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

The discrete variational method (DVM) in density functional theory (DFT) wa s employed to investigate the electronic structure of the complexes: [Fe(CN )(5)NO](2-) (nitroprusside), [Fe(CN)(5)NO](3-), [Fe(CN)(4)NO](2-), [Ru(CN)( 5)NO](2-) and [Ru(CN)(5)NO](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 i s bent. From self-consistent spin-polarized calculations, the distribution of the unpaired electron in the paramagnetic complexes [Fe(CN)(5)NO](3-), [ Fe(CN)(4)NO](2-) and [Ru(CN)(5)NO](3-) was obtained, as well as spin-densit y maps. A long-standing controversy regarding the configuration of [Fe(CN)( 5)NO](3-) was elucidated, and it was found that the unpaired electron in th is complex is in an orbital primarily localized on pi* (NO). Mossbauer quad rupole splittings on Fe and Ru were derived from calculations of the electr ic-field gradients. Magnetic hyperfine coupling constants on N of the NO li gand were also obtained for the paramagnetic complexes. (C) 2000 Elsevier S cience B.V. All rights reserved.