Investigation of Acidic and Coordination Properties of Octabromo-Substituted Porphyrins in the System of 1,8-Diazabicyclo[5,4,0]unde-7-ene-Acetonitrile

Abstract

Acidity and metal ion coordination are described for three porphyrin derivatives, different in their macrocycle conformation and electronic substitution effects due to bromine substitution in pyrrole rings and trifluorometyl or phenyl groups in meso-positions. Combination of these facts allows modulating both steric and electronic effects on the macrocycle π-conjugated system. The role of electronic substitution effects in the macrocycle deprotonation and metal ion complex formation is found dominating with comparable resonance and inductive contributions, whereas non-planar conformation of reactive species contributes to the reaction rates to a lesser extent. The interaction of two single-electron (a_1ue_g) and (a_2ue_g) configurations is studied as a function of non-planar distortions of the molecular structure for the three tetrapyrrole compounds. The additive influence of disturbing factors on the configuration interaction of single-electron (a_1ue_g) and (a_2ue_g) configurations in the tetrapyrrole macrocycle is demonstrated.