An expansible metalla-cryptand as a component of a supramolecular combinatorial library formed from di(8-hydroxyquinoline) ligands and gallium(III) or zinc(II) ions

Ethylene-bridged di(8-hydroxquinoline) ligands 1a-c-H-2 can be synthesized in five-step procedures from the corresponding 8-hvdroxyquinolines. X-ray structural analysis shows that fa-H, in the solid state forms a polymer by hydrogen bonding. When the ligands 1a-c-H-2 an mixed with gallium(III) ions, a mixture (supramolecular combinatorial Library) is formed of coordination compounds {(1a-c)(3)Ga-2}(n) which by addition of appropriate guests (M+=Na+, K+, NH4+, Rb+) can be transformed quantitatively into a defined metalla-cryptate [M subset of {(1a - c)(3)Ga-2}](+). Those complexes and the corresponding zinc cryptates [M+ subset of {(1a)(3)Zn-2}](-) (M'(+) = Li+, Na+, K+) can also be obtained directly in metal-directed self-assembly processes in the presence of templates, H-1 NMR studies and the solid-state structures of [K/Na subset of {(1a)(3)Ga-2}](-) show that the metalla-cryptand {(1a)(3)Ga-2} can adjust to the size of the guest present. Thus proton H(2) of the ligand acts as a H-1 NMR spectroscopic probe to predict the size of the cryptate in solution.