Density functional study of electronic, magnetic and hyperfine properties of [M(CN)5NO]2− (M=Fe, Ru) and reduction products Original Research Article

The discrete variational method (DVM) in density functional theory (DFT) was employed to investigate the electronic structure of the complexes: [Fe(CN)5NO]2− (nitroprusside), [Fe(CN)5NO]3−, [Fe(CN)4NO]2−, [Ru(CN)5NO]2− and [Ru(CN)5NO]3−. Total energy calculations revealed that in pentacyanonitrosylferrate(I) and pentacyanonitrosylruthenate(I), which are paramagnetic ions containing one unpaired electron, the M–N–O bond angle is bent. From self-consistent spin-polarized calculations, the distribution of the unpaired electron in the paramagnetic complexes [Fe(CN)5NO]3−, [Fe(CN)4NO]2− and [Ru(CN)5NO]3− was obtained, as well as spin-density maps. A long-standing controversy regarding the configuration of [Fe(CN)5NO]3− was elucidated, and it was found that the unpaired electron in this complex is in an orbital primarily localized on π* (NO). Mössbauer quadrupole splittings on Fe and Ru were derived from calculations of the electric-field gradients. Magnetic hyperfine coupling constants on N of the NO ligand were also obtained for the paramagnetic complexes.