β-Tetrasubstituted meso-Tetra(4′-n-butylphenyl)porphyrins and Their Metal Complexes: Synthesis and Structural Properties

A new family of beta-tetrasubstituted porphyrins, 2,3,12,13-tetra[phenylethynyl (PE)/4-methoxyphenyl (4 ''-CH3OPh)/4-carboxy methylesterphenyl (4 ''-CH3CO2Ph)]-5,10,15,20-tetrakis( 4'-n-butylphenyl) porphyrin, H2T(4'-BuPh) P(R)(4) and their metal (Co-II, Cu-II and Zn-II) complexes were synthesized using H2T(4'-BuPh) PBr4 as the precursor. These porphyrins show red-shifted absorption bands and follow the nature of the beta-pyrrole substituent, R: PE > Br > 4 ''-CO2CH3Ph approximate to 4 ''-OCH3Ph. Crystal structures of MT(4'-BuPh) P(PE)(4) (M = 2H, Co-II, Cu-II and Zn-II) derivatives were determined by single-crystal XRD and they are isomorphous. The normal coordinate structure decomposition analysis of these structures reveal a slight wave-type of distortion of the macrocycle. Electrochemical redox properties of these derivatives show an anodic shift in potentials relative to their metallotetraphenyl-porphyrins (MTPPs), and this has been ascribed mainly to the electronic effect of the substituents.