title: Allosteric deprogramming of a trinuclear heterometallic helicate.
abstract: Two multidentate ditopic ligands L1 and L2 which contain both N-donor and crown ether units have been synthesised. The potentially octadentate ligand L1 forms a trinuclear heterometallic double helicate with Cu(I) and Zn(II) ([Zn2Cu(L1)2](5+)), whereas L2 forms a tetranuclear heterometallic double helicate with the same metal ions ([Zn2Cu2(L2)2](6+)). Both species have been characterised by (1)H NMR, ESI-MS and single crystal X-ray crystallography. Reaction of [Zn2Cu2(L2)2](6+) with Ba(2+) results in the coordination of the crown ether units giving the simple barium coordinated species [Zn2Cu2(L2)2Ba2](10+). However, reaction of [Zn2Cu(L1)2](5+) with Ba(2+) deprograms the ligand and results in the formation of a mixture of species.
authors.affiliation: School of Chemistry, University of Bristol, Cantock's Close, Bristol, UK.
authors.forename: T
authors.initials: T
authors.lastname: Riis-Johannessen
authors.forename: Lindsay P
authors.initials: LP
authors.lastname: Harding
authors.forename: John C
authors.initials: JC
authors.lastname: Jeffery
authors.forename: Ryan
authors.initials: R
authors.lastname: Moon
authors.forename: Craig R
authors.initials: CR
authors.lastname: Rice