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Heterobimetallic cage molecules: solvated Na2M2(psulfonatocalix[4]arene)2, M⊕=⊕Y, Eu |
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CrystEngComm,
Volume 3,
Issue 4,
2000,
Page 18-20
Jerry L. Atwood,
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摘要:
pSulfonated calix[4]arene has been the focus of considerable interest in the fields of materials1and separation science.2In addition to being watersoluble, its cone conformation allows it to possess both inclusion properties3and the ability to pack into a claylike bilayer structure4in the solid state. Some of our recent studies have focused on the supramolecular interactions between sodiumpsulfonated calix[4]arene, 18crown6 and other molecular building blocks. In the presence of large cationic species such as polynuclear aquated Al3+, Cr3+or Rh3+oligomers, ‘Russian Doll’ assemblies result.5In these inclusion complexes within inclusion complexes a Na+ion is coordinated by a crown ether and twotranswater molecules, and this assembly is in turn encapsulated by two calixarenes aligned in a headtohead arrangement. The large polynuclear cationic species serve as supramolecular clamps, effectively overcoming the electrostatic repulsion between the calixarenes. However, when these cations are substituted by larger rare earths such as La3+a perched structure is obtained in which the metal ion is coordinated by 18crown6 and a single sulfonate group on a calixarene,6whereas in the presence of smaller rare earths, such as Y3+and Eu3+, a hydrogen bonded dimeric capsule results.7Here a crown ether devoid of metal ions lies within a cavity created by the headtohead dimerisation of two calixarenes, and aquated rare earth cations are bound to sulfonate groups of both calixarenes, and form hydrogen bonding interactions to the crown ether.In the present study 18crown6 was excluded from the reaction, with sodiumpsulfonated calixarene and either Y3+or Eu3+salts reacted together. A dimeric calixarene supermolecule is once more obtained, though the calixarenes are not arranged in a headtohead fashion as in the aforementioned capsules. Rather, the structure now resembles a skewed cage. It features coordination of both rare earth and sodium ions to the calixarene sulfonate groups, as well as extensive hydrogen bonding by water molecules associated with these metals. A similar structure for a Na+/Yb3+complex has been reported, but the cage assembly and role of the Na+coordination was not evident.8The new Y3+and Eu3+complexes, [Y(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](H2O)6.51and [Eu(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](CH3CN)(H2O)52, crystallise from aqueous solutions or a solvent mixture of water and acetonitrile containing sodiumpsulfonatocalix[4]arene and yttrium or europium trichloride hexahydrate respectively atca.pH 3.Colourless rods deposited within a week. The infrared spectra for the complexes were similar, in each case displaying a shift in the most intense sulfonate absorption fromca.1190 cm−1(for the sodium salt) to 1170 cm−1. This is indicative of metal coordination through the oxygen atoms.9Electron microprobe analysis confirmed the presence of both rare earth and sodium ions in the complexes.The cage complexes crystallise in triclinic cells and their structures were solved in space groupP1&cmb.macr;,Table 1. Complexes1and2both have two sulfonated calixarenes, two rare earth ions aquated with seven water molecules, two sodium ions each aquated with four water molecules, included water and solvent water or water and acetonitrile molecules in the unit cell. The calixarenes are in a cone conformation and associateviacoordinate and hydrogen bonding interactions to form a dimeric structure.Details of data collection and structure refinement for [Y(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](H2O)6.51and [Eu(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](CH3CN)(H2O)52.Property12XRay data were collected on a Bruker SMART CCD for1and an EnrafNonius KappaCCD for2with MoKα radiation (λ⊕=⊕0.71073 Å). C–H hydrogen atoms were fixed at geometrically estimated positions with a riding refinement. Both structures contained disordered solvent water and sulfonate groups. For2the diffraction pattern indicated twinning and the unit cell could be determined for only one twin component, leading to some refinement problems, such as high residual electron density around the Eu, high goodness of fit and some atoms requiring isotropic refinement, due to an unknown contribution to the intensity data for some reflections from the other twin. Owing to the twinning 20 bad reflections were omitted from the refinement.Clickherefor crystallographic data (CCDC nos. 153527 & 153528).FormulaC28H55YNaO33.5S4C30H55EuNNaO32S4Mr1167.881244.94Crystal systemTriclinicTriclinicSpace groupP1&cmb.macr;P1&cmb.macr;T/K173(1)123(1)a/Å12.281(3)12.2930(4)b/Å13.635(3)13.7242(3)c/Å14.122(3)14.1062(4)α/°90.632(4)90.769(2)β/°106.401(4)106.325(1)γ/°90.640(5)90.605(2)U/Å32268.2(9)2283.5(1)Z22ρcalc/g cm−11.7101.811µ/mm−1, abs. correction1.59, semiempirical1.671, no correctionCrystal size/mm0.20 x 0.10 x 0.050.35 x 0.10 x 0.042&thetas;min,max/°3.0, 54.42.9, 55.0Data collected1393536119Unique data,Rint9719, 0.06099774, 0.068Observed data (I⊕>⊕2σ(I))79259030Structure solutionDirect methods (SHELXS97)Direct methods (SIR)Refinement (SHELXL97)Fullmatrix onF2Fullmatrix onF2Parameters601615R1(observed data)0.12040.1016wR2(all data)0.28900.2917S1.1512.622Each rare earth is eight coordinate, bound to a single sulfonate of a calixarene by an Olinkage (Y–O 2.342(7), Eu–O 2.389(7) Å), and seven water ligands (Y–O 2.311(9) to 2.380(7), Eu–O 2.384(7) to 2.438(7) Å). This coordination environment is typical for rare earths.10These M(H2O)7moieties are directed towards the cavity of the calixarene bowl. The sodium ions are six coordinate in a slightly distorted octahedral geometry. Each sodium ion coordinates to one sulfonate group on two calixarenes in acisarrangement, creating a dimer,Fig. 1. There are two such linkages per dimer (Na–O 2.425(8) and 2.349(12) Å for1, Na–O 2.365(15) and 2.413(9) for2), each arising from sulfonate groups on arene rings adjacent to one another within the calixarene cone. Each sodium is coordinated by an additional four water molecules to complete the coordination sphere (with Na–O distances ranging from 2.412(10) to 2.489(10) Å). There are numerous intradimer hydrogen bonding interactions between the water ligands coordinated to both sodium and rare earth cations and sulfonate groups of the calixarenes at O⋯O separations ranging from 2.49 to 2.90 Å.The cage-type calixarene dimer [Y(H2O)7Na(H2O)4(psulfonatocalix[4]arene)]2taken from the crystal structure of Y(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](H2O)6.51. A similar complex is formed with Eu3+in place of Y3+. Hydrogens and one site of the disordered sulfonate group omitted for clarity. Click image orhereto access a 3D representation.Water molecules are included as intracavity guest molecules in both complexes. In complex2, for instance, there are two guest water molecules per calixarene, one contained deeply within the calixarene bowl and the other situated closer to the upper rim of the calixarene. The latter water molecule is at hydrogen bonding distances to a water ligand coordinated to the europium cation at O⋯O separation 2.74 Å, and the other included water (O⋯O 2.61 Å), and is at a distance consistent with the formation of a weak nonclassical hydrogen bond to arene rings of the calixarene (closest O⋯arene centroid distances 3.41 and 3.60 Å).8,11,12The second included water is also at hydrogen bonding distances to water ligands coordinated to the Eu (O⋯O 2.74 Å) and Na (O⋯O 2.70 Å) cations.The extended structure consists of layers of calixarenes oriented in an updown bilayer arrangement (Fig. 2) similar to that found for many solid state structures of sulfonated calix[4]arene.4,13It is stabilised by π–π interactions between neighbouring calixarenes (closest π⋯π centroid separation 3.67 Å for2), as well as hydrogen bonding. Interdimer hydrogen bonds are apparent between the phenolic and sulfonate groups of adjacent calixarenes, as well as between the metalcoordinated water molecules and calixarene sulfonate groups. Additional water molecules in the lattice are also involved in extensive Hbonding to the cationic species present in the structure. Thus the cations reside in aqueous seams which sandwich the organic bilayers. In the case of2the acetonitrile molecules fill gaps within the crystal lattice, that are solely occupied by water in1.Packing diagram from the Xray structure of [Eu(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](CH3CN)(H2O)52, showing the bilayer arrangement of calixarenes. Hydrogens omitted for clarity, Eu shown in green, Na centres in orange. Click image orhereto access a 3D representation.While a mixture of rare earth salt, 18crown6 andpsulfonated calix[4]arene usually leads to the formation of a capsule through the headtohead dimerisation of the calixarenes,7in the absence of 18crown6 such a capsule does not assemble. Rather, both rare earth and sodium ions interact with the calixarenes to form an alternative dimeric assembly with a skewed cagelike structure.Synthesis: spsulfonatocalix[4]arene (6 mg, 7.25 µmol) and two stoichiometric equivalents of YCl3·6(H2O) in 1 mL of water were mixed and the pH was adjusted toca.3 using 0.1 M hydrochloric acid. Crystals of [Y(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](H2O)6.51(5 mg, 57%) appeared on standing for several days. Crystalline1lost solvent on exposure to the atmosphere. Single crystals of [Eu(H2O)7Na(H2O)4(psulfonatocalix[4]arene)](CH3CN)(H2O)52were obtained in a similar manner, however with the sodiumpsulfonatocalix[4]arene dissolved in aqueous acetonitrile.
ISSN:1466-8033
DOI:10.1039/b009437o
出版商:RSC
年代:2000
数据来源: RSC
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