Functionalized Basket-Shaped Hosts. Synthesis and Complexation Studies with (Alkali) Matal and Ammonium and Diammonium Ions

Article abstract of DOI:10.1021/jo00289a015

Functionalized basket-shaped hosts have been synthesized from the concave building block 1,3:4,6-bis(3,6-dihydroxy-1,2-xylylene)tetrahydro-3a,6a-diphenylimidazo<4,5-d>imidazole-2,5(1H,3H)-dione (1).To this end, N-substituted 1,4,10,13-tetraoxa-7-azatridecamethylene bridges were attached to the 3,6- and 3',6'-positions of the xylylene rings of 1.The substituents at the nitrogen atom in the bridge include: 5-hydroxy-3-oxapentyl, benzyl, hydrogen, 5-(N-(benzyloxycarbonyl)-L-histidyl)-3-dioxapentyl, and 5-acetyl-3-oxapentyl.The baskets complex alkali metal and ammonium guests, as well as aliphatic and aromatic diammonium guests, all in a 1:1 ratio.Using the picrate extraction technique, free energies of binding for the new hosts with 19 guests were determined.Extremely strong binding (-ΔG⁰ values up to 18 kcal mol^-1) was observed for the complexes between the hosts and o-phenylenediammonium dipicrate.The origin of this phenomenon is discussed.The host with histidyl substituents easily forms a 1:1 complex with Zn(OTf)2.