Solvent Free, One Pot Synthesis of Symmetric Xanthene Dyes and Their Electrochemical Study

Abstract

The present paper reports the synthesis of xanthene dyes derivatives from 4, 4'-oxydiphthalic anhydride and 1, 4, 5, 8-naphthalenetetracarboxylic dianhydride (3a-e and 6a-e) with different substituted phenols via Friedel-Crafts acylation reaction in the presence of an ammonium chloride catalyst. The structures of all newly synthesized derivatives were confirmed by the chromatographic, spectral and microelemental data. Dianhydride derivatives with 3-N', N'-dimethylaminophenol (3d and 6d) and resorcinol (3e and 6e) have been found to be highly fluorescent. Electrochemical study was done to determine band gap energy, LUMO and HOMO level energy. Band gap and LUMO energy levels were found to be lowest in xanthene derivatives 3c and 6c. Dyes 3d, 3e, 6d and 6e were found useful for differential staining of plant cells.

Identification of Triarylmethane, Phthalocyanine and Xanthene in a Mixture of Dyes by Electron Absorption Spectroscopy

“…3, a) have absorption bands exclusively in the visible region with λmax at ~ 560 nm and a well-defined shoulder at ~ 520 nm, although a peak at 670-67 nm ap pears in samples 38 and 39 , the intensity of which is almost 6 times lower than for the 560 nm band. Probably, the pink color of these samples is due to the presence of xanthene dye rhodamine B (λ max rhodamine = 556 nm [23]) in the composition of the pastes. The absorption bands in the range of 520-560 nm are caused by n-n* transitions between lone electron pairs and n-bonded electrons of the benzoid structure of rhodamine B with increasing ring conjugation with the opening of the five-membered lactone ring [23,24].…”

“…Probably, the pink color of these samples is due to the presence of xanthene dye rhodamine B (λ max rhodamine = 556 nm [23]) in the composition of the pastes. The absorption bands in the range of 520-560 nm are caused by n-n* transitions between lone electron pairs and n-bonded electrons of the benzoid structure of rhodamine B with increasing ring conjugation with the opening of the five-membered lactone ring [23,24]. A small additional band at 670 nm can be identified as a band belonging to a phthalocyanine compound (probably Blue 38 dye) that gives the pastes a purple tint.…”