First hyperpolarizabilities of 1,3,5-tricyano-2,4,6-tris(styryl)benzene derivatives:: ab initio studies and Hammett correlation

First hyperpolarizabilities (beta) of the 1,3,5-tricyano-2,4,6-tris(styryl)benzene derivatives were studied b an ab initio method (HF/6-31G). The beta values of these molecules increase with increase in donor strength, reaching a maximum value of 262 x 10(-30) esu with an oxyanion as the donor. Also, the electronic charge is more delocalized, and the HOMO-LUMO energy gap (DeltaE) and the bond length alternation (BLA) decrease with the same variation of the donor. Noteworthy is the excellent linear relationship between beta and 1/DeltaE(2) and sigma(gas)(+). These results may serve as a useful guideline for the design of two-dimensional octupoles with large first hyperpolarizabilities. Copyright (C) 2004 John Wiley Sons, Ltd.