Electrochemical reduction of bis(β-diketones): 1,10-di(α-cyclohexanone)decane-1,10-dione and 3,14-diacetylhexadecane-2,15-dione. Characterization and electron paramagnetic resonance properties of their electrogenerated mononuclear copper(<scp>II</scp>) complexes
作者:Agus Kuncaka、Alain Louati、Maurice Gross、Catherine Haubtmann、Maxime Bernard、Jean-Jacques André、Yves Frère、Jean-Pierre Brunette
DOI:10.1039/ft9938904299
日期:——
The preparation and characterization of the bis(β-diketone) 1,10-di(α-cyclohexanone)decane-1,10-dione (H2L11) and 3,14-diacetylhexadecane-2,15-dione (H2L22) ligands, are reported. A direct electrochemical generation of CuIIL complexes is achieved. The electrochemical reductions of 1 and 2 have been investigated in tetrahydrofuran at a dropping mercury electrode. Voltammetric, coulometric and UVâvisible results indicate that their two-electron reduced form ultimately generates the corresponding anions (L1)2â and (L2)2â. The reaction of (L1)2â and (L2)2â with CuII trifluoromethanesulfonate gives the corresponding 1 : 1 complexes (CuIIL11â²) and (CuIIL22â²). In frozen-chloroform solutions, the latter complexes show well resolved electron paramagnetic resonance (EPR) spectra. The observed hyperfine splittings due to the nuclear spin I= 3/2 of the copper ion allow the determination of the following magnetic parameters: gâ¥= 2.304, gâ¥= 2.062, aâ¥= 142 à 10â4 cmâ1, aâ¥= 25.2 à 10â4 cmâ1 for 1â², and gâ¥= 2.277, gâ¥= 2.048, aâ¥= 160 à 10â4 cmâ1, aâ¥= 22.4 à 10â4 cmâ1 for 2â². The UVâVIS absorption spectra and the results obtained from the experimental and simulated EPR spectra indicate that the complex 1â² has a square-planar geometry whereas 2â² is a square-planar distorted complex.
报道了双(β-二酮)1,10-二(α-环己酮)癸烷-1,10-二酮(H2L11)和3,14-二乙酰基十六烷-2,15-二酮(H2L22)配体的制备与表征。实现了CuIIL配合物的直接电化学生成。在滴汞电极上,于四氢呋喃中研究了1和2的电化学还原过程。伏安法、库仑法和紫外-可见光谱结果表明,它们的两电子还原产物最终生成了相应的阴离子(L1)2–和(L2)2–。(L1)2–和(L2)2–与CuII三氟甲磺酸盐反应得到相应的1:1配合物(CuIIL11')和(CuIIL22')。在冷冻氯仿溶液中,后两种配合物显示出分辨良好的电子顺磁共振(EPR)谱图。由于铜离子核自旋I=3/2引起的超精细分裂,可以确定以下磁参数:对于1',g⊥=2.304,g‖=2.062,a⊥=142×10–4 cm–1,a‖=25.2×10–4 cm–1;对于2',g⊥=2.277,g‖=2.048,a⊥=160×10–4 cm–1,a‖=22.4×10–4 cm–1。紫外-可见吸收光谱以及实验和模拟EPR谱图的结果表明,配合物1'具有平面正方形几何构型,而2'是扭曲的平面正方形配合物。