Asymmetrically β-Substituted Porphyrins and Chlorins: Synthesis, Spectroscopic, and Electrochemical Redox Properties

Abstract

Asymmetrically β-substituted chlorins, viz. 2,3-bis(dicyanomethyl)-meso-tetraphenylchlorin (1), diethoxycarbonylcyclopropano-meso-tetraphenylchlorin (2) and 2-ethylacetoacetanato-meso-tetraphenylporphyrin (3), and their metal (Ni(II), Cu(II) and Zn(II)) complexes have been synthesized and characterized by various spectroscopic techniques. Cyclic voltammetric (CV) studies were carried out for these porphyriniods in CH2Cl2 containing TBAPF6 as supporting electrolyte. The first ring redox potentials of 1, 2 and their metal complexes are anodically shifted (0.58 - 0.30 V) as compared to meso-tetraphenylchlorin (H2TPC) due to electron withdrawing nature of malononitrile and diethyl malonate substituents. Notably, Ni(II) complex of 3 exhibited metal centered oxidation (NiII/NiIII) due to extended conjugation and electronic nature of β-subtituent.