Trinuclear copper(I)-halide/pseudohalide complexes containing carbon-rich alkynyl functionalized iminopyridine ligand: Synthesis, characterization, luminescence and NLO properties

A new series of trinuclear copper(I) complexes, specifically [Cu₃(L₁)(PPh₃)₃X₃] (1a-d) and [Cu₃(L₂)(PPh₃)₃X₃] (2a-d), have been synthesized by reacting copper salts with iminopyridine ligands in the presence of triphenylphosphine, where X represents Cl, I, N₃, or NCS. This work outlines our synthetic methods and successes, along with detailed spectroscopic and electronic characterizations of the resulting compounds. A comparison between halides and pseudohalides was conducted using thermal and electrochemical analyses. The thermogravimetric profiles clearly demonstrate that halide complexes are less thermally stable than pseudohalide complexes. The complexes demonstrated thermal stability and exhibited quasireversible redox behaviour typical of the Cu(I)/Cu(II) couple. At room temperature, the compounds showed luminescence in the red region, with varying electron-donating and quenching effects depending on the halides and pseudohalides. Furthermore, the second harmonic generation (SHG) efficiency of the complexes was evaluated using the Kurtz-powder method, indicating their promising potential as nonlinear optical materials.