title: Light-emitting molecular machines: pH-induced intramolecular motions in a fluorescent nickel(II) scorpionate complex.
abstract: A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.3, the sulfonamide group deprotonates and coordinates the NiII center, giving rise to a complex of trigonal bipyramidal stereochemistry, as shown by X-ray diffraction studies performed on the crystalline complex salt. At pH 7.5, an OH- ion binds the metal and a six-coordinate species forms. The binding-detachment of the pendant arm to/from the NiII center is signaled by changes in the emission properties of the dansyl subunit in the side chain; the fluorescence of this side chain is high when the pendant arm is not coordinated and low when the sulfonamide group is bound to the metal. The system investigated represents the prototype of a light-emitting molecular machine, driven by a pH change.
authors.affiliation: Dipartimento di Chimica Generale, Università di Pavia, via Taramelli12, Italy. luigi.fabbrizzi@unipv.it
authors.forename: Luigi
authors.initials: L
authors.lastname: Fabbrizzi
authors.forename: Francesco
authors.initials: F
authors.lastname: Foti
authors.forename: Maurizio
authors.initials: M
authors.lastname: Licchelli
authors.forename: Paola M
authors.initials: PM
authors.lastname: Maccarini
authors.forename: Donatella
authors.initials: D
authors.lastname: Sacchi
authors.forename: Michele
authors.initials: M
authors.lastname: Zema
mesh_terms: D018360:Crystallography, X-Ray; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D008027:Light; D020409:Molecular Motor Proteins / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D009038:Motion; D009532:Nickel / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry
chemical_list: D020409:Molecular Motor Proteins; D009942:Organometallic Compounds; D009532:Nickel