A theoretical study on the ESPT mechanism for a novel Bis‐HPBT fluorophore

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-thiazol-2-yl)-6tert-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.

Exploring the possibilities of double proton transfer in hydrazides: A theoretical approach

“…A similar trend is observed for BTN exhibiting a bathochromic shift of 29 cm −1 and that of BTO exhibiting 23 cm −1 with respect to its ground state values. The observed bathochromic shift supports the strengthening of intramolecular hydrogen bond and probable excited state proton transfer concurrent in the system . The effect of redshift observed is strongly connected to the proton transfer barrier; the stronger the redshift, the lower is the potential barrier and the easier the proton transfer .…”

“…The observed bathochromic shift supports the strengthening of intramolecular hydrogen bond and probable excited state proton transfer concurrent in the system. [61][62][63][64] The effect of redshift observed is strongly connected to the proton transfer barrier; the stronger the redshift, the lower is the potential barrier and the easier the proton transfer. [57] The stronger the redshift, the weaker the energy of interaction between proton and proton donor.…”

The alkoxylation effects on the excited‐state intramolecular proton transfer behaviors for 2,6‐bis(benzothiazolyl‐2‐yl)phenol fluorophore: A theoretical research

“…Particularly, due to this kind of spectral properties for ESIPT systems, the development of novel materials for optoelectronics, fluorescence sensors, cell imagines, white light-emitting diodes (LEDs), molecular switches, chemical sensing, and so forth have become the hot topic currently. [39][40][41][42][43][44][45][46][47][48][49][50][51][52] Till now, it cannot be denied that ESIPT materials play important roles in detecting sensitivity of surroundings and in modulating fluorescence as well as many novel developments and applications in recent years. In particular, because the ESIPT processes could also provide the four-level laser scheme for achieving the population inversion, fluorescent ESIPT materials are effective laser dyes.…”

“…Particularly, due to this kind of spectral properties for ESIPT systems, the development of novel materials for optoelectronics, fluorescence sensors, cell imagines, white light‐emitting diodes (LEDs), molecular switches, chemical sensing, and so forth have become the hot topic currently. [ 39–52 ]…”

Photophysical properties and sensing mechanism of fluorescent coumarin–chalcone hybrid for biothiols: A theoretical study

“…In the past decades, quantum chemistry approach based on density functional theory (DFT) and timedependent density functional theory (TDDFT) has been widely applied in elucidating the photophysical properties and sensing mechanisms of fluorescent probes. [42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] To the best of our knowledge, no theoretical study has been reported on the photophysical properties and biothiols recognition mechanism for the studied probe CCH. In continuation of our research on the optical properties of chalcone derivates [58][59][60] and the development of novel fluorescent probes, [61,62] in this study, we aim to investigate the photophysical properties and cysteine recognition reaction of CCH to clarify the excitedstate nature and the sensing mechanism for biothiols.…”