SOLVENT AND ACIDITY DEPENDENCE OF THE ABSORPTION AND FLUORESCENCE OF COUMESTROL

摘要: — The UV absorption and fluorescence of the plant estrogen coumestrol (1) are markedly dependent on solvent acidity. In neutral non-aqueous solvents, emission occurs from uncharged first excited singlet state. aqueous solutions 1, five species—the form, mono- dianions, dications—were found characterized by their absorptions, (including lifetimes quantum yields), pK's ground states. The assignments based absorption, pK(*) data dimethyl ether (2), 3-phenyl-7-hydroxy coumarin (3), 34′-hydroxyphenyl (4), appropriate model compounds literature. Variations in oF and, consequently, τF values ascribed to state proton transfer processes. Fluorescence yields as high ca. 0.7 most organic solvents certain pH ranges should render fluorimetry a suitable method for quantitative assays this which is responsible ‘clover disease’ sheep.