Li Haolong, Bu Weifeng, Qi Wei, Wu Lixin
Key Laboratory for Supramolecular Structure and Materials, Ministry of Education, Jilin University, Changchun 130012, People's Republic of China.
J Phys Chem B. 2005 Nov 24;109(46):21669-76. doi: 10.1021/jp053980o.
A series of europium alkanoates (C(n-1)H(2n-1)CO(2))(3)Eu, (n = 14, 16, 18, 20) have been synthesized and characterized in detail. X-ray diffraction and Fourier transform infrared spectroscopic measurements confirm the multibilayer structure of these homologues. In such bilayers, the europium ionic layers are well separated by the highly ordered alkyl chains which are in an all-trans conformation and perpendicular to both sides of the europium ionic layers. There is a mixed-coordination type of chelating bidentate and bridging bidentate between the carboxylate groups and the europium ions. All samples exhibit characteristic emission of europium, though the luminescent intensity has been partly quenched by the carboxylate groups. Differential scanning calorimetry (DSC) shows multiple melting points for these homologues, and temperature-dependent X-ray diffraction measurements also confirm the existence of the mesophase on heating. This mesophase is not truly liquid crystalline, but is similar to the smectic A phase of organic rodlike molecules. Meanwhile, it seems that with increasing atomic number of lanthanide ions, longer alkyl chains will be required to form such a mesophase for the corresponding lanthanide alkanoates.
已合成并详细表征了一系列链烷酸铕（C(n - 1)H(2n - 1)CO(2))(3)Eu，（n = 14、16、18、20）。X射线衍射和傅里叶变换红外光谱测量证实了这些同系物的多层结构。在这样的双层结构中，铕离子层被高度有序的烷基链很好地隔开，这些烷基链呈全反式构象且垂直于铕离子层的两侧。羧酸根基团与铕离子之间存在螯合双齿和桥连双齿的混合配位类型。所有样品均表现出铕的特征发射，尽管发光强度已被羧酸根基团部分猝灭。差示扫描量热法（DSC）显示这些同系物有多个熔点，并且温度依赖的X射线衍射测量也证实了加热时中间相的存在。这种中间相并非真正的液晶相，但类似于有机棒状分子的近晶A相。同时，似乎随着镧系离子原子序数的增加，形成相应镧系链烷酸酯的这种中间相需要更长的烷基链。
