Anionic Host Research Articles

Strong electron-accepting methylviologen dication confined in magnetic hosts: synthesis, structural characterization, charge-transfer and magnetic properties of {(MV)2[Ni(SCN)5]·Cl·2H2O}nand {(MV)[M(N3)2(SCN)2]}n(M = Mn, Co)

Three hybrid host-guest compounds {(MV)2[Ni(SCN)5].Cl.2H2O}n (1), {(MV)[Mn(N3)2(SCN)2]}n (2) and {(MV)[Co(N3)2(SCN)2}n (3) (where MV2+ = methylviologen dication) have been obtained by self-assembly methods and characterized by X-ray crystallography, spectral methods and magnetic measurements. Compound 1 shows a quasi-two-dimensional structure which is formed by novel single thiocyanate-bridged Ni(II) chains connected through S...S interactions. Compounds 2 and 3 are isostructural, containing single micro(1,3)-azide bridged Mn(II)/Co(II) square layers. MV2+, as a strong electron-acceptor and a template, is embedded between the anionic layers in all three compounds. The charge-transfer (CT) interactions between MV2+ and the anionic hosts have been revealed by structural analysis and UV-vis diffuse reflection spectroscopy. The magnetic studies of the compounds show antiferromagnetic interactions between adjacent metal ions (J = -34.52(7) cm(-1) for 1, J = -3.90(2) cm(-1) for 2 and J = -10.96(6) cm(-1) for 3).

An unusual anionic copper(i) cyanide 3D framework encapsulating a cationic copper(ii) complex as a guest

From the reaction of CuICN with conc-NH4OH, a host-guest type 3D network complex , [[CuII(NH3)4(H2O)](H2O)@[CuI3(CN)5]]n was isolated and characterised. A unique cationic complex guest [CuII(NH3)4(H2O)]2+ is encapsulated in the anionic host cage [CuI3(CN)5]2-.

Intramolecular binding site competition as a means of tuning the response of a colourimetric anion sensor

Two new viologen-based anion hosts, 2 and 3, are reported, incorporating two tripodal binding domains. Binding of carboxylate anions, particularly acetate, malonate and succinate by pyridinium derivative 2 results in an intense purple colouration. DFT calculations on representative system 2·malonate reveal that this absorption arises from charge-transfer from the anion to the bipyridinium unit. Anion binding by 3 does not initially result in a colour change because anions are bound at the periphery of the receptor; however, addition of more that two equivalents of acetate or more than one equivalent of dicarboxylate turn the colourimetric response on.

Polymer-supported cationic templates for molecular recognition of anionic hosts in water

Translocating solution-phase molecular recognition of oppositely charged hosts and guests to the solid phase represents a major challenge; we report a successful immobilisation strategy which allows selective host-guest interactions in water unencumbered by unwanted ion exchange-type interactions.

Hybrid materials with nanoscopic anion-binding pockets for the colorimetric sensing of phosphate in water using displacement assays

Mesoporous amino-functionalised solids containing certain dyes have been used as suitable anion hosts in displacement assays for the colorimetric signalling of phosphate in water.

Anion Binding Involving π‐Acidic Heteroaromatic Rings

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Anion Binding Involving π-Acidic Heteroaromatic Rings

Anions are essential species in biological systems and, particularly, in enzyme-substrate recognition. Therefore, the design and preparation of anion receptors is a topical field of supramolecular chemistry. Most host-guest systems successfully developed are based on noncovalent (ionic and hydrogen-bonded) interactions between anions and ammonium-type functionalities or Lewis acid groups. However, since the past 5 years, an alternative route toward the synthesis of efficient anion hosts has emerged, namely, the use of "anion-pi" interactions involving nitrogen-containing electron-deficient aromatic rings, as the result of several favorable theoretical investigations. In this Account, the state of the (new) art in this growing area of anion-binding research is presented and several selected examples from our work and that of other groups will be discussed.

Intercalation of cation guests into a three-dimensional anionic host framework

A new three-dimensional photoluminescent host–guest open-framework, { [ Cu ( dmp ) 2 + ] · [ 1 / 2 ( H 2 bdc ) · 1 / 2 ( bdc 2 - ) · 2 H 2 O ] } n ( 1) (dmp = 2,9-dimethyl-1,10-phenanthroline, bdc = 1,4-benzene-dicarboxylate), has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, IR spectrum, fluorescent spectrum, and thermogravimetric analyses. The structure of complex 1 features a three-dimensional supramolecular host architecture with photosensitizer-dye cation guests. Although Cu 2+ was used as the starting material, no obvious signal was observed in ESR spectrum of 1, which indicates that all copper atoms in 1 are Cu + and redox reaction occurred under the present hydrothermal condition.

The Simultaneous Presence of Different Varieties of Intermolecular Hydrogen Bonds in a New Layer-Type Anionic Host Lattice Built of Thiourea, Fumaric Acid and Fumarate Anion

A new inclusion complex (n-C4H9)4N+C4H3O4− · C4H4O4 · (NH2)2CS has been prepared and characterized by X-ray crystallography. Crystal data: space group P\( \overline 1 \), a = 8.799(2) A, b = 9.590(1) A, c = 18.684(4) A, α = 89.63(1)°, β = 79.56(1)°, γ = 79.74(1)°, V = 1525.2(5) A3, Z = 2, R1 = 0.0562 and wR = 0.1033. In the title compound, thiourea molecules, fumaric acid and fumarate anions are joined together by typical O–H···O, N–H···O and N–H···S, plus weak C–H···O and C–H···S, hydrogen bonds to generate a hydrogen-bonded layer corresponding to the (100) family of planes. The tetra-n-butylammonium cations are orderly arranged in a sandwich-like packing mode between the stacked layers. The simultaneous presence of different varieties of intermolecular hydrogen bonds is an interesting feature of the title compound.

Synthesis and Evaluation of a Pseudocyclic Tristhiourea-Based Anion Host

A novel methodology for the evaluation of receptor arrangement in structurally flexible anion chemosensors was developed and applied to map the binding site of a new pseudocyclic tristhiourea chemosensor (6). The syntheses of 6 and related macrocyclic chemosensor 10 (a model of the folded monomeric structure of 6) are reported. Both chemosensors were evaluated by titration with a variety of structurally different anions in CH3Cl and DMSO, showing a common preference for F-, CH3CO2-, and H2PO4-. However, within this group of anions, the binding patterns of the chemosensors differed, indicating dissimilarity in the arrangement of the binding sites of 6 and 10.

Steric and electronic factors influencing recognition by a simple, charge neutral norbornene based anion receptor

Based on (1)H NMR studies, subtle electronic factors rather than pre-organisation dictate the binding stoichiometry of the new, norbornene based, anion hosts 1 and 2 with acetate, however, the binding of dihydrogenphosphate appears to be based solely on steric constraints.

Anion‐Binding Properties of the Tripyrrolemethane Group: A Combined Experimental and Theoretical Study

Tripyrrolemethane- and bistripyrrolemethane-containing systems were recently reported to be efficient and selective hosts for anions. Nevertheless, the basic intrinsic properties of tripyrrolemethane as a ligand for anions have not yet been explored. Here we report the study of the anion-binding properties of the tripyrrolemethane group. We applied a combined experimental and theoretical approach to determine the affinity of the tripyrrolemethane system for different anions in the gas phase, in solution and in the crystalline state. In the crystal, the tripyrrolemethane group forms a number of different complexes with the bromide ion, some involving the participation of more than one ligand species. Despite the very similar basicity of fluoride and dihydrogen phosphate, the tripyrrolemethane ligand exhibits a clear preference for the fluoride anion in solution, which indicates an anion-binding system and not merely deprotonation. Although the affinity of the tripyrrolemethane ligand for other ions was negligible in solution, gas-phase studies show that complexation with larger halide ions is favoured over complexation with fluoride.

Encapsulation of Anionic Dye Molecules by a Swelling Fluoromica through Intercalation of Cationic Polyelectrolytes

To develop a novel layered host material with the ability to encapsulate anionic substances, the intercalation of three cationic polyelectrolytes into synthetic sodium fluortetrasilisic mica (Na-TSM) was investigated. With polyethylenimine (PEI) and poly(allylamine hydrochloride) (PAH), the conformation of the intercalated polycation and its ability to accommodate anionic guests depended on its state of protonation. The quaternary ammonium polycation poly(diallyldimethylammonium) (PDDA), which had the lowest charge density of the three polymers studied, adopted a coiled conformation within the anionic host at both high and low pH, resulting in an excess of cationic sites within the interlayer of the polysilicate. Powder X-ray diffraction patterns and adsorption isotherms showed two different stages of PDDA intercalation with different adsorption free energies. Atomic force microscopy images showed that the PDDA−clay nanocomposites maintained the shape of the original nanosheets, indicating the successful ...

Protonen on Tour – DFT-Studie zur H+-Wanderung in [1.1.1]- und [2.2.2]-Cryptanden / Protons on Tour – DFT-study of H+-Migration in [1.1.1]- and [2.2.2]-Cryptands

DFT-calculations (RB3LYP/LANL2DZp) show that the migration of a proton inside [1.1.1]- and [2.2.2]-cryptand from one nitrogen atom to the other follows different paths. While the proton in [H⊂1.1.1]-cryptand moves via an ether oxygen atom (activation energy: 19.2 kcal/mol), the proton in [H⊂2.2.2]-cryptand moves directly from one nitrogenatom to the other (activation energy: 16.1 kcal/mol). Our calculations rule out the application of doubly protonated [2.2.2]-cryptands as anion hosts.

2‐(Guanidiniocarbonyl)furans as a New Class of Potential Anion Hosts: Synthesis and First Binding Studies

AbstractThe synthesis of a new class of potential anion hosts, the 2‐(guanidiniocarbonyl)furans 5a–d, is presented in this study. The facile decomposition of furans under acidic conditions makes the synthesis of these compounds challenging. First binding studies showed that the (guanidiniocarbonyl)furans are much more acidic (pKa ≈ 5.5) than the analogous pyrroles (pKa ≈ 7) previously introduced by us for oxoanion binding in aqueous solvents. Hence, anion binding with the furan derivatives occurs only in acidic solutions below pH = 5. Therefore, carboxylates are not bound efficiently, whereas, for example, the less basic hydrogen sulfate is bound by 5b with an association constant of K = 600 M–1 in aqueous DMSO even in the presence of a large excess of buffer. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Observation of a water–anion layer constructed from water tetramers and nitrate anions in the crystal host of a cobalt complex

A novel self-assembled layer consisting of water tetramers and nitrate anions has been observed in the [Co(1,10-phenanthroline) 2(NO 3)] · (NO 3) · 4H 2O complex. X-ray crystallography and FT-IR spectroscopy indicate that although the water tetramers exist in an energetically less stable uudd configuration, the anionic host environments may play an important role in the formation and stabilization of the water clusters.

Modular assembly of a preorganised, ditopic receptor for dicarboxylates

Two types of calix[4]arene derived hosts for anions with, respectively, 1,3-alternate and cone conformations have been prepared; the 1,3-alternate system binds dicarboxylate anions in a ditopic manner while the cone compounds are deprotonated by carboxylates.

Pyridinium CH⋯anion and π-stacking interactions in modular tripodal anion binding hosts: ATP binding and solid-state chiral induction

The preparation of two new tripodal "pinwheel" type anion hosts based on a triethylbenzene core and bipyridinium or ethylnicotinium arms is reported. The new materials bind anions via CH...anion interactions. Complexes with Br(-) and PF(6)(-) have been characterised by X-ray crystallography as both solvates in a pure form. In the bipyridinium host CH...F interactions to PF(6)(-) induce a chiral C(3) symmetric conformation that is disrupted in the hydrate. The compound is also selective for ATP(2-) in aqueous acetonitrile.

4-(N,N-Dimethylamino)benzoic Acid as a New Class of Simple Chromogenic and Fluorogenic Anion Host Exhibiting High Selectivity to HPO42− and SO42−

Abstract Commercially available 4-(N,N-dimethylamino)benzoic acid (1) was directly applied for anion recognition in CH3CN. It showed remarkable affinity and selectivity to divalent anions HPO42− and SO42− over monovalent anions such as H2PO4−, HSO4−, ClO4−, BF4−, PF6−, and NO3− in terms of UV–vis and fluorescence titrations. The combination of the basicity and charge density of guest anions played an important role in the selectivity of host 1 toward anions.

Metalated Calixarenes and Cyclotriveratrylenes as Anion Hosts

AbstractFor Abstract see ChemInform Abstract in Full Text.