Synthesis, characterization, and electrochemical properties of a first-row metal phthalocyanine series

Abstract

The synthesis and characterization of a 3d-metallophthalocyanine series (^OEtPcM; ^OEtPc = 1,4,8,11,15,18,22,25-octaethoxy-phthalocyanine; M = VO, Cr, MnCl, MnN, Fe, Co, Ni, Cu, Zn) is presented. With the exception of ^OEtPcZn, all species were crystallographically characterized, including the protonated (^OEtPcH₂) and partially lithiated (^OEtPcHLi) precursors. The electrochemical behavior of all species – displaying a mix of metal- and ligand-borne redox events – was investigated and tentatively correlated to the structural properties. It was found that non-labile axial metal–ligand substituents (O²⁻, N³⁻) and the use of coordinating solvents heavily influenced the reversibility of the electrochemical events, suggesting that aggregation is a dominant consideration for well-defined electrochemical behavior. We used this data to outline possible design criteria for Pc-based charge carrier applications in the context of redox-flow batteries and energy storage.