Fluorenones substituted with cis- and trans-styryl and phenylethynyl groups at C-l, C-2, and C-4 were synthesized, as were the trans-2- and trans-4-(3,4-dimethoxystyryl) and beta-methyl-2-styryl derivatives. The static absorption and fluorescence spectra of these compounds were measured, as were their redox potentials in acetonitrile. Transient spectra in a range of solvents were obtained on a microsecond time scale. The compounds showed marked solvent-dependent behavior. In solvents of low polarity, the principal photochemical process for the styryl derivatives is cia-trans isomerization via triplet intermediates. In polar solvents, singlet processes become more important, including photoionization from upper excited states. There are also significant regiochemical differences. The triplets from the 2-substituted fluorenones have microsecond lifetimes and lambda(max) values in the 400-500-nm range, indicating that they have a trans configuration. By contrast, 1- and 4-substituted fluorenones give rise to triplets with much smaller lifetimes and lambda(max) values, suggesting that their predominant configuration is perpendicular. There are analogous differences in the spectra of radical ions produced by photoionization. Those from the 2-derivatives have larger lambda(max) values than those from the 1- and 4-derivatives. The photo- and electrochemical data support the thesis that the fluorenone/side-chain interactions are weaker in the 2- than in the 1- and 4-derivatives.