latter approach is the most suitable one, in particular when sizable ligands are involved. Results obtained for the isolated antennas can be directly compared with those of the corresponding Ln3+ complexes, due to the unanimously accepted assumption that the excitation is ligand-centred.

In this paper we report on the use of an Ullmann-like aryl halide homocoupling reaction to obtain long Graphyne Molecular Wires (GY MWs) organized in dense, ordered arrays. Instead of using highly reactive terminal alkynes, we resort to a precursor wherein the acetylenic functional group is internal, namely protected by two phenyl rings, each bearing a Br atom in the para position to allow for linear homocoupling. In addition, two further factors concur with the production of dense and highly ordered arrays of very long GY MWs, namely the geometric compatibility between the substrate and both the organometallic intermediates and the final polymeric products of the synthesis, coupled with the presence of surface-adsorbed bromine atoms separating the MWs, which minimize inter-wire cross-linking secondary reactions.

For a series of organonitrile [RCN (R = Me, CF3, Ph, CH3Ph, CF3Ph)] ligands, the nature of the N–Pt bond in the related cis-/trans-(RCN)2PtCl2 complexes has been computationally investigated by Density Functional Theory. A fragment based bond analysis has been performed in the canonical Kohn–Sham molecular orbitals framework, and it has been ultimately assessed that this bond is characterized both by N→Pt σ and by N←Pt π contributions. Voronoi Deformation Density charges further confirms the occurrence of N←Pt π interactions. Moreover, the Energy Decomposition Analysis-Natural Orbital for Chemical Valence (EDA-NOCV) method shows that the strength of the N←Pt π interaction is not negligible by contributing to about 30–40% of the total orbital interaction. Finally, the well-known νCN blue-shift occurring upon coordination to PtII, has been thoroughly investigated by exploiting the EDA-NOCV and by evaluating νCN and force constants. The origin of the νCN blue-shift in these systems has been discussed on the basis of the CN bond polarization. N←Pt π backbonding causes only a systematic decrease of the observed νCN blue-shift when compared to the one calculated for RCN–X (X = H+, alkaline, Lewis acids) herein reported (X = purely σ acceptors).

Model peptides relevant to hCtr1 transchelate CuI from the anti-tumour [CuI(PTA)4]+ complex before metal internalization into tumor cells. ESI(+)MS experiments corroborated by DFT calculations indicate that tetracoordinated-CuII and linear-CuI arrangements of in situ generated copper-peptide products play a crucial role in promoting the transfer of copper from the terminal MDH portion into adjacent HSH peptide sequence.

The ETS-NOCV bond analysis has been exploited to quantitatively estimate donation and back-donation properties of [(η5-C5H5)]−, CO, and FeI in the cis-/trans-[(η5-C5H5)Fe(η1-CO)(μ-CO)]2 (cis-I/trans-I) tautomers. Theoretical outcomes indicate that the Fe-CO bond, regardless to the CO monoapto (η1-) or bridging (μ-) coordination, has a sizeable π Fe → CO back-bonding contribution, which is stronger in trans-I than in cis-I. Moreover, [(η5-C5H5)]− has the weakest back-donation acceptor capability. The back-bonding behaviour of the Fe → η1-CO interaction well agrees with the experimental symmetric/antisymmetric infrared νCO (sνηjavax.xml.bind.JAXBElement@fc12185-CO/aνηjavax.xml.bind.JAXBElement@4c260f05-CO) trend for cis-I and trans-I and further confirms the infrared classical behaviour of the η1-CO group in this class of complexes.

A plausible path for the Cu-3(mu(3)-OH)(mu-Pz)(3) core formation is herein proposed by theoretically modelling the reaction in water between [Cu-2(RCOO)(4)](n), (R = CH3(CH2)(2)) and HPz, which yields the hexanuclear species [{Cu-3(mu(3)-OH)(mu-Pz)(3)(RCOO)(2)(CH3OH)(H2O)}(2)]. We focused on the A -> B reaction (A = [Cu-2(RCOO)(4)(H2O)(2)]; B = [Cu-3(mu(3)-OH)(mu-Pz)(3)(RCOO)(2)(CH3OH)(H2O)]) with the final goal of pinpointing stable intermediates, tightened by experimental conditions, by exploiting the outcomes of numerical experiments carried out in the habit of the density functional theory. (C) 2017 Elsevier B.V. All rights reserved.

The investigation of the water interaction/dissociation on perovskite surfaces is of great interest because these processes have different implications on ferroelectric phenomena, water splitting and surface catalysis. In particular, the H2 production has several applications in the photocatalytic environmental cleaning and in the atmospheric chemistry. Some fundamental aspects of the water process are still not well understood; hence the detailed study of more realistic models is essential. We have performed density functional calculations of the water interaction on a stepped SrTiO3 (1 0 0) surface, which contains structural defectivities (edges), oxygen vacancies and metal dopants (Al, Co and Cu). Three different water-surface interaction models can be obtained for both clean and reduced steps: one involving a molecular adsorption and two giving a dissociative process. The presence of both the dopant and the oxygen vacancy drives the stabilization of one specific adsorption type. The H2 formation mechanism is investigated and the crucial role of the dopant on the oxygen vacancy formation emerges. Results demonstrate that the water interaction and/or dissociation on ideal surfaces are not fully transferable on more realistic models, hence this study is relevant to understand the water processes on a model closer to materials exposed to standard experimental conditions.

We have performed density functional calculations on a facetted SrTiO3(1 1 0) surface, a model for stepped (1 0 0) surfaces considering both a pure and a Cu-doped system. The formation of oxygen vacancies and the adsorption of small have been studied in detail. Results show that Cu dopants strongly influence the reactivity of the step, both at the edge and at the facet sites, favoring the formation of oxygen vacancies. The adsorption of small molecules has been studied to obtain information about the role played by the system in catalytic processes. It is found that adsorption energies of NO, CO, CO2 and O2 at the vacancies of present in doped steps is always unfavored. The extraction of oxygen atom by direct CO adsorption on the oxidation mechanism has also been investigated for both pure unreduced and for reduced doped steps. In both cases, the desorption of CO2 is an endothermic process, but the presence of the dopant significantly reduces the desorption energies.

A new model with the aim to predict the temperature dependence of europium emission in coordination systems is presented. The model has been developed from a library of Eu(3+)complexes of general formulaEuL(3)A(2), whereLis a beta-diketone, andAis an ancillary ligand. Three possible deactivation channels have been considered: two competitive metal-related terms describing the primary deactivation channels,i. e. back energy transfer and multiphonon quenching, and a third ligand-related term to describe non-radiative deactivation of the antenna triplet. As many parameters as possible are taken from measurable chemical-physical properties, such as ligand triplet and multiphonon quenching energies. The other parameters have been deduced from selectedEuL(3)A(2)compounds and used asone-size-fits-allvalues. The model proved to be very effective in describing the interplay between back energy transfer and multiphonon deactivation channels. Finally, the model has been implemented in a freeware standalone MATLAB application. Users need to input only the energy of the sensitizer triplet level and choose the coordinated quencher, if present. It simulates the range of applicability of the molecular thermometers and the shape of the thermometric sensitivity curveS(r)employing as thermometric parameter either emission intensity or lifetime.

The unoccupied electronic structures of three closed-shell, highly popular organoiron complexes ([Fe(CO)

Model peptides relevant to hCtr1 transchelate CuI from the anti-tumour [CuI(PTA)

Correction for 'New light on an old debate: does the RCN-PtCl

For a series of organonitrile [RCN (R = Me, CF

The reaction mechanism between trans-[PtIICl2(N CMe)2] and ammonia to give trans-Z,Z-[PtIICl(NH3){HN = C(NH2)Me}2]Cl has been studied at DFT level. Results showed that, in dichloromethane solution at 263.15 K, the chloride substitution by the ammonia on platinum is a process kinetically more favoured than the ammonia nucleophilic addition to the nitrile of about three orders of magnitude, and hence the nucleophilic addition reaction occurs after. Finally, both nucleophilic addition steps are geometrically driven to give products in the E configuration even if the final products were experimentally observed in the Z configuration. For trans-Z,Z-[PtIICl(NH3)(N CMe)2, the isomerization mechanism has been investigated for both nucleophilic addition steps by considering the deprotonation → isomerization → protonation sequence on nitrogens. The deprotonation steps could involve either the coordinated or the aminic nitrogen of the formed amidine. Outcomes indicated that the path involving the deprotonation of the aminic nitrogen is favoured.

The adsorption of tetrahydroxyquinone (THQ) on the Cu(111) surface at different temperatures gives rise to different ordered structures, unveiled by density functional theory (DFT) modelling of scanning tunnelling microscopy (STM) topography and by X-ray absorption spectroscopy (XAS) measurements. After annealing, the THQ films generated tetrameric Cu clusters embedded in a metal–organic tetraoxyquinone (TOQ) network, whose electronic properties were thoroughly studied. The remarkable agreement between the STM results and periodic calculations was exploited to model C and O K-edge XA spectra recorded before (room temperature, RT) and after annealing (high temperature, HT). The subsequent analysis of the C and O TOQ@Cu(111) K-edge XA spectra provides definitive information about the structural arrangement of the TOQ@Cu(111) coordination network, confirming the complete THQ dehydrogenation upon annealing, suggested by the simulations of the STM images. The obtained information is crucial to rationalize the evolution of THQ@Cu(111) upon heating, shedding light into the potential reactivity of the HT coordination network, and, more generally, to investigate the nature and character of low-lying virtual states, the most involved states in the chemical reactions.

The Fe(II) spin state in the condensed phase of [Fe(II)Cl2(tpm)] (tpm = [tris(pyrazol-1-yl)methane]; 1) catalyst has been determined through a combined experimental and theoretical investigation of X-Ray Absorption Spectroscopy (XAS) at the FeL2,3-edges and NK-edge. Results indicated that in this phase a mixed singlet/triplet state is plausible. These results have been compared with the already know Fe singlet spin state of the same complex in water solution. A detailed analysis of the electronic structure and bonding mechanism of the catalyst showed that the preference for the low-spin diamagnetic ground state, strongly depends upon the ligands, the bulk solvent and the interaction of the complex’s vacant site (the sixth) with a further ligand. Moreover, comparison of the electronic properties of the complex in condensed phase and water solution showed an increased Lewis acidity of the catalyst in solution phase, due to a decreasing of the LUMO energy of about 8 kcal/mol. These results gave an overall picture of the electronic behavior of the complex investigated, on going from condensed to water solution phase, explaining the preferred use of 1 as catalyst in homogeneous catalysis. The N Fe(II) interaction has been thoroughly investigated by means of DFT Kohn-Sham and EDA bond analysis applied to i) the isolated [Fe(II)Cl2(tpm)] and ii) the [Fe(II)Cl2(tpm)] interacting with water as a solvent within the Conductor-like Screening Mode (COSMO) framework. Results showed that both tpm→Fe(II) σ and tpm⟵Fe(II) π Charge Transfer (CT) interactions characterize the Fe(II)–tpm interaction. Moreover, the three tpm N atoms do not equally interact with the Fe(II) and one of them shares a suitable available iron-based d virtual orbital, to bind a further ligand in trans position.

The energetics of the catalytic oxidation of CO on a complex metal oxide are investigated for the first time via density functional theory calculations. The catalyst, Co-doped SrTiO3, is modelled using periodically repeated slabs based on the SrTiO3(100) surface. The comparison of the energy profiles obtained for the pure host and the Co-doped material reveals the actual pathway followed by the reaction, and shows that Co doping enhances the catalytic properties of SrTiO3 by reducing the energy cost for the formation of oxygen vacancies.

Copper complexes of tetraphenylporphyrin (H2TPP) and tetrakis(pentafluorophenyl) porphyrin (H2TPP(F)) deposited as thin films on Au(111) have been studied experimentally and theoretically. Core level emissions from C 1s, N 1s, F 1s and Cu 2p as well as valence states of CuTPP and CuTPP(F) have been investigated using surface photoelectron spectroscopy. The interpretation of experimental results has been guided by theoretical calculations carried out on isolated species in the habit of the density functional theory. Reference to experimental and theoretical outcomes pertaining to H2TPP and H2TPP(F) allowed a confident and detailed assignment of the title molecules' X-ray and ultraviolet photoemission data. With specific reference to the latter, similar to copper phthalocyanine (CuPc), whose coordinative pocket mirrors the CuTPP/CuTPP(F) ones, the lowest ionization energy of the title compounds implies electron ejection from a ring orbital rather than from the Cu 3d-based singly occupied molecular orbital. Moreover, analogous to CuPc, the ionic contribution appears to play an important role in the Cu-N bonding. Nevertheless, differences in the number, symmetry, nature and relative position of CuTPP/CuTPP(F) occupied frontier orbitals compared to CuPc may be stated only by considering in great detail the Cu-ligand covalent interactions.

The reaction of copper(II) chloroacetate (1d) with pyrazole (Hpz) mainly yielded the mononuclear compound [Cu(μ-ClCH2COO)2(Hpz)2] (2m), which self-assembled generating a one-dimensional coordination polymer. Moreover, the concomitant isolation of the tetranuclear [{Cu2(μ-pz)(μ-OCH2COO)(Hpz)(MeOH)}2(μ-ClCH2COO)2] (3t) and hexanuclear [{Cu3(μ3-OH)(μ-pz)3(Hpz)2}2(μ-ClCH2COO)2](Cl)2 (4h) species evidenced the occurrence of a peculiar, previously unreported, dehydrochlorination reaction and the formation of the trinuclear triangular moiety [Cu3(μ3-OH)(μ-pz)3]. Theoretical calculations based on density functional theory including solvation effects indicate a possible pathway for the formation of 3t. Interestingly, besides the energy minimum corresponding to 3t, a further relative energy minimum is found for a species which can be considered a possible reaction intermediate.

The NO reduction in a CO–NO atmosphere at the Co- and Cu-doped SrTiO3(100) surfaces is investigated by density functional theory calculations. The energy profiles for several mechanisms are computed and compared. On this basis, a rationale for the available experimental data is proposed. Oxygen vacancies formed as intermediate species in the CO oxidation process play a key role in the NO reduction. Their concentration is also relevant because, if low, formation of N2O prevails on that of N2, leading to an incomplete reduction. The formation of oxygen vacancies is favored by Co and Cu impurities, the latter being most effective. Overall, doping promotes the catalytic reduction of NO on SrTiO3.

Dioxygen adsorbs in the end-on configuration on-top of the Fe atoms of an iron phthalocyanine monolayer supported on Ag(100) and is partly cleaved at room temperature to produce O/FePc/Ag(100). Scanning tunnelling microscopy coupled to density functional theory calculations gives the first experimental evidence of the substrate involvement in the O2 bond dissociation.

First principle quantum mechanical calculations are able to provide results comparable in accuracy to experimental measurements; moreover, it is unanimously recognized that the information they afford is often more accessible than that provided by conventional spectroscopy. Here we focus on the modelling and, possibly, on the prediction of X-ray absorption spectroscopy (XAS) evidences at the L2,3-edge of first row transition metal (M) macrocyclic complexes, which have been attracting an increasing interest because of their widespread technological applications. The comparison of homogeneous theoretical results with those achieved for complexes of the same central M ions but different ligands ultimately confirms the role played by the M chemical environment, the M electronic configuration and the M oxidation number in determining the appearance of L2,3 XAS features, which may be then exploited as a M fingerprint.

The electronic properties of three vanadium phthalocyaninato (Pc) based complexes (PcV, PcVO, and PcVI; I-III, respectively) were theoretically investigated and corresponding VL2,3-edge XAS spectra modeled. Ground state (GS) DFT outcomes indicated that II is more stable than III by 141 kcal/mol; moreover, the Ziegler transition state method allowed us to estimate the PcV-X bond dissociation energy and to quantify ?/? contributions to the V-X interaction. As such, the Nalewajski-Mrozek V-X and V-N bond multiplicity indexes (V-O/V-I = 2.48/1.22; V-N = 0.64, 0.51, and 0.58 in I-III, respectively) state that the V-X bond strength and nature affect the V-N interaction. The coordination of X to V in the I -> II/I -> III reactions implies the transfer of two/one electrons from I to X. In both cases, the oxidation involves only the V ion; moreover, V 3d based orbitals from which electrons are transferred were identified. Literature I/IIL2,3-edge XAS data were modeled by exploiting the DFT/ROCIS method. The same protocol was adopted to predict IIIL2,3-edge XAS spectra. Theoretical results indicated that, along the whole series, spectral features lying at the lowest excitation energies (EEs) are mostly generated by states having the same GS spin multiplicity and involve 2pV -> SOMO (single occupied molecular orbital) single electronic excitations. XAS features at higher EEs include only states with the same GS spin multiplicity in I, while states with both ?S = 0 and ?S = +1 (S = total spin quantum number) are present in II and III with significant, in some cases prevailing, contributions from metal to ligand charge transfer (MLCT) excitations. Beyond the role played by MLCT transitions in determining XAS patterns, it is noteworthy that they involve only Pc-based empty orbitals with no participation of the X-based virtual levels.

We study the electronic structure of Co, Ni, and Cu impurities and of their vacancy-associated complexes in SrTiO 3 crystals by means of density functional theory (DFT) and DFT + U calculations. Simple substitutionals prefer low-spin states, as expected from ligand field theory. On the other hand, the formation energy of vacancies (which tend to stay close to the impurity) is rather low for all the doped systems, and decreases with Z. This reflects the low stability of the +IV oxidation state for the impurities. Contrary to simple impurities, high-spin states are predicted to be stable when impurities are associated to vacancies.