Synthesis, crystal structure and luminescent properties of a dinuclear copper(I) complex containing 2, 9-di-n-butyl-1, 10-phenanthroline

A new neutral dinuclear copper(I) complex bearing N-ligands 2, 9-di-n-butyl-1, 10-phenanthroline (dnbp), [CuI(dnbp)]2, was synthesized by the reaction of CuI and dnbp in tetrahydrofuran solution. The complex was characterized by single crystal X-ray diffraction, 1H NMR, UV-Vis spectra, and photoluminescence spectra. The results show that the complex consists of a distorted tetrahedral Cu2I2 core, in which two copper(I) ions are linked by two iodo-bridges, and two dnbps chelated with copper(I) ions, respectively. The complex shows small angle of I-Cu-I (106.08°), and long Cu⋯Cu distance (0.3149 nm) which suggests a negligible interaction between two copper ions. These features can be attributed to the bulk steric hindrance of dnbp ligands. The complex belongs to trigonal system with space group of R-3 and cell dimensions a=4.40414(11) nm, b=4.40414(11) nm, c=1.085 92(4) nm, γ=120°, V=18.2411(9) nm3. The complex has a low-energy absorption band ranging from 350 nm to 500 nm in dichloromethane solution, which can be assigned to the metal-to-ligand charge transfer (MLCT) transitions. At room temperature, the complex in the solid state exhibits red photoluminescence with a broad emission band from 550 nm to 800 nm and the maximum peak at 653 nm under excitation at 365 nm. The emission lifetime of the complex is 3.1 μs, and photoluminescence quantum yield is 0.013. The luminescence mechanism of the complex belongs to the phosphorescent emission at the exited state, which is formed by electron charge transition from cuprous ion and halogen to ligand dnbps. At 10 K, the maximum emission peak shifts to 645 nm with narrow spectral band width.