Effect of meso-substituents in the modulation of electronic properties of octaalkylporphine

Abstract

The electronic structure of octaalkylporphine bearing different meso-substituents (chloro, formyl, hydroxymethyl, nitro and amino groups) has been studied using AM1 and MMX methods. The electronic effect induced by the substituents at meso position considerably alters the optical transition energies, one-electron electrochemical redox potentials of the porphine ring and the pK values of the porphines. The experimentally determined values correlate well with the theoretical predictions. The small puckering of the porphine plane induced by the meso-substituent as revealed by MMX calculations plays a minor role in the observed physical properties.