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The vibrational spectra of simple C H 3 + —Rg (Rg = He, Ne, Ar, Kr) complexes have been studied by vibrational configuration interaction theory relying on multidimensional potential energy surfaces (PESs) obtained from explicitly correlated coupled cluster calculations, CCSD(T)-F12a. In agreement with experimental results, the series of rare gas atoms leads to rather unsystematic results and indicates huge zero point vibrational energy effects for the helium complex. In order to study these sensitive complexes more consistently, we also introduce configuration averaged vibrational self-consistent field theory, which is a generalization of standard vibrational self-consistent field theory to several configurations. The vibrational spectra of the complexes are compared to that of the methyl cation, for which corrections due to scalar-relativistic effects, high-order coupled-cluster terms, e.g., quadruple excitations, and core-valence correlation have explicitly been accounted for. The occurrence of tunneling splittings for the vibrational ground-state of C H 3 + —He has been investigated on the basis of semiclassical instanton theory. These calculations and a direct comparison of the energy profiles along the intrinsic reaction coordinates with that of the hydronium cation, H3O+, suggest that tunneling effects for vibrationally excited states should be very small. [ABSTRACT FROM AUTHOR]

Nitrogenase converts gaseous dinitrogen into biologically accessible ammonia. The binding of N2 to a reduced and protonated form of the FeMo-cofactor of nitrogenase including its central carbon ligand was investigated by means of density functional calculations. It was found the central ligand to stabilize the cluster. N2 can associate to iron or molybdenum with iron being the preferred binding site. While endo and exo binding modes were investigated the exo modes are more stable. Implications on the mechanism of N2 reduction are discussed. [ABSTRACT FROM AUTHOR]

The energy barrier leading to magnetic bistability in molecular clusters is determined by the magnetic anisotropy of the cluster constituents. By incorporating a highly anisotropic four-coordinate cobalt(II) building block into a strongly coupled fully air- and moisture-stable three-spin system, it proved possible to suppress under-barrier Raman processes leading to 350-fold increase of magnetization relaxation time and pronounced hysteresis. Relaxation times of up to 9 hours at low temperatures were found., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Early actinide ions have large spin-orbit couplings and crystal field interactions, leading to large anisotropies. The success in using actinides as single-molecule magnets has so far been modest, underlining the need for rational strategies. Indeed, the electronic structure of actinide single-molecule magnets and its relation to their magnetic properties remains largely unexplored. A uranium(III) single-molecule magnet, [U III {SiMe 2 NPh} 3 -tacn)(OPPh 3 )] (tacn=1,4,7-triazacyclononane), has been investigated by means of a combination of magnetic, spectroscopic and theoretical methods to elucidate the origin of its static and dynamic magnetic properties., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)