Thermodynamic Synthesis of Rotaxanes by Imine Exchange
摘要:
[GRAPHICS]By utilizing the dynamic nature of imine bonds, it is possible to construct [2]rotaxanes from a ring and a preformed dumbbell under thermodynamic control, These dynamic [a]rotaxanes, which exhibit reversible supramolecular-like behavior in the presence of appropriate catalysts, can be "fixed" by reduction of their imine bonds.
Using the concepts of self-assembly developed for the construction of topologically complex molecules such as [2]-catenanes and rotaxanes, the syntheses of several prophyrin-catenanes are described. The successful insertion of the porphyrin subunit into [2]-catenanes has resulted from the adaptation of previously devised template-directed syntheses based primarily on pi-pi interactions and C-H...O and C-H...pi and hydrogen bonding. Several hydroquinol containing ether chains were successfully synthesized and subsequently strapped across a porphyrin ring; the X-ray crystal structures of two such molecules which vary in the length of the ether chain are reported. These strapped porphyrins were found to complex paraquat with a parallel orientation of the hydroquinol, paraquat, and porphyrin rings. The complexation of paraquat (K-a 1955 and 1640 M(-1), Delta G degrees = -4.5 and -4.4 kcal mol(-1) for 9 and 11, respectively) by these strapped porphyrins led to their subsequent inclusion, using template-directed self-assembly, into structures which represent the first examples of porphyrin-containing [2]-catenanes. The catenanes were subsequently characterized by FAB-MS and thoroughly examined using dynamic H-1 NMR. In the case of the hydroquinol-containing catenanes, a dynamic process was observed in solution in which the bipyridinium subunits of the tetracation were exchanged between ''inside'' and ''outside'' environments (rotation around the hydroquinol ring axis). The diethylene glycol containing catenanes 14 and 15 were observed to maintain an orientation of the tetracation in which the bipyridinium subunits are parallel to the porphyrin ring. The length of the ether strap in these catenanes influenced the rotation rates of the tetracation macrocycles (50 and 80 times per second for 14 and 15 and 2500 and 1500 times per second for 16 and 17, respectively) at ambient temperature. However, in air the catenanes, the overall orientation of the tetracation,with bipyridinium and porphyrin rings coparallel, is retained in solution. As an extension of the original concepts, an analogous strapped porphyrin containing a naphthoquinol moiety was synthesized and found to complex paraquat with K-a = 21 000 M(-1) and Delta G degrees = -5.9 kcal mol(-1). The general applicability of the template-directed synthetic procedure developed for porphyrin catenane synthesis was illustrated by the successful isolation of the naphthalene containing porphyrin [2]-catenane 23 in 45% yield. Tetracation exchange processes similar to those for the hydroquinol catenanes were observed, along with an additional process which was found to be the decomplexation/complexation of the naphthalene ring in what is termed an ''out, turn around, and in again'' process similar to that occurring in nonporphyrinic naphthalene [2]-catenanes.
clipping process. Using threads 13a and 13b that contain two adipamide groups, more complicated systems have been investigated in which [2]rotaxane, [3]rotaxane, and free components are in equilibrium. Concentration- and temperature-dependent 1H NMR spectroscopic studies allowed the identification of all possible elements and the determination of their relative distributions in solution. For example
使用包含弱可逆OsVI-N配位键的双核大环化合物2,研究了[2]-和[3]轮烷的自组装和平衡动力学。当大环化合物2与线程4a-e混合在一起时,它们都包含一个己二酰胺位点,但端基的大小不同,[2]假轮烷和轮烷样复合物立即形成,其缔合常数> 7 x 103M(- 1)在298 K的CDCl3中。通过2D-EXSY实验研究的交换动力学表明,复合物的组装和拆卸是通过两个不同的途径(滑动或截短)发生的,这取决于端基的大小。滑动途径主要是产生假轮烷样复合物的较小端基,而剪切途径是产生轮状烷类复合物的较大端基。在相同条件下,交换势垒(deltaG ++)对于4a是14.3 kcalmol(-1),对于4d是16.7 kcalmol(-1),表明滑动过程比剪切过程至少快一个数量级。使用包含两个己二酰胺基团的线13a和13b,研究了更复杂的系统,其中[2]轮烷,[3]轮烷和游离组分处于平衡状态。浓度和温度相关的1H
Ion-controlled switchable complexation between pentiptycene-based tweezer-like hosts and self-folding guests
作者:Ying Han、Jia-Bin Guo、Jing Cao、Chuan-Feng Chen
DOI:10.1016/j.tet.2013.04.030
日期:2013.6
A couple of self-folding A-D-A guests were synthesized, and it was found that the guests could be included by the pentiptycene-based tweezer-like hosts to form stable 1:1 complexes in solution, which have been evidenced by the 1H NMR, ROESY 2D NMR and ESI MS spectra. Moreover, a potassium ion-controlled switchable process between the host and the self-folding guest was further achieved.
合成了一些自折叠的ADA客体,发现客体可以被基于五萜烯的镊子样主体所包含,从而在溶液中形成稳定的1:1络合物,这已经通过1 H NMR进行了证明, ROESY 2D NMR和ESI MS光谱。而且,进一步实现了宿主和自折叠客体之间钾离子控制的可切换过程。
Efficient Templated Synthesis of Donor−Acceptor Rotaxanes Using Click Chemistry
作者:William R. Dichtel、Ognjen Š. Miljanić、Jason M. Spruell、James R. Heath、J. Fraser Stoddart
DOI:10.1021/ja063127i
日期:2006.8.1
The mild reaction conditions, remarkable functional group compatibility, and complete regioselectivity of the Cu-catalyzed Huisgen 1,3-dipolarcycloaddition ("click chemistry") between organic azides and terminal alkynes have led to a threading-followed-by-stoppering approach to the synthesis of donor-acceptor rotaxanes incorporating cyclobis(paraquat-p-phenylene) (CBPQT4+) as the pi-accepting ring
有机叠氮化物和末端炔烃之间的 Cu 催化的 Huisgen 1,3-偶极环加成(“点击化学”)的温和反应条件、显着的官能团相容性和完全的区域选择性导致了一种先穿后塞的方法合成包含环双(百草枯-对亚苯基)(CBPQT4+)作为π-受体环组分的供体-受体轮烷。轮烷的形成是通过使含有 pi 供体 1,5-二氧萘 (DNP) 识别单元的叠氮化物官能化假轮烷与适当的炔官能化终止剂反应而引发的。在这种有效的、动力学控制的组装后共价修饰中获得的高产率以及合成方案的出色收敛性通过 [2]-、[3]-、
[2]Pseudorotaxanes and [2]Catenanes Constructed by Oxacalixcrowns/Viologen Molecular Recognition Motifs
作者:Hua Liu、Xiao-Yan Li、Xiao-Li Zhao、Yahu A. Liu、Jiu-Sheng Li、Biao Jiang、Ke Wen
DOI:10.1021/ol502869u
日期:2014.11.21
Oxacalix[2]arene[2]pyrazine and functional polyether derived oxacalixcrown-6, -7, and -8 were synthesized, and their host–guest complexation with paraquat to form [2]pseudorotaxanes was studied. The [2]pseudorotaxanes were then successfully used in the construction of two oxacalixcrown-tetracationic cyclophane [CBPQT4+] based [2]catenanes.
Single-color pseudorotaxane-based temperature sensing
作者:Isurika R. Fernando、Semere G. Bairu、Guda Ramakrishna、Gellert Mezei
DOI:10.1039/c0nj00541j
日期:——
Colored pseudorotaxane solutions can be used to assess temperature changes over large temperature windows. The color intensity of our novel pseudorotaxane systems decreases gradually from −50 to +50 °C with no shift in absorption maximum, making these and similar pseudorotaxanes attractive candidates for single-wavelength colorimetric temperature sensors.