Solvent Effects on the Electronic Spectra of Xanthene Dyes

Abstract

Solvent effects on the visible spectra of xanthene dyes were studied in relation to the hydrogen bonding.
The xanthene dyes show a definite blue shift when the solvent is changed from DMA to water. In order to elucidate the shift, solvent effects on the visible spectra of Uranine and Eosin Y were studied. Although dielectric constant of solvent has little effects on the shift, the shift depends on the refractive index and the proton donating ability of the solvents. These facts indicate that the shift observed consists of two contributions, i. e., general solvent effect and hydrogen bond effect.
On the assumption that McRae's theory holds for such protic solvents as NMA and IPA, the shift due to the hrdrogen bond was estimated.