Synthesis and Anion-Selective Complexation of Homobenzylic Tripodal Thiourea Derivatives (original) (raw)

Cryptand-and tripod-type thiourea derivatives 4b and 5ad, which have binding functionalities at the homobenzylic positions, were synthesized as possible neutral receptors toward anions with an expectation that the three binding sites work cooperatively to bind an anion selectively. 1 H NMR spectroscopic monitoring of the titration of cryptand 4b with CH 3 CO 2-, Cl-, and Fin CDCl 2 CDCl 2 at 100°C showed that the binding constants were considerably smaller than those of tripodal thiourea 5a, presumably owing to the presence of strong intramolecular hydrogen bonding in 4b. Complexation constants of tripodal receptors 5a-d with H 2 PO 4-, CH 3 CO 2-, Cl-, and Branions were evaluated by 1 H NMR and/or UV/Vis spectroscopic analysis of the titration in DMSO. Though tripodal receptors 5a,b undergo complexation with phosphate anion in a 1:1 stoichiometry, their asso-[a] Division of Frontier Materials Science,