ABSTRACT
Vanadyl(V) complexes 1 and 2 bearing a nematic liquid crystal (LC) like a p-heptoxyphenyl group or a fluorous-tag p-nonafluoroheptoxyphenyl (NFH) group at the C5 position of the N-salicylidene template were designed and synthesized. Each complex was subjected to MVO3-induced self-assembly to form metal-ion, encapsulated quartet clusters 3-M and 3'-M. The Na+ in cluster complex 3-Na or 3'-Na can be readily replaced by Rb+, Ag+, or Hg2+ in an aqueous layer to form cluster complexes by ion swapping at the H2O/CDCl3 bilayer interface. Selectivity profiles were examined with alkali-metal ions, Ag+, and Hg2+ through metal-ion competition experiments. The 3'-Na has an exclusive selectivity for Hg2+ in the presence of Zn2+ and Cd2+. Cluster complexes 3-M were utilized as chiral dopants to nematic LC materials. The effects of the encapsulated metal ions within the alkali family and Ag+ on Cano's line widths and helical pitch changes were viewed in wedge cells under a polarized microscope. Their correlations with the ionic radius were identified. The subnano information of the metal ions can thus be asymmetrically amplified to Cano's line spacings of the submilimeter domain. Conversely, the effects of the encapsulated alkali metal ions and Hg2+ in 3'-M on the interactions of their NFH tails toward fluorous silica gel (FSG) were performed via HPLC analyses. Their retention times became longer as the sizes of encapsulated, alkali metal ions increased. The increasing ion size from Na+ to Cs+ caused the four lower rim NFH tags of the cluster to be closer due to reduced cone angles. Their interactions among NFH tail groups on FSG became larger, thus leading to distinctive separations with tR from 7.36 to 10.27 min. The retention time difference between 3'-Na and 3'-Hg on HPLC was â¼3.6 min, resulting in discernible separation. The individual ion size differences on the subnano scale can thus be amplified and unambiguously established in the real time domain.
