Squaramido-based receptors

Prohens and co-workers have synthesized compounds 8a and 8b, simple squaramido-based receptors and investigated their ability to coordinate car-boxylate anion in competitive solvents [16]. The amide NH groups of the squaramide form a more open cleft (similar to ureas) than the isophthala-mides. Receptors 8a and 8b therefore adopt a more suitable geometry for the coordination of bidentate anions, such as carboxylate anions, through two approximately linear hydrogen bonds. Proton NMR titration experiments revealed association constants of 217 M and 1980 for the binding of acetate by 8a and 8b respectively in DMSO-de at 295 K. 

Prohens. R. Tomas, S. Morey, J. Deya, P.M. Ballester. P. Costa. A. Squaramido-based receptors Molecular recognition of carboxylate anions in highly competitive media. Tetrahedron Lett. 1998. 39 (9). 1063-1066. 

---

See also in sourсe #XX -- [ ]

---