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A series of copper(I)-diimine complexes, [Cu(bdpp)(bpy)]BF4 (1), [Cu(bdpp) (pen)]BF4 (2), [Cu(bdpp)(damp)]BF4 (3), [Cu(bdpp)(pen)]BF4 (4) (bdpp = 4,6-bis-(biphenyl phosphino) phenoxazine, bpy = 2,2′-bipyridine, phen = 1,10-Phenanthroline, dmp = 2,9-dimethyl-1,10-phenanthroline, bphen = 4,7-diphenyl-1,10-phenanthroline), have been synthesized and characterized by IR, 1H NMR, 31P NMR, XRD and X-ray crystal structure analysis. Structural analysis reveals that each Cu+ in 1–4 is four-coordinated by two N atoms and two P atoms and adopts a distorted tetrahedral geometry. DFT calculations show that the HOMOs in 1–4 are mainly comprised of bdpp and copper d–orbitals, while the LUMOs are mainly dominated by diimine ligands. Calculation of atomic charges indicates that the charges of the central Cu atoms in 1–4 are less than + 1, and the diimine ligands may be the key to the metal charge transfer to the coordinated atom. In 1–4, the maximum phosphorescent lifetimes and quantum yields are up to 349 μs and 22%, respectively. Moreover, complex 3 is used for fabricating the LED device, showing a decent performance with the maximum EQE of 11%.

A mononuclear Cu(I) complex, Cu(dppb)(2,2′-biquinoline)]BF4(1) (dppb = 1, 2-bis(diphenyl phosphino)benzene), has been synthesized and characterized at 100 K, 150 K, 200 K, 250 K and 298 K. The structural analysis reveals that the rise of temperature from 100 K to 298 K leads to the increasement of molecular size, such as the unit-cell parameters and volume, and the change of bond lengths, bond angles, C H…π and π…π interactions. DFT calculations indicate that the HOMO → LUMO energy gap and Mulliken atomic charges are changed by the increase of temperature from 100 K to 298 K, and the component of the HOMOs and LUMOs are barely changed at 100–298 K, which is in accordance with the variation of DOS and PDOS at different temperatures. Meanwhile, the surprising broad blue-yellow excitation bands are observed at 100–298 K and the maximum emission is increasing with the blue shift from 735 nm at 100 K to 685 nm at 298 K. Furthermore, the emission decay time of complex 1 reaches 3 μs at 298 K. In addition, copper(I) complex 1 is used to fabricate the monochromatic LED, which emits a red light.