THEORETICAL AND EXPERIMENTAL STUDIES OF ELECTRONIC EFFECTS AND 2ND-ORDER NONLINEAR-OPTICAL PROPERTIES OF SOME BENZENECARBOTHIOATES AND BENZENECARBODITHIOATES

The relative nonlinear efficiency of some conjugated ester, thioester and dithioester molecules was investigated by quantum chemical semi-em pirical methods, The results of calculations on ground and excited sta tes properties and on ''finite-field'' hyperpolarizabilities beta allo wed to select the best compounds for quadratic nonlinear optics, Some of these molecules were synthesized and the theoretical results were c onfronted with the experimental NLO response obtained by beta EFISH me asurements. It was concluded from this analysis that the dithioester s ubstituent represents an interesting electron-accepting group for appl ications in nonlinear optics and can be used instead of the nitro grou p.