PH-DEPENDENCE OF THE TWISTED INTRAMOLECULAR CHARGE-TRANSFER (TICT) OF P-N, N-DIMETHYLAMINOBENZOIC ACID IN AQUEOUS-SOLUTION

The pH dependence of the twisted intramolecular charge transfer (TICT) of p-N,N-dimethylaminobenzoic acid (DMABOA) in aqueous solution was examined using its typical dual fluorescence. Fluorometric pH titration indicates that the excited state proton exchange is much slower than fluorescence in the acid or conjugate base form of DMABOA, and that the conjugate base form has a higher relative population of the TICT state and a stronger excitation wavelength dependence of TICT fluorescence than the acid form.