Copper-containing surfactants: Synthesis, amphiphilic and mesogenic properties.

摘要

Transition metal surfactants combine redox and optical properties with amphiphilic and mesogenic behavior. They can be used in the development of responsive thin films. This thesis discusses the use of a new pyridine-based bidentate ligand N-(pyridine-2-ylmethyl)alkyl-1-amine, L PyC18, to develop copper-containing surfactants that exhibit mesomorphism. Complexes [(LPyC18)2CuIIY]Y were synthesized, where Y is an anionic ligand bromo, nitro, or perchloro. The nature of these apical ligands determines the mesogenic behavior of [(L PyC18)2CuIIBr]Br, [(LPyC18) 2CuIINO3]NO3, and [(LPyC18 )2CuIIClO4]ClO4: The smallest bromo-substituted species [(LPyC18)2Cu IIBr]Br shows a metastable liquid crystalline phase at 110°C, while the nitro-substituted [(LPyC18)2Cu IINO3]NO3 increases the transition temperature to 136°C, and the bulky perchloro-substituted [(LPyC18) 2CuIIClO4]ClO4 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.; The synthesis and characterization a novel series of single-tail surfactants LPyCXX, (CXX = C18, C16, C 14, C10) and their copper(II)-containing surfactants was also addressed. The organic species and their complexes [LPyC18Cu IICl2], [LPyC16CuIICl2], [LPyC14CuIICl2], [LPyC18Cu IIBr2], [LPyC16CuIIBr 2], and [LPyC10CuIIBr2] were synthesized, isolated and characterized by means of mass spectrometry, infrared and NMR spectroscopy and elemental analyses. Species [LPyC18Cu IICl2], [LPyC16CuIICl 2], [LPyC14CuIICl2], and [L PyC10CuIIBr2] had their molecular structure solved by X-ray diffraction methods showing that the local geometry around the metal center is distorted square planar. Morphology and order of the resulting films were studied by isothermal compression, and Brewster angle microscopy. A biphasic Langmuir film was observed for all but species [LPyC14Cu IICl2] and [LPyC10CuIIBr 2], and dependence on the chain length, and the nature of the halogeno coligand determine the characteristics of the isotherms and their patterning. Species [LPyC14CuIICl2] and [L PyC10CuIIBr2], showing shorter chain lengths failed to exhibit organization at the air/water interface. These results exemplify the first detailed study on the behavior of single-tail metallosurfactants and could lead to possible applications of their patterned films.; Finally, we report on the treatment of the above-described ligands with copper(II) salts to yield double-tail cationic copper(II)-containing surfactants described as [(LPyC14)2CuIIClO 4]ClO4, [(LPyC16)2CuIIClO4]ClO 4, [(LPyC18)2CuIIClO4 ]ClO4, [(LPyC18)2CuIINO 3]NO3, [(LPyC18)2CuIICl]Cl, [(LPyC18)2CuIIBr]Br. All species were isolated as microcrystalline powders ([(LPyC18) 2CuIIClO4]ClO4, [(LPyC18 )2CuIINO3]NO3, [(L PyC18)2CuIIBr]Br) or crystals ([(L PyC14)2CuIIClO4]ClO4, [(LPyC16)2CuIIClO4]ClO 4, [(LPyC18)2CuIICl]Cl) and fully characterized. A general five-coordinate CuN4O geometry in which the copper ion is bound at the basal plane to an amine and a pyridine nitrogen from each ligand, describes these species. Langmuir films of the metallosurfactant [(LPyC18)2CuIIClO 4]ClO4 were deposited and studied as potential primers for liquid crystalline orientation control. We have observed that the orientation of liquid crystals sandwiched between glass plates containing randomly oriented films yields comparable results to the untreated slides. On the other hand, the presence LB-coated films leads to noticeably distinctive optical properties.