Design of novel nonlinear optical chromophores with multiple substitutions

The molecular first hyperpolarizabilities (beta) and electronic properties of some tetra-substituted benzenes/pyrazines which can be described as 1,2- didonor-4,5-diacceptor-benzenes/2,3-didonor-5,6-diacceptor-pyrazines have b een investigated by employing an AM1/FF and ZINDO/S-CI approach. It is foun d that these multiple substituted chromophores possess large beta values wh ich may be attributed to the positive contribution of the off-diagonal tens orial component beta(xyy). Two novel chromophores (1 and 2) containing leng thened conjugation and thermally stable imidazole rings are designed under such a multiple substitutions principle. Chromophore 1 shows a very large m u beta(0) value of approximately 3900x10(-48) esu.dagger The theoretical ca lculation and preliminary experimental results indicate that a good nonline arity-transparency-thermal stability trade-off is achieved for chromophore 2, which possesses a mu beta(0) of 555x10(-48) esu, a rather blue-shifted a bsorption peak at 384 nm in THF and a high decomposition temperature (T-d) of 377 degrees C.