Effective receptors for fluoride and acetate ions: synthesis and binding study of pyrrole- and cystine-based cyclopeptido-mimetics

Two conformationally constrained pseudo-cyclopeptides (1, 2) consisting of pyrrole-, pyridine-, and cystine-moieties were designed and synthesized as neutral receptors for anionic guests. The anion recognition abilities of these two receptors were examined photometrically in acetonitrile solution. The UV–vis study revealed that the [1+1] receptor (1) formed 1:1 complexes with anions, whereas the [2+2] receptor (2) led to 1:2 mode binding with anions. Both receptors displayed good affinity and selectivity for fluoride and acetate ions.