Synthesis, Characterization, Properties, and Theoretical Calculation of an Inorganic–Organic Hybrid Mononuclear Copper(II) Complex Containing 3-Hydroxy-2-methyl-quinoline-4-carboxylate

A novel copper complex [CuL(bipy)(H 2 O)]·H 2 O was synthesized by solvothermal reaction and its crystal structure was determined by single-crystal X-ray diffraction technique. (HL = 3-hydroxy-2-methylquinoline4-carboxylic acid; bipy = 2,2′-bipyrdine) The title complex ( 1 ) crystallizes in the orthorhombic system of the Pbca space group, and exists as an isolated mononuclear structure. The intermolecular hydrogen bonds and the strong π···π stacking interactions yield a three-dimensional (3-D) supramolecular network. Solid-state photoluminescence spectrum uncovers that it shows an emission in the pale blue region of the light spectrum. It has remarkable CIE (Commission Internationale de I’Éclairage) chromaticity coordinates of (0.2656, 0.3162), so it may be a very promising color lighting and display converter. Time-dependent density functional theory (TDDFT) calculation reveals that this emission is caused by to the ligand-to-ligand charge transfer (LLCT). Solid-state diffuse reflectance data shows that there is a narrow optical band gap of 1.38 eV. Therefore, it could be probably a candidate for narrow band gap semiconductors. Graphic Abstract A novel copper (II) complex is synthesized via solvothermal reactions, which is characteristic of an isolated structure, at the same time, it displays a wide and intense photoluminescence emission band in the pale blue region and theoretical study reveals that the photoluminescence emission is originated from the ligand-to-ligand charge transfer transition.