Guest encapsulation underpins the functional properties of self‐assembled capsules yet identifying systems capable of strongly binding small organic molecules in solution remains a challenge. Most coordination capsules rely on the hydrophobic effect to ensure effective solution‐phase association. In contrast, we show that using non‐interacting anions in apolar solvents can maximize favorable interactions between a cationic Pd2L4 host and charge‐neutral guests resulting in a dramatic increase in binding strength. With quinone‐type guests, association constants in excess of 108 m ?1 were observed, comparable to the highest previously recorded constant for a metallosupramolecular capsule. Modulation of optoelectronic properties of the guests was also observed, with encapsulation either changing or switching‐on luminescence not present in the bulk phase. 相似文献
Guest‐induced M18L6–M24L8 capsule–capsule conversion is reported. Both capsules are composed of PdII ethylenediamine units (M) and 1,3,5‐tris(3,5‐pyrimidyl)pyrimidine (L), and form trigonal bipyramidal (M18L6) and octahedral (M24L8) closed‐shell structures with huge hydrophobic inner spaces. The M18L6 trigonal bipyramid is converted to the M24L8 octahedron through encapsulation of large aromatic guests, with the latter capsule possessing a cavity volume three times larger than the former. Despite the dynamic properties of the capsule host, the encapsulated guests are difficult to extract and are thus isolated from the external environment. 相似文献
The host–guest interaction between poly aromatic hydrocarbon/azine and the newly synthesized ExBox4+ complex is studied with the help of density functional theory. The solvent‐phase interaction energy is found to decrease with gradual substitution of methine groups (?CH?) from the six‐membered ring of guest molecules with N atoms in the resultant azine@ExBox4+ complex. The nature of the binding interaction is studied with the help of newly developed noncovalent interaction (NCI) plot program package along with energy decomposition analysis and charge decomposition analysis. The interactions are mostly π‐type van der Waals interactions. 相似文献
Anisotropic expansion of a spherical M2L4 coordination capsule through the elongation of the ligand led to a new M2L′4 capsule. The expanded capsule provides an elliptical cavity encircled by polyaromatic frameworks with large openings and thereby can encapsulate elliptical fullerene C70 and monofunctionalized fullerene C60 in high yields. In addition, selective formation of a new M2L2L′2 capsule occurs by mixing the original M2L4 and expanded M2L′4 capsules in a 1:1 ratio upon addition of C60 or monofunctionalized C60 as a template molecule. 相似文献
Recent advances in host–guest chemistry have significantly influenced the construction of supramolecular soft biomaterials. The highly selective and non‐covalent interactions provide vast possibilities of manipulating supramolecular self‐assemblies at the molecular level, allowing a rational design to control the sizes and morphologies of the resultant objects as carrier vehicles in a delivery system. In this Focus Review, the most recent developments of supramolecular self‐assemblies through host–guest inclusion, including nanoparticles, micelles, vesicles, hydrogels, and various stimuli‐responsive morphology transition materials are presented. These sophisticated materials with diverse functions, oriented towards therapeutic agent delivery, are further summarized into several active domains in the areas of drug delivery, gene delivery, co‐delivery and site‐specific targeting deliveries. Finally, the possible strategies for future design of multifunctional delivery carriers by combining host–guest chemistry with biological interface science are proposed. 相似文献
In order to promote the development of photodynamic therapy (PDT), undesired side effects like low tumor specificity and the “always‐on” phenomenon should be avoided. An effective solution is to construct an adaptive photosensitizer that can be activated to generate reactive oxygen species (ROS) in the tumor microenvironment. Herein, we design and synthesize a supramolecular switch based on a host–guest complex containing a water‐soluble pillar[5]arene ( WP5 ) and an AIEgen photosensitizer ( G ). The formation of the host–guest complex WP5 ? G quenches the fluorescence and inhibits ROS generation of G . Benefitting from the pH‐responsiveness of WP5 , the binding site between G and WP5 changes in an acidic environment through a shuttle movement. Consequently, fluorescence and ROS generation of the host–guest complex can be switched on at pH 5.0. This work offers a new paradigm for the construction of adaptive photosensitizers by using a supramolecular method. 相似文献
Pentacyclic triterpenoids, a class of naturally bioactive products having multiple functional groups, unique chiral centers, rigid skeletons, and good biocompatibility, are ideal building blocks for fabricating versatile supramolecular structures. In this research, the natural pentacyclic triterpenoid glycyrrhetinic acid (GA) was used as a guest molecule for β‐cyclodextrin (β‐CD) to form a GA/β‐CD (1:1) inclusion complex. By means of GA and β‐CD pendant groups in N,N′‐dimethylacrylamide copolymers, a supramolecular polymer hydrogel can be physically cross‐linked by host–guest interactions between GA and β‐CD moieties. Moreover, self‐healing of this hydrogel was observed and confirmed by step‐strain rheological measurements, whereby the maximum storage modulus occurred at a [GA]/[β‐CD] molar ratio of 1:1. Additionally, these polymers displayed outstanding biocompatibility. The introduction of a natural pentacyclic triterpenoid into a hydrogel system not only provides a biocompatible guest–host complementary GA/β‐CD pair, but also makes this hydrogel an attractive candidate for tissue engineering. 相似文献
Upon complexation with PdII ions, precisely designed strandlike ligands with two tris(3,5‐pyridine) units at both terminals were assembled, with the aid of a linear template molecule, into a discrete tubular complex with a length of 3.5 nm. The high stability and the well‐defined structure of the coordination nanotube were revealed by NMR spectroscopy, cold‐spray ionization MS, and single‐crystal X‐ray analysis. Guest lengths were discriminated by the tube: When the association of strandlike guest molecules, in which two biphenylene units are linked with an (OCH2CH2)n linker, were compared, the tube selectively recognized an appropriate guest whose length was comparable to that of the tube. Tetrathiafulvalene (TTF)‐terminated linear guests were directly oxidized to TTF2+ in the tube, but reduced stepwise via TTF+? outside the tube. 相似文献
A new strategy is reported for multicolor fluorescence writing on thin solid films with mechanical forces. This concept is illustrated by the use of a green‐fluorescent pentiptycene derivative 1 , which forms variably colored fluorescent exciplexes: a change from yellow to red was observed with anilines, and fluorescence quenching (a change to black) occurred in the presence of benzoquinone. Mechanical forces, such as grinding and shearing, induced a crystalline‐to‐amorphous phase transition in both the pristine and guest‐adsorbed solids that led to a change in the fluorescence color (mechanofluorochromism) and a memory of the resulting color. Fluorescence drawings of five or more colors were created on glass or paper and could be readily erased by exposure to air and dichloromethane fumes. The structural and mechanistic aspects of the observations are also discussed. 相似文献
A novel pH‐switchable macroscopic assembly is reported using alginate‐based hydrogels functionalized with host (α‐cyclodextrin, αCD) and guest (diethylenetriamine, DETA) moieties. Since the interaction of αCD and DETA is pH sensitive, the host hydrogel and guest hydrogel could adhere together when the pH is 11.5 and separate when the pH is 7.0. Furthermore, this pH‐controlled adhesion and dissociation shows a good reversibility. The host and guest polymers have good biocompatibility; therefore, this pH‐sensitive macroscopic assembly shows great potential in biotechnological and biomedical applications.
Herein, we report a reversible modular chloride transport process based on host–guest competitive interactions between an imidazolium‐based chloride carrier and beta‐cyclodextrin. We report evidence for the formation of the supramolecular complex between 1,3‐bis(2‐(adamantan‐1‐yl)ethyl)imidazolium bis(trifluorometyl‐sulfonyl)imide with two β‐cyclodextrins. Through fluorescence assays in liposomes and black lipid membrane experiments, we demonstrate that the formation of the supramolecular complex results in the inhibition of the chloride transport. We show that the chloride transport process can be entirely restored in the presence of competitive adamantyl‐functionalized guests. This is the first example of an entirely reversible modular chloride transport process in phospholipid bilayers involving a mobile carrier transporter and cyclodextrin supramolecular complex. 相似文献
A new host molecule consists of four terpyridine groups as the binding sites with zinc(II) ion and a copillar[5]arene incorporated in the center as a spacer to interact with guest molecule was designed and synthesized. Due to the 120 ° angle of the rigid aromatic segment, a cross‐linked dimeric hexagonal supramolecular polymer was therefore generated as the result of the orthogonal self‐assembly of metal–ligand coordination and host–guest interaction. UV/Vis spectroscopy, 1H NMR spectroscopy, viscosity and dynamic light‐scattering techniques were employed to characterize and understand the cross‐linking process with the introduction of zinc(II) ion and guest molecule. More importantly, well‐defined morphology of the self‐assembled supramolecular structure can be tuned by altering the adding sequence of the two components, that is, the zinc(II) ion and the guest molecule. In addition, introduction of a competitive ligand suggested the dynamic nature of the supramolecular structure. 相似文献
Host–guest interactions between polyglycerol dendrimers of generations 3 and 4 (PGD‐G3 and G4) and 4‐amino‐3‐hydroxynapthalene‐2‐sulphonic acid (AHSA) were investigated by fluorescence spectroscopy, isothermal titration calorimetry (ITC), and dynamic light scattering (DLS). PGD‐G3 molecules were found to form an associated state with an average diameter of 82.7 nm in aqueous solution, in which PGD‐G3 provided a much more polar microenvironment than glycerol. PGD‐G3 and AHSA interacted attractively, showing a binding constant of 5.3×105 M ?1 with a 2:1 stoichiometry. On the other hand, AHSA interacted with the periphery of PGD‐G4, the majority of which existed as a unimer, forming a less polar microenvironment. The driving force of the interactions for PGD‐G3 and ‐G4 were mainly enthalpically and entropically driven, respectively. The generation‐dependent host–guest interactions were described in conjunction with thermodynamic parameters. 相似文献
Two sets of cyan and yellow fluorescent proteins, monomeric analogues, and analogues with a weak affinity for dimerization were functionalized with supramolecular host–guest molecules by expressed protein ligation. The host–guest elements induce selective assembly of the monomeric variants into a supramolecular heterodimer. For the second set of analogues, the supramolecular host–guest system acts in cooperation with the intrinsic affinity between the two proteins, resulting in the induction of a selective protein–protein heterodimerization at a more dilute concentration. Additionally, the supramolecular host–guest system allows locking of the two proteins in a covalent heterodimer through the facilitated and selective formation of a reversible disulfide linkage. For the monomeric analogues this results in a strong increase of the energy transfer between the proteins. The protein heterodimerization can be reversed in a stepwise fashion. The trajectory of the disassembly process differs for the monomeric and dimerizing set of proteins. The results highlight that supramolecular elements connected to proteins can both be used to facilitate the interaction between two proteins without intrinsic affinity and to stabilize weak protein–protein interactions at concentrations below those determined by the actual affinity of the proteins alone. The subsequent covalent linkage between the proteins generates a stable protein dimer as a single species. The action of the supramolecular elements in concert with the proteins thus allows the generation of protein architectures with specific properties and compositions. 相似文献