Modulation of Excited-State Intramolecular Proton Transfer Reaction of 1-Hydroxy-2-naphthaldehyde in Different Supramolecular Assemblies

摘要

The excited-state intramolecular proton transfer (ESIPT) reaction of 1-hydroxy-2-naphthaldehyde (HN12) has been studied within the interior of the supramolecular assemblies of alpha-, beta-, and gamma-cyclodextrins (CD) and biomimicking environments of ionic (SIDS) and non-ionic (TW-20) micelles. Fluorescence measurements are used to Investigate the effect of various supramolecular assemblies on the ESIPT reaction by monitoring the large Stokes-shifted tautomer emission or HN12. Enhanced tautomer emission in the microencapsulated state predicts favorable ESIPT reaction in the supramolecular assemblies. Benesi-Hildebrand plots have been employed to ascertain that the stoichiometric ratios of the complexes formed between HN12 and CDs are 1:2 1: 1, and 1:1 for alpha-, beta-, and gamma-CD, respectively. The binding constants (K-1) and free-energy change (Delta G) for inclusion complexation are also determined front the linearized Benesi-Hildebrand plots. Steady-state fluorescence anisotropy, REES, excitation anisotropy, and fluorescence lifetime measurements are in line with other experimental findings. Differential action of urea on SDS and TW-20-bound probe has also been investigated.