Synthesis and properties of Zn-porphyrin with bipyridine-terminated side chains: large conformational change induced by metal complexation

Zinc porphyrin (1) containing 2,2′-bipyridyl units at the peripheral ends of both conjugated and alkyl side chains was prepared. Upon addition of Fe(II), the three bipyridyl terminals at both ends bind to Fe(II)s to form 1:2 complex 1·2Fe. The formation of 1·2Fe induced a large conformational change in the alkyl side chains and moderately affected the binding between the zinc porphyrin and an imidazole ligand. These results show that this method is useful for the communication between the porphyrin functional site and the remote metal-binding site.