Unraveling photo-excited behaviors and proton transfer mechanisms for coexisting 5-methoxy-salicylaldhyde azine isomers

Self Cite

Compared with O-HÁÁÁO-type system, the N-HÁÁÁO-type system with excitedstate intramolecular proton transfer (ESIPT) provides a better research object for exploring kinetics and thermodynamics because the existence of amino group can be replaced by various groups. In this work, the ESIPT mechanism of a novel amino type proton donor (3TsAPI) has been studied, and its effects of solvent polarity have been investigated. We optimize the structures of 3TsAPI using density functional theory (DFT)/time-dependent density functional theory (TDDFT) methods, and electronic spectra data are consistent with the experiment. Through the analyses of structural parameters and spectra related to hydrogen bonding, it is found hydrogen bonding is enhanced in S 1 state, and analyses of bond critical point (BCP) parameters and core-valence bifurcation (CVB) indexes show excited-state hydrogen bonding is stronger in solvents with weaker polarity. We construct the potential energy curves and find polarity of solvents can regulate the potential energy barrier of ESIPT process and then further elucidate the ESIPT mechanism of 3TsAPI.

Section: Introductionmentioning

confidence: 99%

Theoretical insights into effects of solvent polarity on excited‐state N–H proton transfer behavior for a new fluorophore of 3‐tosylamino‐N‐cyclohexylphthalimide

Meng

Song

Zhao

et al. 2022

Self Cite

“…[3,4] So far, the generation of excited hydrogen bonds has become the focus of researchers, because the excited hydrogen bonds can affect the fluorescence sensing mechanism of compounds. [5][6][7][8][9][10][11] Thiazole compounds containing hydroxyl are a typical excited state intramolecular proton transfer (ESIPT) system with intramolecular hydrogen bonds. [12][13][14][15][16] Thiazole ring is an important type of five-membered aromatic heterocyclic ring.…”

Section: Introductionmentioning

confidence: 99%

Theoretical study on excited state intramolecular proton transfer mechanism of thiazole complex in different kinds of solvents

Liu

Wang

et al. 2022

The excited state intramolecular proton transfer (ESIPT) processes of 3-(benzo [d]-thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) in four kinds of solvents were studied using density functional theory (DFT) and timedependent DFT (TDDFT) method. As the solvent dielectric constant decreases, the strength of hydrogen bonds (H-bonds) in the excited state decreases. After photoexciation, the electron density rearrangement could be affected by the solvents, while the degree of charge transfer and the hydrogen bond interaction in the excited state became lower as the solvent dielectric constant decreased. The potential energy curves displayed the complete process of ESIPT, indicating that the ESIPT process of BTHMB was affected by the solvent polarity. When the solvent dielectric constant decreased, the tendency of proton transfer followed the trend: acetonitrile (ACN) > dichloromethane (DCM) > chloroform (CHCl 3 ) > 1,4-dioxane (DOX). Therefore, the ESIPT process was affected by the solvent polarity and became more difficult to occur as the solvent dielectric constant decreased. K E Y W O R D Sexcited state intramolecular proton transfer, hydrogen bond, potential energy curves, solvent polarity

“…The designing of molecular sensor involves a variety of sensing mechanism, such as photoinduced electron transfer (PET), [ 13 ] intramolecular charge transfer (ICT), [ 14,15 ] twisted intramolecular charge transfer (TICT), [ 16–19 ] metal‐to‐ligand charge transfer (MLCT), [ 20,21 ] , and excited‐state intramolecular proton transfer (ESIPT). [ 22–26 ] However, the synthesized chemosensors based on the ESIPT process have been studied extensively owing to their significant photo‐physical characteristics. [ 22 ] Moreover, the anion sensing mechanism of ESIPT‐based fluorescent probes has been investigated theoretically with the aid of computational methods.…”

Section: Introductionmentioning

confidence: 99%

Benzothiazole‐based chemosensor: a quick dip into its anion sensing mechanism

Kediya

Manhas

Jha

2021

Density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT) methods have been applied to decipher the F− anion sensing mechanism of a fluorescent probe N‐(2‐(benzothiazole‐2‐yl)phenyl)‐4‐methoxybenzamide (4). The amidic proton (N–H) of the selected probe may exhibit an intramolecular hydrogen bond (IMHB) with the nitrogen atom of benzothiazole moiety. The weak IMHB of N24–H26‐‐‐N12 in the excited state favors reverse proton transfer process in 4. In the ground state of 4, the F− anion interacts via F−‐‐‐H–N bond, which immediately deprotonates the amidic proton, leading to the distortion of the geometry. Subsequent to deprotonation, the significant intramolecular charge transfer (ICT) character was observed in 4. On account of the significant ICT process, the redshift in absorption and emission spectra was observed. These outcomes were employed to delineate the sensing mechanism of molecule 4.