Family of V(III)-Tristhiolato Complexes Relevant to Functional Models of Vanadium Nitrogenase: Synthesis and Electronic Structure Investigations by Means of High-Frequency and -Field Electron Paramagnetic Resonance Coupled to Quantum Chemical Computations.

Abstract

A series of V(III) complexes of varying coordination number (5, 6, and 7) all containing the PS3 ligand (PS3 = trianion of tris(2-thiophenyl)phosphine and its derivatives with other phenyl substituents) has been prepared and structurally characterized. The complexes have general formula [V(PS3)L(n)](0,-), where n = 1 (from L = Cl(-), 1-Me-Im, N(3)(-)), 2 (from L = 2,2'-bpy; counting each N of the bidentate ligand), and 3 (from L = 1-Me-Im, N(2)H(4)). The complexes have also been investigated by direct current (DC) magnetic susceptibility and high-frequency and -field electron paramagnetic resonance (HFEPR). HFEPR, supported by magnetometry, has provided accurate spin Hamiltonian parameters that describe the S = 1 spin ground state of the complexes. Of particular interest are the zero-field splitting (zfs) parameters which, together with structural data, are the empirical starting point for detailed computational studies. The computational methods included density functional theory (DFT), which was only marginally successful, and more advanced ab initio methods (CASSCF and SORCI). The zfs in these complexes is relatively small in magnitude (|D| approximately 1 cm(-1)) and is the result of multiple, often counteracting, spin-orbit coupling (SOC) and spin-spin coupling (SSC) contributions. The specific origin of each of these contributions is described in detail. The results indicate the level of electronic structure calculation possible for transition metal complexes even with multiple unpaired electrons and highly covalent, heavier atom donor ligands.

Di- and Tri-nuclear VIII and CrIII Complexes of Dipyridyltriazoles: Ligand Rearrangements, Mixed Valency and Ferromagnetic Coupling

“…The fitting parameters are g = 1.89(1) and J/k B = −7.8(1) K = 5.42 cm −1 . The g value is in line with what is expected for V III compounds, where the individual g values can vary from 1.83 to 2.03 (Krzystek et al, 2015 ).…”

Progress and Challenges in the Calculation of Electronic Excited States

“…The SORCI method has found large resonance in the last years for medium-sized molecules. [163,169,[183][184][185][186] Further attempts to get a compromise between computational effort and accuracy led in the past to the development of semiempirical methods. An example is the spectroscopically parametrized intermediate neglect of differential overlap technique (INDO/S), which combined with CIS has been also applied in transition metal spectroscopy.…”

Adding Remnant Magnetization and Anisotropic Exchange to Propeller‐like Single‐Molecule Magnets through Chemical Design

“…Comparison with data and theoretical considerations reported in literature, and in particular with the seminal work by Tregenna-Piggott and co-workers, [26] suggests that this is, however, an unreasonable value. In fact, although large and negative D values can be observed in both tetragonally-distorted octahedral [27] and trigonal bipyramidal [28] V III complexes, this is not the case for trigonally distorted octahedral V III systems. Indeed, the combined effect of spin-orbit coupling and trigonal distortion results, for vanadium(III), either in a ground 3 A 2 state with D > 0, or in an orbitally degenerate ground doublet when the 3 E state lies lowest (Figure 8).…”