Novel nitrothien-2-ylporphyrins: Spectroscopic and electrochemical investigation on the role of conformation of porphyrins in their reactions

An efficient and facile methodology for the regioselective nitration of two series of thien-2-ylporphyrins, 5,10,15,20-tetrakis(thien-2-yl)porphyrinato nickel(II) and 5,10,15,20-tetrakis(5-methylthien-2-yl)porphyrinato nickel(II) is presented. X-ray crystal structures of a few of the synthesized compounds are given. The effect of relative orientation of meso thien-2-yl rings with the porphyrin central π-system in determining the site of electrophilic substitution on these molecules is explained through electronic spectroscopy and cyclic voltammetry. The results indicate the important role of conformation of the porphyrin in their subsequent reactions.