A3型Corrole中位取代基对其β位^1H-NMR的影响  

Effect of Meso-Substituents on β ^1H-NMR of A3 Type Corrole

作　　者：刘海洋[1,2] 冷科[1] 胡军[1] 应晓[3] 徐志广[4] 张启光[2] 

机构地区：[1]华南理工大学化学系,广州510641 [2]香港科技大学化学系 [3]华南理工大学应用物理系,广州510641 [4]华南师范大学化学与环境学院,广州510631

出　　处：《物理化学学报》2009年第4期694-700,共7页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(20771039;N-HKUST604/04);香港研究资助局资助项目

摘　　要：采用密度泛函(DFT)方法对八个中位有不同取代基的A3型corrole进行了几何结构优化和核磁共振(NMR)理论计算.几何优化结果显示5,10,15-三苯基corrole的两个环内NH异构体的中位苯环空间排布方向不同.此外,虽然A3型corrole两个环内NH异构体A和B的能量相差不大,但A和B分子的Boltzman分布概率却有较大的不同,且受取代基影响很大.因而在计算NMR时必须对A和B异构体的理论化学位移做Boltzman统计平均处理.NMR计算结果表明,在B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d,p)水平下可以得到较为合理的corrole的1H-NMR化学位移结果.β-位氢的化学位移与取代基Hammett常数σP+的大小成正比关系.此外,由于corrole大环的低对称性,取代基对不同位置β-位氢的NMR影响程度不同,其β-位氢化学位移的大小和顺序与中位取代基的电子效应和corrole的立体结构因素有关.Geometries of eight A3-type corroles bearing different substituents were optimized and their nuclear magnetic resonance（NMR） properties were also calculated using density functional theory （DFT）. Geometry optimization results showed that the NH tautomerization of 5,10,15-tris（phenyl）corrole is accompanied by the twisting of its phenyl groups. Although the total energies of both corrole NH tautomers are similar,the Boltzmann distribution probabilities of the A and B tautomers are significantly different. It is also dependent on the meso-substituents. Boltzman statistic averaging should thus be used to evaluate the 1H-NMR of corrole. NMR calculations performed at B3LYP/6-311＋G （2d,p）//B3LYP/6-31G（d,p） level may give reasonable 1H-NMR chemical shifts for the corrole. β-H chemical shifts were proportional to the Hammett constants σ P＋ of the substituents. Furthermore,because of the low symmetry of corrole,the substituents exerted a different effect on the NMR of β-protons at different positions. The order of 1H-NMR chemical shifts for different β-H is quite sensitive to the nature of meso-substituents. β 1H-NMR is determined by the electronic effect of substituents and the geometrical structure of the corrole.

关 键 词：CORROLE 1H核磁共振 规范不变原子轨道 密度泛函理论 

分 类 号：O641.1[理学—物理化学]