Self-assembled luminescent Cu(i) tetranuclear metallacycles based on 3,3′-bipyridine ligands

Abstract

3,3′-Bipyridine ligand B was reacted with pre-assembled [Cu₂(μ₂-dppm)₂] Cu(I) bimetallic flexible precursor A according to coordination-driven supramolecular chemistry synthetic principles. Outcomes obtained revealed the necessity to formally introduce bridging halide X ions (X = Cl, Br or I) in order to conduct selectively and successfully coordination-driven supramolecular syntheses. Therefore, [Cu₂(μ₂-dppm)₂(μ₂-X)] bimetallic connecting nodes presenting a potential coordination angle of ca. 120° are generated, which lead upon reaction with connecting ligand B to the selective formation of new tetranuclear metallacycles C_X. These derivatives are luminescent in the solid-state at room temperature with high emission quantum yields and a study of the temperature dependence of their photophysical properties was conducted, suggesting a ligand B centered triplet origin for their luminescence.