Complex of TPPS4 and L-ascorbic acid: Protonation of the porphyrin centre

Abstract

The L-ascorbic acid and TPPS₄ complex in water is treated as a close contact associate (intermolecular distance <0.2 nm). The paper presents the modelling of the structures and electronic excitations of two types of complexes using quantum-chemical methods. In both complexes, L-ascorbic acid acts as a reducing agent. In the second complex [L-ascorbic acid + TPPS₄ + L-ascorbic acid], intermolecular charge transfer occurs. Protonation of the TPPS₄ centre can be realized by connecting two L-ascorbic acid molecules as proton sources. The presence of L-ascorbic acid in the solvent enables an efficient protonation of the primary structure: TPPS₄ → H₂TPPS₄.