Low-lying excited states of 7-aminocoumarin derivatives: A theoretical study

Tetsuya Sakata, Yukio Kawashima, Haruyuki Nakano

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13 Citations (Scopus)

Abstract

Excited states of three 7-aminocoumarin derivatives, coumarin 120 (7- amino-4-methylcoumarin), pyrrolyl coumarin 7-(1H-pyrrol-1-yl)-4-methyl-2H-1- benzopyran-2-one, and carbazole-coumarin hybrid 10H-4-methyl-2H-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.

Original languageEnglish
Pages (from-to)1940-1949
Number of pages10
JournalInternational Journal of Quantum Chemistry
Volume109
Issue number9
DOIs
Publication statusPublished - Jul 9 2009

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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