Design And Synthesis Of Aza-ring Chelate Ligand Copper (i) Complexes, Structure And Properties

The thesis has been carried out with a goal of obtaining luminescent copper(I) complexes featuring N-heterocycle chelating ligands. A series of mono- and dinuclear copper(I) complexes via the solution reactions of copper salt reagents with N-heterocycle chelate and mono– or bidentate phosphine mixed ligands. The above all Cu(I) complexes have been characterized by single-crystal X-ray diffraction analysis, and their thermal stabilities, spectroscopic properties, and luminescence mechanism have also been investigated.1. Two luminescent dinuclear copper(I) complexes, [(PPh₃)₂Cu(μ-X)₂Cu(PPh₃)], [X = Br (1); Cl (₂)], have been synthesized via the reactions between triphenylphosphine (PPh₃) and cupous halide (CuBr and CuCl) in dichloromethane. In the above systems, via the introduction of the multi-nitrogen heterocycle ligand namely 3, 5-bis(6-(2,2'-pyridyl)pyrazole (HL), two luminescent dinuclear Cu(I) complexes of the HL ligand, [{Cu(PPh₃)X}₂(μ-HL)] (X = I (3); Br (4)), have been isolated. We obtained a novel luminescent dinuclear Cu(I) complexes [Cu₂(μ-dppm)₂(μ-HL)] (NO3)₂ (5) by using cupric nitrate trihydrate and dppm instead of cupous halide and PPh₃, respectively. The above copper(I) complexes have been characterized by using elemental analyses, infrared spectra, electronic absorption spectra, fluorescence spectra, single-crystal X-ray diffraction analyses, and thermogravimetric analyses. It is demonstrated that complexes 1–5 exhibit the good photoluminescence peoperties in the solid state at room temperature. The solid-state emission of complexes 1 and 2 mainly comes from triphenylphosphine ligand coordinating to the metal Cu(I) ions, while the solid-state emission charge-transfer of complexes 3–5 originates from the metal-to-ligand charge-transfer (MLCT) transitions.₂. The mono- and dinuclear Cu(I) complexes [{Cu(PPh₃)₂}₂](μ-pmtz)](ClO4)₂(6) and [CuI(PPh₃)(pmtz)](7), where pmtz is 3-(2-pyrimidinyl)-1,2,4-triazine, have been synthesized and characterized. Single-crystal X-ray diffraction analysis reveals that the pmtz acts as a bis–bidentate ligand in complex 7, whereas in complex 6 the pmtz coordinates as a bis-bidentate chelate, assembling two identical {Cu(PPh₃)₂} moieties into a cuprous dimmer with a triple-decker sandwich structure involving phenyl/pmtz/phenylπ–πinteractions. The UV-Vis spectra of complexes 6 and 7 show low-energy absorptions at 350–550 nm, assigned to the Cu(I) to pmtz MLCT transition, probably mixed with some XLCT character for 7. The absorption of 6 is blue-shifted relative to that of 7 due to the substitution of the iodide of 6 with theπ-acceptor ligand PPh₃. complexes 6 and 7 are non-emissive, both in solution and in the solid state, most likely owing to the electronic effects induced by the additional nitrogen donor of pmtz compared to ₂,₂'-bipyrimidine.3. Two mononuclear compounds [Cu(bmp)(PPh₃)₂]ClO₄ (8) and [Cu(bmp)(dppb)]ClO₄ (9) were synthesized from the reaction of copper perchlorate with 2-(6-methylpyridine) benzimidazoly (bmp) and phosphine mixed ligands such as triphenylphosohine (PPh3) and 1,4-bis(diphenylphosphino)butane (dppb). In UV-Vis spectra of compounds 8 and 9, the multiple absorption bands at the range 235–350 nm are originated from theπ–π* transitions inside the ligands, while the low-energy absortion bands located at the range 350–450 nm are assigned to the metal-to-ligand charge-transfer (MLCT) transitions. Complexes 8 and 9 exhibit relatively strong emission in both solution and solid states, ascribed to the metal-to-ligand charge-transfer (MLCT) transitions. Moreover, it is found that the maximum of the emission band is related to the P–Cu–P bond angle of the corresponding complexes, and the emission band shows a blue-shifting with the increasing of the P–Cu–P bond angle.