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The properties and reactivities of transition metal complexes are often discussed in terms of Ligand Field Theory (LFT), and with ab initio LFT a direct connection to quantum chemical wavefunctions was recently established. The Angular Overlap Model (AOM) is a widely used, ligand‐specific parameterization scheme of the ligand field splitting that has, however, been restricted by the availability and resolution of experimental data. Using ab initio LFT, we present here a generalised, symmetry‐independent and automated fitting procedure for AOM parameters that is even applicable to formally underdetermined or experimentally inaccessible systems. This method allows quantitative evaluations of assumptions commonly made in AOM applications, for example, transferability or the relative magnitudes of AOM parameters, and the response of the ligand field to structural or electronic changes. A two‐dimensional spectrochemical series of tetrahedral halido metalates ([MIIX4]2−, M=Mn−Cu) served as a case study. A previously unknown linear relationship between the halide ligands' chemical hardness and their AOM parameters was found. The impartial and automated procedure for identifying AOM parameters introduced here can be used to systematically improve our understanding of ligand–metal interactions in coordination complexes. [ABSTRACT FROM AUTHOR]

Abstract: The search for molecular catalysts that efficiently activate or cleave the dinitrogen molecule is an active field of research. While many thermal dinitrogen cleavage catalysts are known, the photochemical activation of N2 has received considerably less attention. In this paper, the first computational study of the osmium dimer [Os(II,III)2(μ‐N2)(NH3)10]5+, which was shown to be capable of dinitrogen photocleavage, is presented. Despite its deceptively simple geometry, it has a complex electronic structure with a valence‐delocalized and electronically degenerate ground state. Using multiconfigurational methods, the electronic structure at the ground state geometry and along the dinitrogen cleavage coordinate was investigated. The results indicate that an unoccupied molecular orbital with σ‐bonding character between osmium and μ‐N atoms and σ‐antibonding dinitrogen character is most affected by N–N distance elongation. This implies that a lower barrier for thermal or photochemical N2 activation in linear M‐N‐N‐M complexes can be achieved by lowering the energetic separation between this unoccupied orbital and the HOMO, representing a specific target for future catalyst design. [ABSTRACT FROM AUTHOR]

Keywords: ab initio calculations; angular overlap model; ligand effects; ligand field theory; transition metal complexes EN ab initio calculations angular overlap model ligand effects ligand field theory transition metal complexes 1 1 1 02/21/22 20220216 NES 220216 B Our work on ligand field theory b - an automated fitting procedure for Angular Overlap Model (AOM) parameters - is reflected by Van Gogh's I Field with Irises near Arles i . Ab initio calculations, angular overlap model, ligand effects, ligand field theory, transition metal complexes The perspective in van Gogh's field resembles a correlation we found between the halide ligands' AOM parameters and their chemical hardness. [Extracted from the article]