A series of merocyanine dyes containing various donors and barbituric acid and cyclobutene-1,2-dione moieties as the acceptors have been synthesized and their first-order hyperpolarizabilities β were determined. The β values of barbituric acid derivatives increase as the strength of the donor is increased from 4-dimethylaminophenyl to trimethylindolinyl to benzothiazolinyl, apparently due to the gradual decrease in the bond length alternation (BLA) from a large positive value to an optimum one by a stronger donor. In contrast, the β values for the cyclobutene-1,2-dione derivatives decrease with the same variation of the donors even though the cyclobutene-1,2-dione is a poorer acceptor than the barbituric acid moiety. The results have been attributed to the electron-donating ability of the donors and the increased distortion of the chromophores from planarity.
|Number of pages||4|
|Journal||Journal of the Chemical Society. Perkin Transactions 2|
|Publication status||Published - 1996 Oct|
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