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A route to assess non-linear light–matter interactions from the increasingly popular GW-Bethe–Salpeter equation (GW-BSE) method is outlined. In the present work, the necessary analytic expressions within the static-screened exchange approximation of the BSE are derived. This enables a straightforward implementation of the computation of the first hyperpolarizability as well as two-photon absorption processes for molecular systems. Benchmark calculations on small molecular systems reveal that the GW-BSE method is intriguingly accurate for predicting both first hyperpolarizabilities and two-photon absorption strengths. Using state-of-the-art Kohn–Sham references as a starting point, the accuracy of the GW-BSE method rivals that of the coupled-cluster singles-and-doubles method, outperforming both second-order coupled-cluster and time-dependent density-functional theory. [ABSTRACT FROM AUTHOR]

A two-component contour deformation (CD) based GW method that employs frequency sampling to drastically reduce the computational effort when assessing quasiparticle states far away from the Fermi level is outlined. Compared to the canonical CD-GW method, computational scaling is reduced by an order of magnitude without sacrificing accuracy. This allows for an efficient calculation of core ionization energies. The improved computational efficiency is used to provide benchmarks for core ionized states, comparing the performance of 15 density functional approximations as Kohn–Sham starting points for GW calculations on a set of 65 core ionization energies of 32 small molecules. Contrary to valence states, GW calculations on core states prefer functionals with only a moderate amount of Hartree–Fock exchange. Moreover, modern ab initio local hybrid functionals are also shown to provide excellent generalized Kohn–Sham references for core GW calculations. Furthermore, the core–valence separated Bethe–Salpeter equation (CVS-BSE) is outlined. CVS-BSE is a convenient tool to probe core excited states. The latter is tested on a set of 40 core excitations of eight small inorganic molecules. Results from the CVS-BSE method for excitation energies and the corresponding absorption cross sections are found to be in excellent agreement with those of reference damped response BSE calculations. [ABSTRACT FROM AUTHOR]

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 increasingly popular GW method is becoming a convenient tool to determine vertical ionization energies in molecular systems. However, depending on the formalism used and the range of orbitals investigated, it may be hampered by a steep computational scaling. To alleviate this issue, correlated natural virtual orbitals (NVOs) based on second-order Møller–Plesset (MP2) and direct MP2 correlation energies are implemented, and the resulting correlated NVOs are tested on GW quasiparticle energies. Test cases include the popular GW variants G0W0 and evGW0 as well as more elaborate vertex corrections. We find that for increasingly larger molecular systems and basis sets, NVOs considerably improve efficiency. Furthermore, we test the performance of the truncated (frozen) NVO ansatz on the GW100 test set. For the latter, it is demonstrated that, using a carefully chosen truncation threshold, NVOs lead to a negligible loss in accuracy while providing speedups of one order of magnitude. Furthermore, we compare the resulting quasiparticle energies to very accurate vertical ionization energies obtained from coupled-cluster theory with singles, doubles, and noniterative triples [CCSD(T)], confirming that the loss in accuracy introduced by truncating the NVOs is negligible compared to the methodical errors in the GW approximation. It is also demonstrated that the choice of basis set impacts results far more than using a suitably truncated NVO space. Therefore, at the same computational expense, more accurate results can be obtained using NVOs. Finally, we provide improved reference CCSD(T) values for the GW100 test set, which have been obtained using the def2-QZVPP basis set. [ABSTRACT FROM AUTHOR]

Molecular rotations and vibrations have been extensively studied by chemists for decades, both experimentally using spectroscopic methods and theoretically with the help of quantum chemistry. However, the theoretical investigation of molecular rotations and vibrations in strong magnetic fields requires computationally more demanding tools. As such, proper calculations of rotational and vibrational spectra were not feasible up until very recently. In this work, we present rotational and vibrational spectra for two small linear molecules, H2 and LiH, in strong magnetic fields. By treating the nuclei as classical particles, trajectories for rotations and vibrations are simulated from ab initio molecular dynamics. Born–Oppenheimer potential energy surfaces are calculated at the Hartree–Fock and MP2 levels of theory using London atomic orbitals to ensure gauge origin invariance. For the calculation of nuclear trajectories, a highly efficient Tajima propagator is introduced, incorporating the Berry curvature tensor accounting for the screening of nuclear charges. [ABSTRACT FROM AUTHOR]

[V2(HCyclal)2] is prepared by controlled oxidation of vanadium nanoparticles at 50 °C in toluene. The V(0) nanoparticles are synthesized in THF by reduction of VCl3 with lithium naphthalenide. They exhibit very small particle sizes of 1.2 ± 0.2 nm and a high reactivity (e.g. with air or water). By reaction of V(0) nanoparticles with the azacrown ether H4Cyclal, [V2(HCyclal)2] is obtained with deep green crystals and high yield. The title compound exhibits a V(III) dimer (V⋯V: 304.1(1) pm) with two deprotonated [HCyclal]3− ligands as anions. V(0) nanoparticles as well as the sole coordination of V(III) by a crown ether as the ligand and nitrogen as sole coordinating atom are shown for the first time. Magnetic measurements and computational results point to antiferromagnetic coupling within the V(III) couple, establishing an antiferromagnetic spin S = 1 dimer with the magnetic susceptibility determined by the thermal population of the total spin ranging from ST = 0 to ST = 2. [ABSTRACT FROM AUTHOR]

As quantum-chemical calculations of molecules in static external magnetic fields are becoming increasingly popular, the description of molecular symmetry under such conditions is also becoming more and more relevant. Using group theory, a general scheme of identifying the molecular point group in an external magnetic field is constructed. For both point groups that are non-existent in the absence of a field (C∞ and C∞h) and their double groups, the character tables are presented. General properties of all possible point groups are discussed, and it is mathematically proven that they are all Abelian. [ABSTRACT FROM AUTHOR]

Binuclear coinage metal phosphine complexes are examined under ion trap isolation in order to elucidate their noncovalent binding, structural properties and intrinsic electronic spectra. Our survey shows an intriguing order of electronic transitions obtained by in situ synthesis and mass-spectrometrically supported UV photodissociation spectroscopy on a series of six isolated homo- and heterobinuclear complexes of type [MM′(dcpm)2]2+ (M, M′ = CuI, AgI, AuI; dcpm = bis(dicyclohexyl-phosphino)methane). This approach provides the unique opportunity to study all possible coinage metal interactions within a fixed ligand framework. A successive blue-shift (33 700–38 500 cm−1; 297–260 nm) of the lowest-energy bright electronic transition energy in gas phase was observed in the order of Cu2 < CuAu < CuAg < Au2 < AgAu < Ag2. This order was reproduced by quantum chemical calculations using a scalar-relativistic GW-Bethe–Salpeter-equation (GW-BSE) approach. Theory ascribes the electronic bands of all complexes to metal-centered 1MC(dσ*–pσ) transitions revealing a strengthening of metal–metal′ (M–M′) binding upon excitation, in agreement to mass spetrometric results. A test of the correlation of transition energies with M–M′ distance by quantum chemical calculations of single point energies as a function of intermetallic distance indicates qualitative agreement with experimental results. However, the experimentally observed high sensitivity of spectroscopic shifts towards metal composition cannot be accounted for solely by M–M′ distance variation. The differences in electronic transitions are qualitatively rationalized by the varying (n + 1)s (n = 3, 4, 5) orbital contributions (increase from Cu2via CuAu/CuAg to Au2/AgAu/Ag2) within the nd(n + 1)s/p-hybridization for the ground electronic state of the different complexes, whereas the excited state (of (n + 1)p orbital character) shows significantly less variation in energy. In particular, the observed spectroscopic and mass spectrometric sequence for the Ag/Au complexes is traced back to the interplay of Pauli repulsion and variation in metal–ligand bond strength within the orbital hybridization model. [ABSTRACT FROM AUTHOR]

The influence of long-range interactions on the structure of complexes of Eu(III) with four 9-hydroxy-phenalen-1-one ligands (HPLN) and one alkaline earth metal dication [Eu(PLN)4AE]+ (AE: Mg, Ca, Sr, and Ba) is analyzed. Through the [Eu(PLN)4Ca]+ complex, which is a charged complex with two metals—one of them a lanthanoid—and with four relatively fluxional π-ligands, the difficulties of describing such systems are identified. The inclusion of the D3(BJ) or D4 corrections to different density functionals introduces significant changes in the structure, which are shown to stem from the interaction between pairs of PLN ligands. This interaction is studied further with a variety of density functionals, wave-function based methods, and by means of the random phase approximation. By comparing the computed results with those from experimental evidence of gas-phase photoluminescence and ion mobility measurements it is concluded that the inclusion of dispersion corrections does not always yield structures that are in agreement with the experimental findings. [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]

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]

A selective synthesis of bi- and trinuclear complexes featuring a tetradentate monoanionic PNNP ligand is presented. The binuclear coinage metal complexes show a typical fourfold coordination for Cu and Ag, which changes to a bifold coordination for Au. The latter is accompanied by an unusual charge separation. Optical properties are investigated using photoluminescence spectroscopy and complemented by time-dependent density-functional-theory calculations. All compounds demonstrate clearly distinguished features dependent on the metals chosen and differences in the complex scaffold. [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]

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 CO 2 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 CO 2 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 CO 2 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 CO 2 . 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 CO 2 reduction., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The carbonyl cluster compound [GeRu 6 (CO) 18 HI] is unique in regard to its structure and bonding with a GeRu 6 cluster core, a planar GeRu 4 HI 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 Ru 4 (Ru 2 ) 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., (© 2024 The Authors. Advanced Science published by Wiley‐VCH GmbH.)

[V 2 (HCyclal) 2 ] is prepared by controlled oxidation of vanadium nanoparticles at 50 °C in toluene. The V(0) nanoparticles are synthesized in THF by reduction of VCl 3 with lithium naphthalenide. They exhibit very small particle sizes of 1.2 ± 0.2 nm and a high reactivity ( e.g. with air or water). By reaction of V(0) nanoparticles with the azacrown ether H 4 Cyclal, [V 2 (HCyclal) 2 ] is obtained with deep green crystals and high yield. The title compound exhibits a V(III) dimer (V⋯V: 304.1(1) pm) with two deprotonated [HCyclal] 3- ligands as anions. V(0) nanoparticles as well as the sole coordination of V(III) by a crown ether as the ligand and nitrogen as sole coordinating atom are shown for the first time. Magnetic measurements and computational results point to antiferromagnetic coupling within the V(III) couple, establishing an antiferromagnetic spin S = 1 dimer with the magnetic susceptibility determined by the thermal population of the total spin ranging from S T = 0 to S T = 2.

The synthesis of C∧C∧P pre-ligands based on a dicyclohexylphosphine-substituted biphenyl framework is reported. The pre-ligands form the respective non-palindromic pincer complexes of Pt II and Pd II via double oxidative addition and subsequent comproportionation or C-H activation. The complexes of Pt II as well as Pd II emit similar green phosphorescence efficiently in the solid state, the former also in solution albeit with less intensity. The most fascinating photophysical feature, however, is a direct singlet-triplet (S 0 → T 1 ) excitation of this phosphorescence in the spectral window between the emission and the major singlet-singlet UV absorption. The S 0 → T 1 excitation spectra show a rich vibronic pattern, which is especially pronounced for the solid samples at cryogenic temperatures. The molar extinction of the lowest-energy singlet-triplet absorption band of the homologous Pt and Pd complexes as well as that of the Pt complex with a different (NHC) ancillary ligand were determined in tetrahydrofuran solutions. Quantum efficiencies of triplet formation (by intersystem crossing) via the "standard" excitation pathway S 0 → S n → T 1 were determined for the Pt complexes and found to be different in dependence of the ancillary ligand.

Heteroleptic copper(I) complexes, with a diimine as a chromophoric unit and a bulky diphosphine as an ancillary ligand, have the advantage of a reduced pseudo Jahn-Teller effect in their excited state over the corresponding homoleptic bis(diimine) complexes. Nevertheless, their lowest absorption lies generally between 350 to 500 nm. Aiming at a strong absorption in the visible by stable heteroleptic Cu(I) complexes, we designed a novel diimine based on 4-(benzo[ g ]quinoxal-2'-yl)-1,2,3-triazole derivatives. The large π-conjugation of the benzoquinoxaline moiety shifted bathochromically the absorption with regard to other diimine-based Cu(I) complexes. Adding another Cu(I) core broadened the absorption and extended it to considerably longer wavelengths. Moreover, by fine-tuning the structure of the dichelating ligand, we achieved a panchromatic absorption up to 700 nm with a high molar extinction coefficient of 8000 M -1 cm -1 at maximum ( λ = 570 nm), making this compound attractive for light-harvesting antennae.

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 ., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Chemical and spectroscopic characterization of the mononuclear photosensitizers [(DPEPhos)Cu(I)(MPyrT)] 0/+ (CuL, CuLH) and their dinuclear analogues (Cu 2 L', Cu 2 L'H 2 ), 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 Cu 2 L' and Cu 2 L'H 2 . 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., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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-[Fe 4 L 4 ] 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., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

A selective synthesis of bi- and trinuclear complexes featuring a tetradentate monoanionic PNNP ligand is presented. The binuclear coinage metal complexes show a typical fourfold coordination for Cu and Ag, which changes to a bifold coordination for Au. The latter is accompanied by an unusual charge separation. Optical properties are investigated using photoluminescence spectroscopy and complemented by time-dependent density-functional-theory calculations. All compounds demonstrate clearly distinguished features dependent on the metals chosen and differences in the complex scaffold.