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

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