NMR研究N-甲基咪唑与双过氧钒配合物的相互作用

为探讨过氧钒配合物上有机配体对反应平衡的影响, 在模拟生理条件下(0.15 mol/L NaCl溶液), 应用多核(¹H, ¹³C和⁵¹V)多维(COSY) NMR以及变温技术等谱学方法研究双过氧钒配合物OV(O₂)₂LL']ⁿ? n＝1～3, LL'＝oxalate (缩写为oxa)、picolinate(缩写为pic)、bipyridine(缩写为bipy)和1,10-phenanthroline(缩写为phen), 与它们配位的含钒物种分别缩写为bpV(oxa), bpV(pic), bpV(bipy)和bpV(phen)]与N-甲基咪唑(缩写为N-Me-Im)的相互作用, 实验结果表明N-Me-Im与4种双过氧钒配合物的反应活性从强到弱的顺序为: bpV(oxa)＞bpV(pic)＞bpV(bipy)＞bpV(phen). 研究表明金属中心上配体的配位能力和空间位阻都对反应平衡产生较大的影响, 同时竞争配位的结果导致新的过氧物种OV(O₂)₂(N-Me-Im)]^?的生成, 而利用上述谱学方法则有助于揭示此类相互作用体系的反应过程和配位方式.

NMR Studies on Interactions between Diperoxovanadate Complexes and 1-Methylimidazole

To understand the effects of organic ligands of the diperoxovanadate complexes on the reaction equilibrium, the interactions between a series of diperoxovanadate complexes OV(O₂)₂LL']ⁿ? n＝1～3; LL'＝oxalate, abbr. oxa; picolinate, abbr. pic; 2,2'-bipyridine abbr. bipy; and 1,10-phenanthroline, abbr. phen. The corresponding peroxovanadate species abbreviate bpV(oxa), bpV(pic), bpV(bipy), and bpV(phen)] and 1-methylimidazole (abbr. N-Me-Im) in solution were explored using multinuclear (¹H, ¹³C, and ⁵¹V) magnetic resonance, COSY, and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological conditions. The experimental results indicated the activity order of these four complexes with 1-methylimidazole as follows: bpV(oxa)＞bpV(pic)＞bpV(bipy)＞bpV(phen). Both the coordinating capability and the steric effect of the organic ligands affect the reaction equilibrium. At the same time, a new six-coordinated peroxovanadate species OV(O₂)₂(N-Me-Im)]^? is formed due to the competitive coordination.