Polar derivatives of the [closo-1-CB9H10](-) cluster as positive Delta epsilon additives to nematic hosts

Polar (mu approximate to 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) angstrom, b = 10.481(3) angstrom, c - 12.098(3) angstrom, alpha - 93.804(9)degrees, beta - 90.249(10)degrees, gamma - 102.587(10)degrees, 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 (Delta epsilon = -0.59) were investigated using thermal and dielectric methods. The results for 1 and 2 showed virtual [T-NI] values of 139 degrees C and 92 degrees C, and Delta epsilon 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 S-app 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 reversible arrow M-2) of 1 and 2, respectively, in solutions of ClEster.