Synthesis, crystal structure and photoluminescence of phosphorescent copper (I) complexes containing hole-transporting carbazolyl group

Two mononuclear Cu (I) complexes based on a 2-(2-pyridyl)benzimidazolyl derivative ligand containing the hole-transporting ligand 1-[4-(9-carbazolyl)butyl]-2-(2-pyridyl)benzimidazole (L), [Cu(L)(PPh3)2](BF4) (1) and [Cu(L)(DPEphos)](BF4) (2), where DPEphos is bis[2-(diphenylphosphino)phenyl]ether, were synthesized and characterized by elemental analysis, 1H NMR and FT-IR spectra. The structure of complex 2 was determined by X-ray single crystal analysis. It was demonstrated that the central Cu (I) ion in the complex has a distorted tetrahedral geometry and is tetra-coordinated by the two nitrogen atoms from L ligand and two phosphorus atoms from DPEphos ancillary ligand. The photophysical properties of the complexes were examined by using UV–Vis, photoluminescence spectroscopic analysis. The complexes exhibit weak MLCT absorption bands at 410 and 490 nm, and display strong phosphorescence in the solid states at T = 298 K, which is completely quenched in solution.

Graphical abstractTwo novel copper (I) complexes based on 2-(2′-pyridyl)benzimidazolyl derivative ligand containing hole-transporting carbazole (L), [Cu(L)(DPEphos)](BF4) and [Cu(L)(PPh3)2](BF4), were synthesized and characterized. Among them, [Cu(L)(DPEphos)](BF4) has been structurally characterized by X-ray crystallography. The complexes exhibit strong green–yellow or yellow–orange emissions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two new Cu (I) complexes containing hole-transporting carbazolyl group were synthesized and characterized. ► The complexes exhibit strong phosphorescence in the solid states. ► The complexes could be used as emitting dopants in OLED applications.