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TDDFT and MS‐CASPT2 Study of the Excited States of Para ‐Methoxymethylcinnamate
Author(s) -
Moon Jiwon,
Baek Heehyun,
Lim Jeong Sik,
Kim Joonghan
Publication year - 2018
Publication title -
bulletin of the korean chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.237
H-Index - 59
ISSN - 1229-5949
DOI - 10.1002/bkcs.11403
Subject(s) - adiabatic process , excitation , excited state , time dependent density functional theory , chemistry , atomic physics , complete active space , density functional theory , population , computational chemistry , physics , basis set , quantum mechanics , demography , sociology
The vertical and adiabatic excitation energies of the ππ*, ππ*′, and nπ* states of the trans and cis isomers of para ‐methoxymethylcinnamate ( p ‐MMC) were calculated using time‐dependent density functional theory and multistate complete active space second‐order perturbation theory (MS‐CASPT2) with reasonably sized basis sets. The adiabatic excitation energies of the ππ* state of trans ‐ p ‐MMC calculated by TD‐CAM‐B3LYP and MS‐CASPT2 are in excellent agreement with the experimental value. The nπ* state lies at a higher energy than the ππ* state in the adiabatic excitation energy calculations, indicating that the barrier to internal conversion from the ππ* state to the nπ* state will be considerable. This result is opposite to the previous theoretical result. The microsolvation effect of a water molecule on p ‐MMC is examined by calculating the excitation energies. The origin of the stabilization of the ππ* state and destabilization of the nπ* state by microsolvation has also been elucidated using natural population analysis.