3RD-HARMONIC GENERATION IN ORGANOMETALLIC RUTHENIUM(II) DERIVATIVES CONTAINING COORDINATED P-SUBSTITUTED BENZONITRILES

A family of eta 5-monocyclopentadienylruthenium(II) derivatives posses sing coordinated p-substituted benzonitriles has been studied by optic al third-harmonic generation (THG) at the fundamental wavelength of la mbda=1064 nm. Thin films of the compounds in a polymer matrix of poly( methyl methacrylate) (PMMA) were studied using the Maker fringe techni que. For the compound possessing the p-NCC6H4C6H4NO2 coordinated nitri le the second hyperpolarizability, lambda(- 3 omega;omega,omega,omega) , was determined to be 2.3 x10(-33) esu. Spectroscopic results show ev idence of pi back-donation resulting in an extension of the electronic pi-system. We propose that this rr back-donation is the origin of thi s significant value of gamma.