Influence of the Apical Ligand in the Thermotropic Mesomorphism of Cationic Copper-Based Surfactants
摘要:
A new pyridine-based bidentate ligand L-PyC18 was used to develop copper-containing surfactants that exhibit mesomorphism, Complexes [(L-PyC18)(2)(CuY)-Y-II]Y Were synthesized, where Y is an anionic ligand bromo (1), nitrato (2), or perchlorato (3). The nature of these apical ligands determines the mesogenic behavior of 1-3: The smallest bromo-substituted species 1 shows a metastable liquid crystalline phase at 110 degrees C, the nitrato-substituted 2 increases the transition temperature to 136 degrees C, and the bulky perchlorato-substituted 3 shows reversible mesophases at 153 degrees C. The behavior of these complexes shows similarities and suggests that at low temperatures the crystals of these compounds are bilayered structures with interdigitated alkyl tails. At higher temperatures the tails undergo rapid conformational changes that force these layers to swell until the opposing alkyl chains are separated from each other, and the mesophase is a monolayer smectic A. Small changes in the geometry of cationic mesogens can be imposed by the presence of apically coordinated anions, allowing for tuning in the properties of the resulting mesophases.
我们讨论了阳离子金属表面活性剂[(L Py14)2 Cu II ClO 4 ] ClO 4(1),[(L Py16)2 Cu II ClO 4 ] ClO 4(2),[(L Py18)2 Cu II ClO 4 ] ClO 4(3),[(L Py18)2 Cu II NO 3 ] NO 3(4),[(L Py18)2 Cu II Cl] Cl(5)和[(L Py18)2 Cu II Br] Br(6)通过用铜处理含有四,六或十八烷基链的合适的烷基胺甲基-2-吡啶配体来获得盐。这些金属表面活性剂在红外光谱带,具有同位素模式的光谱质量和元素组成之间显示出极好的一致性。可用于单晶X射线数据1,2,5和先前公布3揭示了在基面上结合到每个烷基胺甲基吡啶配体的胺和吡啶上的三角双锥体铜(II)离子和在顶端位置上结合了阴离子大肠菌素。除了具有最短十四烷基(C 14)链的表面活性剂外,这些物质还产生具有45–55