Molecules with a large second order electrical polarizability, (beta) , should have both strong electronic acentricity and intense charge-transfer transitions. We report values of (beta) for a number of mixed valency metal complexes in which charge transfer occurs between two redox active metal ions within the same molecule. Because these species are ions the EFISH experiment is inapplicable, so our measurements rely on Hyper-Raleigh Scattering. The compounds discussed here contain metal ions linked by a cyanide bridge. Charge asymmetry in the bridge is maintained by stabilizing the lower oxidation state with (pi) -acceptor ligands and the higher oxidation state with (sigma) -donor ligands. Results are reported for five homo and hetero-bimetallic ions in a variety of solvents. (beta) values are about 10-28 e.s.u., at 1.06 micrometers , and are comparable with those of organic compounds with larger donor-acceptor separations.
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