Anion-driven mesogenicity: a comparative study of ionic liquid crystals based on the [closo-1-CB9H10] and [closo-1-CB11H12] clustersElectronic Supplementary Information (ESI) available: synthesis details and analytical data for mesogens and their intermediates, additional powder XRD data, and molecular modeling details. See DOI: 10.1039/c2jm15448j

• Main Authors: Ringstrand, Bryan, Jankowiak, Aleksandra, Johnson, Lillian E, Kaszynski, Piotr, Pociecha, Damian, Grecka, Ewa
• Format: Article
• Language: English
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm15448j

A series of structurally analogous esters derived from monocarbaborates, [ closo -1-CB 9 H 10 ] ( A ) and [ closo -1-CB 11 H 12 ] ( B ), containing a maximum of 4 rings in the rigid core were prepared and investigated by thermal, optical, and XRD methods. Ion pairs containing a total of 4 rings with either N -butyl-4-heptyloxypyridinium ( Pyr ) or cetyltrimethylammonium ( Cetyl ) cation form a SmA phase ranging from 90 C to 229 C. Ion pairs 1e[Pyr] and 2e[Pyr] containing an azo group in the anisometric anion exhibit an enantiotropic nematic phase above the SmA phase. The cesium salt 1h[Cs] did not exhibit mesogenic behavior. Partial binary phase diagrams were investigated for 1d[Pyr] and 2d[Pyr] in 2e[Pyr] , and for 1f[Pyr] in non-ionic mesogens. Variable temperature powder XRD analysis of 5 ionic liquid crystals, 1e[Pyr] , 1f[Pyr] , 2f[Pyr] , 1g[Pyr] , and 2g[Pyr] , demonstrated about 20% interdigitation in the SmA phase and provided thermal expansion coefficients. Ion pairs of anisometric anions derived from the [ closo -1-CB 9 H 10 ] and [ closo -1-CB 11 H 12 ] clusters exhibit SmA, nematic, and soft crystalline phases