Fluorescence and Absorption Properties of Perylenyl and Perylenoyl Probe Molecules in Solvents and Liquid Crystals

Article abstract of DOI:10.1021/ja00258a021

Light spectroscopic properties of fluorescent derivatives of perylene in solvents lyotropic liquid crystals have been investigated.These were 2,5,8,11-tetra-tert-butylperylene, methyl 4-(3-perylenyl)butyrate, methyl 3-(3-perylenoyl)propionate, 3-(3-perylenoyl)propionic acid, 9-(3-perylenoyl)nonanoic acid, and N-<9-(3-perylenoyl)nonanoyl>sphingosine-1-phosphocholine.The first two compounds are hereafter referred to as perylenyls, while the latter four are named perylenoyls.Absorption and fluorescence spectra and fluorescence lifetimes of the perylenyls are found to be very similar to those of perylene.Both absorption and fluorescence spectraa of the perylenoyls are broadened and red-shifted compared to those of perylene.The fluorescence spectrum is strongly red-shifted with increasing solvent polarity, which is not the case for the perylenyls.Photophysical data of the perylenyl and the perylenoyl molecules in various solvents, micelles, and liquid crystals are given.It is shown that the absorption and fluorescence dipole moments for the S₀ <*> S₁ transitions are parallel in both kinds of chromophores.The orientation of these probe molecules in a macroscopically aligned liquid crystal has been obtained from linear dichroism measurements mand time-resolved fluorescence anisotropy.It is concluded that the orientation of a probe in its electronic ground state may differ from that in the excited state.Information about rotational motions of the different fluorophores solubilized in micelles and liquid crystals was obtained from the fluorescence anisotropy.The fluorescent moiety of the probe undergoes rotational motions locally in the amphiphile aggregate which are typically about 1-3 ns.A slower correlation time ranging from 10 to 40 ns is ascribed to translational diffusion of the fluorophore in the aggregate.