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- Title
Theoretical Investigation of Excited-State Intramolecular Double-Proton Transfer Mechanism of Substituent Modified 1, 3-Bis (2-Pyridylimino)-4,7-Dihydroxyisoindole in Dichloromethane Solution.
- Authors
Liu, Xiumin; Yuan, Heyao; Wang, Yuxi; Tao, Yaping; Wang, Yi; Hou, Yingmin
- Abstract
In this paper, density functional theory (DFT) and time-dependent DFT (TDDFT) methods were used to investigate substituent effects and excited-state intramolecular double-proton transfer (ESIDPT) in 1, 3-bis (2-pyridylimino)-4, 7-dihydroxyisoindole (BPI–OH) and its derivatives. The results of a systematic study of the substituent effects of electron-withdrawing groups (F, Cl and Br) on the adjacent sites of the benzene ring were used to regulate the photophysical properties of the molecules and the dynamics of the proton-transfer process. Geometric structure comparisons and infrared (IR) spectroscopic analysis confirmed that strengthening of the intramolecular hydrogen bond in the first excited state (S1) facilitated proton transfer. Functional analysis of the reduced density gradient confirmed these conclusions. Double-proton transfer in BPI–OH is considered to occur in two steps, i.e., BPI–OH (N) → BPI–OH (T1) → BPI–OH (T2), in the ground state (S0) and the S1 state. The potential-energy curves (PECs) for two-step proton transfer were scanned for both the S0 and S1 states to clarify the mechanisms and pathways of proton transfer. The stepwise path in which two protons are consecutively transferred has a low energy barrier and is more rational and favorable. This study shows that the presence or absence of coordinating groups, and the type of coordinating group, affect the hydrogen-bond strength. A coordinating group enhances hydrogen-bond formation, i.e., it promotes excited-state intramolecular proton transfer (ESIPT). DFT and TDDFT methods are used to investigate substituent effects and ESIDPT in BPI-OH and its derivatives. Double-proton transfer in BPI-OH is considered to occur in two steps, i.e., BPI-OH (N) →BPI-OH (T1) →BPI-OH (T2), in the S0 and S1 states. Modification with electron-withdrawing groups (F, Cl, and Br) favors proton-transfer reactions.
- Subjects
INTRAMOLECULAR proton transfer reactions; DICHLOROMETHANE; DENSITY functional theory; ACTIVATION energy; EXCITED states; HYDROGEN bonding
- Publication
Journal of Computational Biophysics & Chemistry, 2021, Vol 20, Issue 7, p707
- ISSN
2737-4165
- Publication type
Article
- DOI
10.1142/S2737416521500423