Excited state dynamics of a double ESIPT unit comprising fluorophore

Abstract

A comprehensive experimental and computational analysis on the photophysical characteristics of a double ESIPT unit based fluorescent molecule, 2,2′-(1,4-phenylenebis(1H-benzo[d]imidazole-1,2-diyl))diphenol (PBIDP), was carried out. Photoluminescence spectra and lifetime decays have been measured in various polar and nonpolar solvents to explore the fluorescence properties. Furthermore, time-resolved area normalized emission spectra are exploited to identify the different conformers to the unsymmetrical keto emission band correlating with their lifetime values. To corroborate the experimental observations, computations have been enacted by calculating the relative energy, excitation and emission energies of different conformers. Especially, the simulation facilitates to trace the reason behind the triple emissions, uncovering the proton transfer dynamics in the double ESIPT based PBIDP system. Additionally, to understand the ESIPT mechanism in the fluorophore, the potential energy curve and transition state in the ground, and excited state were calculated.