Highly quadrupolar derivatives of the [closo-B10H10]2- anion: Investigation of liquid crystalline polymorphism in an homologous series of 1,10-bis(4-alkoxypyridinium) zwitterions

A series of pyridinium bis-zwitterions [closo-B10H8-1,10-2 (4-ROC5H4N)] (1[u]) was obtained in 55-60% yield by reacting [closo-B10H8-1,10-2(1Ph)] (3) with 4-alkoxypyridines and the resulting derivatives were analyzed for their liquid crystalline properties. Optical, thermal and XRD analyses revealed the formation of a nematic and rare lamellar phases, Lama, driven by dipolar interactions. Upon elongation of the terminal alkoxy chain, the nematic phase is gradually replaced by the lamellar polymorphism. The solidstate structures of 1[8], 1[12] and 1[16] were established by single crystal XRD:1[12] p-1,z=2,a= 9.6262 (2) angstrom,b = 12.0464(2) angstrom, c=12.611150(10) angstrom,beta=103.9910(10)degrees;1[12] p-1,Z=2,a=9.6262,(2) angstrom,b = 12.0464(2) angstrom, c=17.9226(3)angstrom, alpha=80.5940(10)degrees, beta= 83.0700(10)degrees, gamma=74.9860(10)degrees; 1[16] p-1, Z=2,a=9.6827 (3) angstrom,b = 11.6711 (5) angstrom, c= 22.8486(7) angstrom, alpha=77.416(3)degrees, beta = 86.925(2)degrees,gamma=66.202 (4)Alpha degrees