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A detailed theoretical study on the excited‐state hydrogen‐bonding dynamics and the proton transfer mechanism for a novel white‐light fluorophore
Author(s) -
Gao Haiyan,
Yang Guang,
Jia Min,
Song Xiaoyan,
Zhang Qiaoli,
Yang Dapeng
Publication year - 2019
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201800045
Subject(s) - chemistry , time dependent density functional theory , excited state , density functional theory , intramolecular force , fluorophore , proton , hydrogen bond , molecular dynamics , chemical physics , computational chemistry , photochemistry , atomic physics , molecule , fluorescence , stereochemistry , physics , organic chemistry , quantum mechanics
In this work, density functional theory (DFT) and time‐dependent DFT (TDDFT) methods were used to investigate the excited‐state dynamics of the excited‐state hydrogen‐bonding variations and proton transfer mechanism for a novel white‐light fluorophore 2‐(4‐[dimethylamino]phenyl)‐7‐hyroxy‐6‐(3‐phenylpropanoyl)‐4 H ‐chromen‐4‐one ( 1 ). The methods we adopted could successfully reproduce the experimental electronic spectra, which shows the appropriateness of the theoretical level in this work. Using molecular electrostatic potential (MEP) as well as the reduced density gradient (RDG) versus the product of the sign of the second largest eigenvalue of the electron density Hessian matrix and electron density (sign[ λ 2 ] ρ ), we demonstrate that an intramolecular hydrogen bond O1–H2···O3 should be formed spontaneously in the S 0 state. By analyzing the chemical structures, infrared vibrational spectra, and hydrogen‐bonding energies, we confirm that O1–H2·O3 should be strengthened in the S 1 state, which reveals the possibility of an excited‐state intramolecular proton transfer (ESIPT) process. On investigating the excitation process, we find the S 0 → S 1 transition corresponding to the charge transfer, which provides the driving force for ESIPT. By constructing the potential energy curves, we show that the ESIPT reaction results in a dynamic equilibrium in the S 1 state between the forward and backward processes, which facilitates the emission of white light.