Influence of symmetry on the vibrational spectra of Zn(TPP), Zn(TPC), and Zn(TPiBC)

To evaluate the effects of sequential pyrrole ring reduction, we have examined the vibrational spectra of tetracoordinate Zn(II) complexes of meso-tetraphenylporphyrin [Zn(TPP)], meso-tetraphenylchlorin [Zn(TPC)], and meso-tetraphenylisobacteriochlorin [Zn(TPiBC)]. The phenyl substituents of these macrocycles fall into distinct symmetry classes; for Zn(TPP), all four phenyl groups are equivalent; for Zn(TPC), the phenyl groups are of two different types; and for Zn(TPiBC), there are three types of phenyl substituent