Premium
Effect of pH on the Fluorescence and Absorption Spectra of Hypericin in Reverse Micelles ¶
Author(s) -
Chowdhury P. K.,
Ashby K. D.,
Datta A.,
Petrich J. W.
Publication year - 2000
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1562/0031-8655(2000)0720612eopotf2.0.co2
Subject(s) - chemistry , deprotonation , micelle , hypericin , absorbance , fluorescence , absorption (acoustics) , photochemistry , heptane , titratable acid , chromatography , organic chemistry , aqueous solution , biochemistry , medicine , ion , physics , quantum mechanics , acoustics , pharmacology
The well‐characterized, monodispersed nature of reverse micelles formed by sodium bis(2‐ethylhexyl)sulfosuccinate/heptane and their usefulness in approximating a membrane‐like environment have been exploited to investigate the effect of pH and water pool size on the photophysical properties of hypericin (Hyp). Our measurements reveal two titratable groups of pK a ∼1.5 and ∼12.5. These are assigned to the HypH + /Hyp equilibrium (the deprotonation of a carbonyl group) and the Hyp − /Hyp 2− equilibrium (the deprotonation of a peri hydroxyl group). The low‐energy absorbance maxima of HypH + , of Hyp and Hyp − and of Hyp 2− are 583, 594 and 613 nm, respectively. Neither at pH 13 nor at 1 M HCl is the system entirely in the Hyp 2− or the HypH + forms. Ours is the first study of Hyp in reverse micelles as well as the first time‐resolved study of Hyp as a function of pH.