Design principles for ESIPT-based fluorophores: effects of heteroatoms, substituents and solvent polarity in benzazole derivatives

Abstract Excited-state intramolecular proton transfer (ESIPT) plays a pivotal role in governing the photophysical behaviour of benzazole-based fluorophores. However, the synergistic effects of heteroatom identity, substituent electronic properties and solvent polarity remain insufficiently understood. Here, we use density functional theory (DFT) and time-dependent DFT calculations to investigate the ESIPT activity of a series of 2-(2′-hydroxyphenyl)benzazole derivatives containing different hete