Nonlinear optical properties of open-shell polychlorotriphenylmethyl radicals

The second-order nonlinear optical (SONLO) response of a series of the highly chemically and thermally stable polychlorotriphenylmethyl monoradicals 1-8 has been studied by Hyper-Rayleigh Scattering. These radicals exhibit relatively high nonlinear optical (NLO) responses with beta values ranging from 118 x 10(-30) to 755 X 10(-30) esu which may result from an enhancement of the SONLO activities according to their open-shell electronic state. Hyperpolarizability data for radicals 1-8 have also been correlated with their redox potentials, correlation that has turned out to be linearly proportional either with the oxidation or the reduction potentials. These data have been justified in terms of molecular orbital energies. Finally we have successfully explored the capacity of radicals 1-8 to participate in a molecular switching array involving two main steps, an acid/base reaction and a redox process. The presence of open-shell character for this family of compounds makes them attractive candidates to design new multifunctional materials that would simultaneously possess magnetism and NLO. (C) 2003 Elsevier Science Ltd. All rights reserved.