取代吡啶与双过氧钒配合物相互作用的NMR和理论研究

为探讨有机配体上取代基团对反应平衡的影响, 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(DOSY)以及变温NMR技术研究双过氧钒配合物OV(O2)2(D2O)]－/OV(O2)2(HOD)]－(简写为bpV)与取代吡啶的相互作用. bpV与有机配体的反应性从强到弱的顺序为: 皮考林酸根＞异烟酸根＞异烟酸甲酯＞皮考林甲酯, 这说明吡啶环上同一位置上的不同取代基团和同一取代基团在不同位置上都影响反应平衡, 竞争配位导致一系列新的6配位(配体为异烟酸根和异烟酸甲酯)或7配位(配体为皮考林酸根和皮考林甲酯)的过氧钒物种OV(O2)2L]n－ (L＝取代吡啶, n＝1或2)生成, 密度泛函计算结果较合理地解释了实验结果, 并表明溶剂化在反应中起重要作用.

NMR and Theoretical Study on Interactions between Diperoxovanadate Complex and Substituted Pyridines

To understand the substitution group effects of organic ligands on the reaction equilibrium,the interactions between diperoxovanadate complex OV(O2)2(D2O)]-/OV(O2)2(HOD)]-(abbr. bpV) and a series of substituted pyridines were explored using multinuclear(1H,13C,and 51V) magnetic resonance,DOSY,and variable temperature NMR in 0.15 mol/L NaCl ionic medium for mimicking the physiological condition. The reactivity order among the substituted pyridines and bpV is picolinate>isonicotinate> methyl isonicotinate>methyl picolinate. The competitive coordination results in the formation of a series of new six-coordinated(isonicotinate and methyl isonicotinate) or seven-coordinated(picolinate and methyl picolinate) peroxovanadate species OV(O2)2L]n-(L=substituted pyridines,n=1 or 2). Both the different substitution groups at the same position and the same groups at the different substitution position affect these reactions. The results of density functional calculations provide someway a reasonable explanation for the relative reactivity of the substituted pyridines. Solvation effects play an important role in these reactions.