Copper-hydrides have been intensively studied for a long time due to their utilization in a variety of technologically important chemical transformations. Nevertheless, poor stability of the species severely hinders its isolation, storage and operation, which is worse for nano-sized ones. We report here an unprecedented strategy to access to ultrastable copper-hydride nanoclusters (NCs), namely, using bidentate N-heterocyclic carbenes as stabilizing ligands in addition to thiolates. In this work, a simple synthetic protocol was developed to synthesize the first large copper-hydride nanoclusters (NCs) stabilized by N-heterocyclic carbenes (NHCs). The NC, with the formula of Cu31(RS)25(NHC)3H6 (NHC = 1,4-bis(1-benzyl-1H-benzimidazol-1-ium-3-yl) butane, RS = 4-fluorothiophenol), was fully characterized by high resolution Fourier transform ion cyclotron resonance mass spectrum, nuclear magnetic resonance, ultra-violet visible spectroscopy, density functional theory (DFT) calculations and single-crystal X-ray crystallography. Structurally, the title cluster exhibits unprecedented Cu4 tetrahedron-based vertex-sharing (TBVS) superstructure (fusion of six Cu4 tetrahedra). Moreover, the ultrahigh thermal stability renders the cluster a model system to highlight the power of NHCs (even other carbenes) in controlling geometrical, electronic and surface structure of polyhydrido copper clusters.

Stern-Gerlach (SG) experiments on aluminum clusters indicate that some small-sized aggregates exhibit a deflection signal consistent with the existence of magnetic moments. However, in the particular case of Al6 and Al8 clusters, electronic structure investigations show ambiguity on the 0 K ground spin state. In this work extensive computations of the electronic structure have been carried out in order to determine the ground state of these structures. Electron correlation has been introduced at MP2, MP4, and CCSD(T) theory level as well as by DFT computations with different density functionals. DFT-based Born-Oppenheimer molecular dynamics results at different simulation temperatures complete this investigation. One of our main conclusions is that singlet spin states are systematically the more stable configuration at 0 K. These Al clusters exhibit almost degenerate electronic structures at singlet and triplet spin states. The geometries are similar, and the paths connecting both structures allow an intersystem crossing through a spin-orbit coupling mechanism, indicating a dynamical interchange of both spin states at finite temperatures.

The Marcus–Hush theory has been successfully applied to describe and predict the activation barriers and hence the electron-transfer (ET) rates in several physicochemical and biological systems. This theory assumes that in the ET reaction, the geometry of the free Gibbs energy landscape is parabolic, with equal curvature near the local minimum for both reactants and products. In spite of its achievements, more realistic models have included the assumption of the two parabolas having not the same curvature. This situation is analyzed by the Nelsen’s four-point method. As a benchmark to compare the Marcus–Hush approximation to a precise calculation of the excitation energy, we studied the non-ET process of the electronic excitation of the aluminum dimer that has two local minima ( 3 ∑ g – and 3 ∏ u electronic states) and allows to obtain analytically the Marcus–Hush nonsymmetric parameters. We appraise the ability of the Marcus–Hush formula to approximate the analytical results by using several averages of the two reorganization energies associated with the forward and backward transitions and analyze the error. It is observed that the geometric average minimizes the relative error and that the analytical case is recovered. The main results of this paper are obtained by the application of the Nelsen’s four-point method to compute the reorganization energies of a large set of potential π-conjugated molecules proposed for organic photovoltaic devices using the above-mentioned averages for the Marcus–Hush formula. The activation energies obtained with the geometric average are significantly larger for some donor–acceptor pairs in comparison with the previously employed arithmetic average, their differences being suitable for experimental testing.

The magnetic response of valence electrons in doped gold-based M@Au8L8q superatoms (M = Pd, Pt, Ag, Au, Cd, Hg, Ir, and Rh; L = PPh3; and q = 0, +1, +2) is studied by calculating the gauge including magnetically induced currents (GIMIC) in the framework of the auxiliary density functional theory. The studied systems include 24 different combinations of the dopant, total cluster charge, and cluster structure (cubic-like or oblate). The magnetically induced currents (both diatropic and paratropic) are shown to be sensitive to the atomic structure of clusters, the number of superatomic electrons, and the chemical nature of the dopant metal. Among the cubic-like structures, the strongest aromaticity is observed in Pd- and Pt-doped M@Au8L80 clusters. Interestingly, Pd- and Pt-doping increases the aromaticity as compared to a similar all-gold eight-electron system Au9L8+1. With the recent implementation of the GIMIC in the deMon2k code, we investigated the aromaticity in the cubic and butterfly-like M@Au8 core structures, doped with a single M atom from periods 5 and 6 of groups IX–XII. Surprisingly, the doping with Pd and Pt in the cubic structure increases the aromaticity compared to the pure Au case not only near the central atom but encompassing the whole metallic core, following the aromatic trend Pd > Pt > Au. These doped (Pd, Pt)@Au8 nanoclusters show a closed shell 1S21P6 superatom electronic structure corresponding to the cubic aromaticity rule 6n + 2.

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