Exploring the ESIPT process and fluorescence properties of 2‑(2′-Hydroxyaryl)benzazole derivatives by expanding the π-conjugation framework

Abstract

Herein, we used the time-dependent density functional theory to investigate the ESIPT process and fluorescence properties of 2‑(2′-Hydroxyaryl)benzazole (HBO) derivatives (1–3 compounds) by expanding the π-conjugation framework. Calculated parameters show that the intramolecular hydrogen bond (Intra-HB) is enhanced in the excited state with the expansion of the π-conjugation framework. Potential energy curves results also well prove that the weakened intra-HB is difficult to undergo the ESIPT process, which in turn controls the single- and dual-fluorescence emission. Exploring frontier molecular orbital, we clarify the intramolecular charge transfer is an important factor affecting the intra-HB strength.