Influence of the Apical Ligand in the Thermotropic Mesomorphism of Cationic Copper-Based Surfactants

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• 作者：Jeffery A. Driscoll ; Paul H. Keyes ; Mary Jane Heeg ; Paul A. Heiney ; Claudio N. Verani
• 刊名：Inorganic Chemistry
• 出版年：2008
• 出版时间：August 18, 2008
• 年：2008
• 卷：47
• 期：16
• 页码：7225-7232
• 全文大小：422K
• 年卷期：v.47,no.16(August 18, 2008)
• ISSN：1520-510X

文摘

A new pyridine-based bidentate ligand L^PyC18 was used to develop copper-containing surfactants that exhibit mesomorphism. Complexes [(L^PyC18)₂Cu^IIY]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 °C, the nitrato-substituted 2 increases the transition temperature to 136 °C, and the bulky perchlorato-substituted 3 shows reversible mesophases at 153 °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.