Supramolecular inclusion of a pillared double-layered host by an anion-directed second-sphere coordination

In this paper, we have illustrated the utilisation of a second-sphere coordination approach to construct supramolecular inclusion solids with varieties of guest molecules. A flexible molecule N,N,N′,N′-tetra-p-methylbenzyl-ethylenediamine (L1) bearing doubly protonated H-bond donors was designed, capable of forming N–H…Cl hydrogen bonds with a crystallographically unique chloride anion, to construct an anion-directed ligand. The pillared double-layered host framework was constructed by an anion-directed ligand and primary coordination sphere [CoCl₄]^2 ?  through weak C–H…Cl hydrogen-bonding interactions. A variety of guest molecules, such as p-anisaldehyde, 1,4-dimethoxy-2,5-bis(methoxymethyl)benzene, can be included, leading to the formation of novel supramolecular inclusion solids: [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₈H₈O₂]·0.25[CH₃OH] (1) and [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₁₂H₂₀O₄]·0.5[CH₃OH] (2).

We have presented herein the utilisation of a second-sphere coordination approach to construct supramolecular inclusion solids with a variety of guest molecules. A novel type of a pillared double-layered host framework was constructed by a second-sphere coordination between the anion-directed ligand (L1 = N,N,N′,N′-tetra-p-methylbenzyl-ethylenediamine) and [CoCl₄]^2 ?  through weak C–H…Cl hydrogen-bonding interaction, and a variety of guest molecules, such as p-anisaldehyde, 1,4-dimethoxy-2,5-bis(methoxymethyl)benzene, can be included, leading to the formation of supramolecular inclusion solids: [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₈H₈O₂]·0.25[CH₃OH] (1) and [L1]·4[H]⁺·[CoCl₄]^2 ? ·2Cl^? ·1.5[C₁₂H₂₀O₄]·0.5[CH₃OH] (2)

     

Structural effects on the solid‐state photodimerization of 2‐pyridone derivatives in inclusion compounds

The structures of six crystalline inclusion compounds between various host molecules and three guest molecules based on the 2‐pyridone skeleton are described. The six compounds are 1,1′‐biphenyl‐2,2′‐dicarboxylic acid–2‐pyridone (1/2), C₁₄H₁₀O₄·2C₅H₅NO, (I–a), 1,1′‐biphenyl‐2,2′‐dicarboxylic acid–4‐methyl‐2‐pyridone (1/2), C₁₄H₁₀O₄·2C₆H₇NO, (I–c), 1,1′‐biphenyl‐2,2′‐dicarboxylic acid–6‐methyl‐2‐pyridone (1/2), C₁₄H₁₀O₄·2C₆H₇NO, (I–d), 1,1,6,6‐tetraphenyl‐2,4‐hexadiyne‐1,6‐diol–1‐methyl‐2‐pyridone (1/2), C₃₀H₂₂O₂·2C₆H₇NO, (II–b), 1,1,6,6‐tetraphenyl‐2,4‐hexadiyne‐1,6‐diol–4‐methy‐2‐pyridone (1/2), C₃₀H₂₂O₂·2C₆H₇NO, (II–c), and 4,4′,4′′‐(ethane‐1,1,1‐triyl)triphenol–6‐methyl‐2‐pyridone–water (1/3/1), C₂₀H₁₈O₃·3C₆H₇NO·H₂O, (III–d). In two of the compounds, (I–a) and (I–d), the host molecules lie about crystallographic twofold axes. In two other compounds, (II–b) and (II–c), the host molecules lie across inversion centers. In all cases, the guest molecules are hydrogen bonded to the host molecules through O—H...O=C hydrogen bonds [the range of O...O distances is 2.543 (2)–2.843 (2) Å. The pyridone moieties form dimers through N—H...O=C hydrogen bonds in five of the compounds [the range of N...O distances is 2.763 (2)–2.968 (2) Å]. In four compounds, (I–a), (I–c), (I–d) and (II–c), the molecules are arranged in extended zigzag chains formed via host–guest hydrogen bonding. In five of the compounds, the guest molecules are arranged in parallel pairs on top of each other, related by inversion centers. However, none of these compounds underwent photodimerization in the solid state upon irradiation. In one of the crystalline compounds, (III–d), the guest molecules are arranged in stacks with one disordered molecule. The unsuccessful dimerization is attributed to the large interatomic distances between the potentially reactive atoms [the range of distances is 4.027 (4)–4.865 (4) Å] and to the bad overlap, expressed by the lateral shift between the orbitals of these atoms [the range of the shifts from perfect overlap is 1.727 (4)–3.324 (4) Å]. The bad overlap and large distances between potentially photoreactive atoms are attributed to the hydrogen‐bonding schemes, because the interactions involved in hydrogen bonding are stronger than those in π–π interactions.     

Clathrate compounds of tetracyano complexes of nickel and platinum with phenol

The double cyanides of nickel and platinum form structures capable of enclosing also phenol, for example, as guest molecule. Such clathrates are Ni(NH₃)₂Pt(CN)₄ 2 C₆H₅OH and Ni(en)₂Pt(CN)₄ · 0.14 C₆H₅OH. In the case of the tetracyano complexes, different thermal stabilities of their clathrate compounds could be achieved by alteration of the constituents of the cage structure and also of the guest molecules. According to the thermal behaviour, the clathrates may be divided into two groups: those which release the guest molecules in the first step of thermal decomposition (Ni(NH₃)₂Pt(CN)₄· 2 C₆H₅OH), and those which lose the guest component only after partial destruction of the host cage (Ni(en)₂Pt(CN)₄ · 0.14 C₆H₅OH). The temperature ranges of loss of the guest component may determine the interval for their use in sorptive experiments. The temperature range for release of phenol from Ni(NH₃)₂Pt(CN)₄ · · 2 C₆H₅OH is 55–244°, and from Ni(en)₂Pt(CN)₄ · 0.14 C₆H₅OH is 139–284°. The model host molecules NiPt(CN)₄ · 6 H₂O and Ni(en)₃Pt(CN)₄ · 3 H₂O were also studied by thermal analysis.     

Synthesis and crystal structures of 2,4,6-pyridine-tricarboxylic anions/guanidinium and tetraalkylammonium inclusion compounds

Two different hydrogen-bonded inclusion compounds, [2,4,6-C₅H₂N(COO^?)₃]_0.5·[C(NH₂) ₃ ⁺ ]_0.5·[(C₂H₅)₄N⁺]·2H₂O (1) and [2,4,6-C₅H₂N(COO^?)₃]·[C(NH₂) ₃ ⁺ ]·[(C₂H₅)₄N⁺]·[(C₃H₇)₄N⁺]·6H₂O (2) are reported in this paper, in which 2,4,6-pyridine-tricarboxylic anions, guanidiniums and water molecules jointly construct host lattices while tetraalkylammonium cations are accommodated as guest species. Both two compounds formed sandwich-like hydrogen-bond inclusion compounds. In compound 1, the dimers composed of 2,4,6-pyridine-tricarboxylic anions and guanidiniums form 2D hydrogen-bonded layers by connecting with water molecules. In compound 2, 2,4,6-pyridine-tricarboxylic anions, guanidiniums and water molecules contribute to generate an undulate rosette hydrogen-bonded architecture. Interestingly, in compound 2, there are two species of guest molecules, tetraethylammonium and tetrapropylammonium, which are alternately arranged between the neighboring layers. Mixed guest cations accommodated in hydrogen-bonded inclusion compounds are seldom seen.     

Niclosamide methanol solvate and niclosamide hydrate: structure,solvent inclusion mode and implications for properties

Structural studies have been carried out of two solid forms of niclosamide [5‐chloro‐N‐(2‐chloro‐4‐nitrophenyl)‐2‐hydroxybenzamide, NCL], a widely used anthelmintic drug, namely niclosamide methanol monosolvate, C₁₃H₈Cl₂N₂O₄·CH₃OH or NCL·MeOH, and niclosamide monohydrate, denoted H_A. The structure of the methanol solvate obtained from single‐crystal X‐ray diffraction is reported for the first time, elucidating the key host–guest hydrogen‐bonding interactions which lead to solvate formation. The essentially planar NCL host molecules interact viaπ‐stacking and pack in a herringbone‐type arrangement, giving rise to channels along the crystallographic a axis in which the methanol guest molecules are located. The methanol and NCL molecules interact via short O—H...O hydrogen bonds. Laboratory powder X‐ray diffraction (PXRD) measurements reveal that the initially phase‐pure NCL·MeOH solvate readily transforms into NCL monohydrate within hours under ambient conditions. PXRD further suggests that the NCL monohydrate, H_A, is isostructural with the NCL·MeOH solvate. This is consistent with the facile transformation of the methanol solvate into the hydrate when stored in air. The crystal packing and the topology of guest‐molecule inclusion are compared with those of other NCL solvates for which the crystal structures are known, giving a consistent picture which correlates well with known experimentally observed desolvation properties.     

Metal ion-assisted assembly of one-dimensional polyrotaxanes incorporating cucurbit[6]uril

Three cucurbit[6]uril (CB[6])-based polyrotaxanes [Cu(H₂ C6N4)(CB[6])]Cl₄·12H₂O (1), [Co(H₂ C6N4)(CB[6])]Cl₄·14H₂O (2) and [Ag(C6N4)(CB[6])]NO₃·7H₂O (3) are prepared using N,N′-bis(4-pyridylmethyl)-1,6-hexanediamine (C6N4) threading into CB[6]'s and metal ions' assistance. Single-crystal X-ray diffraction analyses reveal that polyrotaxanes 1, 2 and 3 all have 1D chain structure where 1 and 2 are linear and 3 has two shapes, linear and sawtooth, respectively. The effects of guest molecules, metal and counter ions as well as intermolecular weak interactions on the architectures of polyrotaxanes are discussed.     

Three polymorphs of an inclusion compound of 2,2′‐(disulfanediyl)dibenzoic acid and trimethylamine

Polymorphism is the ability of a solid material to exist in more than one form or crystal structure and this is of interest in the fields of crystal engineering and solid‐state chemistry. 2,2′‐(Disulfanediyl)dibenzoic acid (also called 2,2′‐dithiosalicylic acid, DTSA) is able to form different hydrogen bonds using its carboxyl groups. The central bridging S atoms allow the two terminal arene rings to rotate freely to generate various hydrogen‐bonded linking modes. DTSA can act as a potential host molecule with suitable guest molecules to develop new inclusion compounds. We report here the crystal structures of three new polymorphs of the inclusion compound of DTSA and trimethylamine, namely trimethylazanium 2‐[(2‐carboxyphenyl)disulfanyl]benzoate 2,2′‐(disulfanediyl)dibenzoic acid monosolvate, C₃H₁₀N⁺·C₁₄H₉O₄S₂⁻·C₁₄H₁₀O₄S₂, (1), tetrakis(trimethylazanium) bis{2‐[(2‐carboxyphenyl)disulfanyl]benzoate} 2,2′‐(disulfanediyl)dibenzoate 2,2′‐(disulfanediyl)dibenzoic acid monosolvate, 4C₃H₁₀N⁺·2C₁₄H₉O₄S₂⁻·C₁₄H₈O₄S₂²⁻·C₁₄H₁₀O₄S₂, (2), and trimethylazanium 2‐[(2‐carboxyphenyl)disulfanyl]benzoate, C₃H₁₀N⁺·C₁₄H₉O₄S₂⁻, (3). In the three polymorphs, DTSA utilizes its carboxyl groups to form conventional O—H…O hydrogen bonds to generate different host lattices. The central N atoms of the guest amine molecules accept H atoms from DTSA molecules to give the corresponding cations, which act as counter‐ions to produce the stable crystal structures via N—H…O hydrogen bonding between the host acid and the guest molecule. It is noticeable that although these three compounds are composed of the same components, the final crystal structures are totally different due to the various configurations of the host acid, the number of guest molecules and the inducer (i.e. ancillary experimental acid).     

Comparative X-ray structural study of laterally mono-ethyl substituted 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra-methoxycalix[4]arene and its non-substituted parent compound including guest free and solvated forms. Chemical straightening of guest channels

Three solvate crystal structures of the laterally ethyl substituted tetra-tert-butyltetramethoxycalix[4]arene 1 [(1·THF (1a), 1·CHCl₃ (1b) and 1·CH₂Cl₂ (1c)] are compared to the corresponding solvent-free structure (1) using single crystal X-ray structure determination, isostructurality and molecular isometricity calculations. To study the effect of the lateral substitution, the laterally non-substituted host with the guest THF (2a) is also included to the comparison. The calixarene molecules in the different structures all adopt the partial cone conformation with different affection of the respective guest molecules, always being positioned interstitially. Depending on the lateral substitution and the size of the included guests, the molecular conformation of the calix[4]arene shows small differences relating to the alignment of the arene units. The channels disposable of the solvent guest molecules in the crystal structures straighten as the effect of lateral substitution of the host calix[4]arene. The orthorhombic crystal structures of 1a–c are isostructural irrespective of the included solvent molecules, while 1 and 2a crystallise in the same monoclinic space group.     

The Role of Chloro Substituents in Solid Inclusion Formation. Crystal Structures Formed by a Bulky Hydroxy Host with Ethyl Acetate (2:1) and Cyclohexylamine (1:2) as Guest

Abstract

Two inclusion compounds of the 11-[bis(p‐chlorophenyl)hydroxymethyl]-9,10-dihydro-9,10-ethanoanthracene host (1) have been studied by X-ray diffraction in order to find an explanation of the exceptional clathrate formation ability of the present chloro-containing host as compared with that of closely related chlorine-free host analogues. Crystal data: 1·ethyl acetate (2:1), C₂₇H₂₂OCl₂·½(C₄H₈O₂), M_w = 501.45, P2_1/c, a = 8.9060(5), b = 11.1109(6), c = 25.642(1) Å, β = 99.03(1)°, Z = 4, R = 0.047 for 2029 F values with I>2σ(I); 1·cyclohexylamine (1:2), 2[C₂₉H₂₂OCI₂·2(C₆H₁₃N)], M_w = 1311.50, Pc, a = 12.144(2), b = 12.689(3), c =23.119(8) Å, β = 91.68(1)°, Z = 2, R = 0.054 for 3073 F values with I>2σ(I). Although the two solid inclusion compounds differ in host‐guest stoichiometry, space group symmetry and also in host‐guest recognition mode, both co-crystals are held together by numerous C?H…X (X = O, N or Cl) interactions, in which the chloro-substituents of 1 play a very active role. The observed frequent participation of chlorine in intermolecular interactions in these compounds suggests an ability of the (C?)Cl substituents to effectively enhance the crystal formation in the absence of more dominant forces.     

Complexation with Diol Host Compounds. Part 35: Inclusion Compounds of 1,1,6,6-Tetraphenylhexa-2,4-diyne-1,6-diol with CCl4, CHCl3, CH2Cl2 and CH3CN

Inclusion compounds were formed with 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol (H) and carbon tetrachloride, chloroform, dichloromethane and acetonitrile. 1 (H·1/2CCl⁴), 2 (H·1/2CHCl³) and 3 (H·1/2CH²Cl²) are true clathrates with the guest molecules situated in cages created by the host. 4 (H·2CH³CN) exhibits a different packing arrangement with the guest molecules located in channels. The crystal structures and stability of these inclusion compounds were investigated.     

Syntheses,characterization, and crystal structures of two fluorinated gallium phosphates templated by organic amines

Two fluorinated gallium phosphates templated by organic amines, (C₄H₁₅N₃)[Ga₃F₂(PO₄)₃] (1) and [(C₂H₁₀N₂)(C₂H₉N₂)][Ga₃F₄(HPO₄)₄] (2), have been synthesized under hydrothermal and solvothermal conditions, respectively. The compounds were characterized by elemental analyses, FT-IR spectroscopy, and powder X-ray diffraction. Their crystal structures were determined from single-crystal X-ray diffraction. The crystal structure of 1 has a 3-D framework with 10-membered ring channels along the b-axis. The crystal structure of 2 is an infinite 1-D chain structure, further forming a 3-D supramolecular structure with pseudo 10-membered ring channels along the a-axis through O–H?···?O hydrogen bonds. The protonated organic amine cations are located in the inorganic channel and interact with the polyanion framework both electrostatically and via N–H?···?O and N–H?···?F hydrogen bonds.     

Preparation,Structure and Thermal Decomposition of Cu(II) Complexes with 2-Chloro- and 2,3-Dichlorobenzoic Acids and Imidazole

The reaction products of Cu(II) 2-chlorobenzoate and imidazole (1), and of Cu(II) 2,3-dichlorobenzoate and imidazole (2) formulated as CuL'₂·3imd and CuL"·3imd (L' = C₇H₄ClO₂, L" = C₇H₄Cl₂O₂ ^?, imd = imidazole), were prepared and characterized by means of structural and spectroscopic measurements and thermochemical properties. The blue (1) and green (2) compounds crystallize in the monoclinic system with space group C2/c, cell parameters a = 20.753(4), b = 8.414(2), c = 14.429(3) Å, β = 90.15(3)°, V = 2519.5(9) &Aringsup3;, Z = 4 for (1) and a = 21.335(4), b = 8.417(2), c = 15.030(3) Å, β = 94.11(3)°, V = 2692.1(10) &Aringsup3;, Z = 4 for (2). The complexes decompose at 483 K.     

N—H...S and C—H...S hydrogen bonds in two tetraalkylammonium dithiobiurea(1–) inclusion compounds

Two inclusion compounds of dithiobiurea and tetrapropylammonium and tetrabutylammonium are characterized and reported, namely tetrapropylammonium carbamothioyl(carbamothioylamino)azanide, C₁₂H₂₈N⁺·C₂H₅N₄S₂⁻, (1), and tetrabutylammonium carbamothioyl(carbamothioylamino)azanide, C₁₆H₃₆N⁺·C₂H₅N₄S₂⁻, (2). The results show that in (1), the dithiobiurea anion forms a dimer via N—H...N hydrogen bonds and the dimers are connected into wide hydrogen‐bonded ribbons. The guest tetrapropylammonium cation changes its character to become the host molecule, generating pseudo‐channels containing the aforementioned ribbons by C—H...S contacts, yielding the three‐dimensional network structure. In comparison, in (2), the dithiobiurea anions are linked via N—H...S interactions, producing one‐dimensional chains which pack to generate two‐dimensional hydrogen‐bonded layers. These layers accommodate the guest tetrabutylammonium cations, resulting in a sandwich‐like layer structure with host–guest C—H...S contacts.     

AN OCTAPHENYL-SUBSTITUTED BICYCLIC ORGANOMETALLIC INCLUSION HOST

Abstract

As part of a study involving design of new organometallic hosts, Pd₂(dpm)₂Cl₂ 5 was reacted with 4-isocyanoacetophenone 6 to produce the organometallic insertion product 7. This forms an unstable ternary inclusion compound (7)·(chloroform)·(dimethyl sulfoxide) whose X-ray crystal structure [C₅₉H₅₁Cl₂NOP₄Pd₂·CHCl₃·C₂H₆OS, P2₁2₁2₁, a = 14.734(2), b = 15.782(2), c = 26.682(4) Å, Z = 4, R = 0.043] was determined. The host phenyl groups intermesh producing a helical arrangement of molecules of 7 generated by a 2₁ screw axis. Chloroform guests form a second helix intertwining that of the organometallic host through involvement in C = O…H-CCl₃ hydrogen bonds. The dimethyl sulfoxide guests exhibit no significant short intermolecular contacts.     

Supramolecular architecture built of Co(II) and a tripodal ligand containing 1-D water tapes with (H2O)16 cluster units

The reaction of Co(NO₃)₂?·?6H₂O with a tripodal ligand leads to a new complex {[Co(L)]?·?2NO₃?·?8H₂O} (1) confirmed by single-crystal X-ray diffraction, infrared spectroscopy, and elemental analysis. The particular interest of 1 is in the formation of a 1-D water tape consisting of (H₂O)₁₆ cluster units, the neighboring water tapes are connected by free nitrate anions via hydrogen bonds into a 2-D guest layer. These guest layers are alternately packed face-to-face with the 2-D host layers along the a-axis to form a 3-D supramolecular architecture. There exist C–H?···?N and C–H?···?O weak hydrogen bonds between the guest layer and host layer. These weak hydrogen bonds and water–nitrate, water–water hydrogen bonds are important for the stability of the overall structure.     

2(S)‐Amino‐3‐[1H‐imidazol‐4(5)‐yl]­propyl cyclo­hexylmethyl ether di­hydro­chloride and 2(S)‐amino‐3‐[1H‐imidazol‐4(5)‐yl]­propyl 4‐bromo­benzyl ether di­hydro­chloride

(Cyclo­hexyl­methyl­oxy­methyl)(1H‐imidazol‐4‐io­methyl)‐(S)‐ammonium dichloride, C₁₃H₂₅N₃O⁺·2Cl^?, and (4‐bromo­benzyl)(1H‐imidazol‐4‐io­methyl)‐(S)‐ammonium dichloride, C₁₃H₁₈BrN₃O⁺·2Cl^?, are model compounds with different biological activities for evaluation of the hist­amine H3‐receptor activation mechanism. Both title compounds occur in almost similar extended conformations.     

Syntheses, crystal structures and spectral properties of three chiral complexes [M((R, R)-et-pybox)Cl2] (M=Zn and Mn) and [Ni((R, R)-et-pybox)(H2O)2Cl]Cl

Three chiral complexes: [M((R, R)-et-pybox)Cl₂] (M=Zn, 1, and Mn, 2) and [Ni((R, R)-et-pybox)(H₂O)₂Cl]Cl (3) ((R, R)-et-pybox is C₂-symmetric 2,6-bis[4′-(R)-ethoxyoxazolin-2′-yl]pyridine) have been synthesized and characterized by elemental analysis, IR, UV, TG and single-crystal X-ray diffraction. Single-crystal X-ray diffraction analyses show that 1 is isostructural to 2, the obtained complexes are of isolated mononuclear and the metal atoms of 1 and 2 have distorted trigonal bipyramidal coordination environment. A feature of interest is noted in the unit cell of 3, there exist two types of molecules, which similarly have a distorted octahedral geometry but only slightly differ in the orientation of the coordinated atoms to the central Ni atom. These two types of molecules interact with each other by O–H···Cl hydrogen bonds, giving rise to one-dimensional ribbon structure.     

Synthesis and guest exchange reactions of inclusion compounds of cucurbit[8]uril with nickel(II) and copper(II) complexes

Inclusion compounds of the macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex, {trans-[Ni(en)₂(H₂O)₂]@CB[8]}Cl₂ · 23.5H₂O, the copper(II) complex, {2[Cu(dien)(bipy)(H₂O)]@CB[8]}(ClO₄)₄ · 11H₂O, and the organic molecules, 2(pyCN)@CB[8]} · 16H₂O and {2(bpe)@CB[8]} · 17H₂O, where bipy is 4,4′-bipyridyl, pyCN is 4-cyanopyridine, and bpe is trans-1,2-bis(4-pyridyl)ethylene, were synthesized. The inclusion compounds with organic molecules were synthesized starting from inclusion compounds of cucurbit[8]uril with cyclam and ethylenediamine complexes of copper(II) and nickel(II) by the guest exchange method, which is based on the replacement of one guest with another in the cavity of the cavitand The resulting compounds were characterized by X-ray diffraction, ESR, ¹H NMR, IR, and electronic absorption spectroscopy, and electrospray mass spectrometry. Photochemically induced [2+2]-cycloaddition of two 1,2-bis(4-pyridyl)ethylene molecules included in cucurbit[8]uril was studied. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 25–34, January, 2006.     

Heteropolymolybdate–amino acid complexes: synthesis,characterization and biological activity

Three Keggin-type polyoxometalates functionalized by amino acids, (C₅H₁₃N₂O₂)₂(H₃O)PMo₁₂O₄₀·8H₂O 1, (C₅H₁₄N₂O₂)₂SiMo₁₂O₄₀·12H₂O 2 and (C₅H₁₄N₂O₂)₂GeMo₁₂O₄₀·12H₂O 3, were synthesized and characterized by elemental analysis, IR and ¹H?NMR spectra and single-crystal X-ray diffraction. The X-ray crystallographic study showed that the structures of the three compounds involved N–H···O and O–H···O hydrogen bonds among the protonated ornithine cations, water molecules and the heteropolyanion cluster, and thus represent a model interaction between polyoxometalates and proteins. These complexes display inhibitory actions to the human cancer cells Hela and PC-3?m in vitro.     

Adsorption behaviour of a CdII–triazole MOF for butan‐2‐one in a single‐crystal‐to‐single‐crystal (SCSC) fashion: the role of hydrogen bonding and C—H…π interactions

The adsorption behaviour of the Cd^II–MOF {[Cd(L)₂(ClO₄)₂]·H₂O ( 1 ), where L is 4‐amino‐3,5‐bis[3‐(pyridin‐4‐yl)phenyl]‐1,2,4‐triazole, for butan‐2‐one was investigated in a single‐crystal‐to‐single‐crystal (SCSC) fashion. A new host–guest system that encapsulated butan‐2‐one molecules, namely poly[[bis{μ₃‐4‐amino‐3,5‐bis[3‐(pyridin‐4‐yl)phenyl]‐1,2,4‐triazole}cadmium(II)] bis(perchlorate) butanone sesquisolvate], {[Cd(C₂₄H₁₈N₆)₂](ClO₄)₂·1.5C₄H₈O}_n, denoted C₄H₈O@Cd‐MOF ( 2 ), was obtained via an SCSC transformation. MOF 2 crystallizes in the tetragonal space group P4₃2₁2. The specific binding sites for butan‐2‐one in the host were determined by single‐crystal X‐ray diffraction studies. N—H…O and C—H…O hydrogen‐bonding interactions and C—H…π interactions between the framework, ClO₄^? anions and guest molecules co‐operatively bind 1.5 butan‐2‐one molecules within the channels. The adsorption behaviour was further evidenced by ¹H NMR, IR, TGA and powder X‐ray diffraction experiments, which are consistent with the single‐crystal X‐ray analysis. A ¹H NMR experiment demonstrates that the supramolecular interactions between the framework, ClO₄^? anions and guest molecules in MOF 2 lead to a high butan‐2‐one uptake in the channel.