13C nuclear magnetic resonance studies of porphyrins and related compounds: chlorophyll derivatives

Abstract

¹³ C N.m.r. spectra of the methyl esters of deuteroporphyrin-IX, protoprophyrin-IX, chlorin-e₆, rhodin-g₇, and derivatives of pyromethylphaeophorbide-a have been measured in deuteriochloroform. The introduction of a meso-bromine substituent into the pyromethylphaeophorbide-a system causes large chemical shift changes in the neighbourhood of the substituent which are rationalised in terms of a distortion of the macrocycle. Shift differences found between chlorin-e₆ and rhodin-g₇ trimethyl esters are rationalised in terms of a preferred conformation of the formyl group in the latter. A comparison of our data with previously reported data on chlorophyll-a is made.