Heteroleptic Cu(I) complexes bearing methoxycarbonyl-imidoylindazole and POP ligands – an experimental and theoretical study of their photophysical properties

Four new mixed ligand Cu(I) complexes bearing methoxycarbonyl imidoyl-indazole and bis[2-(diphenylphosphino)-phenyl]ether (POP) ligands were synthesized and characterized by variable-temperature NMR, FT-IR, EA and HRMS. For three of them, the molecular structures were obtained by X-ray diffraction analysis. The electrochemical and absorption–emission properties of all the complexes were investigated by using cyclic voltammetry, UV-Vis spectroscopy, and spectrofluorometric measurements in a CH2Cl2 solution at room temperature and in different solid-state matrices. In addition, quantum chemical computations were performed to gain insight into their electronic and photophysical properties. The complexes showed an MLCT band, which is more influenced by the position of the electron-withdrawing methoxycarbonyl substituent in the indazole ring rather than by the p-extension introduced by the alkene moiety. Besides, all the complexes were found to be weak emitters in the CH2Cl2 solution while they were brighter emitters in the solid-state.