title: Synthesis and Evaluation of 1,8-Disubstituted-Cyclam/Naphthalimide Conjugates as Probes for Metal Ions.
abstract: Fluorescent molecular probes for metal ions have a raft of potential applications in chemistry and biomedicine. We report the synthesis and photophysical characterisation of 1,8-disubstituted-cyclam/naphthalimide conjugates and their zinc complexes. An efficient synthesis of 1,8-bis-(2-azidoethyl)cyclam has been developed and used to prepare 1,8-disubstituted triazolyl-cyclam systems, in which the pendant group is connected to triazole C4. UV/Vis and fluorescence emission spectra, zinc binding experiments, fluorescence quantum yield and lifetime measurements and pH titrations of the resultant bis-naphthalimide ligand elucidate a complex pattern of photophysical behaviour. Important differences arise from the inclusion of two fluorophores in the one probe and from the variation of triazole substitution pattern (dye at C4 vs. N1). Introducing a second fluorophore greatly extends fluorescence lifetimes, whereas the altered substitution pattern at the cyclam amines exerts a major influence on fluorescence output and metal binding. Crystal structures of two key zinc complexes evidence variations in triazole coordination that mirror the solution-phase behaviour of these systems.
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Joseph K-H
authors.initials: JK
authors.lastname: Wong
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Sandra
authors.initials: S
authors.lastname: Ast
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Mingfeng
authors.initials: M
authors.lastname: Yu
authors.affiliation: Institute for Chemistry University of Potsdam Karl-Liebknecht St. 24-25 14476 Potsdam Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Flehr
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Counsell
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia; Crystal Structure Analysis Facility The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Turner
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Patrick
authors.initials: P
authors.lastname: Crisologo
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Matthew H
authors.initials: MH
authors.lastname: Todd
authors.affiliation: School of Chemistry The University of Sydney Sydney NSW 2006 Australia.
authors.forename: Peter J
authors.identifier: 0000-0002-0767-5196
authors.initials: PJ
authors.lastname: Rutledge
keywords: chromophores; click triazoles; fluorescent probes; macrocyclic compounds; photophysics