Simona Asaftei

Thermotropic ionic liquid crystals by molecular assembly and ion pairing of 4,4′-bipyridinium derivatives and tris(dodecyloxy)benzenesulfonates in a non-polar solvent

The present work reports a simple and versatile pathway to incorporate redox-active 4,4′-bipyridinium (“viologen”) units with two, three, or six charges into dynamically ordered liquid crystalline structures by ionic interactions. A detailed analysis of the structure–property relationship was supported by molecular modelling experiments. Three redox-active 4,4′-bipyridinium (“viologen”) cores, 1,1′-dimethyl (4-pyridin-4-ylpyridinium) di- (MV2+2+2+2+), 1,1′,1′′-[benzene-1,3,5-triyltris(methylene)]tris(4-pyridin-4-ylpyridinium) tri- (V3+3+3+3+3+), and 1,1′,1′′-[benzene-1,3,5-triyltris(methylene)]tris[(methyl) 4-pyridin-4-ylpyridinium] hexa- (MV6+6+6+) cationic halides, were combined with an anionic caesium 3,4,5-tris(dodecyloxy)benzene sulfonate (DOBS) under phase transfer conditions to yield complexes of constant stoichiometry. The formed complexes, MV2+2+2+(DOBS)222, V3+3+3+(DOBS)333 and MV6+6+6+(DOBS)666, were characterized by NMR spectroscopy. Depending on the molecular structure, significantly different characteristics in electrochemical behaviour of ionic liquid crystals (ILCs) with two DOBS anions and a rod-like core (MV2+2+2+2+) were observed compared with ILs with three and six DOBS anions and y-shaped cores (V3+3+3+3+3+), and (MV6+6+6+) cations respectively. We report for the first time a new electroactive thermotropic liquid crystal, MV2+2+2+(DOBS)222, which changes colour from yellow to blue-green above 75 °C typically for redox units in the reduced state. The reduced states of the MV2+2+2+(DOBS)222 complex at E = −2 V exhibit reversible redox waves and have influence on molecular arrangement in the crystal structure as seen by polarisation microscopy. Our ionic liquid crystals have potential applications, due to their low melting temperature, wide temperature range, ionic conductivity, and thermal- and electro-chromism, for instance, for the design of electrochromic displays.

Examination of structure-activity relationship of viologen-based dendrimers as CXCR4 antagonists and gene carriers.

Chemokine receptors and their ligands play a central role in cancer metastasis, inflammatory disorders, and viral infections. Viologen dendrimers (VGD) emerged recently as a promising class of synthetic polycationic ligands for chemokine receptor CXCR4. The objective of this study was to evaluate the potential of VGD as novel dual-function polycations capable of simultaneous CXCR4 antagonism and gene delivery. As part of our systematic studies, we have synthesized a library of VGD with differences in molecular architecture, number of positive charges, and type of capping group. The ability of VGD to condense DNA was evaluated, and physicochemical and biological properties of the resulting polyplexes were studied. We have evaluated the effect of VGD surface charge, size, capping group, and molecular architecture on physicochemical properties of polyplexes, transfection efficiency, CXCR4 antagonism, and cytotoxicity in human epithelial osteosarcoma (U2OS) and in human liver hepatocellular carcinoma (HepG2) cells. We found that properties and behavior of the polyplexes are most dependent on the number of positive charges and molecular weight of VGD and to a lesser extent on the type of a capping group. Using TNFα plasmid, we have demonstrated that VGD prevents CXCR4-mediated cancer cell invasion and facilitates TNFα-mediated cancer cell killing. Such dual-function carriers have potential to enhance the overall therapeutic outcomes of cancer gene therapy.

P-118: High Resolution Electrochromic Displays for E-Readers

Displays incorporating nanostructured films modified with electrochromic molecules have shown great promise commercially in low information content applications. The materials are amenable to print techniques such as screenprinting and inkjet printing. We report on progress in providing solutions to medium resolution screenprinted displays and high-resolution inkjet printed displays that demonstrate excellent visual quality and superb stability.