Air- and Water-Stable Heteroleptic Copper (I) Complexes Bearing Bis(indazol-1-yl)methane Ligands: Synthesis, Characterisation, and Computational Studies

Abstract

A series of four novel heteroleptic Cu(I) complexes, bearing bis(1H-indazol-1-yl)methaneanalogues as N,N ligands and DPEPhos as the P,P ligand, were synthesised in high yields undermild conditions and characterised by spectroscopic and spectrometric techniques. In addition, theposition of the carboxymethyl substituent in the complexes and its effect on the electrochemical andphotophysical behaviour was evaluated. As expected, the homoleptic copper (I) complexes with theN,N ligands showed air instability. In contrast, the obtained heteroleptic complexes were air- andwater-stable in solid and solution. All complexes displayed green-yellow luminescence in CH2Cl2at room temperature due to ligand-centred (LC) phosphorescence in the case of the Cu(I) complexwith an unsubstituted N,N ligand and metal-to-ligand charge transfer (MLCT) phosphorescence forthe carboxymethyl-substituted complexes. Interestingly, proper substitution of the bis(1H-indazol1-yl)methane ligand enabled the achievement of a remarkable luminescent yield (2.5%) in solution,showcasing the great potential of this novel class of copper(I) complexes for potential applications inluminescent devices and/or photocatalysis.