Structural Aspects of Rubidium Ion Selectivity by Tribenzo-21-crown-7(1)(a).
The structural origins of the selectivity of rubidium ion over other alkali metal ions by tribenzo-21-crown-7 is investigated from single-crystal X-ray diffraction: data for Cs(tribenzo-21-crown-7)(NO(3)), monoclinic, P2(1)/c, a = 9.598(2) Å, b = 23.466(3) Å, c = 23.973(5) Å, beta = 93.31(1) degrees, V = 5390(2) Å(3), Z = 8; data for [Rb(4,4'-bis-tert-butylbenzo,benzo-21-crown-7)(dioxane)(1.5)(H(2)O)(0.18)][Cl].(dioxane)1.82(H(2)O), triclinic, P&onemacr;, a = 11.687(3) Å, b = 12.800(4) Å, c = 17.680(3) Å, alpha = 75.31(2) degrees, beta = 80.01(2) degrees, gamma = 69.09(2) degrees, V = 2379.8(10) Å(3), Z = 2; data for Na(4,4'-bis-tert-butylbenzo,benzo-21-crown-7)ReO(4).0.5(i-PrOH), monoclinic, P2(1)/c, a = 24.300(5) Å, b = 14.066(3) Å, c = 22.676(5) Å, beta = 108.06(3) degrees, V = 7369(3) Å(3), Z = 8; data for and 4,4'-bis-tert-butylbenzo,benzo-21-crown-7, monoclinic, P2(1)/n, a = 16.427(2) Å, b = 11.3675(9) Å, c = 33.137(3) Å, beta = 94.469(8) degrees, V = 6169.0(10) Å(3), Z = 8. The structures reported here are the first reported for a tribenzo-21-crown-7, and the alkali metal ion complexes are the first reported structures of these ions with any 21-crown-7 ether. Different crown conformations are observed for each structure. Molecular mechanics calculations were performed on all conformers, and the results are related to the observed extraction selectivity for rubidium.
Bryan
Jeffrey C.
JC
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352.
Sachleben
Richard A.
RA
Lavis
Jérôme M.
JM
Davis
Matthew C.
MC
Burns
John H.
JH
Hay
Benjamin P.
BP