Strong metal-to-ligand charge transfer bands observed in Ni K- and L-edge XANES of planar Ni complexes

Abstract

Polarized Ni K-edge and L-edge XANES spectra were measured for some planar Ni complexes with low-spin 3d8 configuration, K2Ni(CN)4·H2O, Ni(Hdmg)2 (Hdmg: 2,3-butanedione dioximato) and [(n-C4H9)4N]2[Ni(mnt)2] (mnt: 1,2-dicyanovinylene-1,2-dithiolato). In all the spectra, strong satellite bands are found in addition to the lowest Ni 1s, 2p→3d* atomic lines. These are mostly assigned to the metal-to-ligand charge transfer (MLCT) transitions to unoccupied states with dominant ligand π* components, in good agreement with ab initio molecular orbital predictions. The low-lying ligand π* orbital is essential in interpreting the metal K-edge and L-edge XANES of 3d transition metal compounds.