title: Chiral probe development for circularly polarised luminescence: comparative study of structural factors determining the degree of induced CPL with four heptacoordinate europium(III) complexes.
abstract: A series of bright, europium(iii) complexes has been prepared based on an achiral heptadentate triazacyclononane ligand bearing two strongly absorbing, coordinated aralkynyl pyridyl moieties. The binding of chiral carboxylates, including α-hydroxy acids such as lactate and mandelate, has been monitored by emission spectroscopy and is signalled by the switching on of strong circularly polarised emission. In each case, an R-chiral carboxylate gave rise to emission typical of a Δ complex, most clearly shown in the form of the ΔJ = 4 transition manifold around 700 nm. Variations in the sign and magnitude of the CPL allow the enantiomeric purity and absolute configuration of the acid to be assessed in a sample. Analysis of the relative energies of the parent aqua complexes and their stereoisomeric adducts has been aided by lifetime measurements and density functional theory calculations.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK. david.parker@dur.ac.uk.
authors.forename: Emily R
authors.initials: ER
authors.lastname: Neil
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fox
authors.forename: Robert
authors.initials: R
authors.lastname: Pal
authors.forename: Lars-Olof
authors.initials: LO
authors.lastname: Pålsson
authors.forename: Benjamin A
authors.initials: BA
authors.lastname: O'Sullivan
authors.forename: David
authors.initials: D
authors.lastname: Parker