Carboxylic acid functionalized imidazolium salts: sequential formation of ionic, zwitterionic, acid-zwitterionic and lithium salt-zwitterionic liquid crystals
作者:Joseph C. Y. Lin、Chao-June Huang、Yi-Ting Lee、Kwang-Ming Lee、Ivan J. B. Lin
DOI:10.1039/c1jm10580a
日期:——
Carboxylic acid functionalized imidazolium salts, their deprotonated carboxylate zwitterions and acid-zwitterion adducts have been studied, and are denoted as [N-Cn,N′-CO2H-Im][X] (Cn = CnH2n+1; X = Cl−, Br−, BF4− and PF6−), [N-Cn,N′-CO2-Im] and [(N-Cn,N′-CO2-Im)2H][anion] (anion = NO3− and Br−), respectively. Crystal structures of [N-C10,N′-CO2-Im]Br and [N-Cn,N′-CO2-Im]·2H2O studied by single-crystal X-ray diffraction indicate that carboxylic acid and carboxylate groups provide rich C–H⋯Br and/or C–H⋯O hydrogen bonding interactions in the construction of helical architecture. Except the PF6− salts, all the other types of compounds with long alkyl chains exhibit wide range SmA mesophase. Zwitterions and adducts represent two new classes of imidazolium based liquid crystals. The adducts [(N-Cn,N′-CO2-Im)2H]Br display wider mesophase range than the other series of compounds. Mixtures of lithium salts with zwitterion of [N-C10,N′-CO2-Im] form lithium containing liquid crystals at or near room temperature. A preliminary study of the mixtures of [N-C10,N′-CO2-Im]/[LiClO4] (3 : 1) and [N-C10,N′-CO2-Im]/[LiBF4] (3 : 1) placed between two ITO glasses shows that lithium ion conductivities increase upon increasing the temperature in the mesophase, yet decrease beyond the clearing temperature.
功能化羧酸的咪唑盐、去质子化的羧酸盐双性离子及酸-双性离子加合物已经被研究,分别表示为[N-Cn,N′-CO2H-Im][X](Cn = CnH2n+1;X = Cl−, Br−, BF4−和PF6−)、[N-Cn,N′-CO2-Im]和[(N-Cn,N′-CO2-Im)2H][anion](anion = NO3−和Br−)。通过单晶X射线衍射研究的[N-C10,N′-CO2-Im]Br和[N-Cn,N′-CO2-Im]·2H2O的晶体结构表明,羧酸和羧酸盐基团在螺旋结构的形成中提供了丰富的C–H⋯Br和/或C–H⋯O氢键作用。除了PF6−盐类外,所有其他类型的长烷基链化合物均展现出宽范围的SmA中间相。双性离子和加合物代表了两种新的基于咪唑的液晶类别。加合物[(N-Cn,N′-CO2-Im)2H]Br显示出比其他系列化合物更宽的中间相范围。锂盐与双性离子[N-C10,N′-CO2-Im]的混合物在室温或接近室温时形成含锂的液晶。对[N-C10,N′-CO2-Im]/[LiClO4](3:1)和[N-C10,N′-CO2-Im]/[LiBF4](3:1)混合物的初步研究显示,放置在两块ITO玻璃之间时,锂离子导电性在中间相的温度升高时增加,但在清晰温度以上时减少。