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Inspired by nature, artificial hydrogen bond‐based anion receptors have been developed to achieve high anion selectivity; however, their binding affinity is usually low. The potency of these receptors is usually increased by the introduction of aryl substituents, which withdraw electrons from their binding site through the resonance effect. Here, we show that the polarization of the C(sp3)‐H binding site of bambusuril receptors, and thus their potency to bind anions, can be modulated by the inductive effect. The presence of electron‐withdrawing groups on benzyl substituents of bambusurils significantly increases their binding affinities to halides, resulting in the strongest iodide receptor reported to date with an association constant greater than 1013 M−1 in acetonitrile. A Hammett plot showed that while the bambusuril affinity toward halides linearly increases with the electron‐withdrawing power of their substituents, their binding selectivity remains essentially unchanged. [ABSTRACT FROM AUTHOR]

Inspired by nature, artificial hydrogen bond‐based anion receptors have been developed to achieve high anion selectivity; however, their binding affinity is usually low. The potency of these receptors is usually increased by the introduction of aryl substituents, which withdraw electrons from their binding site through the resonance effect. Here, we show that the polarization of the C(sp3)‐H binding site of bambusuril receptors, and thus their potency to bind anions, can be modulated by the inductive effect. The presence of electron‐withdrawing groups on benzyl substituents of bambusurils significantly increases their binding affinities to halides, resulting in the strongest iodide receptor reported to date with an association constant greater than 1013 M−1 in acetonitrile. A Hammett plot showed that while the bambusuril affinity toward halides linearly increases with the electron‐withdrawing power of their substituents, their binding selectivity remains essentially unchanged. [ABSTRACT FROM AUTHOR]

Highlights • A new supramolecular polymer was fabricated by crown ether-based host‒guest interaction and Ag-coordination. • The supramolecular polymer displayed sensitive property to H 2 S. • The supramolecular polymer was made into a thin film and used as a convenient test kit for detecting H 2 S. • The thin film was more stable under moisture and sunlight than simple silver ion. Abstract A supramolecular polymer was fabricated via crown ether-based host–guest interaction and Ag-coordination. It displayed hydrogen sulfide sensitive property. In addition, the supramolecular polymer was made into a thin film which can be used to detect hydrogen sulfide. [ABSTRACT FROM AUTHOR]

• Curcubit[8]uril and 1,2-bis(4-pyridyl)ethylene form a 1:2 inclusion complex. • The crystal structure of [(C 48 H 48 N 32 O 16)@2(C 12 H 12 N 2)4(Cl)] is reported. • The host-guest complex is weakly fluorescent. • Addition of the insecticide pymetrozine greatly enhanced the fluorescence. • The system is capable of detecting pymetrozine. Herein, we report a simple fluorescence-enhanced system for the selective recognition and determination of the insecticide pymetrozine. 1H NMR spectroscopic data indicate that 1,2-bis(4-pyridyl)ethylene (BPE) is partially encapsulated in the cavity of the cucurbit[8]uril (Q[8]) in aqueous solution, forming a stable 1:2 host-guest inclusion complex. Good evidence is also provided by other characterization techniques including single crystal X-ray diffraction, UV–Vis and fluorescence spectroscopies. This host-guest inclusion complex shows weak fluorescence in aqueous solution. Interestingly, the addition of pymetrozine greatly enhanced the fluorescence of the host-guest inclusion complex. In contrast, no significant fluorescence enhancement was observed on addition of 10 other pesticides. The concentration of pymetrozine in aqueous solution was easily detected based on the linear relationship between fluorescence intensity and pymetrozine concentration. Therefore, this paper reports a new method to identify and determine pymetrozine by fluorescence enhancement. T his paper demonstrated a simple and validated fluorescence enhancing method for the selective recognition and determination of the pymetrozine. 1,2-bis(4-pyridyl)ethylene (BPE) can be encapsulated into the cucurbit[8]uril (Q[8]) in aqueous solution to form stable 1:2 host−guest inclusion complex. Interestingly, the addition of the pymetrozine dramatically enhanced the fluorescence intensity of the inclusion complex. In contrast, the addition other pesticides gives no fluorescence variation. Accordingly, a new fluorescence enhancing method for the recognition and determination of the pymetrozine was established. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel host−guest recognition motif based on a water-soluble pillar[7]arene ( WP7) and a 2,7-diazapyrenium salt ( DMDAP) was prepared. According to the integrated results of 1H NMR, 2D NOESY, UV-vis spectroscopy and fluorescence titration experiments, we demonstrated that the molecular recognition of WP7 to DMDAP in water not only has high association constant but also has pH-responsiveness. Subsequently, we took advantage of this molecular recognition motif to fabricate a supra-amphiphile based on WP7 and an amphiphilic 2,7-diazapyrenium derivative DAPAC. Its controllable self-assembly in water was also investigated by means of TEM and DLS techniques. [ABSTRACT FROM AUTHOR]

Non-covalent self-assembly of multi-components is a promising strategy for constructing supramolecular hydrogels. However, it remains challenging to achieve the multi-responsiveness to external stimuli for supramolecular hydrogels through a low-molecular-weight hydrogelator. Herein, we report a host−guest complex as low-molecular-weight hydrogelator for constructing graphene oxide (GO)-based supramolecular hybrid hydrogels. A 1:2 homoternary complex (CB[8]· NMAH + 2) was formed through host−guest encapsulation of two protonated naphthalen-2-ylmethanamine (NMAH +) molecules in cucurbit[8]uril (CB[8]) host and worked as dynamically assembled electrostatic cross-linker in the presence of GO. The resulted GO hydrogels showed shear-thinning, self-healing properties, and were stimuli-responsive to pH and competing guests. The proposed concept of "assembled electrostatic cross-linker" (AEC) would be extended to construct other novel stimuli-responsive supramolecular materials. [Display omitted] • A facile gelation strategy was proposed by designing a low-molecular-weight host−guest hydrogelator. • The host−guest complex worked as a dynamically reversible cross-linker to yield GO -based hydrogels. • The strategy is expected to open a new route for designing and constructing novel multifunctional supramolecular materials. [ABSTRACT FROM AUTHOR]

• Separation ability of the three COFs-coated CEC were evaluated by separating 8 phthalates. • Relationship between CEC separation ability of three COFs and their structures were investigated. • Docking and DFT were proceeded to get insight into the host−guest interactions. • Reason for the different separation ability was explored on molecular level. Covalent organic frameworks (COFs) have great potential applications in chromatographic separation. So it is crucial to understand the relationship between the separation ability of COFs and their structures. Here we report a strategy to evaluate the separation ability of three 2D COFs and explore the relationship between separation ability and their molecular structures. The three 2D COFs (COF-LZU1, COF-42 and COF-LZU8) have one same building unit 1,3,5-triformylbenzene, while varied from the conjugated linking units and functional side-chains. They were used to construct coated capillary column for capillary electrochromatographic separation of same groups of phthalates. They exhibited different separation efficiencies. COF-42 and COF-LZU8 coated capillary columns provided good signal resolutions and high column efficiencies with high theoretical plate numbers. It is demonstrated that COFs with hydrazone unit and longer side-chains provided higher selectivity and resolutions for the phthalates separation. Molecular simulations and DFT calculations were further proceeded to explore the deep reason why the three COFs coated CEC displayed different separation ability based on the host−guest interactions on molecular level. This work highlights a new opportunity to select or design functional COFs and improve their efficiency in chromatographic separation based on host−guest chemistry. [ABSTRACT FROM AUTHOR]

Cocaine (Coc) is one of the illegal drugs and is harmful to digestive, immune, cardiovascular and urogenital systems. To achieve drug abuse control and legal action, it is essential to develop an effective method for cocaine analysis. In this work, an aptasensor has been developed using atom transfer radical polymerization (ATRP) based on host−guest chemistry for electrochemical analysis of cocaine. The NH 2 −DNA (Apt1) was immobilized on the indium tin oxide (ITO) electrode via addition reaction, and Fc−DNA (Apt2) was introduced to ITO relying on the specific recognition of cocaine. The Apt2 can initiate host−guest chemistry between Apt2 and ATRP initiators (β−CD−Br 15), then the β−CD−Br 15 further triggers ATRP. Moreover, ATRP avoids the sluggish kinetics and poor coupling capability sustained. The result shows a sensitive and selective analysis of cocaine within a linear range from 0.1 ng/mL to 10 μg/mL (R2 = 0.9985), with the detection limit down to 0.0335 ng/mL. Thus, this strategy provides a universal method for the analysis of illegal drugs. [Display omitted] • Firstly, it was reported for cocaine detection based on host−guest chemistry and atom transfer radical polymerization (ATRP). • Ultra-high efficiency was discovered in the synthesized macroinitiator β−CD−Br 15. • This biosensor was successfully achieved in biological samples. [ABSTRACT FROM AUTHOR]

In this work, the selectivity of two well-known cryptands, ([2.2.1]cryptand (221) and [2.2.2]cryptand (222), for sodium and potassium cations in both the gas phase and solution are compared to that of two familiar crown ethers, 18-crown-6 (18C6) and dibenzo-18-crown-6 (DB18C6). Intrinsic cation affinity of hosts, cavity size fitting, deformation/strain of hosts as well as solvent effect, for complexation of hosts with cations were calculated at DFT (BP86 and B97-1) level of theory using def2-TZVP triple zeta basis set. The resulting data show that the larger stability of [M ⊂ 221 + and [M ⊂ 222 + complexes relative to [M ⊂ 18C6 + and [M ⊂ DB18C6 + complexes is due to the larger intrinsic affinity of 222 and 221 hosts for both Na+ and K+ cations. On the other hand, the data show that the size match is in disagreement with larger intrinsic affinity of [Na ⊂ Host + complexes compared to [K ⊂ Host + complexes studied here. The results also show that the intrinsic affinities of all four hosts for Na+ are greater than those for K+, but the hosts 222 , 18C6 and DB18C6 are K+-selective in solution due to the solvent effect. Thus, obviously the main reason for higher selectivity of 222 , 18C6 and DB18C6 hosts for K+ compared to Na+ is the solvent effect and not a greater affinity and/or a better size match. The above conclusions were further confirmed by a good correlation between the experimental and calculated formation constants in solution. Unlabelled Image • The selectivity of well-known cryptands and crown ethers for Na+ and K+ cations are studied. • The size match is in disagreement with larger intrinsic affinity of [Na ⊂ Host + complexes. • The solvent effect is the main reason for higher selectivity of most hosts for potassium. • There is a good correlation between the experimental and calculated logK values in solution. [ABSTRACT FROM AUTHOR]