Synthesis and crystal structures of five-coordinated β-pyrrole tetra(phenyl/cyano) substituted zinc(II)-tetraphenylporphyrins

Crystal structures of a series of 2,3,5,10,12,13,15,20-octaphenylporphinato zinc(II) complexes with varying axial ligands have been examined to elucidate the role of fifth ligand on the stereochemistry of the porphyrin macrocycle. The nonplanarity of the macrocycle varies in the order, ZnOPP < ZnOPP(pyridine) < ZnOPP(H2O). The electron deficient porphyrin complex of five-coordinated Zn(II), ZnTPP(CN)4(CH3OH) showed enhanced nonplanarity of the macrocycle and it is less than that of ZnOPP(H2O)·TCE complex. Normal coordinate structure decomposition analysis of the out-of-plane displacement of the porphyrin ring in these structures revealed negligible wave distortion in planar four-coordinated ZnOPP and saddle, ruffled and domed distortions in other five-coordinated Zn(II)-porphyrins. The pronounced distortion of the macrocyclic ring in these structures is possibly due to the axial ligand, solvate and/or intermolecular interactions compared to steric crowding of the peripheral substituents.

Graphical abstractCrystal structures of four and five-coordinated 2,3,12,13-tetra(phenyl/cyano)-5,10,15,20-tetraphenylporphinato zinc(II) complexes revealed dramatic variation in nonplanarity of the macrocycle and follow the order: ZnOPP < ZnOPP(pyridine) < ZnTPP(CN)4(CH3OH) < ZnOPP(H2O). The normal coordinate structure decomposition analysis of the porphyrin ring in these structures shows mainly saddle, ruffled and domed distortions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► This article reports the synthesis and unique trend in stereochemistry of the macrocycle with the variation in axial ligand of the Zn(II)-porphyrins. ► Crystal structures of four and five-coordinated 2,3,12,13-tetra(phenyl/cyano)-5,10,15,20-tetraphenylporphinato zinc(II) complexes revealed dramatic variation in nonplanarity of the macrocycle and follow the order: ZnOPP < ZnOPP(pyridine) < ZnTPP(CN)4(CH3OH) < ZnOPP(H2O). ► The normal coordinate structure decomposition analysis of the porphyrin ring in these structures shows mainly saddle, ruffled and domed distortions.