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Date of Publication:2022-10-08

Journal:NEW JOURNAL OF CHEMISTRY

Volume:38

Issue:2

Page Number:568-573

ISSN No.:1144-0546

Abstract:Excited state hydrogen-bonding dynamics of coumarin in ethanol solvent has been studied using TDDFT/6-311++G(d,p) and a conductor-like polarizable continuum model. The geometry, hydrogen bond binding energy and frequency analysis indicate that the intermolecular hydrogen bond between C102 and ethanol is strengthened in the excited state. The binding energy is increased from 27.81 kJ mol(-1) in the ground state to 32.36 kJ mol(-1) in the S-1 state. The C=O and O-H stretching bands in C102-EtOH are strongly red-shifted due to the formation of the intermolecular hydrogen bond. In the excited state, redshift occurs for the C=O and O-H in the C102-EtOH complex. The excitation energy and frontier molecular orbital analysis indicate that S1 of the C102-EtOH complex is the locally excited state. S1 corresponds to the orbital transition from the HOMO to the LUMO with the pi pi(star) character. Furthermore, the internal conversion from the excited to ground state is enhanced by hydrogen bond strengthening.

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