Absorption and Luminescence Spectroscopy of Partially Protonated Dimeric Forms of Porphyrins

A. V. Udaltsov¹

¹School of Biology, Lomonosov Moscow State University, Moscow, 119899 Russia; fax: (095) 939-4945; E-mail: avu@2.physchem.bio.msu.ru

Submitted April 4, 1997; revision submitted June 10, 1997.

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Absorption and luminescence properties of meso-tetra-(p-aminophenyl)porphine (porphyrin II) associated forms exhibiting donor--acceptor type intermolecular interaction of have been studied in solution and in thin films. Absorption properties of partially protonated dimeric forms of meso-tetraphenylporphine (porphyrin I) were investigated in water--dioxane mixtures. Dimerization of the porphyrin I was shown to proceed in the presence of hydrochloric acid with increasing water content. The spectrum of the final product of dimerization corresponded to a doubly protonated dimeric form. The equilibrium constant of protonated porphyrin I dimerization was determined as 1.9·10⁹ M^-1. The similarity of singly protonated dimeric forms of porphyrin I and polymer-bound porphyrin II was proposed on the basis of their split spectra in the Soret region corresponding to the permitted electronic transitions.

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KEY WORDS: porphyrin dimers, interaction with proton, partial protonation, exciton interaction, absorption and fluorescence spectroscopy.

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