The effect of fluoroalkyl chains in metallomesogens on mesomorphic properties

Metal-containing liquid crystals (metallomesogens) combine the specific properties metal- containing compounds with the order and mobility of the liquid crystalline state. However, the presence of metal atoms in these molecular systems provides the possibility to design a wide variety of molecules, which were expected to exhibit interesting mesomorphic and physical properties. Introduction of semiperfluorinated alkyl chains into building of metal-containing liquid crystal systems induce important modifications of melting point, transition temperatures, mesophase shape and stability and physical properties due to the incompatibility and micro-segregation of these chains from other units in the molecules. In this research, chrial imine ligands carrying semiperfluorinated achiral terminal chains and their chloro-bridged dinuclear palladium(II) complexes have been synthesized. The structures of synthesized compounds were characterized by spectroscopic methods (UV, 1H- and 13C-NMR, MS) and elemental analysis. The mesomorphic properties were investigated using polarized optical microscopy and differential scanning calorimetry. As a result, the influence of (i) the presence of fluorine atom in the achiral terminal chains, non-fluorinated chrial alkyl chain and metal atom in the complexes, (ii) number of fluorine atoms in the fluoroalkyl chains and (iii) number of semifluorinated alkyl chains on the mesomorphic properties of these synthesized compounds which have calamitic molecular shape were discussed. Keywords: Liquid crystals, metallomesogens, semiperfluorinated mesogen, imine, palladium(II) complex.