Anisotropic charge-transfer effects in the asymmetric Fe(CN)(5)NO octahedron of sodium nitroprusside: a soft X-ray absorption spectroscopy study

The electronic structure of Na-2[ Fe(CN)(5)NO]center dot 2H(2)O (sodium nitroprusside: SNP) was investigated by using soft X-ray absorption (XA) spectroscopy. The Fe L-2,L-3-edge XA spectrum of SNP exhibited distinct and very large satellite peaks for L-3 and L-2 regions, which is different from the spectra of hexacyanoferrates and the other iron compounds. A configuration-interaction full-multiplet calculation, in which the ligand molecular orbitals for the C-4v symmetry were taken into account, revealed the Fe2+ low-spin state with very strong effects of metal-to-ligand charge-transfer from the Fe 3d to NO 2p orbitals.