Synthesis, Characterization And Photophysical Properties Of Nitrogen Heterocyclic Chelating Ligand Cuprous Complexes

Luminescent copper???complexes have attracted considerable research attention and exhibit good potential as emitters used in organic light-emitting devices?OLEDs?,light-emitting electrochemical cells?LEECs?,and biological systems,because of their intriguing emission properties,the absence of a higher lying metal centred d-d state,and the abundant resource and low toxicity of copper metal.Two mononuclear Cu???complexes,[Cu?mbpy??dppe?]?ClO₄??1?and [Cu?mbpy??dppp?]?ClO₄??CH₂Cl₂?2?,have been synthesized by using 6-methoxycarbonyl-2,2?-bipyridine?mbpy?as N-heterocyclic bidentate chelating ligand and 1,2-bis?diphenylphosphino?ethane?dppe?and 1,3-bis?diphenylphosphino?propane?dppp?as auxiliary ligand.They have been well characterized by elemental analysis,infrared spectroscopy,UV-Vis absorption spectroscopy and single-crystal X-ray diffraction.As revealed by crystal structure analysis,compounds 1 and 2 are all mononuclear Cu???complexes and the central Cu???ion coordinates with two N atoms of the 2,2-bipyridyl ring and two P atoms of bisphosphine ligand to generate a distorted tetrahedral configuration.Complexes 1 and 2 have a weak low-energy absorption band in the 350⁵25 nm region,assigned to charge-transfer transitions with appreciable metal-to-ligand charge-transfer?MLCT?character.A family of new mono-and dinuclear Cu???triphenylphosphine complexes with functionalized 3-?pyrimidine-2-yl?-1,2,4-triazole ligands has been synthesized and characterized.These Cu???complexes exhibit diverse molecular structures,in which the functionalized 3-?pyrimidine-2-yl?-1,2,4-triazole adopts neutral mono-and bis-bidentate chelating coordination modes and mono-anionic bis-bidentate chelating coordination manner with NH deprotonation of the 1,2,4-triazolyl ring.All these Cu???complexes display a relatively weak low-energy absorption in CH₂Cl₂ solution,which is markedly influenced by the substituent on the 1,2,4-triazolyl ring and the coordination mode of 3-?pyrimidine-2-yl?-1,2,4-triazole.These Cu???complexes are all emissive in solution and solid states at ambient temperature,and their luminescence properties can be well modulated via the introduction of one {Cu?PPh₃?₂} moiety and structural modification of 3-?pyrimidine-2-yl?-1,2,4-triazole involving NH deprotonation and the variation of substituent on the 1,2,4-triazolyl ring.It is demonstrated that the introduction of the trifluoromethyl group and the N?H deprotonation have a major influence on the structures and luminescence properties of the resulting Cu???species.The results presented herein might provide some new insights into the design and synthesis of phosphorescent materials of the 1,2,4-triazole-based copper???complexes with potentially high emission efficiency.