title: Coumarin-based luminescent ligand that forms helicates with dicationic metal ions.
abstract: The potentially hexadentate ligand L, which contains two terminal coumarin fluorophores, forms dinuclear double-stranded helicates with dicationic metal ions, giving species of the generic form [M(2)L(2)](4+). In solution the free ligand was fluorescent with emission attributed to the coumarin fluorophores (lambda(em) = 437 nm). The luminescent properties of the corresponding dimetallic helicates complexes were examined and revealed that the Zn(2+) complex demonstrates enhanced emission when compared to the parent ligand, whereas Co(2+), Cu(2+), Cd(2+) and Hg(2+) induce varying degrees of fluorescence quenching. In particular, comparative luminescence measurements at 77 K and room temperature showed that the quenching mechanism for [Cu(2)L(2)](4+) can be attributed to a photoinduced electron transfer. ESI-MS selectivity studies showed that in the presence of a mixture of metal dications no preference for any one metal ion was observed.
authors.affiliation: Department of Chemical and Biological Sciences, University of Huddersfield, Huddersfield HD1 3DH.
authors.forename: Sam J
authors.initials: SJ
authors.lastname: Bullock
authors.forename: Cara E
authors.initials: CE
authors.lastname: Felton
authors.forename: Rebecca V
authors.initials: RV
authors.lastname: Fennessy
authors.forename: Lindsay P
authors.initials: LP
authors.lastname: Harding
authors.forename: Michael
authors.initials: M
authors.lastname: Andrews
authors.forename: Simon J A
authors.initials: SJ
authors.lastname: Pope
authors.forename: Craig R
authors.initials: CR
authors.lastname: Rice
authors.forename: T
authors.initials: T
authors.lastname: Riis-Johannessen