Dimerization in TMPA-Based Copper(I) Complexes: Implications for Redox Kinetics and Thermodynamics

Copper complexes of tris(2-pyridylmethyl)amine (TPA, TMPA, or TPMA) are widely studied for their redox activity and catalytic versatility. This study investigates solvent-dependent speciation of copper(I)-TMPA complexes, revealing a monomer-dimer equilibrium in solution. Using electrochemical analysis, variable-temperature NMR spectroscopy, and X-ray crystallography, we identify an embraced dimer with a lower reduction potential and faster electron transfer than the monomer. Notably, while the monomer displays strong solvent dependence, the dimer's redox properties remain largely invariant, reflecting its intrinsic stability.