title: Metal-induced assembling/disassembling of fluorescent naphthalenediimide derivatives signalled by excimer emission.
abstract: The new quadridentate bischelating ligands 2 and 3 display in solution the typical absorption and emission properties expected for naphthalenediimide derivatives. Spectrophotometric studies show that systems 2 and 3 interact with Zn(II), Cd(II) and Cu(I) in CHCl3 or MeCN according to an apparent 1:1 stoichiometry. Molecular modelling, ESI-MS and 1H NMR experiments indicate that the complex species formed in the presence of stoichiometric amounts of metal ion are nonhelical [2 + 2] adducts. The metal-induced self-assembling process is signalled by an intense excimer-type emission caused by the intramolecular interaction of two naphthalenediimide subunits that face each other in the [2 + 2] adduct, as shown by molecular modelling studies. In the presence of excess metal ion, a disassembling process takes place, leading to a dinuclear complex with a 2:1 metal/ligand stoichiometry, in which the intramolecular excimer is no longer allowed to form because the interaction between the naphthalenediimide subunits has been lost. Thus, the overall metal-induced assembling/disassembling process is signalled by the appearance and disappearance of the excimer band in the emission spectrum.
authors.affiliation: Dipartimento di Chimica Generale, Università di Pavia, via Taramelli 12 27100 Pavia, Italy.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Licchelli
authors.forename: Laura
authors.initials: L
authors.lastname: Linati
authors.forename: Alessio
authors.initials: A
authors.lastname: Orbelli Biroli
authors.forename: Eleonora
authors.initials: E
authors.lastname: Perani
authors.forename: Antonio
authors.initials: A
authors.lastname: Poggi
authors.forename: Donatella
authors.initials: D
authors.lastname: Sacchi