Theoretical study of the electronic excited states and fluorescence spectra of squaraine in solution

Hitoshi Ozawa, Kazunori Yashiro, Takuma Yamamoto, Satoshi Yabushita

研究成果: Article査読

1 被引用数 (Scopus)


Bis[4-(dimethylamino)phenyl]squaraine (SQ-DMA) has been used as a long wavelength fluorescence dye. In spite of various experimental and theoretical studies, its excited state properties and the relaxation mechanism have not been elucidated. In this work, we tried to clarify these points from a theoretical point of view. The heats of reaction from the planar to possible twisted conformers in the first excited state S1 in solvents were calculated to be significantly endothermic, thus the twisted structures turn out to be less important, which contradicts earlier proposals made in experimental studies. This behavior is in a sharp contrast with that of the related molecule 4-(N,N-dimethylamino)benzonitrile, and is explained by the difference in their electronic characters of their relevant excited states; the S1 state of SQ-DMA is a simple HOMO-to-LUMO excited state with a delocalized character. Furthermore, the theoretically simulated absorption and fluorescence spectra with the planar structure of SQ-DMA are in good agreement with the corresponding experimental results. These results suggest that the responsible S1 state is the lowest 1B1u state with a planar D2h structure.

ジャーナルJournal of Solution Chemistry
出版ステータスPublished - 2014 10月 21

ASJC Scopus subject areas

  • 生物理学
  • 生化学
  • 分子生物学
  • 物理化学および理論化学


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