Abstract

The search for suitable NLO active materials in view of applications in photonics and optoelectronics has been focused mainly on organic products,¹ though in recent years the interest in organometallic compounds has increased drastically.² Most of these studies were centred on metallocenes and related materials which show hyperpolarisabilities of the order of 10⁻²⁹ esu, but also metal mononitrosyl complexes and metal bipyridine complexes have been the subject of investigation. Using the hyper-Rayleigh scattering technique we determined the quadratic hyperpolarisability of a series of ruthenium σ-arylacetylides and detected only a small increase upon lengthening of the π-system. In contrast to a recent theoretical study³ the measured hyperpolarisabilities reach to the largest (10⁻²⁷ esu) known for organometallic compounds.^4,5 The effect of the oxidation state of the metal donor is probed by analysing the second harmonic response of both Ru(II) and Ru(III) derivatives. The molecular hyperpolarisability is found to correlate well with the electron density on the metal. In conclusion two types of bimetallic complexes, both with a weakly coupled metal pentacarbonyl acceptor, have been studied and are compared with mixed valence compounds.⁵ In all cases a good correlation is found between the quadratic hyperpolarisability and the absorption band closest to the harmonic wavelength.

© 1996 IEEE