Dinuclear and Tetranuclear Copper(I) Triazenido Complexes: Structural Insights and Electrochemical Properties

We report the synthesis and structural characterization of a series of bi- and tetranuclear Cu(I) complexes based on symmetrical triazene ligands. These ligands, which feature a central -N═N-N- backbone for metal coordination, offer tunable electronic and steric environments through substitution at the aryl ring with electron-donating and electron-withdrawing groups. A library of triazene ligands was prepared via diazotization and coupling strategies, followed by metalation under mild conditions to afford discrete Cu(I) assemblies. X-ray crystallographic analysis of six representative examples revealed both dinuclear and tetranuclear Cu(I) cores exhibiting short Cu···Cu distances (<2.6 Å), consistent with intramolecular cuprophilic interactions. DFT and experimental studies indicate the preference for dinuclear or tetranuclear clusters appears to be influenced by ligand substitution patterns and reaction conditions, highlighting key structural factors that control assembly of multinuclear Cu(I)-triazenido systems. Electrochemical studies, conducted in the absence and presence of acid, reveal substituent-dependent redox behavior across the series. Analysis of acid-free data demonstrates systematic modulation of Cu-centered redox processes by variations in ligand substitution, while proton-responsive current enhancement is observed under acidic conditions. These results establish structure-property relationships linking ligand substitution, nuclearity, and electronic properties in multinuclear Cu(I) complexes.