FUNCTIONALIZED BASKET-SHAPED HOSTS - SYNTHESIS AND COMPLEXATION STUDIES WITH (ALKALI) METAL AND AMMONIUM AND DIAMMONIUM IONS

Functionalized basket-shaped hosts have been synthesized from the concave building block l,3:4,6-bis(3,6-dihydroxy-l,2-xylylene)tetrahydro-3a,6a-diphenylimidazo[4,5-d]imidazole-2,5(1H,3H)-dione (1). To this end, N-substituted l,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 in the bridge include: 5-hydroxy-3-oxapentyl, benzyl, hydrogen, 5-(N-(benzyloxycarbony1)-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 (-ΔG° 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. © 1990, American Chemical Society. All rights reserved.