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  • ditopic receptor  (2)
  • Molecular asymmetry  (1)
  • acetonitrile  (1)
  • calix(aza)crowns  (1)
  • 1
    ISSN: 1572-8927
    Schlagwort(e): Electrolytic conductance ; molar conductance ; ion pair formation ; complex formation ; 18-crown-6 ; calix[4]arene-bis-crown-6 ; lithium perchlorate ; sodium perchlorate ; potassium perchlorate ; rubidium perchlorate ; cesium perchlorate ; acetonitrile ; methanol ; propylene carbonate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Résumé The interactions of Li+, Na+, K+, Rb+, and Cs+ with the “double-crown calix,” calix[4]arene-bis-crown-6, have been studied in methanol, acetonitrile, and propylene carbonate at 25°C using precise conductivity measurements. For Li+ and Na+ in solutions containing this calix[4]arene, only 1:1 cation:ligand complexes are formed which permit the determination of the thermodynamic complexation formation constants,K f. The conductivity data strongly suggest that 2:1 cationcalixarene complexes form with K+, Rb+, and Cs+. The existence of 2:1 complexes was experimentally confirmed for the potassium systems by a mass spectroscopic method.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 27 (1997), S. 169-178 
    ISSN: 1573-1111
    Schlagwort(e): Bridged calix[4]arene ; ditopic receptor ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal structures of a new solvate of the ditopic receptor 1,3-calix[4]-bis-crown-6, Bis-C6, and of 1,3-calix[4]-bis-(benzo-crown-6), Bis-benzoC6, are reported. Bis-C6.3 CH3CN (1) crystallizes in the monoclinic space group P21/n, a = 14.388(3), b = 26.947(8), c = 14.707(4) Å, β = 113.19(3)°, V = 5241(5) Å3, Z = 4. Refinement led to a final conventional R value of 0.092 for 2723 reflections. The structure of (1) differs from the previously reported structure of Bis-C6.4 CH3CN by the conformation of one crown either chain. Two acetonitrile molecules are in the close neighbourhood of the crown ether cavities. Bis-benzoC6.3 CH3CN (2) crystallizes in the monoclinic space group P21/c, a = 10.391(4), b = 17.264(11), c = 30.426(9) Å, β = 94.62(3)°, V = 5440(7) Å3, Z = 4. Refinement led to a final conventional R value of 0.106 for 2965 reflections. Two acetonitrile molecules are located near the crown ether cavities, as in (1). One of the crown ether conformations is the same as in the binuclear caesium complex of Bis-benzoC6, supporting the hypothesis of a preorganization of this ligand towards the complexation of this ion; the second crown ether chain is partially disordered.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 15 (1993), S. 341-349 
    ISSN: 1573-1111
    Schlagwort(e): Molecular asymmetry ; calixarene ; acetone ; clathrate ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal and molecular structure of the 1:1 clathrate of the asymmetric calix[4]arene,1, and acetone has been determined by X-ray analysis. The crystal data are: tetragonal, space groupP4/n,a=b=12.574(6),c=12.572(6) Å,V=1988(2) Å3,Z=2,D x =1.111 g cm−3,D m =1.108 g cm−3. Least-squares refinement based on 1131 observed reflections withF 0〉3σ(F 0) and anisotropic temperature factors led toR=0.096. In spite of the molecular asymmetric calixarene1 the crystal structure has high symmetry, because a part of the host and guest molecules are in disordered states.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 19 (1994), S. 137-148 
    ISSN: 1573-1111
    Schlagwort(e): 1,2- and 1,3-Calix[4]-bis-crowns ; double calix[4]arenes ; double calixcrowns ; calix(aza)crowns ; Na+/Cs+ selectivity ; soft metal complexation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis of 1,2- and 1,3-calix[4]-bis-crowns, double calix[4]arenes and double calixcrowns have been shown to depend on the reaction conditions (nature of the base, structure of the ditosylates, and the stoichiometry of the reactants). The 1,3-alternate conformation of the 1,3-calix[4]-bis-crowns was shown to be favourable to the selective complexation of cesium cation. The observed Na+/Cs+ selectivity was exploited in separation processes using them as carriers in transport through supported liquid membranes (SLMs). The best Na+/Cs+ selectivity (1/45 000) was observed for the naphthyl derivative 7. Calix(aza) crowns and 1,3-calix[4]-bis-(aza)-crowns were also produced through the preliminary formation of the Schiff base-calixarenes, which were further hydrogenated. The syntheses consisted of the 1,3-selective alkylation of calixarenes followed by cyclization into a 1,3-bridged calixarene or by the direct 1,3-capping of the calixarene with appropriate ditosylates. Soft metal complexation by these ligands is also presented.
    Materialart: Digitale Medien
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  • 5
    ISSN: 1573-1111
    Schlagwort(e): Bridged calix[4]arene ; caesium complex ; ditopic receptor ; crystal structure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The crystal structures of two binuclear complexes between caesium and 1,3-calix[4]-bis-crowns have been determined. Cs2 Bis-benzoC6(NO3)2. 3CHCl3 (1) in whichBis-benzoC6 is 1,3-calix[4]-bis-benzo-crown-6, crystallizes in the orthorhombic system: space groupPca2 1 a=19.513(10),b=15.382(5),c=23.708(9) Å,V=7116(5) Å3,Z=4. Refinement led to a final conventionalR value of 0.065 for 2321 reflections. The structure of (1) is analogous to those already reported withBis-C6, (in whichBis-C6 is, 1,3-calix[4]-bis-crown-6) and NO 3 − as a counter-ion. Cs2 Bis-C6(NCS)2 (2) crystallizes in the monoclinic system: space, groupC2 a=36.57(2),b=11.47(1),c=13.65(1) Å, β=109.03(5)°.,V=5415(6) Å3,Z=4. Refinement led to a final conventionalR value of 0.063 for 2227 reflections. Compound (2) is made of dimers bridged by a disordered NCS− ion. The crown ether chain conformations are discussed.
    Materialart: Digitale Medien
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