紫精寡聚体的水相折叠和堆积及葫芦[n]脲(n=7,8)调控  

Folding and Aggregation of Oligoviologens in Water and Cucurbit[n]uril(n=7,8)Modulation

作　　者：彭文昶 王辉[1] 张丹维[1] 黎占亭[1,2] Peng Wen-Chang;Wang Hui;Zhang Dan-Wei;Li Zhan-Ting(Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials,Department of Chemistry,Fudan University,Shanghai 200438;Key Laboratory of Synthetic and Self-Assembly Chemistry for Organic Functional Molecules,Shanghai Institute of Organic Chemistry,Chinese Academy of Sciences,Shanghai 200032)

机构地区：[1]复旦大学化学系上海市分子催化和功能材料重点实验室,上海200438 [2]中国科学院上海有机化学研究所有机功能分子合成与组装化学重点实验室,上海200032

出　　处：《有机化学》2022年第3期863-870,共8页Chinese Journal of Organic Chemistry

基　　金：国家自然科学基金(Nos.21890732,21890730,21921003)资助项目.

摘　　要：为探索紫精正离子自由基线性分子的水相构象和簇集,制备了一系列具有不同长度和连接基团的水溶性紫精寡聚体.重水中1H NMR实验显示,在水中葫芦[7]脲(CB[7])及葫芦[8]脲(CB[8])包结其对-二甲基苯单元而不是联吡啶单元.紫外可见吸收实验表明,在连二亚硫酸钠水溶液中,线性分子的紫精基团被还原为相应的正离子自由基,分子骨架通过折叠发生堆积形成褶皱型二聚体,并导致自由基堆积三聚体络合物的形成.动态光散射实验揭示,这些自由基受疏水作用驱动通过折叠构象形成稳定的二聚体,再进一步堆积形成纳米尺寸的簇集体.加入葫芦[7]脲导致这些折叠体的紫精正离子自由基与葫芦[7]脲形成1∶1包结络合物,从而诱导纳米簇集结构解聚.而CB[8]也可以通过与紫精正离子自由基形成1∶2包结络合物,促使纳米簇集体和折叠体的解聚.在线性分子中引入刚性连接基团可以进一步促进其正离子自由基的堆积.尽管线性紫精正离子自由基结构在乙腈中堆积形成折叠体二聚体文献已有报道,本项研究揭示这类分子在水中的堆积进一步增强,其折叠体二聚体可以进一步堆积,形成纳米尺度的簇集体.To study the conformations and aggregation of linear viologen radical cation-incorporated molecules in water,a series of water-soluble oligoviologens with different length and linkers were prepared.1H NMR experiments in deuteroxide showed that cucurbit[7]uril(CB[7])and cucurbit[8]uril(CB[8])encapsulate their p-xylylene linkers instead of the bipyridinium units.UV-vis absorption experiments indicated that in the aqueous solution of sodium dithionite the viologen units of the oligomers were reduced to the radical cation species which were driven to dimerize through pleated conformations,leading to the formation of trisradical cation species.Dynamic light scattering experiments revealed that the foldamer dimers further aggregated to afford nanoscale particles.Adding CB[7]decomposed all the aggregated foldamer nanoparticles through 1∶1 encapsulation of the viologen radical cation units,whereas the addition of CB[8]broke the foldamers and their large aggregates through 1∶2 encapsulation of the viologen radical cations.Introducing a rigid linker to the linear viologen molecule could further enhance their stacking in the radical cation state.Although the folding and dimerization of linear viologen radical cation molecules have been established in acetonitrile in the literature,this study demonstrates that in water such multiple viologen radical cation molecules not only undergo folding to form stable dimers,but also further aggregate to give rise to nanoscale particles.

关 键 词：折叠 簇集 自由基正离子 葫芦[n]脲(n=7 8) 4 4'-二吡啶盐 水相 

分 类 号：O641.3[理学—物理化学]