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Dr. Katia Nchimi‐Nono Parastoo Dalvand Dr. Kuldeep Wadhwa Selbi Nuryyeva Shaikha Alneyadi Dr. Thirumurugan Prakasam Dr. Albert C. Fahrenbach Prof. John‐Carl Olsen Dr. Zouhair Asfari Carlos Platas‐Iglesias Dr. Mourad Elhabiri Prof. Ali Trabolsi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(24):7334-7344
Suppression of the dimerization of the viologen radical cation by cucurbit[7]uril ( CB7 ) in water is a well‐known phenomenon. Herein, two counter‐examples are presented. Two viologen‐containing thread molecules were designed, synthesized, and thoroughly characterized by 1H DOSY NMR spectrometry, UV/Vis absorption spectrophotometry, square‐wave voltammetry, and chronocoulometry: BV 4+, which contains two viologen subunits, and HV 12+, which contains six. In both threads, the viologen subunits are covalently bonded to a hexavalent phosphazene core. The corresponding [3]‐ and [7]pseudorotaxanes that form on complexation with CB7 , that is, BV 4+?( CB 7)2 and HV 12+?( CB 7)6, were also analyzed. The properties of two monomeric control threads, namely, methyl viologen ( MV 2+) and benzyl methyl viologen ( BMV 2+), as well as their [2]pseudorotaxane complexes with CB7 ( MV 2+? CB7 and BMV 2+? CB7 ) were also investigated. As expected, the control pseudorotaxanes remained intact after one‐electron reduction of their viologen‐recognition stations. In contrast, analogous reduction of BV 4+?( CB 7)2 and HV 12+?( CB 7)6 led to host–guest decomplexation and release of the free threads BV 2( . +) and HV 6( . +), respectively. 1H DOSY NMR spectrometric and chronocoulometric measurements showed that BV 2( . +) and HV 6( . +) have larger diffusion coefficients than the corresponding [3]‐ and [7]pseudorotaxanes, and UV/Vis absorption studies provided evidence for intramolecular radical‐cation dimerization. These results demonstrate that radical‐cation dimerization, a relatively weak interaction, can be used as a driving force in novel molecular switches. 相似文献
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Host–Guest Chemistry of a Water‐Soluble Pillar[5]arene: Evidence for an Ionic‐Exchange Recognition Process and Different Complexation Modes
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Borja Gómez Dr. Vitor Francisco Dr. Fernando Fernández‐Nieto Prof. Luis Garcia‐Rio Dr. M. Martín‐Pastor Dr. M. Rita Paleo Prof. F. Javier Sardina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12123-12132
The complexation of an anionic guest by a cationic water‐soluble pillararene is reported. Isothermal titration calorimetry (ITC), 1H NMR, 1H and 19F DOSY, and STD NMR experiments were performed to characterize the complex formed under aqueous neutral conditions. The results of ITC and 1H NMR analyses showed the inclusion of the guest inside the cavity of the pillar[5]arene, with the binding constant and thermodynamic parameters influenced by the counter ion of the macrocycle. NMR diffusion experiments showed that although a fraction of the counter ions are expelled from the host cavity by exchange with the guest, a complex with both counter ions and the guest inside the pillararene is formed. The results also showed that at higher concentrations of guest in solution, in addition to the inclusion of one guest molecule in the cavity, the pillararene can also form an external complex with a second guest molecule. 相似文献
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A series of bis‐thiourea‐functionalized [n]polynorbornane hosts ( 1 – 6 ) with increasing size were synthesized and their anion‐binding properties were evaluated by using 1H NMR spectroscopic titration and Job’s plot analysis. The larger bis‐thiourea‐[3]polynorbornane scaffolds 4 and 5 bound acetate in a 1:1 (cooperative) arrangement, whereas the corresponding smaller norbornane host 2 , identical in preorganization, bound acetate in a 1:2 (independent) arrangement. In contrast, the size of the framework had no influence on the binding of dihydrogenphosphate. These results clearly highlight the subtle influence that the framework itself can have on host–guest interactions. 相似文献
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Yan‐Long Ma Dr. Hua Ke Dr. Arto Valkonen Prof. Kari Rissanen Prof. Wei Jiang 《Angewandte Chemie (International ed. in English)》2018,57(3):709-713
Positive cooperativity achieved through activating weak non‐covalent interactions is common in biological assemblies but is rarely observed in synthetic complexes. Two new molecular tubes have been synthesized and the syn isomer binds DABCO‐based organic cations with high orientational selectivity. Surprisingly, the ternary complex with two hosts and one guest shows a high cooperativity factor (α=580), which is the highest reported for synthetic systems without involving ion‐pairing interactions. The X‐ray single‐crystal structure revealed that the strong positive cooperativity likely originates from eight C?H???O hydrogen bonds between the two head‐to‐head‐arranged syn tube molecules. These relatively weak hydrogen bonds were not observed in the free hosts and only emerged in the complex. Furthermore, this complex was used as a basic motif to construct a robust [2+2] cyclic assembly, thus demonstrating its potential in molecular self‐assembly. 相似文献
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Dr. Jiang‐Fei Xu Linghui Chen Prof. Xi Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):11938-11946
By employing noncovalent interactions, chemists have constructed a variety of molecular aggregates with well‐defined structures and fascinating properties. In fabricating stable and large molecular assemblies, noncovalent interactions with high binding strength are needed. This Concept summarizes some strategies to modify and optimize the structures of building blocks for making weak noncovalent interactions stronger. The strategies include: 1) Preorganization of binding sites; 2) spatial confinement effects; 3) multivalent enhancement; 4) synergistic binding with multiple forces. Examples of the fabrication of supramolecular architectures by utilizing these strategies are presented and discussed. Guidance is offered in the construction and fabrication of stable molecular assemblies and supramolecular materials. 相似文献
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Supramolecular Alternating Polymer from Crown Ether and Pillar[5]arene‐Based Double Molecular Recognition for Preparation of Hierarchical Materials
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Hui Li Prof. Dr. Xiaodong Fan Miao Qi Zhen Yang Haitao Zhang Prof. Dr. Wei Tian 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(1):101-105
A novel supramolecular alternating polymer is constructed based on double molecular recognition events of benzo‐21‐crown‐7 with a secondary ammonium salt and of pillar[5]arene with a neutral guest. The resulting polymer is utilized to prepare hierarchical materials with different dimensionalities for the first time. These materials included zero‐dimensional spherical aggregates, one‐dimensional nanofibers, two‐dimensional microstructured films, and three‐dimensional ordered glue. This development will be helpful for designing and preparing supramolecular hierarchical materials with different dimensionalities. 相似文献
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Photoresponsive Hybrid Raspberry‐Like Colloids Based on Cucurbit[8]uril Host–Guest Interactions
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Yang Lan Yuchao Wu Dr. Athan Karas Prof. Oren A. Scherman 《Angewandte Chemie (International ed. in English)》2014,53(8):2166-2169
Hybrid raspberry‐like colloids (HRCs) were prepared by employing cucurbit[8]uril (CB[8]) as a supramolecular linker to assemble functional polymeric nanoparticles onto a silica core. The formed HRCs are photoresponsive and can be reversibly disassembled upon light irradiation. This facile supramolecular approach provides a platform for the synthesis of colloids with sophisticated structures and properties. 相似文献
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Mickaël Ménand Dr. Ivan Jabin Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(7):2159-2169
Versatile concave receptors with binding properties that can be controlled by external stimuli are rare. Herein, we report on a calix[6]crypturea ( 1 ) that features two different binding sites in close proximity, that is, a tris(2‐aminoethyl)amine (tren)‐based tris‐ureido cap that provides convergent hydrogen‐bond‐donor sites and a hydrophobic cavity suitable for the inclusion of organic guests. The binding properties of this heteroditopic receptor have been evaluated by NMR spectroscopic studies. Compound 1 behaves as a remarkably versatile host that strongly binds neutral molecules, anions, or contact ion pairs. Within each family of guests, compound 1 is able to discriminate between different guests with a high degree of selectivity. Indeed, neutral molecules that possess hydrogen‐bond donor and acceptor groups, chloride anions, and linear ammonium ions associated to F? or Cl? are particularly well recognized. In comparison with all the related receptors, compound 1 displays several unique features: 1) charged or neutral species are also recognized in polar or protic solvents, 2) thanks to the flexibility of the calixarene structure, induced‐fit processes allow the binding of large, biologically relevant ammonium salts such as neurotransmitters, and 3) the protonation of the basic cap leads to a positively charged receptor, 1? H+, which is reluctant to host anions and in which host properties are now governed by strong charge–dipole interactions with the guests. In other words, compound 1 presents an acid–base controllable tris‐ureido recognition site protected by a hydrophobic corridor that can select guests through induced‐fit processes. Thus, its versatile host properties can be allosterically controlled by protonation and selective guest‐switching processes are possible. To illustrate all these remarkable features, a sophisticated three‐pole supramolecular switch, based on the interconversion of host–guest systems displaying either charged or neutral guests, is described. 相似文献
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Viktor Kolman Radek Marek Prof. Dr. Zora Strelcova Petr Kulhanek Dr. Marek Necas Prof. Dr. Jan Svec Vladimir Sindelar Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(28):6926-6931
In this study, we have investigated the supramolecular interaction between series of 1‐alkyl‐3‐methylimidazolium guests with variable alkyl substituent lengths and cucurbit[6]uril (CB6) in the solution and the solid state. Correct interpretation of 1H NMR spectra was a key issue for determining the binding modes of the complexes in solution. Unusual chemical shifts of some protons in the 1H NMR spectra were explained by the polarization of the imidazolium aromatic ring upon the complexation with the host. The formation of 1:1 complex between 1‐ethyl‐3‐methylimidazolium and CB6 is in disagreement with previously reported findings describing an inclusion of two guest molecules in the CB6 cavity. 相似文献
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High Affinity Recognition of a Selected Amino Acid Epitope within a Protein by Cucurbit[8]uril Complexation
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Dr. Silvia Sonzini Dr. Alessio Marcozzi Dr. Raphael J. Gubeli Dr. Christopher F. van der Walle Dr. Peter Ravn Prof. Andreas Herrmann Prof. Oren A. Scherman 《Angewandte Chemie (International ed. in English)》2016,55(45):14000-14004
Supramolecular interactions between the host cucurbit[8]uril (CB[8]) and amino acids have been widely interrogated, but recognition of specific motifs within a protein domain have never been reported. A phage display approach was herein used to select motifs with the highest binding affinity for the heteroternary complex with methyl viologen and CB[8] (MV?CB[8]) within a vast pool of cyclic peptide sequences. From the selected motifs, an epitope consisting of three amino acid was extrapolated and incorporated into a solvent‐exposed loop of a protein domain; the protein exhibited micromolar binding affinity for the MV?CB[8] complex, matching that of the cyclic peptide. By achieving selective CB[8]‐mediated conjugation of a small molecule to a recombinant protein scaffold we pave the way to biomedical applications of this simple ternary system. 相似文献
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Intermolecular interactions in solution play an important role in molecular recognition, which lies at the heart of supramolecular and combinatorial chemistry. Diffusion NMR spectroscopy gives information over such interactions and has become the method of choice for simultaneously measuring diffusion coefficients of multicomponent systems. The diffusion coefficient reflects the effective size and shape of a molecular species. Applications of this technique include the estimation of association constants and mapping the intermolecular interactions in multicomponent systems as well as investigating aggregation, ion pairing, encapsulation, and the size and structure of labile systems. Diffusion NMR spectroscopy can also be used to virtually separate mixtures and screen for specific ligands of different receptors, and may assist in finding lead compounds. 相似文献
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