Structural investigation of nickel(II) bacteriopetroporphyrins related to the bacteriochlorophylls c and d: evidence for localized conformational distortion in the c-series

The structures of two bacteriochlorophyll c and one bacteriochlorophyll d related to the bacteriochlorophylls of Chlorobiaceae and Chloroflexaceae are determined. The three compounds show S4-ruffling effect common in Ni(II) porphyrins and all have four alternating meso-carbons above and below the nitrogen plane and out-of-plant rotations of the pyrrole rings. The deviations from the least-squares plane of the four nitrogen atoms in all the compounds revealed a localized distortion at the methyl substituent at C(20) position.