【作者】 伍平；

【导师】 王官武；

【作者基本信息】 中国科学技术大学 ， 有机化学， 2009， 博士

【摘要】 富勒烯及其衍生物在材料,生物,医药等领域有巨大的潜力。富勒烯理论研究对富勒烯实验研究有重要的指导作用。我们的工作主要目的是通过对富勒烯的内嵌³He或者¹H NMR的理论研究归属富勒烯及其衍生物的结构以及计算说明一些富勒烯反应的机理。本论文对富勒烯内嵌原子/分子的化学位移,富勒烯与环氧化合物反应的立体选择性以及和富勒烯三唑啉结构的衍生物热裂解放氮的机理进行了量化研究,本文的主要研究工作如下:应用GIAO-B3LYP/3-21G//AM1方法预测了³He@C_n（n=82、84和86）所有异构体的化学位移。并跟高碳富勒烯C₈₂、C₈₄和C₈₆混合物的³He@C_n的³He NMR谱图进行对比,结合理论计算和实验工作,对难以分离的³He@C_n（n=82、84和86）的³He NMR谱图进行了结构归属。用GIAO-HF/3-21G//AM1、GIAO-HF/3-21G//PM3、GIAO-B3LYP/3-21G//AM1和GIAO-B3LYP/3-21G//PM3方法计算了富勒烯及其衍生物的内嵌H₂、H₂O和NH₃的内嵌¹H NMR化学位移,发现GIAO-B3LYP/3-21G//PM3的计算值和实验值的的线性关系非常好,而且这种方法消耗的资源特别小。以此为基础,我们预测了一系列化合物的内嵌¹H NMR化学位移,发现C₆₀或C₇₀对其内嵌H₂、H₂O和NH₃的屏蔽作用是固定的,对化学位移的影响基本相同。用富勒烯反应机理计算的常用方法AM1方法搜索了环氧化合物和C₆₀反应的反应路径。用B3LYP/6-31G^*//AM1得到的能垒图定性的说明了反应的选择性。通过对反应机理的讨论,推测出其中两个环氧化合物3b或者3c与C₆₀反应选择性的温度效应可能存在非线性的Eyring-plots。并通过进一步的实验证实了3b与C₆₀反应选择性的温度效应确实存在非线性的Eyring-plots,而3c与C₆₀反应选择性跟温度无关。通过文献调研,推测出富勒烯三唑啉结构的衍生物热裂解放氮过程的机理存在漏洞,提出可能的协同机理。基于文献沿用的B3LYP/6-31G^**//AM1方法,找到了一个新的有利的协同反应途径,并且纠正了原文献的错误。为了确认协同途径,我们尝试了密度泛函方法和ONIOM方法,分别用B3LYP/STO-3G、B3LYP/3-21G^*和ONIOM（B3LYP/6-31G^*:AM1）方法搜索了反应路径,并且用B3LYP/6-31G^**做了单点能计算。计算结果证明了协同机理才是该反应的有利途径,并且能解释叠氮苯和C₆₀偶极加成产物热分解的实验现象。更多还原

【Abstract】 Fullerenes and their derivatives have been expected to have applications in material science,biological science and medical science.Theoretical studies on fullerenes should be important to the experimental investigation of fullerenes.Our aims are assigning the structure of fullerenes and their derivatives,and exploring the fullerene reaction mechanisms by theoretical studies.The endohedral ³He and ¹H NMR chemical shifts were studied theoretically.The stereoselectivity for the reaction of epoxides with C₆₀,and the mechanism of N₂ extrusion after the 1,3-diploar cycloaddition of azides with C₆₀ were also studied.The main works are the followings:The endohedral ³He NMR chemical shifts for ³He@C_n（n=82,84 and 86）, which were difficult to be separated individually,were predicted by the GIAO-B3LYP/3-21G//AM1 method.In comparison of the predicated values with the experimental data,we assigned their structures successfully.The accurate prediction for endohedral ³He NMR chemical shifts of fullerenes and their derivatives encouraged us to attempt the possible linear relation between the experimental and theoretical endoheral ¹H NMR chemical shifts of fullerenes and their derivatives.Among the four methods of GIAO-HF/3-21G//AM1,GIAO-HF/3-21G//PM3,GIAO-B3LYP/3-21G//AM1 and GIAO-B3LYP/3-21G//PM3,the theoretical value at the level of GIAO-B3LYP/3-21G//PM3 had excellent linear relation with the experimental ¹H NMR chemical shifts of fullerenes and their derivatives,and its cost was much less in comparison with other higher-level NMR calculations.We studied the stereoselectivity for the reaction of C₆₀ with epoxides at the level of B3LYP/6-31G^*//AM1.After the discussions on the theoretical results,the possibility of non-linear Eyring-plots for the reaction temperature effect was concluded.Further experiments confirmed our conclusion.A new concerted mechanism for the N₂ extrusion from the cycloaddition product of azides to C₆₀ was proposed.With the same calculation at the level of B3LYP/6-31G^**//AM1,the new concerted mechanism was located.More sophisticated studies done at the levels of B3LYP/STO-3G,B3LYP/3-21G^* and ONIOM（B3LYP/6-31G^*:AM1） confirmed the preferenceof the concerted reaction mechanism,which could also explain the experimental phenomena.更多还原