Syntheses and functional studies of chiral metal organic cages and supramolecular assemblies derived from imido and amido p v scaffolds

Abstract

Chiral Metal organic supramolecular architectures have received much attention due to their unique and fascinating structures and material applications These have been useful in various fields of research such as chiral recognition and separation asymmetric catalysis nonlinear optical biomedical research and enzyme mimetics This presentation focuses on the use of chiral phosphonium and phosphoramide ligands towards the formation of various discrete chiral hydrogen bonded frameworks and metal organic cages and their applications in chiral recognition and separation A facile deprotonation protocol involving enantiopure phosphoramide ligands and Pd II ions generated the trinuclear complex of the chiral tris imido phosphate trianions Pd3 PO N CH CH3 Ph 3 3 This in situ generated imido Pd3 species readily self assembles in the presence of oxalate dianions to yield an enantiomeric pair of tetrahedral cages of formula Pd3XRRR 4 C2O4 6 and Pd3XSSS 4 C2O4 6 Further these cages were shown to exhibit moderate enantioselective separation capabilities for epichlorohydrin 946 butyrolactone 3 methyl and 3 ethyl cyclopentanone via crystallization inclusion method Single crystal X ray analysis of 177 946 butyrolactoneat 177 1 system showed that guest recognition predominantly takes place at the extrinsic cavities of the cage Further by utilizing the same PBUs with chloranilate dianions we have synthesized iso structural chiral tetrahedral cages Pd3XRRR 4 C6O4Cl2 6 and Pd3XSSS 4 C6O4Cl2 6 Due to the presence of quinoid portals in these tetrahedral cages they exhibit considerable enantioselective separation capabilities towards a series of styrene epoxides via the crystallization inclusion method The highest enantioseparation of 80 has been observed for the R Fluoro styrene oxide compound using the cage Pd3XRRR 4 C6O4Cl2 6 Use of other anilate ligands such as Dihydroxy benzoquinone DHBQ and bromanilate anions resulted in the formation of elusive polyradical cages Pd3XRRR or SSS 4 L 6 L C6O4H2 C6O4Br2 The Triplet and sin