Premium
Time‐dependent density functional theory study on hydrogen‐bonded intramolecular charge‐transfer excited state of 4‐dimethylamino‐benzonitrile in methanol
Author(s) -
Zhao GuangJiu,
Han KeLi
Publication year - 2008
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.20957
Subject(s) - chemistry , intramolecular force , intermolecular force , photochemistry , hydrogen bond , excited state , density functional theory , triple bond , time dependent density functional theory , benzonitrile , molecule , computational chemistry , double bond , atomic physics , stereochemistry , organic chemistry , physics
The time‐dependent density functional theory (TDDFT) method was carried out to investigate the hydrogen‐bonded intramolecular charge‐transfer (ICT) excited state of 4‐dimethylaminobenzonitrile (DMABN) in methanol (MeOH) solvent. We demonstrated that the intermolecular hydrogen bond C≡N···HO formed between DMABN and MeOH can induce the C≡N stretching mode shift to the blue in both the ground state and the twisted intramolecular charge‐transfer (TICT) state of DMABN. Therefore, the two components at 2091 and 2109 cm −1 observed in the time‐resolved infrared (TRIR) absorption spectra of DMABN in MeOH solvent were reassigned in this work. The hydrogen‐bonded TICT state should correspond to the blue‐side component at 2109 cm −1 , whereas not the red‐side component at 2091 cm −1 designated in the previous study. It was also demonstrated that the intermolecular hydrogen bond C≡N···HO is significantly strengthened in the TICT state. The intermolecular hydrogen bond strengthening in the TICT state can facilitate the deactivation of the excited state via internal conversion (IC), and thus account for the fluorescence quenching of DMABN in protic solvents. Furthermore, the dynamic equilibrium of these electronically excited states is explained by the hydrogen bond strengthening in the TICT state. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008