Ferrocenyl donor-organic acceptor complexes for second order nonlinear optics

First hyperpolarizability (beta) of a set of donor-acceptor complexes deriv ed by functionalizing two organic accepters with a donor such as ferrocene or an aromatic ring through a -C=N- linkage has been measured by hyper-Rayl eigh scattering in solution. Spectral analysis of the second harmonic scatt ered light reveals that there is a significant two-photon fluorescence (TPF ) contribution to the total signal in some compounds. In fact, the TPF cont ribution was as high as similar to 25% in two compounds. The measured beta values after correcting for TPF indicate that these molecules possess high second order nonlinearity, much larger than similar organic compounds or ch arge transfer complexes formed by ferrocenyl donors and organic accepters. The dispersion free beta values of these complexes have been calculated usi ng two different methods depending on the nature of the complex. The conven tional nonresonant two-state model which gives a good estimate of the intri nsic second order polarizability away from resonance, has been applied to c ompounds with no absorption around the second harmonic wavelength. Another model in which a damping parameter related to the inhomogeneous line width of the absorption band near the second harmonic frequency is used for obtai ning reliable values of beta (0). has been employed for the other compounds . In conjugation with anthraquinone as acceptor, ferrocene as a donor appea rs to be a better choice for quadratic nonlinear optics applications than c onventional organic donors. (C) 2001 Published by Elsevier Science B.V.