Journal of Physical Chemistry, Vol.99, No.12, 4317-4323, 1995
Spectroscopic Properties of Hypericin in Solution and at Surfaces
The absorption and fluorescence spectra of hypericin were studied in a wide variety of organic solvents. Three distinct types of hypericin absorption spectra were observed and are representative of hypericin in monomeric, aggregated, and protonated states. The shifts in the absorption maxima of the two transitions in the visible region of the spectrum are related to the solvent’s hydrogen bonding donor ability in the case of protic solvents and to the solvent’s polarizability in the case of aprotic solvents. In addition, the surface-enhanced resonance Raman scattering (SERRS) spectra of neutral hypericin, protonated hypericin, and deprotonated hypericin were studied in order to corroborate previously assigned electronic transition dipoles. The SERRS data support the assignment of the S-1 transition as polarized through the short axis of the hypericin skeleton and the St transition as polarized through the carbonyl axis of the molecule.
Keywords:TIME-RESOLVED FLUORESCENCE;STENTOR-COERULEUS;PHOTODYNAMIC-ACTION;PIGMENT HYPERICIN;PHOTORECEPTOR;PSEUDOHYPERICIN;INACTIVATION;MITOXANTRONE;AGENTS;VIRUS