Metal-Ion Specific Recognition with Amplified Transcription from Subnanometer to Submillimeter or Real-Time Domain by Self-Assembled Vanadyl Quartets

Abstract

Vanadyl(V) complexes 1 and 2 bearing a nematic liquid crystal (LC) like a p-heptoxyphenyl group or a fluorous-tag pnonafluoroheptoxyphenyl (NFH) group at the C5 position of the Nsalicylidene template were designed and synthesized. Each complex was subjected to MVO 3 -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 Hg 2+ in an aqueous layer to form cluster complexes by ion swapping at the H 2 O/CDCl 3 bilayer interface. Selectivity profiles were examined with alkali-metal ions, Ag + , and Hg 2+ through metal-ion competition experiments. The 3′-Na has an exclusive selectivity for Hg 2+ in the presence of Zn 2+ and Cd 2+ . 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 Hg 2+ 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 t R from 7.36 to 10.27 min. The retention time difference between 3′-Na and 3′-Hg on HPLC was ∼3.6 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.

Asymmetric Radical-Type 1,2-Alkoxy-Sulfenylation of Benzoxazole-2-Thiols to Vinylarenes Catalyzed by Chiral Vanadyl Complexes

“…Therefore, one can conclude that the best results were derived from catalysts 4c and 4d . − This trend may have to do with delicate hydrogen-bonding interactions between methanol and the 3-chloro or 3-bromo group in the salicylidene template, but it also exerts enough steric shielding effect to steer the methoxy trapping event to the benzylic position of styrene (vide infra). Further improvements in terms of yields and extent of asymmetric induction can be achieved by performing these two catalytic reactions at 0 °C (data in parentheses in entries 3 and 4).…”