Solvent-dependent fluorescence lifetimes of estrone, 17β-estradiol and 17α-ethinylestradiol

The fluorescence lifetimes of the estrogens, estrone, 17β-estradiol and 17α-ethinylestradiol, were studied in various solvents. The fluorescence lifetimes of 17β-estradiol and 17α-ethinylestradiol decreased from 4.7 to 0.9 ns as the solvent hydrogen bond accepting ability increased, in good agreement with other phenolic molecules. Estrone's two fluorescence bands had distinct lifetimes, with the 304 nm band having a lifetime shorter than 200 ps, reflecting efficient energy transfer to the carbonyl group, which had lifetimes ranging from 4.4 to 4.9 ns depending on the solvent. Solvent effects on the (1) ππ*, (1) πσ* and (1) nπ* states that are relevant to estrogen photophysics can adequately explain these trends. The solvent dependence on the excited states of these potent endocrine disruptors has significant implications for their photochemistry.