Spectral and photophysical properties of cytisine in acetonitrile - Theory and experiment.

Spectral and photophysical properties of (-)-cytisine that is used as a smoking cessation aid, and which derivatives are promising tools in a treatment of neurological diseases, were investigated in acetonitrile, non-specifically interacting solvent with a polarity similar to water. The two chair conformers of cytisine were found the most stable in the ground state S and the lowest excited singlet state S(π,π*), wherein axial one was characterized by a significantly larger abundance, fluorescence lifetime 0.15 ns and fluorescence quantum yield 0.008. The S(π,π*) excited state of both cytisine conformers deactivated almost exclusively via internal conversion.