Unexpected Tricopper(II) Clusters Formation in Tripodal Ligand Framework and Their Application on Click Reaction

ABSTRACT This study describes the synthesis and characterization of a novel tripodal ligand, tris(5‐phenylethyliminopyrrol‐2‐ylmethyl)amine (H 3 tpa PEA ; 1 ), derived from a known scaffold. The ligand was synthesized via Vilsmeier–Haack formylation followed by condensation, with NMR and X‐ray crystallography confirming its C 3 ‐symmetric structure. Two copper complexes were prepared: a tricopper cluster [tpa PEA Cu 3 (μ 3 ‐SO 4 )(μ 3 ‐OH)] ( 2 ) with rare μ 3 ‐SO 4 and μ 3 ‐OH bridging ligands, and [tpa PEA 2 Cu 3 ] ( 3 ) featuring tetracoordinated copper centers. Structural analyses revealed unique geometries and coordination environments, suggesting enhanced reactivity potential. Both complexes catalyzed CuAAC azide–alkyne cycloaddition reactions, with complex 3 demonstrating superior efficiency, achieving complete conversion in 5 min due to its accessible coordination sites. This research enhances understanding of multinuclear copper complex structures and their catalytic functions, emphasizing the crucial influence of ligand design and bridging ligands in maximizing catalytic efficiency.