Porphyrin substituent regiochemistry, conformation and packing – the case of 5,10-diphenylporphyrin

Abstract

5,10-Disubstituted porphyrins are more recent additions to the family of meso-substituted porphyrins. A crystallographic comparison of 5,10-diphenylporphyrin with the regioisomeric 5,15-disubstituted system reveals striking differences in their conformation. In the free base porphyrins the former uses mainly out-of-plane distortion to alleviate steric strain while in-plane core elongation predominates in the latter. In contrast, the structure of the Cu(II) complex is planar and forms strong π−π aggregates with very small lateral shifts. Macroscopically, the packing is similar to that of porphyrin sponges of the 5,10,15,20-tetraphenylporphyrin type.

Conformational control of cofactors in nature – the influence of protein-induced macrocycle distortion on the biological function of tetrapyrroles

“…31,118,119 Additional effects are altered axial ligand affinities in metal complexes and different orbital interactions with coordinated metals. 6,79,120 This simplified picture also neglects the effects of in-plane distortion, 49,69 which has not been studied to the same detail yet as out-ofplane distortions. Nevertheless, all affected parameters are crucial for the in vivo function of porphyrins, especially with regard to electron and exciton transfer properties.…”