DFT analysis of hyperfine couplings in d and f metal complexes with tetrahydro borate ligands

Abstract

Metal complexes with BH4- ligands show extravagant structural and dynamic properties, and possess many important and applicable qualities (potent reducing agents and catalysts, materials for hydrogen storage). Electron paramagnetic resonance (EPR) is very important for the characterization of complex compounds, the determination of their electronic configuration and geometry. Also, Density Functional Theory (DFT) can predict EPR parameters and explain them more profoundly. Hence, in this paper hyperfine coupling constants of d and f metal complexes with BH4- ligands have been determined by DFT calculations, and analyzed in detail. Of particular importance is the analysis and prediction of hyperfine coupling constants for lanthanide complexes with BH4- ligands, given that there is not much data in the literature. Calculations predicted that proton hyperfine coupling constants are very small in the case of complexes of f elements, and are present only due to weak polarization. The increase of covalence and the number of unpaired electrons does not significantly affect the change of constants of BH4- ligands, but only of protons that are bound by σ bonds.