Syntheses, structural, theoretical studies and thermal behaviors of two luminous copper(I) halide complexes of dipyrido[3,2-f:2,3-h]-quinoxaline

• Two new luminous copper(I) complexes containing triphenylphosphine and dipyrido[3,2-f:2,3-h]-quinoxaline have been synthesized for the first time.
• Their structures were studied by X-ray, TGA, fluorescence and IR.
• Complexes 1 and 2 display a favorable pairwise π–π stacking.
• The vertical electronic excitation energies of 1 and 2 in ethanol solution were obtained through TD-DFT/PCM calculations.

Two new copper(I) complexes containing PPh3 and Dpq, [Cu(Dpq)(PPh3)X] (X = I (1); Br (2)), {PPh3 = triphenylphosphine, Dpq = dipyrido[3,2-f:2,3-h]-quinoxaline} have been synthesized and characterized by elemental analysis, IR spectroscopy, X-ray single crystal analysis, fluorescent analysis, thermal gravimetric analysis and DFT calculations. Single crystal X-ray diffraction analysis reveals that complexes 1 and 2 are mononuclear with similar structures and display a favorable pairwise π–π stacking. Density functional theory and time-dependent density functional theory calculations at the B3LYP/LanL2DZf+6-31G∗ level were performed on both complexes to rationalize their experimental absorption spectra. In addition, 1 and 2 exhibit intense luminescence in ethanol solution at room temperature.