title: Inversion of selectivity in anion recognition with conformationally blocked calix[4]pyrroles.
abstract: Two calixpyrrole derivatives were synthesised. A p-dimethylaminobenzoyl group was electronically attached to a pyrrole ring, establishing an intramolecular hydrogen bond in a 1,3-alternate conformation. The formation of the H-bond was corroborated by IR, NMR, and X-ray measurements. NMR titration studies reveal that the H-bond is strong enough to block the conversion to a cone conformation, allowing them to only acquire a partial cone conformation. Affinity constants for several anions were calculated, and a noticeable increase was observed for tridentate tetrahedral anions, while the K(a) of spheric or bidentate anions decreased. In the presence of several acids, the synthesised compounds can act as chemosensors by a double process: protonation of the amino group and coordination of the generated anion. In addition, a displacement approach gives rise to a proof of concept for sulphonate recognition.
authors.affiliation: Centro de Reconocimiento Molecular y Desarrollo Tecnológico, Unidad Mixta Universidad de Valencia - Universidad Politécnica de Valencia, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad de Valencia, Doctor Moliner 50, 46100 Burjassot, Valencia, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Gotor
authors.forename: Ana M
authors.initials: AM
authors.lastname: Costero
authors.forename: Salvador
authors.initials: S
authors.lastname: Gil
authors.forename: Margarita
authors.initials: M
authors.lastname: Parra
authors.forename: Luis E
authors.initials: LE
authors.lastname: Ochando
authors.forename: Katherine
authors.initials: K
authors.lastname: Chulvi
mesh_terms: D000143:Acids / Q000032:analysis*; D000838:Anions / Q000032:analysis*; D047250:Calixarenes / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D011166:Porphyrins / Q000138:chemical synthesis / Q000737:chemistry*; D013451:Sulfonic Acids / Q000032:analysis*
chemical_list: D000143:Acids; D000838:Anions; D011166:Porphyrins; D013451:Sulfonic Acids; C469811:calix(4)pyrrole; D047250:Calixarenes