A theoretical investigation on excited-state single or double proton transfer process for aloesaponarin I

Abstract

The excited-state proton transfer (ESPT) dynamical behavior of aloesaponarin I (ASI) was studied using density functional theory (DFT) and time-dependent DFT (TDDFT) methods. Our calculated vertical excitation energies based on TDDFT reproduced the experimental absorption and fluorescence spectra well [Nagaoka et al. J. Phys. Chem. B, 117, 4347 (2013)]. Two intramolecular hydrogen bonds were confirmed to be strengthened in the S1 state, which makes ESPT possible. Herein, the ESPT process is more likely to happen, along with one hydrogen bond (O1–H2⋯O3). Qualitative analyses about charge distribution further demonstrate that the ESPT process could occur because of the intramolecular charge transfer. Our constructed potential energy surfaces of both S0 and S1 states show that a single proton transfer reactive is more reasonable along with the intramolecular hydrogen bond (O1–H2⋯O3) rather than O4–H5⋯O6 in the S1 stated potential energy surface. Then, ASI-SPT* decays to the ground state with a 640 nm fluorescence; subsequently, the ASI-SPT form shows that reverse ground state single-proton transfer back to the ASI structure occurs. Particularly, dependent on relatively accurate potential energy barriers among these excited-state stable structures, we confirmed the excited-state single proton transfer process rather than using the controversial nodal plane model.

Theoretical Elaboration about Excited State Behaviors and Fluoride Anion Sensor Mechanism for 2-{[2-(2-Hydroxy-Phenyl)-1H-Benzoimidazo-5-yl]-Phenyl-Methylene} Malononitrile

“…As far as we know, the theoretical constructed potential energy curves could provide reasonable explanations about the excited state dynamical processes [64][65][66][67][68][69][70][71][72]. Thus, in this work, we adopt this manner to explore the ESIPT behavior for HBPMM system.…”

“…The constructed potential energy curve is based on shortening the distance of F atom and the H atom of hydroxyl for HBPMM molecule, which is selected from 2.20 Å to 0.80 Å with fixing the step of 0.05 Å. Similar with discussing the ESIPT mechanism about HBPMM above, the investigation about potential energy curve should be a good manner to deal with the protonated and deprotonated reactions in both ground and exited states [64][65][66][67][68][69][70][71][72]. It could be clearly found that the potential energy curve decreases along with the shortening of H and F atoms until the length of H-F reaching around 1.0 Å.…”

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 ]…”

Theoretical unraveling detailed excited state proton transfer mechanism for 2,5‐bis (benzoxazol‐2‐yl)thiophene‐3,4‐diol‐ethyl compound in different solvents

“…In effect, HBs play vital roles in various fields including biological molecules and organic and organometallic compounds. [1][2][3][4][5][6][7] Particularly, by virtue of strong direction interaction, HB has become inevitable architectures for constructing elementary building blocks in nature, which is also the significant active site in biological systems. Thus, insights into the HB effects and interactions would be important to probe into and explain novel phenomena occurring in solutions, in crystal forms, and in living organisms.…”