POLYMER-BOUND PYRROLE COMPOUNDS .5. ON THE OPTICAL-PROPERTIES OF AN INSOLUBLE POLYSTYRENE MATRIX BEARING DIPYRROLES AND TETRAPYRROLES COVALENTLY ANCHORED

The absorption and fluorescence spectra of samples of variable particle size, consisting of an insoluble polystyrene matrix bearing different covalently attached di- and tetrapyrroles, are studied and compared with solutions of the same chromophores present as their methyl ester derivatives. The specific chromophores consist of xanthobilirubinic acid, N'-methyl xanthobilirubinic acid, bilirubin IX-alpha, biliverdin IX-alpha, mesoporphyrin IX and Zn(II) mesoporphyrin IX, anchored as esters to alpha-4-[(ylmethyl-3-nitrobenzamido)benzyl]-poly(styrene-co-1%-divinylbenzene). The spectral differences observed are: (1) an apparent decrease in the extinction coefficient of the high energy band relative to the low energy band of the verdin and porphyrin chromophores; and (2) variable shifts of the absorption wavelength maxima depending on the specific system. Scattering by the polymer is mainly responsible for the first, but chromophore aggregation also contributes to band shifts. Both phenomena are more important in particles of comparatively larger size, as has been confirmed by comparing spectroscopic properties of micellar and vesicular systems containing the same chromophores. The present systems are interesting because: (1) one can derive qualitative information on several aspects of the polymer matrix itself, such as the interactions of a given site with its immediate surroundings; and (2) they serve as models for investigations of chromophore-imbedded tissue optics, and in general, of energy absorption by dyes in a light-scattering medium.