Effects of different substituents of methyl 5-R-salicylates on the excited state intramolecular proton transfer process

Abstract

The proton transfer reaction in methyl 5-R-salicylate is found to be highly sensitive to the presence of specific substituents in resonance with the hydroxyl group, leading to different fluorescence behaviors of methyl 5-R-salicylate with different substituents (J. Catalán, J. Phys. Chem. B, 2015, 119, 2132). But a detailed survey of its reaction mechanism is lacking. In our research, the hydrogen bond strengthening behavior in excited states is affected by the different substituents that have been reported for the first time. Absorption and emission spectra calculated for the work presented here agree well with experimental results. At the same time, in order to provide a reliable description of the reaction energy profiles, we compare the barrier differences obtained using CAM-B3LYP and B3LYP methods, and we visually observe the effect of different substituents on the ESIPT reactions in methyl 5-R-salicylates by combining the potential energy curves. So the excited state intramolecular proton transfer (ESIPT) reactions in methyl 5-R-salicylate molecules are investigated in detail using density functional theory (DFT) and time dependent density functional theory (TDDFT) methods. It can be confirmed that the mobility of the intramolecular π electrons is affected by an increase in the resonant strength of the different substituents and hydroxyl groups. As a consequence, a hydrogen bonding interaction gradual weakening mechanism has been perfectly verified, that is, the ESIPT reaction is more difficult to occur from MS → 5MeMS → 5FMS → 5ClMS → 5BrMS → 5MeOMS → 5AmMS molecules.

A theoretical investigation on the excited state intramolecular single or double proton transfer mechanism of a salicyladazine system

“…Thus, determining the potential energy barrier for the ESIPT process is crucial under different conditions. Generally, the theoretical investigations provide direct approaches to solve this problem in recent years . The overall ESIPT reaction is complicated, and unraveling the detailed mechanism of ESIPT seems to be more and more important experimentally and theoretically.…”

Effect of water on excited‐state double proton transfer in 7‐azaindole‐H2O complex: A theoretical study

“…Proton transfer (PT) reaction has been highly concerned by experimental and theoretical researchers because of its significance in many chemical and biological phenomena . A large number of studies on excited‐state intermolecular reaction (ESPT) have been widely reported in order to abstract the useful information and to control such reactions.…”

Photo‐excited intramolecular charge transfer and excited state intramolecular proton transfer behaviors for HPIBT system: A theoretical investigation

“…[1][2][3][4][5][6][7][8][9][10] Given various photochemical phenomena (i.e., quenching of fluorescence, shifts of spectra, charge transfer, and so on) involved in the hydrogen bond, [11][12][13][14][15][16] more and more researchers are paying attention to excited-state hydrogen bonding interactions and dynamics. As one of the most correlative hydrogen bonding dynamics in both biological and chemical processes, [17][18][19][20][21][22][23] excited-state intramolecular proton transfer (ESIPT) should be prevalent in nature. [24,25] From both experimental and theoretical viewpoints, [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] ESIPT has currently become a hot research topic.…”

“…During the past several decades, ESIPT molecules have attracted considerable attention due to their tremendous applications in diverse fields, such as fluorescence probes, fluorescence sensors, organic lasers, organic light emitting diodes, optical storage, molecular switches, and others. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Because of the wide applications based on ESIPT reaction, the kinetic processes and reaction mechanisms have currently become particularly significant. To further research this kind of reaction at the theoretical level, density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods have become the most popular computing methods to explore elementary cases about electronic structures and electronic states.…”

“…To further research this kind of reaction at the theoretical level, density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods have become the most popular computing methods to explore elementary cases about electronic structures and electronic states. [18][19][20][21][22][23][24] As far as we know, 2-(2-hydroxyphenyl)benzothiazole (HBT) should be one of the most classical ESIPT-active luminogens, which has been extensively investigated due to its facile synthetic route and excellent photo stability. Very recently, Wang and coworkers designed and synthesized a novel active luminogen based on benzimide-HBT form (abbreviated as 5-benzothiazol-2-yl-6-hydroxy-2-methyl-isoindole-1,3-dione ("HPIBT") in this work).…”