Circularly polarized luminescence studies of the optical activity induced in the europium(III) chelate of 4,4,4-trifluoro-1-(2-thienyl)butane-1,3-dionate through adduct formation with cinchona alkaloids

Abstract

The optical activity induced in the title compound by association with cinchonine, cinchonidine, quinine, and quinidine has been studied by means of circularly polarized luminescence (c.p.l.) spectroscopy. Optical activity was induced in each case, and generally the sign of the induced c.p.l. could be correlated with the absolute configuration of the alkaloid. The intensities of the c.p.l. and total emission spectra indicated that adduct formation was characterized by stereoselectivity; stronger induced chirality was noted when the alkaloid had the S configuration at the hydroxy-carbon. Other spectral features indicated that the presence of the methoxy-group (quinine and quinidine) exerted a secondary influence on adduct formation, presumably through an electronic effect.