Chiral probe development for circularly polarised luminescence: comparative study of structural factors determining the degree of induced CPL with four heptacoordinate europium(iii) complexesElectronic supplementary information (ESI) available. See DOI: 10.1039/c5dt02358k

• Main Authors: Neil, Emily R, Fox, Mark A, Pal, Robert, Pålsson, Lars-Olof, O'Sullivan, Benjamin A, Parker, David
• Format: Journal Article
• Language: English
• Published: 11.08.2015
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c5dt02358k

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 Δ J = 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. Induced CPL signatures arising from the reversible binding of chiral carboxylates allow their absolute configuration and enantiomeric purity to be assessed.