title: Induced fit interanion discrimination by binding-induced excimer formation.
abstract: The synthesis, photophysical, and anion-binding properties of a series of di-, tri-, and tetrapodal anion-binding hosts based on aminopyridinium units with pyrenyl reporter groups are described. The ditopic mesitylene-derived calix[4]arene-based host 4 binds strongly to dicarboxylates, particularly malonate, in a 2:1 anion:host ratio but is essentially nonemissive in the presence of all anions except chloride because of intramolecular quenching by the pyridinium units. Addition of chloride results in a conformational change, giving an initial increase in emission assigned to intramolecular excimer formation. Further chloride addition also results in an increase in the intensity of the pyrenyl monomer emission as chloride binding reduces the acceptor ability of the pyridinium groups. This behavior is not exhibited by control compounds 5 and 6, which lack the ditopic geometry and calixarene spacer unit; however, tripodal 6 forms 1:2 anion:host complexes with a range of anions.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, United Kingdom.
authors.forename: Maria H
authors.initials: MH
authors.lastname: Filby
authors.forename: Sara Jane
authors.initials: SJ
authors.lastname: Dickson
authors.forename: Nelsi
authors.initials: N
authors.lastname: Zaccheroni
authors.forename: Luca
authors.initials: L
authors.lastname: Prodi
authors.forename: Sara
authors.initials: S
authors.lastname: Bonacchi
authors.forename: Marco
authors.initials: M
authors.lastname: Montalti
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Paterson
authors.forename: Terry D
authors.initials: TD
authors.lastname: Humphries
authors.forename: Claudio
authors.initials: C
authors.lastname: Chiorboli
authors.forename: Jonathan W
authors.initials: JW
authors.lastname: Steed