Spectroscopic study of solvent effects on the electronic absorption spectra of flavone and 7-hydroxyflavone in neat a binary solvent mixtures

MATIAS I. SANCHO; MARIA C. ALMANDOZ; SONIA E. BLANCO; EDUARDO A. CASTRO

INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES

MOLECULAR DIVERSITY PRESERVATION INTERNATIONAL-MDPI

Lugar: Basilea; Año: 2011 vol. 12 p. 8895 - 8912

1422-0067

The solvatochromic characteristics of flavone and 7-hydroxyflavone wereinvestigated in neat and binary solvent mixtures. The spectral shifts of these solutes werecorrelated with the Kamlet and Taft parameters (alpha, beta and pi*) using linear solvation energyrelationships. The multiparametric analysis indicates that both specific hydrogen bonddonor ability and non-specific dipolar interactions of the solvents play an important role inabsorption maxima of flavone in pure solvents. The hydrogen bond acceptor ability of thesolvent was the main parameter affecting the absorption maxima of 7-hydroxyflavone. Thesimulated absorption spectra using a TD-DFT method were in good agreement with theexperimental ones for both flavones. Index of preferential solvation was calculated asa function of solvent composition. Preferential solvation by ethanol was detected incyclohexane-ethanol and acetonitrile-ethanol mixtures for flavone and in acetonitrile-ethanolmixtures for 7-hydroxyflavone. These results indicate that intermolecular hydrogen bondsbetween solute and solvent are responsible for the non-linear variation of the solvatochromicshifts on the mole fraction of ethanol in the analyzed binary mixtures.