Raman Spectra of Porphyrins

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Abstract
The spectroscopy of porphyrins has been developing rapidly during the last two decades, this class of compounds being of great biological importance and possessing a number of significant properties. Different spectroscopic techniques, viz., electronic spectroscopy including fine-structure quasiline spectra (Shpolsky effect), infrared spectroscopy, luminescence, flash photolysis, ESR and NMR spectroscopy etc., have been applied to the study of these molecules (see reference 1 for a review). However until recently there were no publications on Raman spectra of porphyrins and related compounds although it is evident that a complete analysis of molecular vibrations is impossible without knowing the Raman frequencies, especially for centrosymmetrical molecules. We have obtained Raman spectra of two porphin derivatives, viz., copper and nickel octamethylporphin 2 which seems to be, together with data on hemoglobin and cytochrome3-5 and on chlorophylls 6, the first observation of Raman spectra of porphyrins. In this paper Raman spectra of several metalloporphyrins are presented including metal complexes of porphin, octamethylporphin, etioporphyrin I, meso-tetraphenylporphin and tetrabenzporphin. For some of them Shpolsky spectra have been obtained and a juxtaposition is made of the two kinds of spectral data concerning the frequencies of molecular no- modss. Also some data of infrared spectra are presented.

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