中文摘要：

目的：研究多巴胺（DA）最稳定构象DAl在气相、油相环己烷和水相中的构象及其性质变化。方法：用B3LYP／6—31l＋＋G（2d，p）对DA不同构象进行全优化，得到最稳定的DAl，再以其二面角由（C4-C9-C10-N11）为变量，研究在0°-360°范围内不同环境中DAl的构象结构和性质变化，溶剂效应用PCM考虑。采用TD—B3LYP／6—311＋＋G（2d,P）计算UV—Yis谱，并在OPBE／6—31l＋＋G（2d,P）／／B3LYP／6—31l＋＋G（2d，p）水平上计算’H、12C-NMR。结果：4=180°时，DAl在三相中的能量最低。当0°≤中≤60°时，水相中DAl构象转变能垒最高，而60°≤由≤120°范围内则是最低。不同环境中，DAl构象变化的势能曲线遵循正弦函数变化。随着溶剂极性增大，DAl中O-H、N．H和C—N键长逐渐增大。水相中DAl的构象变化引起UV—Vis变化复杂，而气相中最大吸收峰对应单-的HOMO与LUMO＋I之间的电子跃迁。环境极性增加，1H—NMR的化学位移值增大而增大，而13C—NMR的化学位移呈逐渐降低。结论：溶剂极性影响DAl的构象变化的能垒高低．随由的增大，DAl的构象结构和性盾均呈现一定的峦化规律．

英文摘要：

Objective： To study the changes of conformations and properties for the most stable conforma-tion DA1 of dopamine （DA） in gas, cyclohexane, and water phases. Methods： Different initial conformations of DA were optimized fully at the B3LYP/6-311 ＋＋G （2d, p） level. The dihedral angle dp （C4--C9-C 10-N 11） in DA 1 was varied at 5 ° step size increased in 0-360 ° range to study the conformation and properties with the polarizable continuum model （PCM）. TD-B3LYP/6-311＋＋G （2d, p） were used to obtain UV-Vis absorption spectra, and calculated XH,13C-NMR at the OPBE/6-311＋＋G （2d, p）//B3LYP/6-311＋＋G （2d, p） level. Results： The lowest energy conformer was qb =180 ° in three phases. As 0 ° 〈 qb 〈 60 °, the rotation energy barrier of DAI in water phase was the highest, but as 60 ° 〈 qb 〈120 °was the lowest. In the different solvents, the potential energy curves of DA1 conformational isomerization could be fitted fairly well by sine function. With the increase of solvent polarity, the bond length of O-H, N-H and C-N elongated slightly. The UV-Vis spectra of DA1 in water was the most changeful, however, its the maximum peak in gas corresponding to HOMO to LUMO＋I electron transition. 1H-NMR chemical shift values increased when solvent polarity raised, while 13C-NMR chemical shift values reversed. Conclusion： The energy barrier of the conformational isomerization of DA1 is affected by solvent polarity. With the increase of qb, the conformations and properties of DA1 present somewhat regular pattern.