ZINC(II) BIS(DIPYRROMETENATES) AS NEW FLUORESCENT CHEMOSENSORS OF N- AND O-CONTAINING ANALYTES

Abstract

The results of spectral studies of the fluorescence of binuclear zinc(II) bis(dipyrrinate)s with 3,3′-, 2,3′- and 2,2′-bis(dipyrrine)s of the composition [Zn2L2] in binary mixtures of cyclohexane and N- and O -containing solvent Х (acetone, DMF, DMSO, TEA) are presented. Spectrophotometric studies have shown that additive in cyclohexane of analyte upto χХ<0.2 leads to red shift (to ~10 nm) of emission band maximum and to a sharp decrease in fluorescence quantum yield (φ) of [Zn2L2] luminophores. The observed effect is due to the additional coordination processes of the electron-donor molecules X, leading to the formation of solvates [Zn2L2Xn]. The efficiency of fluorescence quenching of [Zn2L2], formed by 3,3′, 2,3′- or 2,2′-bis(dipyrrine)s, is different. Zinc(II) 3,3′-bis(dipyrrometenat) demonstrates the highest sensitivity to fluorescence at the presence of X, as compared with the 2,3′- and 2,2′-analogues. The interpretation of found experimentally linear correlations of φ and calculated on the Stern-Volmer model of the apparent quenching fluorescence constants of helicates from the electron-donating ability of the analytes was given. Indicators of intensity relative change at different wavelengths of the [Zn2L2] fluorescence spectrum were suggested as analytical criterion of the analyte identification. The detection limits of toxicants X by means of [Zn2L2] amounted upto ~ 10–7– 10–5 mol/l in organic media. High specificity of spectral-luminescence characteristics changing in the presence of particular N- and O-containing analytes provides the possibility of using [Zn2L2] helicates as new fluorescent selective chemosensors of the electron-donor molecules in liquid media.