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A novel mononuclear Cu(I) complex was synthesized via coordination with a benzoquinoxalin‐2'‐one‐1,2,3‐triazole chelating diimine and the bis[(2‐diphenylphosphino)phenyl] ether (DPEPhos), to target a new and efficient photosensitizer for photocatalytic CO2 reduction. The Cu(I) complex absorbs in the blue‐green region of the visible spectrum, with a broad band having a maximum at 475 nm (ϵ =4500 M−1 cm−1), which is assigned to the metal‐to‐ligand charge transfer (MLCT) transition from the Cu(I) to the benzoquinoxalin‐2'‐one moiety of the diimine. Surprisingly, photo‐driven experiments for the CO2 reduction showed that this complex can undergo a photoinduced electron transfer with a sacrificial electron donor and accumulate electrons on the diimine backbone. Photo‐driven experiments in a CO2 atmosphere revealed that this complex can not only act as a photosensitizer, when combined with an Fe(III)‐porphyrin, but can also selectively produce CO from CO2. Thus, owing to its charge‐accumulation properties, the non‐innocent benzoquinoxalin‐2‐one based ligand enabled the development of the first copper(I)‐based photocatalyst for CO2 reduction. [ABSTRACT FROM AUTHOR]

The carbonyl cluster compound [GeRu6(CO)18HI] is unique in regard to its structure and bonding with a GeRu6 cluster core, a planar GeRu4HI unit, extensive multi‐center bonding, and an aromatic ring current similar to benzene (9‐10 nA T−1). The open‐shell cluster core is a Ge‐centered five‐membered Ru4(Ru2) ring with CO ligands and an additional H and I atom, each bridging two Ru atoms on opposite sides of the cluster core. The compound is prepared at 130 °C in a weakly‐coordinating ionic liquid. [ABSTRACT FROM AUTHOR]

Nanophotonic concepts can improve measurement techniques by enhancing and tailoring the light–matter interaction. However, the optical response of devices that implement such techniques can be intricate, depending on the sample under investigation. Nanophotonics is therefore a ripe field for applying the concept of a digital twin: a digital representation of an entire real‐world device. In this work, the concept of a digital twin is detailed with the example of a nanophotonically enhanced chiral sensing platform. In that platform, helicity‐preserving cavities enhance the interaction between chiral molecules and light, allowing faster measurement of the circular dichroism of the molecules. The sheer presence of the molecules affects the cavity's functionality, demanding a holistic treatment to understand the device's performance. In the digital twin, optical and quantum chemistry simulations are fused to provide a comprehensive description of the system and predict the circular dichroism spectrum. Performing simulations in lockstep with the experiment will allow a clear interpretation of measurement results. This work also demonstrates how to design a cavity‐enhanced circular dichroism spectrometer by utilizing the digital twin. The digital twin can be used to guide experiments and analyze results, and its underlying concept can be translated to many other optical experiments. [ABSTRACT FROM AUTHOR]

The article titled "Cover Feature: Dual Role of a Novel Heteroleptic Cu(I) Complex in Visible-Light-Driven CO2 Reduction" explores the use of a CuI complex in the photocatalytic reduction of CO2. The complex serves as both a photosensitizer, transferring electrons to an iron porphyrin that reduces CO2, and a photocatalyst, directly converting CO2 to carbon monoxide. The research article provides more detailed information on this topic. The article also includes artwork by C. Bizzarri and V. Pani. [Extracted from the article]

The synthesis and characterisation of a homologous series of quinoid sulfur‐containing imidazolyl‐substituted heteroacenes is described. The optoelectronic and magnetic properties were investigated by UV/vis, fluorescence and EPR spectroscopy as well as quantum‐chemical calculations, and were compared to those of the corresponding benzo congener. The room‐temperature and atmospherically stable quinoids display strong absorption in the NIR region between 678 and 819 nm. The dithieno[3,2‐b:2′,3′‐d]thiophene and the thieno[2′,3′:4,5]thieno[3,2‐b]thieno[2,3‐d]thiophene derivatives were EPR active at room temperature. For the latter, variable‐temperature EPR spectroscopy revealed the presence of a thermally accessible triplet state, with a singlet‐triplet separation of 14.1 kJ mol−1. [ABSTRACT FROM AUTHOR]

Chemical and spectroscopic characterization of the mononuclear photosensitizers [(DPEPhos)Cu(I)(MPyrT)]0/+ (CuL, CuLH) and their dinuclear analogues (Cu2L', Cu2L'H2), backed by (TD)DFT and high‐level GW‐Bethe‐Salpeter equation calculations, exemplifies the complex influence of charge, nuclearity and structural flexibility on UV‐induced photophysical pathways. Ultrafast transient absorption and step‐scan FTIR spectroscopy reveal flattening distortion in the triplet state of CuLH as controlled by charge, which also appears to have a large impact on the symmetry of the long‐lived triplet states in Cu2L' and Cu2L'H2. Time‐resolved luminescence spectroscopy (solid state), supported by transient photodissociation spectroscopy (gas phase), confirm a lifetime of some tens of μs for the respective triplet states, as well as the energetics of thermally activated delayed luminescence, both being essential parameters for application of these materials based on earth‐abundant copper in photocatalysis and luminescent devices. [ABSTRACT FROM AUTHOR]

Chiral magnetic materials are proposed for applications in second‐order non‐linear optics, magneto‐chiral dichroism, among others. Recently, we have reported a set of tetra‐nuclear Fe(II) grid complex conformers with general formula C/S‐[Fe4L4]8+ (L: 2,6‐bis(6‐(pyrazol‐1‐yl)pyridin‐2‐yl)‐1,5‐dihydrobenzo[1,2‐d : 4,5‐d′]diimidazole). In the grid complexes, isomerism emerges from tautomerism and conformational isomerism of the ligand L, and the S‐type grid complex is chiral, which originates from different non‐centrosymmetric spatial organization of the trans type ligand around the Fe(II) center. However, the selective preparation of an enantiomerically pure grid complex in a controlled manner is difficult due to spontaneous self‐assembly. To achieve the pre‐synthesis programmable resolution of Fe(II) grid complexes, we designed and synthesized two novel intrinsically chiral ligands by appending chiral moieties to the parent ligand. The complexation of these chiral ligands with Fe(II) salt resulted in the formation of enantiomerically pure Fe(II) grid complexes, as unambiguously elucidated by CD and XRD studies. The enantiomeric complexes exhibited similar gradual and half‐complete thermal and photo‐induced SCO characteristics. The good agreement between the experimentally obtained and calculated CD spectra further supports the enantiomeric purity of the complexes and even the magnetic studies. The chiral resolution of Fe(II)‐ [2×2] grid complexes reported in this study, for the first time, might enable the fabrication of magneto‐chiral molecular devices. [ABSTRACT FROM AUTHOR]

Four new heteroleptic Cu(I) complexes based on 1, 2, 3‐triazolyl‐quinoline or quinoxaline and a chelating diphosphine were prepared and fully characterised. The mononuclear derivatives absorb in the visible region, up to 600 nm, while the dinuclear complex has a long‐tail absorption up to 800 nm, showing an additional electronic state corroborated by theoretical calculations. Although a methylene group between the triazole and the quino(xa)line moiety increases the bite angle and decreases the luminescence in solution, all complexes emit brightly in the solid‐state. Their redox properties in the excited state were determined, proving their ability in serving as photoredox catalysts in atom transfer radical addition successfully. [ABSTRACT FROM AUTHOR]

Combining phase‐dependent photoluminescence (PL) measurements and quantum chemical calculations is a powerful approach to help understand the influence of the molecular surroundings on the PL properties. Herein, a phosphine functionalized amidinate was used to synthesize a recently presented bimetallic gold complex, featuring an unusual charge separation. The latter was subsequently used as metalloligand to yield heterotetrametallic complexes with an Au‐M‐M‐Au "molecular wire" arrangement (M=Cu, Ag, Au) featuring metallophilic interactions. All compounds show bright phosphorescence in the solid state, also at ambient temperature. The effect of the molecular environment on the PL was studied in detail for these tetrametallic complexes by comparative measurements in solution, in the solid state and in the gas phase and contrasted to time‐dependent density functional theory computations. [ABSTRACT FROM AUTHOR]

We herein report on new synthetic strategies for the preparation of pyridine and imidazole substituted 2,2'‐dihalo biphenyls. These structures are pre‐ligands suitable for the preparation of respective stannoles. The latter can successfully be transmetalated to K[AuCl4] forming non‐palindromic [(C^C^D)AuIII] pincer complexes featuring a lateral pyridine (D=N) or N‐heterocyclic carbene (NHC, D=C') donor. The latter is the first report on a pincer complex with two formally anionic sp2 and one carbenic carbon donor. The [(C^C^D)AuIII] complexes show intense phosphorescence in solution at room temperature. We discuss the developed multistep strategy and touch upon synthetic challenges. The prepared complexes have been fully characterized including X‐ray diffraction analysis. The gold(III) complexes' photophysical properties have been investigated by absorption and emission spectroscopy as well as quantum chemical calculations on the quasi‐relativistic two‐component TD‐DFT and GW/Bethe–Salpeter level including spin–orbit coupling. Thus, we shed light on the electronic influence of the non‐palindromic pincer ligand and reveal non‐radiative relaxation pathways of the different ligands employed. [ABSTRACT FROM AUTHOR]

The photoexcitation of a triangular silver(I) hydride complex, [Ag3(μ3‐H)(μ2‐dcpm)3](PF6)2 ([P](PF6)2, dcpm=bis(dicyclohexylphosphino)methane), designed with "UV‐silent" bis‐phosphine ligands, provokes hydride‐to‐Ag3 single and double electron transfer. The nature of the electronic transitions has been authenticated by absorption and photodissociation spectroscopy in parallel with high‐level quantum‐chemical computations utilizing the GW method and Bethe–Salpeter equation (GW‐BSE). Specific photofragments of mass‐selected [P]2+ ions testify to charge transfer and competing pathways resulting from the unique [Ag3(μ3‐H)]2+ scaffold. This structural motif of [P](PF6)2 has been unequivocally verified by 1H NMR spectroscopy in concert with DFT and X‐ray diffraction structural analysis, which revealed short equilateral Ag–Ag distances (dAgAg=3.08 Å) within the range of argentophilic interactions. The reduced radical cation [P].+ exhibits strong oxophilicity, forming [P+O2].+,which is a model intermediate for silver oxidation catalysis. [ABSTRACT FROM AUTHOR]

A software update solving the Bethe−Salpeter equation (BSE) is reported for the ESCF module of the TURBOMOLE program for the theoretical description of electronically excited states of atoms and molecules. A resolution-of-the-identity (RI) approximation is used for all two-electron electron-repulsion integrals that are required for solving the equation. Symmetry is utilized for the point group D2h and its subgroups, and the BSE approach can be applied in either a spin-restricted or a spin-unrestricted Kohn−Sham formalism. Triplet as well as singlet excited states of closed-shell atoms and molecules can be treated in the spin-restricted formalism. As a side product, the present software update also allows for the application of the RI approximation to the Hartree−Fock exchange contribution that occurs when a hybrid functional is used in time-dependent density-functional theory. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Reaction of [Si(3,5-Me2pz)4] (1) with [Cu(MeCN)4][BF4] (2) gave the mono- and dinuclear copper complexes [Cu2(FTp*)2] (3) and [Cu(FTp*)2] (4). Both complexes contain the so-far unprecedented boron-fluorinated FTp* ligand ([FB(3,5-Me2pz)3]- with pz=pyrazolyl) originating from 1, acting as a pyrazolyl transfer reagent, and the [BF4]- counter anion of 2, serving as the source of the {BF} entity. The solid-state structures as well as the NMR and EPR spectroscopic characteristics of the complexes were elaborated. Pulsed gradient spin echo (PGSE) experiments revealed that 3 retains (almost entirely) its dimeric structure in benzene, whereas dimer cleavage and formation of acetonitrile adducts, presumably [Cu(FTp*)(MeCN)], is observed in acetonitrile. The short Cu⋯Cu distance of 269.16 pm in the solid-state is predicted by DFT calculations to be dictated by dispersion interactions between all atoms in the complex (the Cu-Cu dispersion contribution itself is only very small). As revealed by cyclic voltammetry studies, 3 shows an irreversible (almost quasi-reversible at higher scan rates) oxidation process centred at Epa=-0.23 V (E01/2=-0.27 V) (vs. Fc/Fc+). Oxidation reactions on a preparative scale with one equivalent of the ferrocenium salt [Fc][BF4] (very slow reaction) or air (fast reaction) furnished blue crystals of the mononuclear copper(II) complex [Cu(FTp*)2] (4). As expected for a Jahn-Teller-active system, the coordination sphere around copper(II) is strongly distorted towards a stretched octahedron, in accordance with EPR spectroscopic findings. [ABSTRACT FROM AUTHOR]

Reactions of the tris(3,5-dimethylpyrazolyl)methanide amido complexes [M′{C(3,5-Me2pz)3}{N(SiMe3)2}] (M′=Mg ( 1 a), Zn ( 1 b), Cd ( 1 c); 3,5-Me2pz=3,5-dimethylpyrazolyl) with two equivalents of the acidic Group 6 cyclopentadienyl (Cp) tricarbonyl hydrides [MCp(CO)3H] (M=Cr ( 2 a), Mo ( 2 b)) gave different types of heterobimetallic complex. In each case, two reactions took place, namely the conversion of the tris(3,5-dimethylpyrazolyl)methanide ligand (Tpmd*) into the -methane derivative (Tpm*) and the reaction of the acidic hydride MH bond with the M′N(SiMe3)2 moiety. The latter produces HN(SiMe3)2 as a byproduct. The Group 2 representatives [Mg(Tpm*){MCp(CO)3}2(thf)] ( 3 a/ b) form isocarbonyl bridges between the magnesium and chromium/molybdenum centres, whereas direct metal-metal bonds are formed in the case of the ions [Zn(Tpm*){MCp(CO)3}]+ ( 4 a/ b; [MCp(CO)3]− as the counteranion) and [Cd(Tpm*){MCp(CO)3}(thf)]+ ( 5 a/ b; [Cd{MCp(CO)3}3]− as the counteranion). Complexes 4 a and 5 a/ b are the first complexes that contain ZnCr, CdCr, and CdMo bonds (bond lengths 251.6, 269.8, and 278.9 pm, respectively). Quantum chemical calculations on 4 a/ b* (and also on 5 a/ b*) provide evidence for an interaction between the metal atoms. [ABSTRACT FROM AUTHOR]

Keywords: density functional theory; EPR spectroscopy; heteroacenes; UV spectroscopy; radicals EN density functional theory EPR spectroscopy heteroacenes UV spectroscopy radicals 1 1 1 04/26/22 20220422 NES 220422 B The cover feature picture shows b the successive expansion of a quinoid imidazolylidene-substituted central sulfur-containing heterocyclic core, which is accompanied by a continuous decrease in the HOMO/LUMO gap. Density functional theory, EPR spectroscopy, heteroacenes, UV spectroscopy, radicals. [Extracted from the article]

Oriented circular dichroism (OCD) is explored and successfully applied to investigate chiral surface-anchored metal-organic frameworks (SURMOFs) based on camphoric acid (D- and Lcam) with the composition [Cu2(Dcam)2 x(Lcam)2−2 x(dabco)] n (dabco=1,4-diazabicyclo-[2.2.2]-octane). The three-dimensional chiral SURMOFs with high-quality orientation were grown on quartz glass plates by using a layer-by-layer liquid-phase epitaxy method. The growth orientation, as determined by X-ray diffraction (XRD), could be switched between the [001] and [110] direction by using either OH- or COOH-terminated substrates. These SURMOFs were characterized by using OCD, which confirmed the ratio as well as the orientation of the enantiomeric linker molecules. Theoretical computations demonstrate that the OCD band intensities of the enantiopure [Cu2(Dcam)2(dabco)] n grown in different orientations are a direct result of the anisotropic nature of the chiral SURMOFs. Finally, the enantiopure [Cu2(Dcam)2(dabco)] n and [Cu2(Lcam)2(dabco)] n SURMOFs were loaded with the two chiral forms of ethyl lactate [(+)-ethyl- D-lactate and (−)-ethyl- L-lactate)]. An enantioselective enrichment of >60 % was observed by OCD when the chiral host scaffold was loaded from the racemic mixture. [ABSTRACT FROM AUTHOR]

A novel dibenzoylmethane-fullerene e, e, e-tris adduct was synthesized by the application of a variation of the Bingel-Hirsch conditions and characterized among others by X-ray crystallography. In addition, the corresponding hexakis adduct was detected by MALDI-TOF-MS analysis. Its existence was supported by density-functional-theory (DFT) computations. Furthermore a new synthesis of bis(benzoyl)methanofullerene was established, and its molecular structure was elucidated by X-ray crystallography. DFT computations reproduced the experimentally determined conformation and predict a low energy barrier for the rotation of the two benzoyl moieties. [ABSTRACT FROM AUTHOR]

2,2'-Biphenols are a large and diverse group of compounds with exceptional properties both as ligands and bioactive agents. Traditional methods for their synthesis by oxidative dimerisation are often problematic and lead to mixtures of ortho- and para-connected regioisomers. To compound these issues, an intermolecular dimerisation strategy is often inappropriate for the synthesis of heterodimers. The 'acetal method' provides a solution for these problems: stepwise tethering of two monomeric phenols enables heterodimer synthesis, enforces ortho regioselectivity and allows relatively facile and selective intramolecular reactions to take place. The resulting dibenzo[1,3]dioxepines have been analysed by quantum chemical calculations to obtain information about the activation barrier for ring flip between the enantiomers. Hydrolytic removal of the dioxepine acetal unit revealed the 2,2′-biphenol target. [ABSTRACT FROM AUTHOR]

The total synthesis of plakotenin, a cytotoxic marine natural product, using a biomimetic Diels-Alder reaction is described in detail. Two approaches were used, whereby the Diels-Alder reaction occurs at different stages of the synthesis. Homo- and nor-plakotenin, related natural products, were also prepared, as well as iso-plakotenin, a diastereoisomer of plakotenin. The syntheses prove the relative and absolute stereochemistry of the latter. The chemical biology of the plakotenins was investigated on selected compounds. [ABSTRACT FROM AUTHOR]

We have prepared digold(I) complexes with the rigid-backbone diphosphane ligands PhanePhos, xyl-PhanePhos, and Ph2-GemPhos. All complexes were characterized by single-crystal X-ray diffraction, NMR, IR, Raman, and photoluminescence (PL) spectroscopy. [PhanePhos(AuCl)2] and [GemPhos(AuCl)2] show a very similar ligand scaffold, but different (aurophilic vs. nonaurophilic) intramolecular Au-Au distances. Absorption and PL spectra of both compounds are quite similar. Theoretical investigations reveal that the excited states are of different character (i.e., influenced by the Au-Au contacts). The respective transition energies, however, lie close to each other, thus resulting in similar experimental spectra. The gold atoms appear to produce a significant heavy-atom effect in the electronic relaxation dynamics. Thus, [PhanePhos(AuCl)2] and [GemPhos(AuCl)2] both show bright-green millisecond-long phosphorescence at low temperatures, although the latter is quenched at ambient temperature. [PhanePhos(AuCl)2] and [GemPhos(AuCl)2] were also used as catalysts in the intra- and intermolecular hydroamination of alkynes. Good to quantitative conversions on a reasonable time scale were observed. The overall performance of these catalysts in the studied reactions was similar, showing that Au-Au contacts do not have a major influence on the catalytic performance. [ABSTRACT FROM AUTHOR]

A new scheme that combines conventional matrix diagonalization with the recently proposed diagonalization-free algorithm has been developed to obtain the density matrix for the next self-consistent-field iteration from the Fock matrix of the current iteration. In this manner, the advantages of the two methods are combined. The more rapid convergence of the diagonalization-free algorithm for density matrices rather close to self consistence and the more robust convergence of the conventional matrix diagonalization further away from self-consistence. The scheme has been implemented in the one- and two-component self-consistent-field procedures in the program system TURBOMOLE. The number of iterations is typically reduced by about 10%, but savings are usually much larger for slowly converging cases. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 [ABSTRACT FROM AUTHOR]

A detailed description of the explicitly correlated second-order Møller-Plesset perturbation theory (MP2-F12) method, as implemented in the T program package, is presented. The T implementation makes use of density fitting, which greatly reduces the prefactor for integral evaluation. Methods are available for the treatment of ground states of open- and closed-shell species, using unrestricted as well as restricted (open-shell) Hartree-Fock reference determinants. Various methodological choices and approximations are discussed. The performance of the T implementation is illustrated by example calculations of the molecules leflunomide, prednisone, methotrexate, ethylenedioxytetrafulvalene, and a cluster model for the adsorption of methanol on the zeolite H-ZSM-5. Various basis sets are used, including the correlation-consistent basis sets specially optimized for explicitly correlated calculations (cc-pVXZ-F12). © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011 [ABSTRACT FROM AUTHOR]

The physical interactions among electrons and nuclei, responsible for the chemistry of atoms and molecules, is well described by quantum mechanics and chemistry is therefore fully described by the solutions of the Schrödinger equation. In all but the simplest systems we must be content with approximate solutions, the principal difficulty being the treatment of the correlation between the motions of the many electrons, arising from their mutual repulsion. This article aims to provide a clear understanding of the physical concept of electron correlation and the modern methods used for its approximation. Using helium as a simple case study and beginning with an uncorrelated orbital picture of electronic motion, we first introduce Fermi correlation, arising from the symmetry requirements of the exact wave function, and then consider the Coulomb correlation arising from the mutual Coulomb repulsion between the electrons. Finally, we briefly discuss the general treatment of electron correlation in modern electronic-structure theory, focussing on the Hartree-Fock and coupled-cluster methods and addressing static and dynamical Coulomb correlation. © 2007 Wiley Periodicals, Inc. J Comput Chem 28: 1307–1320, 2007 [ABSTRACT FROM AUTHOR]

The recently developed singles-and-doubles linear-r12 corrected coupled-cluster model CCSD(R12) has been extended by inclusion of triples corrections in exactly the same manner as in the popular CCSD(T) model. The resulting model is denoted CCSD(T)(R12). An orthonormal auxiliary basis set is used for the resolution-of-the-identity approximation to calculate the three- and four-electron integrals needed in the linear-r12 Ansatz. CCSD(T)(R12) reaction energies are calculated for a test set of 15 chemical reactions involving 23 small molecules. The CCSD(T)(R12), CCSD(R12), and MP2-R12 results are compared with experimental data obtained by correcting experimental enthalpies of reaction for zero-point vibrational energies and finite temperature contributions. Conventional MP2, CCSD, and CCSD(T) results are presented for comparison. An estimate of the basis set limit is obtained by an aug-cc-pV(Q + d)Z/aug-cc-pV(5 + d)Z CCSD(T) extrapolation for a subset of 12 reactions. All CCSD(T) results are compared with the extrapolated values, and the errors are analyzed for the CCSD(T) and CCSD(T)(R12) models in various basis sets. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [ABSTRACT FROM AUTHOR]

In a previous contribution, we established the suitability of density functional theory (DFT) for the calculation of molecular anharmonic force fields. In the present work, we have assessed a wide variety of basis sets and exchange-correlation functionals for harmonic and fundamental frequencies, equilibrium, and ground-state rotational constants, and thermodynamic functions beyond the rigid rotor-harmonic oscillator (RRHO) approximation. The fairly good performance of double-zeta plus polarization basis sets for frequencies results from an error compensation between basis set incompleteness and the intrinsic error of exchange-correlation functionals. Triple-zeta plus polarization basis sets are recommended, with an additional high-exponent d function on second-row atoms. All conventional hybrid generalized gradient approximation (GGA) functionals perform about equally well: high-exchange hybrid GGA and meta-GGA functionals designed for kinetics yield poor results, with the exception of of the very recently developed BMK functional, which takes a middle position along with the HCTH/407 (second-generation GGA) and TPSS (meta-GGA) functionals. Second-order Møller–Plesset perturbation theory (MP2) performs similarly to these functionals but is inferior to hybrid GGAs such as B3LYP and B97-1. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [ABSTRACT FROM AUTHOR]

Highlights from the article: Keywords: charge transfer; hydride ligands; mass spectrometry; metal-metal interactions; photochemistry; silver The unique [Ag SB 3 sb ( SB 3 sb -H)] SP 2+ sp scaffold, featuring argentophilic interaction, was unequivocally verified by SP 1 sp H NMR spectroscopy in concert with X-ray structural analysis and DFT. Photochemistry, mass spectrometry, silver, charge transfer, hydride ligands, metal-metal interactions.