Twisted intramolecular charge transfer of <em>p</em>-N,N- dimethylamino-benzaldehyde in cyclodextrin environments

Abstract

Twisted intramolecular charge transfer (TICT) of <em>p</em>-N.N- dimethylaminobenzaldehyde (DMABA) has been studied in different aqueous cyclodextrin (&alpha;-. &beta;- and &upsih;-) environments. The tluorophore forms 1:1 complexes with all the three cyclodextrins (CD). The TICT emission is extremely weak in pure water but it is enhanced as the probe is encapsulated within the cyclodextrin cavities. The relative enhancement of the emission from the TICT species to the locally excited (LE) species is maximum in the &alpha;-CD environment and minimum in the &upsih;-CD environment. This differential enhancement of the two emission bands in different aqueous CD solutions has been explained on the basis of the polarity factor. It has been suggested that the polarity of the microenvironment is the principal controlling factor for the TICT process.