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Paper
J. Mater. Chem., 2009, 19, 9204 - 9212, DOI: 10.1039/b913701g
Polar derivatives of the [closo-1-CB9H10]- cluster as positive
additives to nematic hostsBryan Ringstrand, Piotr Kaszynski, Adam Januszko and Victor G. Young Jr.
Polar (µ
16 D) and UV transparent >250 nm quinuclidinium (1) and sulfonium (2) zwitterionic derivatives of the [closo-1-CB9H10]- anion were synthesized and studied as additives to nematic hosts. The molecular and crystal structures for 1 [C19H44B9N triclinic, P-1, a = 9.766(2) 
, b = 10.481(3) , c = 12.098(3) , 
= 93.804(9)°, 
= 90.249(10)°, 
=102.587(10)°, Z = 2] were determined by X-ray crystallography and compared with the results of HF/6-31G(d) calculations. Low concentration solutions (<10 mol%) of 1 and 2 in ClEster host (
= -0.59) were investigated using thermal and dielectric methods. The results for 1 and 2 showed virtual [TNI] values of 139 °C and 92 °C, and extrapolated to infinite dilution of 70 ± 1 and 61 ± 2, respectively. Dielectric results were analyzed using the Maier-Meier relationship and calculated molecular parameters. The apparent order parameter Sapp was found to be 0.63 and 0.50 for 1 and 2, respectively, which is smaller than that for the pure host (S = 0.66). Analysis of the Kirkwood factors g obtained for each concentration gave an association constant K of 63 ± 2 and 37 ± 1 (model 1) for the assumed dimerization of molecules (2M 
M2) of 1 and 2, respectively, in solutions of ClEster.
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