Spectral characteristics of 2-(4 '-N,N-dimethylaminophenyl)pyrido[3,4-d]imidazole in AOT/n-heptane/water reverse micelles

Spectral characteristics of 2-(4'-N,N-dimethylaminophenyl)pyrido[3,4-d]imid azole (DMAPPI) have been studied in AOT/n-heptane/water reverse micelles at w(0) greater than or equal to 0. Absorption, fluorescence excitation and f luorescence spectra have revealed that the monocation (MC) of DMAPPI, proto nated at the imidazole nitrogen (MC2) (Scheme 2) is present in the S-0 stat e at w(0=0), along with the MC, protonated at pyridine nitrogen (MC3) and o nly normal emission is observed from both MC2 and MC3. With increase in w(0 ) (water amount), the equilibrium is shifted towards the MC, protonated at -NMe2 group (MC1) and MC3 in the S. state. Biprotonic phototautomerism is o bserved in MC1 to generate MC2 in the S, state. The twisted intramolecular charge transfer (TICT) emission replaces the normal emission in MC3. All th e MCs are present near the anionic polar head group of ACT in the bound wat er region. (C) 2001 Elsevier Science B.V. All rights reserved.