Resonance Raman spectra of hydroxyphenyl squaraines: acid-base versus aggregation equilibria

• Published in: Journal of Raman spectroscopy Vol. 37; no. 1-3; pp. 142 - 147
• Main Authors: Lopes, José Guilherme S., Farani, Régis A., de Oliveira, Luiz Fernando C., Santos, Paulo S.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-01-2006
• Subjects: 6-trihydroxyphenyl) squaraine; acid-base equilibria; Agglomeration; Band spectra; bis(2,4,6‐trihydroxyphenyl) squaraine; Electronics; Raman spectra; Raman spectroscopy; resonance Raman spectroscopy; SAXS; Spectral lines; squaraine; Tuning
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.1448

The optical and resonance Raman spectra (RR) of bis(phloroglucinol)squaraine (I) and bis(resorcinol)squaraine (II) were investigated, revealing that the equilibria between the neutral and anionic species present in solution explain the experimental observations much better than the previously proposed aggregation equilibria. In particular, the RR spectra were invaluable to assign characteristic modes of (I) and its monoanion, since the tuning of the excitation line to the electronic transition band of the neutral or monoanionic specie leads to the enhancement of the respective modes that are exclusive of each species. In addition, small angle X‐ray scattering (SAXS) experiments with (I) did not show any evidence of aggregation. Copyright © 2006 John Wiley & Sons, Ltd.