Unconventionally shaped chromonic liquid crystals formed by novel silver(i) complexes

Abstract

The synthesis of the first chiral Ag(I) bis chelated bipyridine ionic complexes showing chromonic liquid crystalline behaviour in water is reported. Single crystal X-ray analysis revealed a pre-chromonic organization in the crystalline state, with silver(I) cations stacking into columns reinforced by hydrogen bonding with the acetate counterions and water molecules. Due to the presence of molecules with an unconventional shape for the generation of typical chromonic phases, a full characterization based on phase diagram analysis, completely resolved by POM, DSC and X-ray powder diffraction measurements, has been conducted. Moreover, cryo-TEM experiments have been carried out in order to confirm the appearance of nematic columnar phases. A “route” to drive the alignment of the liquid crystalline phases of these compounds has been developed, which is particularly important for future application in biophotonic devices. Finally, the presence of transient twisted periodical stripe structures has been observed, when an initial planar alignment is destroyed in favour of a homeotropic configuration of the molecules dictated by the confining surfaces.