Relationship Between Conformational Flexibility and Chelate Cooperativity
作者:M. Cristina Misuraca、Tudor Grecu、Zoraida Freixa、Valentina Garavini、Christopher A. Hunter、Piet W.N.M. van Leeuwen、M. Dolores Segarra-Maset、Simon M. Turega
DOI:10.1021/jo2000397
日期:2011.4.15
of EM for a noncovalent intramolecular interaction. Introduction of rotors reduces the value of EM from this maximum in accord with a random walk analysis of the encounter probability of the chain ends (r−3/2). Noncovalent EMs never reach the very high values observed for covalent processes, which places limitations on the magnitudes of the effects that one is likely to achieve through the use of chelate
合成了一个由四个双氨基甲酸酯(AA)和四个双酚(DD)组成的家族,并使用1表征了所有AA • DD组合之间的氢键相互作用在四氯化碳中的1 H NMR滴定。化学双突变体循环分析表明,在这些系统中没有次级静电相互作用或变构协同作用,因此该系统为研究化学结构与螯合协同作用之间的关系提供了理想的平台。测量了12种不同系统的有效摩尔浓度(EMs),其中连接两个H键位点的链中的转子数从5变为20。对于所有12种络合物,缔合常数的变化幅度均小于一个数量级, EM的变化非常小(0.1-0.9 M)。结果提供了EM和连接链中的转子数(r)之间的关系:EM≈10 r -3/2。10 M的值是非共价分子内相互作用的EM值的上限。根据对链条末端相遇概率(r -3/2)的随机游动分析,引入转子会从该最大值减小EM的值。非共价EM从未达到共价过程中观察到的很高的值,这限制了通过在超分子组装和催化中使用螯合剂的协同作用
Effect of molecular structure on mesomorphism. 12. Flexible-center Siamese-twin liquid crystalline diesters - a "prepolymer" model
作者:Anselm C. Griffin、Thomas R. Britt
DOI:10.1021/ja00406a056
日期:1981.8
Acyclic cucurbit[n]urils capped with alkylene linkers: synthesis and molecular recognition properties
作者:Shweta Ganapati、Lyle Isaacs
DOI:10.1080/10610278.2018.1539228
日期:2019.3.4
We report the synthesis and characterization of three new acyclic cucurbit[n]uril-type receptors that feature a covalent capping group in the form of an alkylene linker (2a - 2c) that we hypothesized would have higher binding affinity toward alkylammonium ions in water. Hosts 2a - 2c have lower aqueous solubility (<= 2 mM) than the prototypical acyclic CB[n]-type host 1 (346 mM). Hosts 2a - 2c do not undergo significant intermolecular self-association over the experimentally accessible concentration range. In contrast, the results of H-1 NMR experiments shows that the alkylene linkers of 2b and 2c undergo self-inclusion and that this process is reversed upon addition of ammonium ions 6-10 as guests. The host center dot guest K-a values were determined for hosts 1 and 2a - 2c toward guests 6-10 by isothermal titration calorimetry. We find that 2a - 2c bind less strongly toward guests 6-10 than host 1 due to the energetic penalty associated with expulsion of the alkylene linker from its own cavity.[GRAPHICS].
AN IMPROVED SYNTHESIS OF<i>bis</i>(<i>p</i>-PHENYLENE)-32-CROWN-4