基于硫脲衍生物的钳形分子受体的晶体结构及其对F－离子的选择性识别

设计并在超声波辐射下合成了3种基于硫脲衍生物的氢键型钳形分子受体, 单晶结构表明该类主体分子可与DMF形成1∶1型氢键配合物. 在DMF中利用紫外-可见吸收光谱研究了其与4种卤素离子的相互作用, 发现该类中性受体可与阴离子形成主客体配合物, 表现为对F^－有识别作用, 而其它3种卤素离子的加入则无类似的光谱变化, 这可归因于F^－与主体化合物发生氢键作用. 计算表明, 主体与阴离子形成1∶1型的配合物, 结合能力随苯环上取代基亲电性不同而规律变化. ¹H NMR滴定进一步证实了氢键作用的存在及参与类型.     

A Halogen‐Bonding Bis‐triazolium Rotaxane for Halide‐Selective Anion Recognition

A systematic study on the anion‐binding properties of acyclic halogen‐ and hydrogen‐bonding bis‐triazolium carbazole receptors is described. The halide‐binding potency of halogen‐bonding bis‐iodotriazolium carbazole receptors was found to be far superior to their hydrogen‐bonding bis‐triazolium‐based analogues. This led to the synthesis of a mixed halogen‐ and hydrogen‐bonding rotaxane host containing a bis‐iodotriazolium carbazole axle component. The rotaxane’s anion recognition properties, determined by ¹H NMR titration experiments in a competitive aqueous solvent mixture, demonstrated the preorganised halogen‐bonding interlocked host cavity to be halide‐selective, with a strong binding affinity for bromide.     

Urea and thiourea based anion receptors in solution and on polymer supports

Herein we report the development of a new series of surface bound anion sensors exploiting the urea or thiourea motif capable of binding anions through hydrogen bonding interactions. The use of high resolution magic angle spinning ¹H NMR allows the direct comparison of the anion binding properties of these receptors in solution versus those tethered to polymer resins. Some intramolecular hydrogen bonding and solvent effects were observed at the solution:surface interface however in general the anion binding properties of the polymer bound urea and thiourea receptors were maintained.     

Mixed dicationic and monocationic benzidine species in the proton‐transfer compound of benzidine with 3,5‐dinitro­salicylic acid

The crystal structure of the proton‐transfer compound of 1,1′‐biphenyl‐4,4′‐diamine (benzidine) with 3,5‐dinitro­salicylic acid, viz. 1,1′‐biphenyl‐4,4′‐diaminium bis­(4′‐amino‐1,1′‐bi­phenyl‐4‐aminium) tetra­kis(2‐carb­oxy‐4,6‐dinitro­phenol­ate) ethanol disolvate, C₁₂H₁₄N₂²⁺·2C₁₂H₁₃N₂⁺·4C₇H₃N₂O₇⁻·2C₂H₆O, shows the presence of both diprotonated and monoprotonated benzidine cations. The diprotonated species lie across crystallographic inversion centres in the unit cell, while the monoprotonated species occupy general sites. All amine H atoms participate in hydrogen bonding with carboxyl, phenolate and nitro O‐atom acceptors of the salicylate anions, which also participate in hydrogen bonding with the disordered ethanol solvent mol­ecules. Significant inter‐ring anion–anion and anion–monocation π–π inter­actions are also present, giving a three‐dimensional framework structure.     

Chloride‐Anion‐Templated Synthesis of a Strapped‐Porphyrin‐Containing Catenane Host System

The synthesis, structure and anion‐recognition properties of a new strapped‐porphyrin‐containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor–acceptor and coordinative pyridine–zinc interactions. The [2]catenane incorporates a three‐dimensional, hydrogen‐bond‐donating anion‐binding pocket; solid‐state structural analysis of the catenane?chloride complex reveals that the chloride anion is encapsulated within the catenane’s interlocked binding cavity through six convergent CH????Cl and NH???Cl hydrogen‐bonding interactions and solution‐phase ¹H NMR titration experiments demonstrate that this complementary hydrogen‐bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution.     

Metal–Organic Cyclohelicates as Optical Receptors for Glutathione: Syntheses,Structures, and Host–Guest Behaviors

Two trinuclear zinc‐based cyclohelicates, Zn–PDB (PDB=[5‐(dibenzylamino)‐N1′,N3′‐bis(pyridin‐2‐ylmethylene)isophthalohydrazide]) and Zn–PMB (PMB=[5‐(bodipy‐oxy)‐N1′,N3′‐bis(pyridin‐2‐ylmethylene)isophthalohydrazide]) containing dibenzylamino and BODIPY groups, respectively, were generated by incorporating two amide‐containing tridentate chelators into meta‐positions of a substituted phenyl ring. Single‐crystal structure analysis and related spectroscopic characterizations demonstrated the formation of macrocyclic helicals both in the solid state and in solution. The host–guest behavior of the cyclohelical hosts towards γ‐glutamyl‐cysteinyl‐glycine (GSH) and its component amino acids was investigated by spectroscopic titrations. UV/Vis absorption titration and NMR titrations of Zn–PDB and Zn–PMB upon addition of the above‐mentioned guests suggested that the Glu residue of GSH was positioned within the cavity. The COO⁻ groups interacted with metal ions through static interactions. The Cys moiety of GSH interacted with the amide groups sited in host molecules through hydrogen‐bonding interactions to produce measurable spectral changes. Fluorescent titrations of Zn–PMB upon the addition of GSH and ESI‐MS investigations of the titration solutions confirmed the host–guest interaction modes and revealed the possible 1:1 complexation stoichiometry. These results showed that the recognition of a substrate within the cavity of functionalized metal–organic cage‐like receptors could be a useful method to produce supramolecular sensors for biomolecules.     

Halogen‐ and Hydrogen‐Bonding Catenanes for Halide‐Anion Recognition

Halogen‐bonding (XB) interactions were exploited in the solution‐phase assembly of anion‐templated pseudorotaxanes between an isophthalamide‐containing macrocycle and bromo‐ or iodo‐functionalised pyridinium threading components. ¹H NMR spectroscopic titration investigations demonstrated that such XB interpenetrated assemblies are more stable than analogous hydrogen bonding (HB) pseudorotaxanes. The stability of the anion‐templated halogen‐bonded pseudorotaxane architectures was exploited in the preparation of new halogen‐bonding interlocked catenane species through a Grubbs’ ring‐closing metathesis (RCM) clipping methodology. The catenanes’ anion recognition properties in the competitive CDCl₃/CD₃OD 1:1 solvent mixture revealed selectivity for the heavier halides iodide and bromide over chloride and acetate.     

[1l‐3,4‐Bis‐O‐(diphenylphosphino)‐1,2,5,6‐tetra‐O‐methyl‐chiro‐inositol‐κ2P,P′][η4‐(Z,Z)‐cycloocta‐1,5‐diene]rhodium(I) tetrafluoridoborate chloroform solvate

The title compound, [Rh(C₈H₁₂)(C₃₄H₃₈O₆P₂)]BF₄·CHCl₃, a novel asymmetric hydrogenation catalyst, crystallizes with two independent almost identical cations and anions. Cell‐packing interactions are provided by nonclassical hydrogen bonding between phenyl and chloroform H atoms and fluoro and chloro donors of the BF₄⁻ anion and the chloroform solvent molecule.     

Dual Role of the 1,2,3‐Triazolium Ring as a Hydrogen‐Bond Donor and Anion–π Receptor in Anion‐Recognition Processes

Several bis(triazolium)‐based receptors have been synthesized as chemosensors for anion recognition. The central naphthalene core features two aryltriazolium side‐arms. NMR experiments revealed differences between the binding modes of the two triazolium rings: one triazolium ring acts as a hydrogen‐bond donor, the other as an anion–π receptor. Receptors 9²⁺?2BF₄ ^? (C₆H₅), 11²⁺?2BF₄ ^? (4‐NO₂?C₆H₄), and 13²⁺?2BF^4? (ferrocenyl) bind HP₂O₇^3? anions in a mixed‐binding mode that features a combination of hydrogen‐bonding and anion–π interactions and results in strong binding. On the other hand, receptor 10²⁺?2 BF₄ ^? (4‐CH₃O?C₆H₄) only displays combined Csp₂?H/anion–π interactions between the two arms of the receptors and the bound anion rather than triazolium (CH)⁺???anion hydrogen bonding. All receptors undergo a downfield shift of the triazolium protons, as well as the inner naphthalene protons, in the presence of H₂PO₄^? anions. That suggests that only hydrogen‐bonding interactions exist between the binding site and the bound anion, and involve a combination of cationic (triazolium) and neutral (naphthalene) C?H donor interactions. Theoretical calculations relate the electronic structure of the substituent on the aromatic group with the interaction energies and provide a minimum‐energy conformation for all the complexes that explains their measured properties.     

酰氨基硫脲类新型分子钳受体的合成及其对氟离子的识别性能研究

本文设计并高产率合成了三种新型阴离子识别受体化合物,它们对F-的识别选择性较卤素其他阴离子的高。其对F-的识别性能通过紫外—可见光谱和核磁共振氢谱进行了检测,光谱数据表明,在DMSO溶液中受体与F-通过氢键相互作用形成1:1配合物。与以前我们报道的受体化合物相比,由于此类分子钳受体化合物具有更多的阴离子识别位点,因此具有更好地阴离子识别性能。     

Can a Proton be Encapsulated in Tetraamido/Diamino Quaternized Macrocycles in Aqueous Solution and Electric Field?

The proton‐binding behavior of solvated tetraamido/diamino quaternized macrocyclic compounds with rigid phenyl and flexible phenyl bridges in the absence or presence of an external electric field is investigated by molecular dynamics simulation. The proton can be held through H‐bonding interactions with the two carbonyl oxygen atoms in macrocycles containing rigid (phenyl) and flexible (propyl) bridges. The solute–solvent H‐bonding interactions cause the macrocyclic backbones to twist to different extents, depending on the different bridges. The macrocycle with the rigid phenyl linkages folds into a cuplike shape due to π–π interaction, while the propyl analogue still maintains the ellipsoidal ringlike shape with just a slight distortion. The potential energy required for proton transfer is larger in the phenyl‐containing macrocycle than in the compound with propyl units. When an external electric field with a strength of 2.5 V nm^?1 is exerted along the carbonyl oxygen atoms, a difference in proton encircling is exhibited for macrocycles with rigid and flexible bridges. In contrast to encapsulation of a proton in the propyl analogue, the intermolecular solute–solvent H‐bonding and intramolecular π–π stacking between the two rigid phenyl spacers leads to loss of the proton from the highly distorted cuplike macrocycle with phenyl bridges. The competition between intra‐ and intermolecular interactions governs the behavior of proton encircling in macrocycles.     

Halotriazolium Axle Functionalised [2]Rotaxanes for Anion Recognition: Investigating the Effects of Halogen‐Bond Donor and Preorganisation

The anion‐templated synthesis of three novel halogen‐bonding 5‐halo‐1,2,3‐triazolium axle containing [2]rotaxanes is described, and the effects of altering the nature of the halogen‐bond donor atom together with the degree of inter‐component preorganisation on the anion‐recognition properties of the interlocked host investigated. The ability of the bromotriazolium motif to direct the halide‐anion‐templated assembly of interpenetrated [2]pseudorotaxanes was studied initially; bromide was found to be the most effective template. As a consequence, bromide anion templation was used to synthesise the first bromotriazolium axle containing [2]rotaxane, the anion‐binding properties of which, determined by ¹H NMR spectroscopic titration experiments, revealed enhanced bromide and iodide recognition relative to a hydrogen‐bonding protic triazolium rotaxane analogue. Two halogen‐bonding [2]rotaxanes with bromo‐ and iodotriazolium motifs integrated into shortened axles designed to increase inter‐component preorganisation were also synthesised. Anion ¹H NMR spectroscopic titration experiments demonstrated that these rotaxanes were able to bind halide anions even more strongly, with the iodotriazolium axle integrated rotaxane capable of recognising halides in aqueous solvent media. Importantly, these observations suggest that a halogen‐bonding interlocked host binding domain, in combination with increased inter‐component preorganisation, are requisite design features for a potent anion receptor.     

Two terphenyl‐based diol hosts and corresponding solvent inclusions with dimethylformamide and acetonitrile

Having reference to an elongated structural modification of 2,2′‐bis(hydroxydiphenylmethyl)biphenyl, (I), the two 1,1′:4′,1′′‐terphenyl‐based diol hosts 2,2′′‐bis(hydroxydiphenylmethyl)‐1,1′:4′,1′′‐terphenyl, C₄₄H₃₄O₂, (II), and 2,2′′‐bis[hydroxybis(4‐methylphenyl)methyl]‐1,1′:4′,1′′‐terphenyl, C₄₈H₄₂O₂, (III), have been synthesized and studied with regard to their crystal structures involving different inclusions, i.e. (II) with dimethylformamide (DMF), C₄₄H₃₄O₂·C₂H₆NO, denoted (IIa), (III) with DMF, C₄₈H₄₂O₂·C₂H₆NO, denoted (IIIa), and (III) with acetonitrile, C₄₈H₄₂O₂·CH₃CN, denoted (IIIb). In the solvent‐free crystals of (II) and (III), the hydroxy H atoms are involved in intramolecular O—H...π hydrogen bonding, with the central arene ring of the terphenyl unit acting as an acceptor. The corresponding crystal structures are stabilized by intermolecular C—H...π contacts. Due to the distinctive acceptor character of the included DMF solvent species in the crystal structures of (IIa) and (IIIa), the guest molecule is coordinated to the host via O—H...O=C hydrogen bonding. In both crystal structures, infinite strands composed of alternating host and guest molecules represent the basic supramolecular aggregates. Within a given strand, the O atom of the solvent molecule acts as a bifurcated acceptor. Similar to the solvent‐free cases, the hydroxy H atoms in inclusion structure (IIIb) are involved in intramolecular hydrogen bonding, and there is thus a lack of host–guest interaction. As a result, the solvent molecules are accommodated as C—H...N hydrogen‐bonded inversion‐symmetric dimers in the channel‐like voids of the host lattice.     

Crystal structure and hydrogen bonding in the hydrated cocrystalline salt tryptaminium–3,5‐dinitrobenzoate–quinoline–water (3/3/2/2)

The study of ternary systems is interesting because it introduces the concept of molecular preference/competition into the system where one molecule may be displaced because the association between the other two is significantly stronger. Current definitions of a tertiary system indicate that solvent molecules are excluded from the molecule count of the system and some of the latest definitions state that any molecule that is not a solid in the parent form at room temperature should also be excluded from the molecule count. In the structure of the quinoline adduct hydrate of tryptaminium 3,5‐dinitrobenzoate, 3C₁₀H₁₃N₂⁺·3C₇H₃N₂O₆⁻·2C₉H₇N·2H₂O, the asymmetric unit comprises multiple cation and anion species which are conformationally similar among each type set. In the crystal, a one‐dimensional hydrogen‐bonded supramolecular structure is generated through extensive intra‐ and inter‐unit aminium N—H…O and N—H…N, and water O—H…O hydrogen bonds. Within the central‐core hydrogen‐bonding associations, conjoined cyclic R₄⁴(10), R₅³(10) and R₄⁴(12) motifs are generated. The unit is expanded into a one‐dimensional column‐like polymer extending along [010]. Present also in the crystal packing of the structure are a total of 19 π–π interactions involving both cation, anion and quinoline species [ring‐centroid separation range = 3.395 (3)–3.797 (3) Å], as well as a number of weak C—H…O hydrogen‐bonding associations. The presence of the two water molecules in the crystal structure is considered to be the principal causative factor in the low symmetry of the asymmetric unit.     

Head‐to‐Tail Intermolecular Hydrogen Bonding of OH and NH Groups with Fluoride

To explore the anion‐recognition ability of the phenolic hydroxyl group and the amino hydrogen, we synthesized three different acridinedione (ADD) based anion receptors, 1 , 2 and 3 , having OH, NH, and combination of OH and NH groups, respectively. Absorption, emission and ¹H NMR spectral studies revealed that receptor 1 , having only a phenolic OH group, shows selective deprotonation of the hydroxyl proton towards F^?, which results in an “ON–OFF”‐type signal in the fluorescence spectral studies. Receptor 2 , which only has an amino hydrogen, also shows deprotonation of the amino hydrogen with F^?, whereas receptor 3 (having both OH and NH groups) shows head‐to‐tail intermolecular hydrogen bonding of OH and NH groups with F^? prior to deprotonation. The observation of hydrogen bonding of the OH and NH groups in a combined solution of 1 and 2 with F^? in a head‐to‐tail hetero‐intermolecular fashion, and the absence of head‐to‐head and tail‐to‐tail intermolecular hydrogen bonding in 1 and 2 with F^?, prove that the difference in the acidity of the OH and NH protons leads to the formation of an intermolecular hydrogen‐bonding complex with F^? prior to deprotonation. The presence of this hydrogen‐bonding complex was confirmed by absorption spectroscopy, 3D emission contour studies, and ¹H NMR titration.     

Stabilizing Otherwise Unstable Anions with Halogen Bonding

Both hydrogen bonding (HB) and halogen bonding (XB) are essentially electrostatic interactions, but whereas hydrogen bonding has a well‐documented record of stabilizing unstable anions, little is known about halogen bonding's ability to do so. Herein, we present a combined anion photoelectron spectroscopic and density functional theory study of the halogen bond‐stabilization of the pyrazine (Pz) anion, an unstable anion in isolation due to its neutral counterpart having a negative electron affinity (EA). The halogen bond formed between the σ‐hole on bromobenzene (BrPh) and the lone pair(s) of Pz significantly lowers the energies of the Pz(BrPh)₁⁻ and Pz(BrPh)₂⁻ anions relative to the neutral molecule, resulting in the emergence of a positive EA for the neutral complexes. As seen through its charge distribution and electrostatic potential analyses, the negative charge on Pz⁻ is diluted due to the XB. Thermodynamics reveals that the low temperature of the supersonic expansion plays a key role in forming these complexes.     

Anion⋅⋅⋅Si Interactions in an Inverse Sandwich Complex: A Computational Study

Combination of an electron‐rich molecule (e.g. chloride anion or nitrile group) with a chlorinated cyclohexasilane ring produces a supramolecular inverse sandwich complex formed by two guests (Cl^? or R?C≡N) strongly bonded to both faces of a planar host (Si₆ ring). In‐depth theoretical studies were carried out to investigate the nature of the bonding interactions that generate such a stable complex. Second‐order Møller–Plesset perturbation theory (MP2) calculations confirmed that the presence of the Cl substituents is fundamental to the stability of the supramolecular assemblies. The density functional theory (DFT) functional wB97XD gave an estimation of the contribution of dispersion interactions to the binding energy. These interactions become more important as the Cl atoms of the rings are systematically replaced by methyl groups or hydrogen atoms. Analysis of the topology of the electron density and the reduced density gradient gave insight into the binding of the studied supramolecular assemblies.     

A Chiral Halogen‐Bonding [3]Rotaxane for the Recognition and Sensing of Biologically Relevant Dicarboxylate Anions

The unprecedented application of a chiral halogen‐bonding [3]rotaxane host system for the discrimination of stereo‐ and E/Z geometric isomers of a dicarboxylate anion guest is described. Synthesised by a chloride anion templation strategy, the [3]rotaxane host recognises dicarboxylates through the formation of 1:1 stoichiometric sandwich complexes. This process was analysed by molecular dynamics simulations, which revealed the critical synergy of halogen and hydrogen bonding interactions in anion discrimination. In addition, the centrally located chiral (S)‐BINOL motif of the [3]rotaxane axle component facilitates the complexed dicarboxylate species to be sensed via a fluorescence response.     

Electrochemical measurement of switchable hydrogen bonding in an anthraquinone-based anion receptor

The electrochemistry of a novel anion receptor is presented. The receptor 1,3-diphenylcarboxamidoanthraquinone (AAR) in the absence of an appropriate anion behaves as an anthraquinone system in the presence of a strong hydrogen bond donor. In this case, the electrochemical evidence supports the suggestion that the hydrogen bonding with the anthraquinone occurs at least partially through intra- or intermolecular interactions. It is suggested that these interactions stabilise both the semiquinone and dianion species resulting from reduction of AAR. However, in the presence of a suitable competitive anion (specifically F⁻), the hydrogen-bond donor groups bind to the anion rather than the quinone oxygen atoms. This removes the hydrogen bonding interaction to the redox-active quinone centre and hence alters the electrochemistry significantly. In the presence of F⁻, two one-electron quasireversible electrochemical processes are observed.     

Easily‐prepared Hydroxy‐containing Receptors Recognize Anions in Aqueous Media

Despite their ready availability, O?H groups have received relatively little attention as anion recognition motifs. Here, we report two simple hydroxy‐containing anion receptors that are prepared in two facile steps followed by anion exchange, without the need for chromatographic purification at any stage. These receptors contain a pyridinium bis(amide) motif as well as hydroxyphenyl groups, and bind mono‐ and divalent anions in 9:1 CD₃CN:D₂O, showing a selectivity preference for sulfate. Notably, a “model” receptor that does not contain hydroxy groups shows only very weak sulfate binding in this competitive solvent mixture. In the solid state, X‐ray crystallographic studies show that the receptors tend to form extended assemblies with anions; however, ¹H and DOSY NMR studies as well as molecular dynamics simulations show that only 1:1 complexes are present in solution. Molecular dynamics simulations suggest that one of the receptors suffers from competing intramolecular hydrogen bonding, while another binds partially‐hydrated anions, with the receptor's O?H groups forming hydrogen bonds to water molecules within the anion's coordination sphere.