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A theoretical study on the ESPT mechanism for a novel Bis‐HPBT fluorophore
Author(s) -
Lu Xuemei,
Zhai Yuchuan,
Zhang Meixia,
Song Yuzhi
Publication year - 2018
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.3821
Subject(s) - chemistry , intramolecular force , hydrogen bond , density functional theory , excited state , photochemistry , time dependent density functional theory , molecular orbital , proton , computational chemistry , molecule , atomic physics , stereochemistry , physics , organic chemistry , quantum mechanics
Abstract In this work, based on the density functional theory and time‐dependent density functional theory methods, the properties of the 2 intramolecular hydrogen bonds (O1‐H2···N3 and O4‐H5···N6) of a new photochemical sensor 4‐(3‐(benzo[d]thiazol‐2‐yl)‐5‐tert‐butyl‐4‐hydroxybenzyl)‐2‐(benzo[d]thiazol‐2‐yl)‐6‐tert‐butyl phenol (Bis‐HPBT) have been investigated in detail. The calculated dominating bond lengths and bond angles about these 2 hydrogen bonds (O1‐H2···N3 and O4‐H5···N6) demonstrate that the intramolecular hydrogen bonds should be strengthened in the S 1 state. In addition, the variations of hydrogen bonds of Bis‐HPBT have been also testified based on infrared vibrational spectra. Our theoretical results reproduced absorption and emission spectra of the experiment, which verifies that the theoretical level we used is reasonable and effective in this work. Further, hydrogen bonding strengthening manifests the tendency of excited state intramolecular proton transfer (ESIPT) process. Frontier molecular orbitals depict the nature of electronically excited state and support the ESIPT reaction. According to the calculated results of potential energy curves along stepwise and synergetic O1‐H2 and O4‐H5 coordinates, the potential energy barrier of approximately 1.399 kcal/mol is discovered in the S 1 state, which supports the single ESIPT process along with 1 hydrogen bond of Bis‐HPBT. In other words, the proton transfer reaction can be facilitated based on the electronic excitation effectively. In turn, through the process of radiative transition, the proton‐transfer Bis‐HPBT‐SPT form regresses to the ground state with the fluorescence of 539 nm.