Rational design, synthesis, and application of a new receptor for the molecular recognition of tricarboxylate salts in aqueous media
A. Frontera, J. Morey, A. Oliver, M. N. Piña, D. Quiñonero, A. Costa, P. Ballester, P. M. Deyà, E. V. Anslyn
J. Org. Chem. 2006, 71, 7185-7195
Abstract: A rational design of a tripodal receptor for the molecular recognition of tricarboxylate salts in aqueous media, based on squaramide, has been performed using high-level DFT calculations (RI-BP86/SVP level of theory) in solution using the COSMO treatment, including some preliminary ab initio calculations at the higher RI-MP2/TZVP level of theory, comparing the ability of squaramide to bind carboxylate salts with two widely used guanidinium salts. The tripodal receptor has been synthesized using a new methodology that has been recently reported by some of us, and its capability of recognizing several mono-, di-, and tricarboxylate salts has been studied experimentally by means of microcalorimetry experiments in a very high competitive media, H2O:EtOH 1:3. These experiments give enthalpic and entropic data, which are unfortunately scarce in the literature of molecular recognition of anions. Finally, a fluorimetric ensemble of the receptor with fluorescein has been found to be useful for the fluorimetric determination of zinc citrate in a commercial toothpaste using competition assays.
