Synthesis of antipodal β-trisubstituted meso-tetraphenylporphyrins and the crystal structure of hexaphenylporphinatozinc(II) bispyridinate complex

Abstract

A series of antipodal β-trisubstituted meso-tetraphenylporphyrins, H2TPP(R)3 (R = CH3, Ph, PE, and 2′-thienyl) derivatives and their metal (Cu(II) and Zn(II)) complexes were synthesised and characterised by electronic absorption, 1H NMR spectroscopy and mass spectrometry. The magnitude of the red-shift in absorption bands in these free-base porphyrins depend on the nature of the substituent and follow the general trend: PE >2′-thienyl > Br > Ph > CH3. Synthesis, characterisation and crystal structure of 2,5,10,12,15,20-hexaphenylporphinato zinc(II) bispyridinate, ZnTPP(Ph)2(Py)2 complex is also reported. It shows planar geometry of the porphyrin ring with two β-phenyls located at the antipodal 2,12-pyrrole positions. The two axially coordinated pyridine ring planes are oriented almost parallel to each other and they are in staggered conformation relative to opposite pyrrolic nitrogens. The normal-coordinate structural decomposition analysis of the ZnTPP(Ph)2(Py)2 complex revealed slight wave distortion of the macrocycle.