Substituent Effect on Porphyrin Ring Distortion

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10672026
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Physical pharmacy
• Research Institution: Teikyo University
• Principal Investigator: TAKEDA Jun Teikyou University, Faculty of Pharmaceutical Science, Lecturer, 薬学部, 講師 (40197306)
• Project Period (FY): 1998 – 1999
• Keywords: Porphyrin / Nonplanar Porphyrin / Distortion / Substituent Effect

Research Abstract

A series of porphyrin with meso-(2,6-difluoro- or dichlorophenyl) substituents has been synthesized by mixed condensation of pyrrole, diphenylpyrrole, and 2,6-difluoro- or 2,6-dichlorobenzaldehyde. The porphyrins reported here are abbreviated as follows: tetraaryl-lporphrins (TXPP), hexaarylporphyrins (HXPP), trans-octarylporphyrins (trans-OXPP), cis-octarylporphyrins (cis-OXPP), decaarylporphyrins (DecXPP), and dodecaarylporphyrins (DXPP), where X=F or Cl.
Increase of the phenyl substituents have large effect on the UV-visible spectra, gradually red-shifting the Soret bands in the order of TXPP<HXPP<trans-OXPP,cis-OXPP<DecXPP<DXPP. However, the magnitude of the red shift is different between X=F series and X=Cl series. It is tempting to suppose that the magnitude of porphyrin ring distortion is different between X=F seris and X=Cl seris. It is possible that interaction between lone pair of fluorin atoms and porphyrin π orbitals reduce the porphyrin ring distortion.
From the acid-base properties of these porphyrins, it is supposed that conjugation between porphyrin ring and meso-phenyl ring has influence upon the porphyrin ring distortion. Furthermore, an unusual stability in the acid monocation state of TXPP (X=F and X=Cl) is observed from the acid-base titration experiments.