Linear and nonlinear optical characterizations of a monomeric symmetric squaraine-based dye in solution

Carlo Toro, Leonardo De Boni, Sheng Yao, James P. Ritchie, Artm E. Masunov, Kevin D. Belfield, Florencio E. Hernandez

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32 Scopus citations


The photophysical properties of a symmetric squaryllium dye, namely, 2,4-bis[4-(N,N -dibutylamino)-2-hydroxyphenyl] squaraine (SQ), in its monomer form in acetone solution, have been thoroughly studied by means of one-photon absorption (1PA) and two-photon absorption (2PA), excitation anisotropy, fluorescence emission, fluorescence quantum yield, and excited state absorption. The results show that there is a strong one-photon allowed absorption band in the near IR region associated with intramolecular charge transfer. Higher one-photon allowed and forbidden singlet excited states were also revealed by absorption and excitation anisotropy. A relatively high fluorescence quantum yield (0.44) was measured for this dye. The nonlinear optical characterization of SQ in solution confirms the ability of squaraine dyes to be used as good two-photon absorbers. Additionally, it was found that this dye presents both saturable and reverse saturable absorption effects. Density functional theory calculations of the 1PA and 2PA electronic spectra of SQ were carried out to support the experimental data. A detailed analysis of the symmetry and energy of the orbitals involved in the lowest five electronic transitions is presented and discussed in relation to the behavior observed experimentally.

Original languageEnglish (US)
Article number214504
JournalJournal of Chemical Physics
Issue number21
StatePublished - 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy
  • Physical and Theoretical Chemistry


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