Density functional theory study of the electron paramagnetic resonance parameters and the magnetic circular dichroism spectrum for model compounds of dimethyl sulfoxide reductase.

We report a density functional theory (DFT) study of electron paramagnetic resonance (EPR) parameters for complexes modeling the paramagnetic center Mo(V) of the molybdoenzyme dimethyl sulfoxide reductase. We pay special attention to the Mo-OH link to find the most likely geometry and orientation of the metal center in the enzyme and provide an analysis of the physical origin of the g-values in terms of magnetically induced orbital mixing. We also present a study of the magnetic circular dichroism (MCD) spectrum for a complex that models the Mo(V) center of the enzyme. The calculation of the MCD-parameters that give rise to the spectrum was performed using a newly implemented method based on time-dependent DFT. On the basis of the theoretical calculations, it was possible to give a full assignment of the bands of the MCD spectrum for the enzyme.