【摘要】 用修饰的α-,β-,γ-环糊精(CDs)的包结增感作用研究(Z)-环辛烯(1Z)向手性(E)-异构体(1E)的超分子对映差向光异构反应。建立定量圆二色(CD)和差圆二色(DCD)公式,研究修饰α-,β-,γ-环糊精衍生物与1Z包结反应的构象、化学量和稳定常数。实验发现结合诱导的CD光谱变化是温度和修饰环糊精浓度的临界函数。同时发现光稳态E/Z随照射时间增长而增加最后达到光稳定状态,但明显依赖于增感剂结构和溶液中甲醇含量,它与环糊精手性空腔被客体1Z占有率有直接关系。考查含o-,m-,p-羧酸甲酯基团的苯甲酸β-环糊精酯衍生物的光增感和对映差向能力,更好地认识到在CDs空腔内的有效光能转换是怎样发生的。用邻苯二甲酸β-环糊精酯的对映体过剩(ee)从2.9%增加到24%。有趣的是产物的ee值与取代基常数(Hammett,σ)间没有明显的关系,却与某些苯甲酸-βCD酯的主体占有率有直接关系,即是通过分析在不同甲醇含量的水溶液中被一些-βCD衍生物增感的对映差向光异构反应中的ee,得出被底物1Z占有主体空腔的百分率。更多还原

【Abstract】 Supramolecular enantiodifferentiating photoisomerization of(Z)-cyclooctene(1Z) to chiral(E)-isomer(1E) has been studied via inclusion and sensitization by modified α-,β-,γ-cyclodextrins(CDs).Quantitative circular dichroism(CD) and differential circular dichroism(DCD) formula are established for studing the conformation,stoichiometry and stability constant of the complexation of 1Z with the modified α_,β_,and γ-cyclodextrin derivatives.We found experimentally that the CD spectral change induced upon complexation is a critical function of temperature and concentration of modified β-cyclodextrin.In addition,it is found that the photostationary-state E/Z increases with increasing irradiation time to reach a photostationary state,but significantly depends on the sensitizer structure and the methanol content in solution,which is directly related to the occupancy of the CD’s chiral cavity by guest 1Z.Photosensitizing and enantiodifferentiating abilities of the β-CD-benzoate derivatives,possessing o-,m-,p-methoxycarbonyl group,are examined to better understand how the effective photoenergy transfer occurs inside the CDs cavity,and the enantiomeric excess(ee) is enhanced from 29% to 24% by using the β-CD-phthalate.Interestingly,the product’s ee obtained did not show a clear relationship with the substituent’s constant(Hammett’s σ),it is found to be directly related to the host occupancy for some β-CD-benzoate,i.e.the percentage of host cavity occupied by the substrate 1Z through the analyses of the ee obtained upon the enantiodifferentiating photoisomerization sensitized by several β-CD derivatives in aqueous solutions of varying methanol contents.更多还原