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ABSTRACT: Hexamethoxy-calix[6]arene has been fully functionalized with p-phosphonic acid groups on the upper rim in 57% yield over three steps, and has been authenticated in the solid state by X-ray diffraction as either a nitrate salt or one of two calcium complexes. The latter differ by the ratio of calcium ions per calixarene, either 3:1 or 4:1. In both structures the coordination sphere of the calcium ions is made up of oxygen atoms from the phosphonic acid groups and from water of crystallization, as part of extended polymeric layers in the extended 3D packing. Hirshfeld surface analysis shows extensive O...H and O...Ca interactions for the phosphonic acid moieties in both calcium structures. MALDI-TOF MS of the hexaphosphonic acid shows nano-arrays consisting of up to a maximum of 28 calixarene units.
Crystal Growth & Design 07/2010; 10(7):3211-3217. · 4.72 Impact Factor
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ABSTRACT: Calix[5]arene forms three inclusion complexes with benzene, which have been structurally authenticated and studied by Hirshfeld surface analysis. Two of them are 1:1 polymorphs (α and β), both with the calix[5]arenes packed in a back-to-back style arrangement. In the α polymorph, three 1:1 supermolecules, [calix[5]arene∩benzene], cooperate in creating a large cavity containing three solvent molecules. In the β polymorph, the calix[5]arenes alternate in an up and down orientation, resulting in a less dense arrangement. The other inclusion complex is 1:2 ([calix[5]arene∩benzene]·benzene) which has a benzene molecule endo and exo relative to the calix[5]arene cavity. Hirshfeld surface analyses are effective in differentiating the intermolecular contacts between this structure and the α and β polymorphs, both for the calix[5]arene and the included benzene guest molecules.
11/2009;
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ABSTRACT: Lower rim O-methyl, -n-butyl, and n-octadecyl calix[4]arenes bearing p-phosphonic acid groups on the upper rim have been prepared in high yield, compounds 12-14. Where possible the compounds have been characterized in the solid state using X-ray diffraction, or as the precursor phosphate esters or a cesium salt. The cone conformation ethyl phosphate ester for the octadecyl compound crystallizes in a bi-layer 39.1 A thick which approaches the 40 A of biological membranes. The 1,3-alternate cone conformation of the cesium salt of the O-methyl phosphonic acid has a metal ion coordinated to two methoxy groups, four O-P (two from neighboring calixarenes), and two eta(3)-C(3) moieties from two 1,3-disposed aromatic rings. MALDI-TOF spectra of compounds 12-14 show successive peaks corresponding to 15, 33 and 16 calixarene units, which is consistent with the intra-molecular H-bonding capabilities of the di-protic phosphonic acid groups where the calixarenes are arranged into layers, including bilayers.
Crystal Growth & Design 01/2009; 9(8):3575-3580. · 4.72 Impact Factor
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ABSTRACT: The saddle-shaped Fe(TMTAA) acts as a shallow cavity divergent receptor toward fullerene C60 molecules involving Fe(II)-η2 coordination on one face of the macrocycle, the 1:1 complex effectively creating a corrugated sheet of inefficiently packed fullerene molecules.
12/2008;
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ABSTRACT: Horning-crown macrocycles, 1(R = (CH2)2) and 2(R = (CH2)3) form inclusion complexes with C60 and C70 fullerenes which have been structurally authenticated using X-ray diffraction data. Macrocycle 1 affords a C60 complex as a toluene solvate with overall composition C60(1)2(tol)2, 3, whereas the larger macrocycle, 2, affords complexes with both C60 and C70 fullerenes, also as toluene solvates: C60(2)(tol)2, (4); C70(2)(tol)2, (5); and C70(2)2(tol)2, (6). The higher degree of flexibility of such macrocyles relative to classical calixarenes is noteworthy in forming fullerene complexes, with the smaller ring size of 1 favoring fullerene complexation toward the smaller C60 molecule. The supramolecular assemblies involve host−guest interactions as well as interaction of fullerenes in zigzag chains with interfullerene contacts close to the van der Waals limit.
12/2008;
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ABSTRACT: The inclusion of o-carborane by p-Bu(t)-calix[7,9]arenes has been investigated by solid state and solution studies, with both resulting complexes in the solid state being rich in carborane with the ratio of calixarene to carborane at 1 : 7 and 2 : 7 respectively. The carboranes reside in clefts within the calixarenes which arise from specific local conformations of adjacent phenolic groups, or are included in the extended structure through other interplay of the calixarenes and carboranes in such clefts.
Dalton Transactions 10/2008; · 3.84 Impact Factor
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ABSTRACT: p-Benzylcalix[6]arene, 1, and C60 form a fullerene rich inclusion complex in toluene, (C60)3(p-benzylcalix[6]arene)(toluene)4.25, 2, which has been structurally authenticated. The fullerene and toluene molecules shroud linear arrays of the calixarenes, which are dethreaded in the presence of methylene chloride to form an all carbon hcp polymorph of fullerene C60. The ease of dethreading relates to the mode of association of p-benzylcalix[6]arene within the molecular crystal consisting of interlocked calixarenes in linear arrays. Similar association has also been seen in the solid-state structure of p-benzylcalix[6]arene, 1, where one calixarene is associated with another through two modes, a frontal host–guest association involving inclusion of the pendent benzyl arms and back-to-back stacking arrangement.
07/2008;
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ABSTRACT: Solid-state inclusion complexes of p-H-calix[5]arene with fluoro-, chloro-, bromo-, and iodobenzene have been structurally authenticated using X-ray diffraction data with a detailed analysis of the Hirshfeld surfaces facilitating an understanding of the type and nature of intermolecular interactions in the supermolecules and extended structures. All but the iodobenzene complexes are isostructural forming columnar arrays involving three crystallographically related 1:1 host–guest supermolecules (halobenzene∩calix[5]arene); three halobenzene molecules from different supermolecules are associated via C−H···X interactions for hydrogen atoms ortho to the halogen atoms, effectively creating a larger cavity from close proximity of three calix[5]arenes. The iodobenzene inclusion complex has sheets of calixarenes rather than columns in the extended packing, presumably due to the increased size of iodine circumventing the formation of the aforementioned interplay of three halobenzene molecules.
02/2008;
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ABSTRACT: Sulfonatocalix[4]arene, 1, and bisphosphonium cation, 2, form extensive self-assembled arrays in the presence of lanthanide metal cations, building up new materials based on both types of ions. Systematic studies using the combinatorial approach reproducibly yielded three novel structures based on these ions. Complexes 3–5, were prepared by varying the ratio of the components, organic and metal ions, in addition to varying the pH and ionic strength of the solutions. The structural motifs in these complexes were found to be lanthanide specific and the complexes were obtained from a 1 : 1 ratio of the organic ions in the presence of an excess of lanthanide metal cations at near neutral pH. Two structures based on bilayers, 3 and 4, are accessible, differing in the ratio of the organic components, 1 and 2, 7 : 6 and 1 : 2, respectively. Complexes 3 and 4 have a supersized bilayer with 3 featuring a 2D channel system associated with a scaffolding role of the bisphosphonium cation. The structural motif in complex 5 is devoid of bilayer arrangements, instead taking on a compact structure.
New Journal of Chemistry 01/2008; · 2.61 Impact Factor
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ABSTRACT: The water-soluble calix[4]arene bearing p-substituted phosphonic acid groups is accessible in five steps in overall 62 % yield, with the hydrogen-bonding prowess of the acidic groups dominating its self-assembly processes. These include the formation of 3.0(3) nm and 20(2) nm nanorafts of the calixarene in water using spinning disc processing, stabilized by acetonitrile, and nanorafts in the gas phase (<or=20 molecules). The 20(2) nm particles transform into 3.0(3) nm particles prior to crystallization into a compact bilayer, whereas crystallization in the presence of large organic molecules gives an expanded bilayer interposed by layers of water molecules.
Chemistry 01/2008; 14(13):3931-8. · 5.93 Impact Factor
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ABSTRACT: Varied temperature sublimation of calix[5]arene results in the formation of two distinctly different crystal structures or polymorphs alpha and beta, the latter of which is based on both 'self-included' and 'back-to-back' helical arrangements of the molecule, while also being active towards CO2 sorption at room temperature and 1 atmosphere pressure.
Chemical Communications 01/2008; · 6.17 Impact Factor
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ABSTRACT: The three isomers of xylene form inclusion complexes with p-H-calix[5]arene with different spatial interplay of the cavitands, which is relevant to using crystallization as a means of separating mixtures of o-, m-, and p-xylenes. Competition experiments involving mixtures of o-/m-xylene, o-/p-xylene, and m-/p-xylene and a mixture of all three isomers showed some selectivity in the inclusion of the xylenes with p-H-calix[5]arene according to the inequality m- > o- > p-xylene. Also reported are the toluene and mesitylene solvates, which are isostructural with the o-xylene and m-xylene inclusion complexes, respectively.
09/2007;
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ABSTRACT: Ytterbium(III) forms a complex with sulfonato-calix[5]arene in water with the calixarene assembled into the common clay bilayered arrangement but having unusually dense packing of the calixarenes, which are squeezed together forming “impenetrable” bilayers. The efficiency of packing of the calixarene relates to its conformational flexibility, and it has implications in providing a protective layer in stabilizing spheroidal nanoparticles.
07/2007;
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ABSTRACT: Magnetite (Fe304) nanoparticles stabilised by sulfonatocalixarene macrocycles are readily accessible by a rapid in situ co-precipitation, and exhibit ferro-fluidic and superparamagnetic behaviour.
Chemical Communications 06/2007; · 6.17 Impact Factor
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ABSTRACT: In toluene fullerene C(70) forms 2:1 complexes with p-benzylcalix[5]arene (1) and p-phenylcalix[5]arene (2), [C(70) subset1(2)].6(C(7)H(8)) and [C(70) subset2(2)].7(C(7)H(8)). The fullerene molecules are completely shrouded by two calix[5]arenes in addition to terminal benzyl groups from other supermolecules, [C(70) subset1(2)], and solvent. Within the capsule-like supermolecules the calixarenes have distinctly different arrangements relative to the principal axis of the fullerene; for [C(70) subset1(2)].6(C(7)H(8)) the oxygen planes of the two calixarenes are skewed by 37.0 and 47.5 degrees , whereas in [C(70) subset2(2)].7(C(7)H(8)) the principal axes of the fullerene and the two encapsulating calixarenes are more closely aligned with the corresponding angles at 9.7 and 8.6 degrees , and features a pentaphenyl inter-calixarene embrace. The Hirshfeld surfaces of these two complexes have been investigated for a detailed understanding of the orientation and nature of interactions of C(70) with the cavitand-type molecules and toluene.
Chemistry 02/2007; 13(14):3907-12. · 5.93 Impact Factor
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ABSTRACT: p-Bu(t)-calix[5]arene forms crystalline inclusion complexes with o- and m-carboranes in toluene or dichloromethane-hexane, but not with the p-isomer, the extended structures being based on 1 : 1 host-guest supermolecules, with the p-Bu(t)-substituents creating a snug fit for o- and m-carborane; p-carborane forms a highly hexane soluble complex, induced by grinding, which crystallizes as fibres. Solution phase studies showed the presence of a 1 : 1 host-guest stoichiometry with all three isomeric carboranes as determined from Job plots. The association constants for the o- and m-carborane complexes are 6.4 +/- 0.3 M(-1) and 3.8 +/- 0.1 M(-1) respectively, whereas the p-isomer is only weakly associated. Competition experiments involving all three isomers show rapid exchange on the NMR time scale, and no selectivity in solution is evident. Selective association involving the o- and m-isomers in the solid state is therefore remarkable, and it is a manifestation of crystal packing forces which embodies the differences in dipole moments of the carboranes.
Dalton Transactions 01/2007; · 3.84 Impact Factor
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ABSTRACT: Nanoparticles of trans-beta-carotene are accessible using spinning disk processing (SDP), by varying the reaction conditions and the choice of surfactant, macrocyclic amphiphiles, sulfonato-calix[4,5,6,8]arenes, and alpha,beta-cyclodextrins. SDP ensures rapid mixing and fast kinetics, and nanoparticles of the carotene formed in the presence of the calixarenes are stable with respect to extraction of the carotene into an organic solvent, unlike in the presence of the cyclodextrins. Insight into the supramolecular structure of the carotene nanoparticles has also been established. The mean particle sizes (dynamic light scattering, DLS) have been optimized at 40(2) and 56(1) nm and 71.4(6) and 82(1) nm, respectively, for each sulfonato-calix[5,6 and 4,8]arene, whereas the cyclodextrins form nanoparticles with a mean diameter of 71(1) and 68.5(6) nm, respectively. Zeta-potential studies show stability of all the colloidal dispersions at pH > 4 with values below -30 mV. UV-visible spectroscopy shows a blue shift indicative of H-aggregates of the carotene within the nanoparticles. The surface area derived from BET studies is 39.12 m(2)/g corresponding to particles of 76.7(5) nm in diameter, in agreement with sizes obtained from DLS and TEM measurements.
Journal of the American Chemical Society 11/2006; 128(42):13847-53. · 9.91 Impact Factor
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ABSTRACT: Three inclusion complexes of calix[5]arenes as dichloromethane (DCM) or chloroform solvates have been structurally authenticated, namely, the complexes of p-But-calix[5]arene, 1, or p-H-calix[5]arene, with DCM, 2, and a new polymorph of the complex of p-phenyl-calix[5]arene with chloroform, 3. Complex 1 has two adjacent tbutyl groups of one calixarene embracing the analogous groups from another calixarene. Complex 2 has a slipped head-to-head arrangement of calixarenes with a DCM molecule in the cavity of each calixarene. In complex 3, the calixarenes form dimers through interdigitation, and these dimers are assembled with back-to-back arrangement of calixarenes from adjacent dimers. All solvate complexes were crystallized in the presence of p-carborane, which has complementarity of size of the cavity of the calixarenes yet is not incorporated in the structures.
10/2006;
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ABSTRACT: Supramolecular complexes of tetra-p-sulfonatocalix[4]arene and guanine, cytosine, benzimidazole, and 2-hydroxybenzimidazole have been isolated in the solid state, and their structures have been elucidated using single-crystal X-ray diffraction data, as have 2-hydroxybenzimidazole complexes and complexes with large cations tetraphenylphosphonium (Ph4P+) and triethylbenzylammonium (Et3BzN+). These large cations disrupt the usual bilayer arrangement of the sulfonated calixarenes, as can benzimadole itself, and a combination of guanine and cytosine, in the absence of the large cations. Some of the structures show a “molecular capsule” type arrangement with two calixarenes arranged with their cavities directed toward each other, effectively shrouding two nucleic acid bases.
04/2006;
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ABSTRACT: In the presence of lanthanide ions, a Co(III) sepulchrate cation [Co(diHOsar)]3+ and sodium p-sulfonatocalix[4]arene form a 1:1 host-guest complex which is self-assembled into a zeolite-like lattice network comprised of parallel, single stranded helices.
Chemical Communications 04/2006; · 6.17 Impact Factor
