Quadratic hyperpolarisability of sulfur-containing systems

Abstract The non-linear optical properties of sulfur-containing systems have been investigated both experimentally and by means of theoretical calculations. A good correlation is obtained between the two sets of results. The effectiveness of the methylthio group has been tested both as an electron donor and acceptor group. Results evidence that it is markedly more efficient as an electron releasing group, with an effect comparable to that of dimethylamino. The sulfur atom, and the sulfone function, have been included as part of a conjugation path connecting two phenyl rings -Φ-X-Φ- (X=S or SO 2 ). They are found to be poor charge transmitters, as a donor and an acceptor group interact weakly through the non-planar -Φ-X-Φ- system. An additive vectorial model of β is shown to account well for such a type of interaction.