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1 November 2000 Effect of pH on the Fluorescence and Absorption Spectra of Hypericin in Reverse Micelles
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Abstract

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 pKa ∼1.5 and ∼12.5. These are assigned to the HypH /Hyp equilibrium (the deprotonation of a carbonyl group) and the Hyp/Hyp2− equilibrium (the deprotonation of a peri hydroxyl group). The low-energy absorbance maxima of HypH , of Hyp and Hyp and of Hyp2− are 583, 594 and 613 nm, respectively. Neither at pH 13 nor at 1 M HCl is the system entirely in the Hyp2− 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.

P. K. Chowdhury, K. D. Ashby, A. Datta, and J. W. Petrich "Effect of pH on the Fluorescence and Absorption Spectra of Hypericin in Reverse Micelles," Photochemistry and Photobiology 72(5), 612-618, (1 November 2000). https://doi.org/10.1562/0031-8655(2000)072<0612:EOPOTF>2.0.CO;2
Received: 2 May 2000; Accepted: 1 August 2000; Published: 1 November 2000
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