Synthesis and molecular hyperpolarisabilities of donor-acceptor bipyridyl metal complexes (M = Re, Zn, Hg)

A series of rhenium(I), zinc(II) and mercury(II) complexes of pi-donor-substituted vinyl bipyridines [donor = 4-R2N-C6H4-; 4-RO-C6H4-; (C5H5)Fe(C5H4-); (C5H5)Ru(C5H4-)] has been prepared and characterized by H-1 NMR and UV-visible spectroscopy. The second-order nonlinear optical properties of bipyridyl ligands and of their complexes have been investigated using EFISH experiments at 1.34 mu m. A significant increase of the molecular hyperpolarizability beta is observed upon coordination. The role of the nature of both the donor group and the metallic moiety on the NLO properties is discussed in detail.