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Benjamin Doistau Arnaud Tron Dr. Sergey A. Denisov Dr. Gediminas Jonusauskas Dr. Nathan D. McClenaghan Geoffrey Gontard Dr. Valérie Marvaud Prof. Dr. Bernold Hasenknopf Dr. Guillaume Vives 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15799-15807
The design and synthesis of switchable molecular tweezers based on a luminescent terpy(Pt‐salphen)2 ( 1 ; terpy=terpyridine) complex is reported. Upon metal coordination, the tweezers can switch from an open “W”‐shaped conformation to a closed “U”‐shaped form that is adapted for selective recognition of cations. Closing of the tweezers by metal coordination (M=Zn2+, Cu2+, Pb2+, Fe2+, Hg2+) was monitored by 1H NMR and/or UV/Vis titrations. During the titration, exclusive formation of the 1:1 complex [M( 1 )] was observed, without appearance of an intermediate 1:2 complex [M( 1 )2]. The crystallographic structure of the 1:1 complex was obtained with Pb2+ and showed a distorted helical structure. Selective intercalation of Hg2+ cations by the closed “U” form was observed. The tweezers were reopened by selective metal decoordination of the terpyridine ligand by using tris(2‐aminoethyl)amine (tren) as a competitive ligand without modification of the Pt–salphen complex. Detailed photophysical studies were performed on the open and closed tweezers. Structured emission was observed in the open form from the Pt–salphen moieties, with a high quantum yield and a long lifetime. The emission is slightly modified upon closing with 1 equivalent of Zn2+ or Hg2+, whereas a dramatic quenching was obtained upon intercalation of additional Hg2+. 相似文献
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M. Jayakannan S. Ramakrishnan 《Journal of polymer science. Part A, Polymer chemistry》2001,39(10):1615-1628
Several segmented polyethylene oxides (SPEOs) were prepared by a melt-transetherification process using 1,4-bis(methoxymethyl)-2,3,5,6-tetramethylbenzene and polyethylene glycols (PEGs) of different molecular weights (di-, tri-, and tetraethylene glycols and PEGs of molecular weights 300, 600, 1000, 1500, and 3400) as the monomers. The effect of polymerization temperature (185 and 150 °C) on the molecular weight of SPEOs was studied, and it was shown that the molecular weight is larger at a higher polymerization temperature. The reversal of the polycondensation (transetherification) equilibrium by treatment of the polyethers with excess methanol transformed them completely into the starting monomers. The analysis of the degraded products by mass and NMR spectroscopies revealed that side reactions, such as the self-condensation of diols, are insignificant. The polymers containing shorter PEG spacers are amorphous, whereas the ones with longer PEG spacers are semicrystalline. The glass-transition temperature (Tg) of the SPEOs decreased with increases in the spacer length and attained the value of PEO at PEG-600, whereas the melting transition (Tm), crystallization temperature (Tc), and their enthalpies of transition, (ΔHm) and (ΔHc), increased with increases in the spacer length. The introduction of “molecular kinks” into SPEOs by the use of another monomer, 1,3-bis(methoxymethyl)-2,4,5,6-tetramethylbenzene, surprisingly, showed little effect on their thermal properties. A “branched-PEO” analogue, containing pendant oligoethyleneoxy units, was also prepared, and its thermal properties were compared with its linear analogue. Preliminary ionic conductance measurements showed that some of these SPEOs could serve as potential candidates for solid polymer–electrolyte applications. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1615–1628, 2001 相似文献
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芳杂环类多重氢键分子钳人工受体对中性分子的识别性能研究 总被引:3,自引:1,他引:2
根据多点氢键识别原理,设计合成了新的分子钳受体1~6。研究了其对巴比妥 、尿素、二苯甲酮、戊二酰亚胺等中性分子的识别性能。用差紫外光谱法测定了结 合常数和自由能变化(ΔG)。结果表明,所有分子钳受体与所考察的客体分子均 形成1:1型超分子配合物,识别作用的推动力主要为多重氢键的协同作用。讨论了 主客体间尺寸/形状、几何互补等因素对形成超分子配合物的影响。并利用~1H NMR、计算机模拟作辅助手段对实验结果和现象进行了解释。 相似文献
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Dr. N. Kodiah Beyeh M. Sc. Altti Ala‐Korpi Dr. Fangfang Pan M. Sc. Hyun Hwa Jo Prof. Eric V. Anslyn Prof. Kari Rissanen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9556-9562
N‐Alkyl ammonium resorcinarene chlorides, stabilized by an intricate array of hydrogen bonds leading to a cavitand‐like structure, bind amides. The molecular recognition occurs through intermolecular hydrogen bonds between the carbonyl oxygen and the amide hydrogen of the guests and the cation–anion circular hydrogen‐bonded seam of the hosts, as well as through CH ??? π interactions. The N‐alkyl ammonium resorcinarene chlorides cooperatively bind a series of di‐acetamides of varying spacer lengths ranging from three to seven carbons. Titration data fit either a 1:1 or 2:1 binding isotherm depending on the spacer lengths. Considering all the guests possess similar binding motifs, the first binding constants were similar (K1: 102 M ?1) for each host. The second binding constant was found to depend on the upper rim substituent of the host and the spacer length of the guests, with the optimum binding observed with the six‐carbon spacer (K2: 103 M ?2). Short spacer lengths increase steric hindrance, whereas longer spacer lengths increase flexibility thus reducing cooperativity. The host with the rigid cyclohexyl upper rim showed stronger binding than the host with flexible benzyl arms. The cooperative binding of these divalent guests was studied in solution through 1H NMR titration studies and supplemented by diffusion‐ordered spectroscopy (DOSY), X‐ray crystallography, and mass spectrometry. 相似文献
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Tomasz Bereźniak Andres Jäschke Jeremy C. Smith Petra Imhof 《Journal of computational chemistry》2012,33(19):1603-1614
The Diels‐Alderase ribozyme is an in vitro‐evolved ribonucleic acid enzyme that catalyzes a [4 + 2] cycloaddition reaction between an anthracene diene and a maleimide dienophile. The ribozyme can in principle be used to selectively synthesize only one product enantiomer, depending on which of the two entrances to the catalytic pocket, “front” or “back”, the substrate is permitted to use. Here, we investigate stereoselection and substrate recognition in the ribozyme by means of multiple molecular dynamics simulations, performed on each of the two substrates individually in the pocket, on the reactant state, and on the product state. The results are consistent with a binding mechanism in which the maleimide likely binds first followed by the anthracene, which enters preferentially through the front door. The free energy profiles for anthracene binding indicate that the pre‐(R,R)‐enantiomer conformation is slightly preferred, in agreement with the experimentally observed small enantiomeric excess of the (R,R)‐enantiomer of the product. The reactant state is stabilized by the simultaneous presence of both substrates bound to their binding sites in the hydrophobic pocket as well as by stacking interactions between them. © 2012 Wiley Periodicals, Inc. 相似文献
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Schmuck C Rupprecht D Junkers M Schrader T 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(24):6864-6873
Covalent fusion of two artificial recognition motifs for arginine and aspartate resulted in a new class of ditopic RGD receptor molecules, 1-4. The two binding sites for the oppositely charged amino acid residues are linked by either flexible linkers of different length (in 1-3) or a rigid aromatic spacer (in 4). These spacers are shown to be critical for the complexation efficiency of the artificial hosts. If the linkers are too flexible, as in 1-3, an undesired intramolecular self-association occurs within the host and competes with, and thereby weakens, substrate binding. The rigid aromatic linker in 4 prevents any intramolecular self-association and hence efficient RGD binding is observed, even in buffered water (association constant of K(a) approximately 3000 m(-1)). A further increase in hydrophobic contacts, as in host 16, can complement the specific Coulomb attractions, thereby leading to an even more stable complex (Ka=5000 m(-1)). The recognition events have been studied with NMR spectroscopy, UV/Vis spectroscopy, and fluorescence titrations. 相似文献
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芳酰胺-吖啶分子钳对中性分子的识别性能. II. 新型吖啶类分子钳的研究 总被引:1,自引:0,他引:1
采用差紫外谱法研究了新型芳酰胺-吖啶分子钳(1~7)对苯胺、苯二胺(邻, 间, 对)等中性分子的识别性能. 测定了结合常数(Ka)和自由能变化(ΔG°), 结果表明, 所有的分子钳受体与所考察的客体分子均形成1∶1型超分子配合物. 识别作用的主要推动力为多重氢键、van der Waals等的协同作用. 主客体间尺寸/形状匹配、几何互补等因素对识别性能均有重要的影响. 利用核磁氢谱与计算机模拟作为辅助手段对主要的实验结果与现象进行了解释. 相似文献
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Comb‐shaped guanidinium functionalized poly(ether sulfone)s for anion exchange membranes: Effects of the spacer types and lengths
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Ying Chen Yanping Tao Jinlei Wang Shanzhong Yang Sheng Cheng Haibing Wei Yunsheng Ding 《Journal of polymer science. Part A, Polymer chemistry》2017,55(8):1313-1321
A series of poly(ether sulfone)‐based anion exchange membranes (AEMs), tethering with guanidinium side chains with different spacers, were synthesized via azide‐alkyne cycloaddition, deprotection, and the subsequent ion exchange reactions. The designed polymer structures were verified by the 1H NMR spectra. Because of the appropriate water uptake and formation of interconnected ionic clusters, the GPES‐3C with propyl spacer showed higher conductivity than the GPES‐1C and GPES‐9C, with methylene and nonyl spacers, respectively. Comparatively, the GPES‐EO AEM with two ethylene oxide (EO) spacers exhibited even higher conductivity, these can be interpreted by interconnectivity of ionic channels and hydrophilicity nature of the EO spacer. Additionally, although the GPES membranes displayed sufficient thermal stability, the chemical stability of as‐prepared materials needs to be much improved for fuel cell applications. Overall, these results demonstrated that the properties of “pendent‐type” AEM can be tuned facilely by the spacer types and lengths. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1313–1321 相似文献
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In biological systems, the selective and high‐affinity recognition of anionic species is accomplished by macromolecular hosts (anion‐binding proteins) that have been “optimized” through evolution. Surprisingly, it is only recently that chemists have systematically attempted to develop anion‐responsive synthetic macromolecules for potential applications in medicine, national security, or environmental monitoring. Recent results indicating that unique features of polymeric systems such as signal amplification, multivalency, and cooperative behavior may be exploited productively in the context of anion recognition and sensing are documented. The wide variety of interactions—including Lewis acid/base, ion‐pairing, and hydrogen bonding—that have been employed for this purpose is reflected in the structural diversity of anion‐responsive macromolecules identified to date. 相似文献
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An Iminocoumarin Sulfonamide Based Turn‐On Fluorescent Probe for the Detection of Biothiols in Aqueous Solution
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Yan‐Ling Yang Fu‐Ming Zhang Prof. Dr. Ya‐Wen Wang Bao‐Xin Zhang Prof. Dr. Ran Fang Prof. Dr. Jian‐Guo Fang Prof. Dr. Yu Peng 《化学:亚洲杂志》2015,10(2):422-426
A new chemodosimeter for the highly selective sensing and imaging of biothiols was designed and realized in phosphate‐buffered saline solution at pH 7.4 through a fluorescence “off–on” response. A unique mechanism featuring a two‐step cascade (biothiols→H2O) sequence for this remarkable recognition is disclosed for the first time. 相似文献
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Xander Schaapkens Joël H. Holdener Jens Tolboom Eduard O. Bobylev Prof. Dr. Joost N. H. Reek Dr. Tiddo J. Mooibroek 《Chemphyschem》2021,22(12):1187-1192
Designing compounds for the selective molecular recognition of carbohydrates is a challenging task for supramolecular chemists. Macrocyclic compounds that incorporate isophtalamide or bisurea spacers linking two aromatic moieties have proven effective for the selective recognition of all-equatorial carbohydrates. Here, we explore the molecular recognition properties of an octa-urea [Pd2L4]4+ cage complex ( 4 ). It was found that small anions like NO3− and BF4− bind inside 4 and inhibit binding of n-octyl glycosides. When the large non-coordinating anion ‘BArF’ was used, 4 showed excellent selectivity towards n-octyl-α-D-Mannoside with binding in the order of Ka≈16 M−1 versus non-measurable affinities for other glycosides including n-octyl-β-D-Glucoside (in CH3CN/H2O 91 : 9). 相似文献
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Baiyi Zu Ying Zhang Xianzhi Guo Huiqi Zhang 《Journal of polymer science. Part A, Polymer chemistry》2010,48(3):532-541
The first application of atom transfer radical “bulk” polymerization (ATRBP) in molecular imprinting is described, which provides molecularly imprinted polymers (MIPs) with obvious imprinting effects towards the template, very fast binding kinetics, and an appreciable selectivity over structurally related compounds. In comparison with the MIP prepared via the normally used traditional “bulk” free radical polymerization (BFRP), the MIPs obtained via ATRBP showed somewhat lower binding capacities and apparent maximum numbers Nmax for high‐affinity sites as well as quite similar binding association constants Ka for high‐affinity sites and high‐affinity site densities, in contrast with the previous reports (e.g., nitroxide/iniferter‐mediated “bulk” polymerization provided MIPs with improved properties). This is tentatively ascribed to the occurrence of rather fast gelation process in ATRBP, which greatly restricted the mobility of the chemical species, leading to a heavily interrupted equilibrium between dormant species and active radicals and heterogeneous polymer networks. In addition, the general applicability of ATRBP was also confirmed by preparing MIPs for different templates. This work clearly demonstrates that applying controlled radical polymerizations (CRPs) in molecular imprinting not always benefits the binding properties of the resultant MIPs, which is of significant importance for the rational use of CRPs in generating MIPs with improved properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 532–541, 2010 相似文献
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The Contrasting Recognition Behavior of β‐Cyclodextrin and Its Sulfobutylether Derivative towards 4′,6‐Diamidino‐2‐phenylindole
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Meenakshi N. Shinde Dr. Achikanath C. Bhasikuttan Dr. Jyotirmayee Mohanty 《Chemphyschem》2015,16(16):3425-3432
The noncovalent interactions between 4′, 6‐diamidino‐2‐phenylindole (DAPI) and sulfobutylether β‐cyclodextrin (SBE7β‐CD) are evaluated by using photochemical measurements and compared with that of native β‐CD. Contrasting recognition behavior and intriguing modulations in the photochemical behavior of DAPI were observed. In particular, a large enhancement in the fluorescence emission and excited‐state lifetime were seen upon binding to SBE7β‐CD, with the SBE7β‐CD inclusion complex being approximately 1000 times stronger than that of β‐CD. The ensuing fluorescence “turn on” was demonstrated to be responsive to chemical stimuli, such as metal ions and adamantylanmine (AD). Upon addition of Ca2+/AD, nearly quantitative dissociation of the complex was established to regenerate the free dye and result in fluorescence “turn off”. The SO3? groups are believed to be critical for the strong and selective binding of the chromophore and the stimuli‐responsive tuning. This is as an important design criterion for the optimization of host–guest properties through supramolecular association, which is relevant for drug‐delivery applications. 相似文献