Steady-state and time-resolved fluorescence anisotropies of hypericin, hypocrellin, and five other analogues have been measured. The steady-state excitation anisotropies for each of these compounds has a broad minimum at ∼400 nm with a negative value. At the blue and red edges of the spectrum the value of the anisotropy is positive. Time-resolved fluorescence anisotropy measurements were performed for both hypericin and hypocrellin at excitation wavelengths of 300 and 570 nm. The limiting anisotropies are in excellent agreement with the corresponding steady-state values. These results are discussed in terms of the directions of the transition dipoles connecting the ground state to various excited states. The role of conformational isomers and tautomers in the ground and excited states is also considered. 17, 1997; In Final Form: NoVember 17, 1997 Steady-state and time-resolved fluorescence anisotropies of hypericin, hypocrellin, and five other analogues have been measured. The steady-state excitation anisotropies for each of these compounds has a broad minimum at ∼400 nm with a negative value. At the blue and red edges of the spectrum the value of the anisotropy is positive. Time-resolved fluorescence anisotropy measurements were performed for both hypericin and hypocrellin at excitation wavelengths of 300 and 570 nm. The limiting anisotropies are in excellent agreement with the corresponding steady-state values. These results are discussed in terms of the directions of the transition dipoles connecting the ground state to various excited states. The role of conformational isomers and tautomers in the ground and excited states is also considered.

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We present novel insights into the interplay between excited state intramolecular proton transfer (ESIPT) and spin-orbit coupling (SOC) in the 10-Hydroxy-11H-benzo[b]fluoren-11-one (10-HHBF) molecule, utilizing the time-dependent density functional theory approach...