Uncovering and controlling the ESIPT behavior for 2,2‐dipicolylamino substituted 2‐(2′‐hydroxybenzofuranyl) benzoxazole: Solvent polarity

Abstract

In view of potential applications of fluorescent probe for the novel 2,2-dipicolylamino substituted 2-(2 0 -hydroxybenzofuranyl) benzoxazole (HBBODipic) dye, herein, we mainly focus on exploring effect of solvent polarity on ESIPT behavior for HBBODipoc. First, we compare the dominating atomic charge distribution, geometric parameters, and infrared (IR) vibrational behaviors of HBBODipic, and we confirm that intramolecular hydrogen bond O-HÁÁÁN could be strengthened in S 1 state and nonpolar solvents are more conducive to the strengthening of hydrogen bonds. Via studying frontier molecular orbitals (MOs), we clarify that intramolecular charge transfer (ICT) occurs in excited molecule and charge redistribution facilitates ESIPT for HBBODipoc. In particular, nonpolar solvent is more propitious to ESIPT process of HBBODipic. Finally, we calculate and compare the potential energy curve of HBBODipic in solvent with different polarities.We present that the ESIPT process of HBBODipic could be regulated by solvent polarity; that is, nonpolar solvents are more favorable for ESIPT reaction for HBBODipic flurophore.

Insights into photo‐induced excited state intramolecular proton transfer behavior for the novel 2‐([1, 1′‐biphenyl]‐4‐yl)‐3‐hydroxy‐4H‐chromen‐4‐one system: Effects of solvent polarity

“…Before insights into the excited state dynamical mechanism in detail, infrared (IR) vibrational spectra are firstly examined and checked for all the optimized structures in five solvents, since all the geometrical stabilities of all configurations mentioned in this work could be guaranteed via IR results with non‐virtual frequencies in all excited states. Since the proton transfer process is accompanied by pre‐existing hydrogen bonding wires, herein, we mainly concentrate on variations of IR spectra involved in O 1 ‐H 2 ···O 3 of B‐bph‐fla‐OH fluorophore 41–44 . As shown in Figure 2, to better compare the hydrogen bonding changes between S 0 and S 1 states, the IR spectrum of O 1 ‐H 2 stretching vibration mode of B‐bph‐fla‐OH has been provided.…”

“…Since the proton transfer process is accompanied by pre-existing hydrogen bonding wires, herein, we mainly concentrate on variations of IR spectra involved in O 1 -H 2 ÁÁÁO 3 of B-bph-fla-OH fluorophore. [41][42][43][44] As shown in Figure 2, to better compare the hydrogen bonding changes between S 0 and S 1 states, the IR spectrum of O 1 -H 2 stretching vibration mode of B-bph-fla-OH has been provided. Similarly, the IR vibrational spectra of H 2 -O 3 of B-bph-fla-OH-T are shown in Figure S2, ESI †.…”