Abstract
A tailor-designed vanadyl methoxides bearing p-heptoxyphenyl group at the C5 position of the salicylidene template was synthesized and then subjected to LiVO3 to form loosely bound, Li+-encapsulated quadruplexes. Quadruplexes bearing encapsulated Pb(II) ion, topped with five different anion ligands can be synthesized by dynamic metal-ion specific swapping with different Pb(II) salts. And NO3- ligand could be replaced by other anions due to different binding ability. The chiral tetrameric vanadyl(V) cluster complex allows for efficient halogen anion specific transport. These cluster complexes were utilized as chiral dopants (1 wt%) to nematic LC materials. A systematic survey on the changes of helical pitch was performed and determined by Grandjean method in wedge cells viewed under polarized microscope. It was found that anion with similar geometries, with decreasing in Lewis basicity of the couter anion, the four lower rim regions of the resulting cluster (i.e, the four p-heptoxyphenyl groups) getting farther, thus inducing more helical twisting to the nematic LC phase. This information can be asymmetrically amplified to 0.6-27.5 m pitch change in LC phase. A linear correlation was found between the induced helical pitch (Y-axis) and the electronegativity of halide anion (X-axis) was established. Besides, we have prepared a new type of calix[4]arene-based chiral oxidovanadium (V) complexes, which was utilized for asymmetric aerobic oxidation and kinetic resolution of benzyl α-hydroxy-phenyl-acetate. The best results of the resolved alcohol we obtained was 75 % ee at 45 % conversion, when the reaction was performed in chlorobenzene 50 ℃.