Synthesis, Crystal Structure and Photoluminescence of a Blue-emitting Dinulear Copper Complex

A binuclear cuprous complex [Cu(mu-I)(NP)](2)center dot CH2Cl2 (1, NP = 1-(2-(diphenylphosphino) phenyl)-3,5-dimethylpyrazole) was synthesized and characterized by elemental analysis, NMR, UV-Vis and X-ray single-crystal structure analysis. It crystallizes in triclinic space group P (1) over bar with a = 9.2838(6), b = 12.2672(7), c = 12.4033(7) angstrom, alpha = 114.941(6), beta = 108.707(5), gamma = 91.717(5)degrees, V = 1190.51(12) angstrom(3), Z = 1, M-r = 1178.58, D-c = 1.644 g/cm(3), F(000) = 582, mu = 13.232 mm(-1), GOOF = 1.016, the final R = 0.0384 and wR = 0.1015 for 4145 observed reflections with I > 2 sigma(I). The Cu atoms in the complex are four-coordinated and adopt a distorted tetrahedral coordination geometry. In the solid state, the complex exhibits blue photoluminescence with a peak maximum of 468 nm, a decay time of 9 mu s, and a photoluminescence quantum yield of 16.8% at room temperature, respectively. The studies of varied temperature emission spectra and decay behaviours of the complex indicate that the complex displays thermally activated delayed fluorescence (TADF) at room temperature. The results of experimental and DFT calculations suggest that the excited states in the solid state are of (M+X+L) LCT character.