Showing papers by "Dorothea Fiedler published in 2007"

Resolution of Chiral, Tetrahedral M4L6 Metal−Ligand Hosts1

Abstract: The supramolecular metal−ligand assemblies of M416 stoichiometry are chiral (M = GaIII, AlIII, InIII, FeIII, TiIV, or GeIV, H41 = N,N‘-bis(2,3-dihydroxybenzoyl)-1,5-diaminonaphthalene). The resolution process of ΔΔΔΔ- and ΛΛΛΛ-[M416]12- by the chiral cation S-nicotinium (S-nic+) is described for the GaIII, AlIII, and FeIII assemblies, and the resolution is shown to be proton dependent. From a methanol solution of M(acac)3, H41, S-nicI, and KOH, the ΔΔΔΔ-KH3(S-nic)7[(S-nic) ⊂ M416] complexes precipitate, and the ΛΛΛΛ-K6(S-nic)5[(S-nic) ⊂ M416] complexes subsequently can be isolated from the supernatant. Ion exchange enables the isolation of the (NEt4+)12, (NMe4+)12, and K+12 salts of the resolved structures, which have been characterized by CD and NMR spectroscopies. Resolution can also be accomplished with 1 equiv of NEt4+ blocking the cavity interior, demonstrating that external binding sites are responsible for the difference in S-nic+ enantiomer interactions. Circular dichroism data demonstrate that th...