Design and synthesis of novel lanthanide complexes for luminescent devices

Europium and terbium complexes of a series of ter- and quarterpyridine-N-oxide ligands have been prepared and structurally characterised by crystallographic studies. The solid-state structures reveal some interesting topologies of the ligands due to the flexibility introduced to the coordination sphere by the N-oxide donors. Europium and terbium complexes were also prepared for a series of quinquepyridine-N-oxides Luminescence studies of the N-oxide complexes in acetonitrile show typical europium and terbium emission spectra, dominated by the 5D07F2 and 5D7F5 transitions respectively. No simple trend was revealed in the relative quantum yields, with [Eu(4-bisphenyl-quarterpyridine-1-quarteroxide)2][ClO4]3 having the most intense luminescence. Decomplexation of the non-oxidised ligand complexes was observed at low solution concentrations in the luminescence spectra and so strong lanthanide-binding groups were introduced to the 6 positions of the external pyridine rings of the ter-, quarter- and quinquepyridine ligands to improve complex stability. Lanthanide-binding groups introduced were hard, anionic carboxylate groups and also, the more organic solvent soluble,tert-butyl amide groups. Europium and terbium complexes of the series of ter-, quarter- and quinquepyridine carboxylic acid andtert-butyl amide ligands were prepared and the ligands shown to be capable of sensitising the trivalent lanthanide europium and terbium ions. Luminescence studies revealed an increased binding strength of the ter-, quarter- and quinquepyridine carboxylic acid ligands with no decomplexation at low solution concentrations being observed. From the relative quantum yields [Eu(4-phenyl-2,2-terpyridine- 6,6-diarboxylic acid)(H2O)2][ClO4]2 was determined to have the most intense luminescence. Also, a trend of the carboxylic acid ligands being more suitable for Eu(III) sensitisation and thetert-butyl ligands being more suitable for Tb(III) sensitisation was revealed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo