链状氢键型冠醚超分子化合物的合成、结构及介电性质

Syntheses,structures and dielectric properties of a chained hydrogen-bonding supramolecular compound containing crown ether

以18-冠醚-6为主体,4-溴苯胺为客体,无机酸为电荷抗衡体,在丙酮溶剂中,通过蒸发法制备了一种新型超分子晶体材料(4-BrC 6H 4NH 3)+(18-crown-6)(ClO 4)-(1),并采用红外光谱(IR)、核磁共振氢谱(1HNMR)、X-射线单晶衍射、X-射线粉末衍射(XRD)、热重(TG)、介电等多种方式对晶体材料进行表征。结果显示,两种温度下化合物1均为正交晶系,空间群为Pnma,其中4-溴苯胺阳离子-NH 3+基团均发生转动产生结构无序。相邻4-溴苯胺阳离子通过氢键N-H…O、N-H…Br相互作用,穿过18-冠醚-6分子中心,在a轴方向上形成一维链状结构。随着温度的升高,氢键N-H…Br的长度也随之增加。温度改变引起4-溴苯胺分子发生动态摆动,导致晶体结构在a轴、c轴方向增长。介电测试结果表明化合物在251 K附近发生明显的阶梯状介电异常。

A novel supramolecular crystal material(4-BrC 6H 4NH 3)+(18-crown-6)(ClO 4)-was prepared by solvent slow evaporation in acetone solvent with crown ether as main body,4-bromophenylamine as guest and inorganic acid as charge counterbalance.The supramolecular crystal materials were characterized by infrared analysis(IR),nuclear magnetic resonance spectroscopy(1HNMR),X-ray single crystal diffraction,X-ray powder diffraction,thermogravimetric analysis(TG、DTA)and dielectric constant measurements.The results show that compound 1 is orthorhombic and Pnma space group at 100 K and 273 K.The-NH 3+group on protonated 4-bromoanilide was obviously disordered at different temperatures.The supramolecular cations interact with each other through N-H…O、N-H…Br hydrogen bonds,and form a one-dimensional chain structure along the a-axis by 18-crown-6.As the increases of temperature,the length of the N-H…Br hydrogen bonds also increases.The dynamic oscillations of 4-bromoaniline molecules were induced by temperature change,leading to the increase length of a-axis and c-axis unit cells of the crystal structure.The results of dielectric studies suggest that the compound occurs obvious stepped dielectric anomaly at 251 K.