共查询到20条相似文献,搜索用时 0 毫秒
1.
Jovana V. Mili Thomas Schneeberger Michal Zalibera Karolina Z. Milowska Quy K. Ong Nils Trapp Laurent Ruhlmann Corinne Boudon Carlo Thilgen Franois Diederich 《Helvetica chimica acta》2019,102(2)
The utility of molecular actuators in nanoelectronics requires activation of mechanical motion by electric charge at the interface with conductive surfaces. We functionalized redox‐active resorcin[4]arene‐quinone cavitands with thioethers as surface‐anchoring groups at the lower rim and investigated their propensity to act as electroswitchable actuators that can adopt two different conformations in response to changes in applied potential. Molecular design was assessed by DFT calculations and X‐ray analysis. Electronic properties were experimentally studied in solution and thin films electrochemically, as well as by X‐ray photoelectron spectroscopy on gold substrates. The redox interconversion between the oxidized (quinone, Q ) and the reduced (semiquinone, SQ ) state was monitored by UV‐Vis‐NIR spectroelectrochemistry and EPR spectroscopy. Reduction to the SQ state induces a conformational change, providing the basis for potential voltage‐controlled molecular actuating devices. 相似文献
2.
3.
Dr. Víctor García-López Dr. Michal Zalibera Dr. Nils Trapp Dr. Martin Kuss-Petermann Prof. Dr. Oliver S. Wenger Prof. Dr. François Diederich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(50):11451-11461
Resorcin[4]arene cavitands, equipped with diverse quinone ( Q ) and [Ru(bpy)2dppz]2+ (bpy=2,2′-bipyridine, dppz=dipyrido[3,2-a:2′,3′-c]phenazine) photosensitizing walls in different configurations, were synthesized. Upon visible-light irradiation at 420 nm, electron transfer from the [Ru(bpy)2dppz]2+ to the Q generates the semiquinone ( SQ ) radical anion, triggering a large conformational switching from a flat kite to a vase with a cavity for the encapsulation of small guests, such as cyclohexane and heteroalicyclic derivatives, in CD3CN. Depending on the molecular design, the SQ radical anion can live for several minutes (≈10 min) and the vase can be generated in a secondary process without need for addition of a sacrificial electron donor to accumulate the SQ state. Switching can also be triggered by other stimuli, such as changes in solvent, host–guest complexation, and chemical and electrochemical processes. This comprehensive investigation benefits the development of stimuli-responsive nanodevices, such as light-activated molecular grippers. 相似文献
4.
Shivanyuk A Saadioui M Broda F Thondorf I Vysotsky MO Rissanen K Kolehmainen E Böhmer V 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(9):2138-2148
In solvents such as chloroform or benzene, tetraurea calix[4]arenes 1 form dimeric capsules in which one solvent molecule is usually included as guest. To explore the structural requirements for the formation of such hydrogen-bonded dimers we replaced one p-tolylurea residue by a simple acetamide function. The resulting calix[4]arene 2 a, substituted at its wide rim with one acetamide and three p-tolylurea functions, assumes a C(1)-symmetrical conformation in apolar solvents as shown by (1)H NMR, which is not compatible with the usual capsule. In the crystalline state, four molecules of 2 a, adopting a pinched cone conformation, assemble into a quasi S(4)-symmetrical tetramer stabilized by a cyclic array of 24 NH.O==C hydrogen bonds and four NH.pi interactions. Four acetamide groups are hydrogen-bonded to each other and pack tightly in the center of the assembly. All polar residues are buried inside the tetramer, the surface of which is lipophilic. Extensive NMR studies revealed similar structures in apolar solvents such as [D]chloroform or [D(6)]benzene for calixacetamides 2 a-c. The formation of these tetramers in solution is critically dependent on the size of the amide fragment, so that propionamide 2 d, butyramide 2 e, and p-tolylamide 2 f form only ill-defined aggregates. This is caused by steric crowding inside the tetrameric assembly. The tetramers persist during molecular dynamics simulations, and the optimized average structure of the MD run is similar to that found in the crystalline state. Theoretical studies revealed that cooperation of hydrogen bonds with multiple NH.pi, C--H.pi, and pi.pi attractions make the tetramer more stable than the capsular dimer with the solvent as guest. In the presence of tetraethylammonium salts, however, compounds 2 a-e form dimeric capsular assemblies, each incorporating a single ammonium cation. Only one of two possible regioisomeric dimers is formed, in which both acetamide groups are surrounded by two urea residues. These examples give striking evidence of how self-assembly in solution can be strongly dependent on subtle structural factors and of how the formation of dimeric capsules can be induced by the presence of an appropriate guest. 相似文献
5.
以去叔丁基硫杂杯[4]芳烃与Mn(II)为研究对象,通过改变体系溶剂分别得到了两个四核化合物Mn4(T4A)2 (1)和Mn4(T4A)2(DMF)2(2) (T4A = thiacalix[4]arene)。当反应溶剂为氯仿(CHCl3)和甲醇的混合溶剂时,形成的是以四核锰为结构单元的二维“笼目”(Kagomé)状超分子化合物1,而当反应溶剂为N,N-二甲基甲酰胺(DMF)和甲醇的混合溶剂时,得到的是格子状二维超分子互穿的三维结构化合物2。化合物1具有很大的溶剂占有空隙,是一个潜在的多孔材料,而化合物2是一个紧密堆积的拓展结构。 相似文献
6.
7.
8.
Arturo Arduini Prof. Rocco Bussolati Dr. Alberto Credi Prof. Giovanni Faimani Dr. Sandrine Garaudée Dr. Andrea Pochini Prof. Andrea Secchi Dr. Monica Semeraro Serena Silvi Dr. Margherita Venturi Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(13):3230-3242
Traffic control : By exploiting the interplay of kinetic and thermodynamic effects, the direction of threading/dethreading in a nonsymmetric calixarene wheel can be selected by an appropriate choice of the head group incorporated in the molecular axle (see figure).
9.
10.
Ali A. Husain Arthur M. Maknenko Prof. Dr. Kirpal S. Bisht 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(18):6223-6227
The synthesis of novel spatially directional multivalent resorcin[4]arene cavitand glycoconjugates (RCGs) and their ability to catalyze organic reactions is reported. The β‐d ‐glucopyranoside moieties on the upper rim of the “bowl”‐shaped resorcin[4]arene cavitand core are capable of multiple hydrogen‐bond interactions resulting in a pseudo‐cavity, which has been investigated for organic transformations in aqueous media. The RCGs have been demonstrated to catalyze thiazole formation, thiocyanation, copper(I)‐catalyzed azide alkyne cycloaddition (CuAAC), and Mannich reactions; they impart stereoselectivity in the three‐component Mannich reaction. Thermodynamic values obtained from 1H diffusion‐ordered spectroscopy (DOSY) experiments suggest that the upper saccharide cavity of the RCG and not the resorcin[4]arene cavity is the site of the complexation event. 相似文献
11.
Dalgarno SJ Hardie MJ Makha M Raston CL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(12):2834-2839
Control over the conformational flexibility of p-sulfonatocalix[6]arene in the solid state is possible in the presence of varied stoichiometric amounts of [18]crown-6 and selected lanthanide(III) chlorides. Complexes 1 and 2 have the calixarene in the elusive up-up double cone conformation, whilst complex 3 has the calixarene in the centrosymmetric up-down double partial cone conformation, whereby it acts as a divergent receptor. Complex 1 has a double molecular capsule arrangement which is composed of two p-sulfonatocalix[6]arenes shrouding two [18]crown-6 molecules, also with both coordinated and homoleptic aquated lanthanide ions around the hydrophilic sulfonate rims of the calixarenes. Complex 2 has a ferris wheel arrangement with one lanthanide metal centre coordinated to a sulfonate group and another coordinated to the crown ether whilst tethered to a sulfonate group of the calixarene. Complex 3 forms from a solution with large excess of [18]crown-6, and possesses a crown ether molecule in each of the partial cones and has homoleptic aquated lanthanide ions involved in a complicated hydrogen-bonding regime within the extended structure. 相似文献
12.
Park SJ Kwon OH Lee KS Yamaguchi K Jang DJ Hong JI 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(17):5353-5359
The acid-assisted and guest-induced formation of superstructures was achieved by the addition of haloacetic acids to a toluene solution of the resorcin[4]arene derivatives 1 and [60]fullerenes. The formation of dimeric superstructures that encapsulated a nanosized guest molecule was observed when appropriate acids, such as haloacetic acids, and suitable guest molecules, such as [60]fullerenes, were co-added to a toluene solution of cavitand 1 that has four pyridine units, whereas a complicated equilibrium between several species was detected without [60]fullerenes, and the formation of discrete superstructures was not monitored in the absence of haloacetic acids. The spectroscopic data indicate that the formed [60]fullerene-encapsulated complexes have the structure of 2. These complexes are self-assembled through pyridinium-anion-pyridinium interactions and by pi-pi and van der Waals interactions. The rate of decomplexation of 2 is estimated to be 3.1 s(-1) from a 2D exchange NMR spectrum. The [60]fullerene encapsulation process can be controlled by modifying the amounts of acids used, changing the temperature of the system, altering the ratio of acid/base, and even through varying the solvent polarity. Moreover, the fluorescence spectra show band-narrowing spectral changes and a retardation of the relaxation characteristics of isolated and isotropic [60]fullerenes, which indicates that the environmental change around [60]fullerene is induced upon its encapsulation. 相似文献
13.
In recent years it has been observed that resorcin[4]arenes and pyrogallol[4]arenes form hydrogen-bonded hexameric capsules in nonpolar solvents. In the present study we have used NMR spectroscopy, with an emphasis on diffusion NMR, to investigate the self-assembly and the aggregation mode of solutions of octahydroxypyridine[4]arene (1 b) in chloroform. In spectroscopic studies, the hexameric capsule of C-undecylresorcin[4]arene (2 b) was used as a reference compound and in some cases also as an internal reference. The current diffusion NMR spectroscopy study shows, in contrast to a previous report, that compound 1 b self-assembles spontaneously into hexameric and dimeric aggregates in solutions in chloroform. The (1)H NMR and diffusion NMR spectroscopic studies on a solution of 1 b in CHCl(3) show the presence of new upfield-shifted peaks, which diffuse with the same diffusion coefficient as the hexameric peaks in the spectrum. Therefore, these new upfield-shifted peaks were attributed to encapsulated CHCl(3) molecules. Interestingly, diffusion NMR measurements showed that the addition of trifluoroacetic acid (6.7 equiv), which had no effect on the hexameric capsules of 2 b, led to the disassembly of the hexamer and the dimer of 1 b into its monomers. Therefore, we conclude that compound 1 b self-assembles spontaneously into hexameric capsules in nonpolar organic solvents, as do resorcin[4]arenes 2 b and 2 c and pyrogallol[4]arenes 3 a and 3 b. 相似文献
14.
Carboxylate‐Driven Supramolecular Assemblies of Protonated meso‐Aryl‐Substituted Dipyrrolylpyrazoles 下载免费PDF全文
Prof. Hiromitsu Maeda Kengo Chigusa Dr. Ryohei Yamakado Dr. Tsuneaki Sakurai Prof. Shu Seki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(26):9520-9527
Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4‐position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single‐crystal X‐ray and synchrotron XRD analyses. In particular, the complexation of protonated dpp species possessing long alkyl chains with dicarboxylates resulted in highly ordered assembled structures, the packing modes of which as lamellar structures were controlled by the lengths of the spacer units between two carboxylate moieties. The charge‐carrier transporting properties of the solid materials were also controlled by bound anions, including dicarboxylates. 相似文献
15.
Two‐Photon‐Responsive Supramolecular Hydrogel for Controlling Materials Motion in Micrometer Space 下载免费PDF全文
Tatsuyuki Yoshii Dr. Masato Ikeda Prof. Dr. Itaru Hamachi 《Angewandte Chemie (International ed. in English)》2014,53(28):7264-7267
Spatiotemporal control of fluidity inside a soft matrix by external stimuli allows real‐time manipulation of nano/micromaterials. In this study, we report a two‐photon‐responsive peptide‐based supramolecular hydrogel, the fluidity of which was dramatically controlled with high spatial resolution (10 μm×10 μm×10 μm). The off–on switching of the Brownian motion of nanobeads and chemotaxis of bacteria by two‐photon excitation was successfully demonstrated. 相似文献
16.
17.
18.
19.
Stereospecific Cyclic Poly(methyl methacrylate) and Its Topology‐Guided Hierarchically Controlled Supramolecular Assemblies 下载免费PDF全文
Jing Ming Ren Prof. Kotaro Satoh Dr. Tor Kit Goh Dr. Anton Blencowe Dr. Kanji Nagai Dr. Kenji Ishitake Dr. Andrew Joseph Christofferson Dr. George Yiapanis Prof. Irene Yarovsky Prof. Masami Kamigaito Prof. Greg Guanghua Qiao 《Angewandte Chemie (International ed. in English)》2014,53(2):459-464
In this study, the stereocomplexation between a novel stereospecific cyclic vinyl polymer, that is, cyclic syndiotactic poly(methyl methacrylate) (st‐PMMA), with the complementary linear isotactic (it‐) PMMA was investigated. Surprising new insight into the effects of the topology (i.e., end groups), size, and tacticity of the assembling components on stereocomplex formation was obtained. Characterization of the stereocomplexes revealed that the self‐assembly of cyclic st‐PMMAs and linear it‐PMMAs resulted in the formation of an unprecedented “polypseudorotaxane‐type” supramolecular assembly. This stereocomplex exhibited remarkably different physical properties as compared to the conventional PMMA triple‐helix stereocomplex as a result of the restricted topology imposed by the cyclic st‐PMMA assembling component. 相似文献
20.
Hiromitsu Maeda Prof. Dr. Yukio Kusunose Masahiro Terasaki Yoshihiro Ito Chikoto Fujimoto Rika Fujii Takashi Nakanishi Dr. 《化学:亚洲杂志》2007,2(3):350-357
X‐ray analysis of some 1,3‐dipyrrolyl‐1,3‐propanediones synthesized from pyrroles and malonyl chloride derivatives revealed 1D supramolecular networks formed by N? H???O?C interactions in the solid state. Micro‐ and nanometer‐scale morphologies of porous, fibrous, and sheet structures were fabricated by hydrogen‐bonding interactions and determined by fine‐tuning the substituents and the solvents used. Of the unique polymorphs, ordered 2D lamellar sheet structures of the derivatives with long alkyl chains (C16H33, C14H29, and so on) were constructed by van der Waals hydrophobic effects between aliphatic chains as well as hydrogen bonding. 相似文献