Influence of nonplanarity and extended conjugation on porphyrin basicity

Inorg Chem. 2002 Dec 30;41(26):6944-6. doi: 10.1021/ic0260522.

Abstract

Thermodynamic basicities of several new nonplanar water soluble tetraaryltetracyclohexano- (Ar(4)TCHP) and tetraaryltetrabenzoporphyrins (Ar(4)TBP) have been measured and correlated with their structural parameters. While the degrees of nonplanarity in these porphyrins are similar, Ar(4)TCHPs exhibit significantly higher basicities than Ar(4)TBPs and than planar tetraarylporphyrins. Low basicities of distorted Ar(4)TBPs are believed to be due to extended pi-conjugation, which causes delocalization of the core electron density in these porphyrins and reduces negative charges at the protonation site.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Crystallography, X-Ray
  • Electrochemistry
  • Hydrogen-Ion Concentration
  • Models, Chemical
  • Molecular Conformation
  • Molecular Structure
  • Porphyrins / chemistry*
  • Thermodynamics

Substances

  • Porphyrins