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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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Sara Norrehed Dr. Henrik Johansson Prof. Dr. Helena Grennberg Prof. Dr. Adolf Gogoll 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(43):14631-14638
The relative stereochemistry of acyclic diamines with several stereogenic centers has been analyzed by NMR spectroscopy in combination with conformational deconvolution. Binding to a bisporphyrin molecular clip improves the stereochemical assignment significantly. The diamines were synthesized from inexpensive sugar alcohols, and their stable hydrochlorides were quantitatively converted into free bases by treatment with ion‐exchange resin. 相似文献
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Chao Yang Lei Liu Ting-Wei Mu Qing-Xiang Guo 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(1-2):97-101
A new method is proposed formeasuring association constants and has been used tostudy the complexation of -cyclodextrin withnine substituted benzenes. Computer simulation wasconducted to compare the performance of the new methodwith that of the Benesi–Hildebrand method. It showedthat the accuracy and success rate of the new methodwere both higher than those of the BH method. Hence,the new method is a recommended approach for aconvenient and reliable measurement of associationconstants. 相似文献
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Nonspherical cages in inclusion compounds can result in non‐uniform motion of guest species in these cages and anisotropic lineshapes in NMR spectra of the guest. Herein, we develop a methodology to calculate lineshape anisotropy of guest species in cages based on molecular dynamics simulations of the inclusion compound. The methodology is valid for guest atoms with spin 1/2 nuclei and does not depend on the temperature and type of inclusion compound or guest species studied. As an example, the nonspherical shape of the structure I (sI) clathrate hydrate large cages leads to preferential alignment of linear CO2 molecules in directions parallel to the two hexagonal faces of the cages. The angular distribution of the CO2 guests in terms of a polar angle θ and azimuth angle ? and small amplitude vibrational motions in the large cage are characterized by molecular dynamics simulations at different temperatures in the stability range of the CO2 sI clathrate. The experimental 13C NMR lineshapes of CO2 guests in the large cages show a reversal of the skew between the low temperature (77 K) and the high temperature (238 K) limits of the stability of the clathrate. We determine the angular distributions of the guests in the cages by classical MD simulations of the sI clathrate and calculate the 13C NMR lineshapes over a range of temperatures. Good agreement between experimental lineshapes and calculated lineshapes is obtained. No assumptions regarding the nature of the guest motions in the cages are required. 相似文献
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Yanfei Wang Benjamin W. Roose John P. Philbin Jordan L. Doman Prof. Ivan J. Dmochowski 《Angewandte Chemie (International ed. in English)》2016,55(5):1733-1736
A supramolecular strategy for detecting specific proteins in complex media by using hyperpolarized 129Xe NMR is reported. A cucurbit[6]uril (CB[6])‐based molecular relay was programmed for three sequential equilibrium conditions by designing a two‐faced guest (TFG) that initially binds CB[6] and blocks the CB[6]–Xe interaction. The protein analyte recruits the TFG and frees CB[6] for Xe binding. TFGs containing CB[6]‐ and carbonic anhydrase II (CAII)‐binding domains were synthesized in one or two steps. X‐ray crystallography confirmed TFG binding to Zn2+ in the deep CAII active‐site cleft, which precludes simultaneous CB[6] binding. The molecular relay was reprogrammed to detect avidin by using a different TFG. Finally, Xe binding by CB[6] was detected in buffer and in E. coli cultures expressing CAII through ultrasensitive 129Xe NMR spectroscopy. 相似文献
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Mohamed F. Shibl Salem A. Hameed Shabaan A.K. Elroby 《International journal of quantum chemistry》2010,110(14):2645-2652
A density functional theory study of the behavior of hemispherands toward alkali metal ions (Li+, Na+, and K+) is performed. The effect of the replacement of the rigid anisyl group(s) by the mobile ether group(s) on the binding energy of hemispherands with alkali metal ions is investigated. The results indicated that the binding energies are inversely proportional to the ionic radius of the cations. Moreover, increasing the flexibility of the ligand results in decreasing the binding toward small ions. The structures of the hosts and the guests are correlated to the binding energies, and the correlations are interpreted in terms of the principle of preorganization. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
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A Metal–Organic Framework with a Pore Size/Shape Suitable for Strong Binding and Close Packing of Methane
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Dr. Jiao‐Min Lin Chun‐Ting He Yan Liu Pei‐Qin Liao Dong‐Dong Zhou Prof. Dr. Jie‐Peng Zhang Prof. Dr. Xiao‐Ming Chen 《Angewandte Chemie (International ed. in English)》2016,55(15):4674-4678
Much effort has been devoted to develop new porous structures for methane storage. We report a new porous coordination framework showing exceptional methane uptakes (e.g. 263 v/v at 298 K and 65 bar) and adsorption enthalpies (21.6 kJ mol?1) as high as current record holders functionalized by open metal sites. Computational simulations demonstrated that the hierarchical pore structure consisting of single‐wall nanocages has suitable sizes/shapes and organic binding sites to enforce not only strong host–methane and methane–methane interactions but also dense packing of methane molecules. 相似文献
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Jalaluddin Ahmed Tatsuyuki Yamamoto Yoshihisa Matsui 《Journal of inclusion phenomena and macrocyclic chemistry》2000,38(1-4):267-276
The longitudinal relaxation times (T1)of 1H NMR signals for a variety of alkanols in D2Omarkedly decreased with increasing concentrations (c)of - and -cyclodextrins (CD). Tetramethylammoniumchloride (TMA) used as an internal reference wasavailable for evaluating an effect of solutionviscosity on relaxation rates R(=1/T1), since TMAshowed no appreciable interaction with CD. Changes inthe ratio of R for alkanol protons to R for TMAprotons with c were analyzed by the curve-fittingmethod to give Ka. These Ka values agreedwell with those obtained by the analysis of changesin , indicating that T1 measurement is available forthe determination of Ka for CD complexes. 2D ROESYspectra provided definite information on the molecularstructures of CD complexes with alkanols. 相似文献
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Viologens readily thread bis‐p‐phenylene crown ethers to form [2]pseudorotaxanes. However, the binding of sterically hindered 3,3′‐dimethylviologens is very weak. Density functional theory (DFT) calculations indicated that the additional energy cost of “flattening” is substantial, 55 kJ mol?1, and prevents the formation of a stable host–guest complex. The structures of [2]pseudorotaxanes determined by X‐ray crystallography are in good agreement with the NMR characterisation and DFT results. Their association constants and thermodynamic parameters in solution were measured by using a dilution method and, for the first time, by host–guest nuclear Overhauser effect (NOE) correlations. The NOE approach was subsequently applied to study the sterically hindered analogues and it was shown that the binding in 3,3′‐dimethyl‐N,N‐dibenzyl [2]pseudorotaxane is by 8.5 kJ mol?1 weaker than in its regular analogue. The proposed technique helps to quantify weak interactions in [2]pseudorotaxanes and can be applied to other host‐guest complexes. 相似文献
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Defect Models of As‐Made High‐Silica Zeolites: Clusters of Hydrogen‐Bonds and Their Interaction with the Organic Structure‐Directing Agents Determined from 1H Double and Triple Quantum NMR Spectroscopy
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Dr. Gunther Brunklaus Dr. Hubert Koller Dr. Stacey I. Zones 《Angewandte Chemie (International ed. in English)》2016,55(46):14459-14463
Internal defect SiOH and SiO? groups evolve during the structure formation of high‐Si zeolites in the presence of a cationic organic structure‐directing agent (SDA). These negatively charged defects do not completely disappear upon calcination. Herein we investigate the clustering of defect groups and their location within the pore walls of four zeolites. ZSM‐12, ZSM‐5, and SSZ‐74 have three clustered SiOH groups which are hydrogen‐bonded to SiO?, whereas SSZ‐24 has only two. These defects interact with the structure‐directing quaternary ammonium ions preferably close to the charge center, unless steric shielding is present. The framework topologies of ZSM‐12, ZSM‐5, and SSZ‐24 have connected six‐rings where the organics interact with the defects. It is suggested that these six‐ring patterns form connectivity defects. SSZ‐74 is unique, it does not contain an extended six‐ring motif, so vacancy defects form instead. 相似文献
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EPR Studies of the Binding Properties,Guest Dynamics,and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule
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Dr. Mehmet Menaf Ayhan Dr. Gilles Casano Dr. Hakim Karoui Prof. Antal Rockenbauer Dr. Valérie Monnier Dr. Micaël Hardy Prof. Paul Tordo Dr. David Bardelang Dr. Olivier Ouari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46):16404-16410
Nitroxide free radicals have been used to study the inner space of one of Rebek’s water‐soluble capsules. EPR and 1H NMR spectroscopy, ESI‐MS, and DFT calculations showed a preference for the formation of 1:2 complexes. EPR titrations allowed us to determine binding constants (Ka) in the order of 107 M ?2. EPR spectral‐shape analysis provided information on the guest rotational dynamics within the capsule. The interplay between optimum hydrogen bonding upon capsule formation and steric strain for guest accommodation highlights some degree of flexibility for guest inclusion, particularly at the center of the capsule where the hydrogen bond seam can be barely distorted or slightly disturbed. 相似文献
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Frontispiece: EPR Studies of the Binding Properties,Guest Dynamics,and Inner‐Space Dimensions of a Water‐Soluble Resorcinarene Capsule
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Dr. Mehmet Menaf Ayhan Dr. Gilles Casano Dr. Hakim Karoui Prof. Antal Rockenbauer Dr. Valérie Monnier Dr. Micaël Hardy Prof. Paul Tordo Dr. David Bardelang Dr. Olivier Ouari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(46)
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Strong Induced‐Fit Binding of Viologen and Pyridine Derivatives in Adjustable Porphyrin Cavities
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Dr. Alexander B. C. Deutman Jan M. M. Smits Dr. René de Gelder Dr. Johannes A. A. W. Elemans Prof. Roeland J. M. Nolte Prof. Alan E. Rowan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(36):11574-11583
The synthesis and binding properties of new porphyrin cage compounds consisting of a rigid diphenylglycoluril part, which is connected via flexible bis(ethyleneoxy) spacers to a (metallo)porphyrin “roof”, are reported. Binding of viologen guests and pyridine ligands in these porphyrin cages are accompanied by significant conformational reorganizations of the hosts. Despite these structural changes, association constants are still very high, revealing that not only receptors that bind guests according to a lock‐and‐key mechanism but also those that bind guests by an induced‐fit mechanism can exhibit strong binding. 相似文献