A study of lanthanide energy transfer systems in aqueous micellar solutions and the photophysical properties of 1,4-bis(phenylethynyl)benzene and other polyarylethynylenes.

Abstract

A literature review of the photophysical properties of luminescent lanthanide complexes and their behaviour in aqueous micellar systems is presented. The effects of the environment and the presence of sensitisers and quenching agents on the fluorescence properties, as well as the energy transfer mechanisms responsible for these properties, are discussed. The study undertaken demonstrated the enhancement of europium phosphorescence due to an aqueous micellar environment. Here the micelles protect the lanthanide excited state from quenching mechanisms. There is some evidence that phenanthrene and 1,10-phenanthroline act as sensitisers and chelated ligands affect the luminescence of europium. A review of recent studies of the physical and luminescence properties of ethynylated aromatic systems in solutions and as liquid crystals is presented. The details of a re-evaluation of the photophysical properties of 1,4-bis(phenylethynyl)benzene (1) are presented along with comparative data from other poly aryl systems studied. All the systems showed similar conventional photophysical properties at room temperature and inhomogeneous fluorescence behaviour in low temperature glasses and in viscous solvents. 1 showed wavelength - dependent excitation and emission spectra, indicative of a slow rate of relaxation of conformers of the excited states compared to the rate of fluorescence.