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Low‐lying excited states of 7‐aminocoumarin derivatives: A theoretical study
Author(s) -
Sakata Tetsuya,
Kawashima Yukio,
Nakano Haruyuki
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.22019
Subject(s) - time dependent density functional theory , excited state , chemistry , carbazole , coumarin , delocalized electron , polarizable continuum model , density functional theory , photochemistry , absorption spectroscopy , homo/lumo , singlet state , solvent effects , solvent , molecule , computational chemistry , organic chemistry , atomic physics , physics , quantum mechanics
Excited states of three 7‐aminocoumarin derivatives, coumarin 120 (7‐amino‐4‐methylcoumarin), pyrrolyl coumarin 7‐(1 H ‐pyrrol‐1‐yl)‐4‐methyl‐2 H ‐1‐benzopyran‐2‐one, and carbazole‐coumarin hybrid 10 H ‐4‐methyl‐2 H ‐2‐oxopyrano[5,6‐ b ]carbazole, have been studied using B3LYP time‐dependent density functional theory (TDDFT). The solvent effect has been taken into account using the polarizable continuum model. The spectra calculated using TDDFT agree well with the experimental absorption spectra. The electronic structures and the solvent effect for the low‐lying singlet excited states have been investigated. The HOMO of the pyrrolyl coumarin is localized on the pyrrolyl ring, while the HOMO in the other 7‐aminocoumarins is delocalized over the entire molecule. This leads to the weak fluorescence of the pyrrolyl coumarins found in experiments. The HOMO and next HOMO in carbazole‐coumarin hybrids have similar orbital energy values, which is not the case in the other 7‐aminocoumarin derivatives. This leads to the additional peaks found in the 30,000–40,000 cm −1 region of the observed absorption spectra, which are specific for carbazole‐coumarin hybrids. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009