VCD Enhancement on Coordination: Mono-nuclear Metal Complexes

This chapter describes the enhancement of VCD signals induced by coordination. The contents are concerned with mono-nuclear metal complexes. A series of tris(2, 4-pentanedionato)metal(III) complexes (denoted as [M(acac)3]; M = Co, Cr, Ir, Rh and Ru) exhibits strong VCD couplets assigned to the C=O stretching vibrations of acac− ligands. The analyses of the VCD spectra unravel the contributions of anharmonicity of potential curves, paramagnetic effects of a central metal ion on vibration, relativistic effects and low-lying excitation energy electronic transitions. VCD is further extended to several other topics of metal complexes: the discrimination of geometric isomers of Ru(III) complex, the reversible transformation of coordination structures of Ni(II) complex, the formation of coordinatively unsaturated Ir(III) complexes, the parity effects for a series of lanthanide(III) complexes and the induction of chirality for a substrate coordinated in a catalytic Cu(II) complex.