Molecular complexation of meso-tetraphenylporphyrins with SO 2

Abstract

When para-substituted meso-tetraphenylporphyrins were reacted with SO 2, only 2:1 (donor:acceptor) molecular complexes were produced. 1H NMR, IR, UV–vis and elemental analysis indicated that the porphyrins act as electron donors and that two SO 2 molecules (as electron acceptors) are bound to the lone electron pairs of the pyrrolenine nitrogens in the porphyrin. Two d orbitals of the sulfur atoms accept the nitrogen lone pairs and the two SO 2 molecules are located above and below the porphyrin. There are two hydrogen bonds present between two pyrrole NH and SO 2 molecules.