LAUSR

Abstract Four new heteroleptic asymmetric fluorinated β-diketone based [Sm(fod)3] adducts with organic ligands of different denticities (monodentate indazole and triphenylphosphine oxide (tppo), bidentate imidazolyl pyridine (impy) and tridentate 2,4,6-tris(2-pyridyl)-s-triazine (tptz)) have been synthesized and characterized in order to examine the suitability of organic co-ligands as a sensitizer for Sm(III) luminescence. The photoluminescence of the complexes is studied in chloroform and solid state. The dominance of the hypersensitive transition 4G5/2 → 6H9/2 reflects the asymmetry around the Sm (III) ion in the present complexes which is supported by the large values of intensity ratio (RSm). The stark splitting in magnetic dipole 4G5/2 → 6H7/2 transition in the cases of eight coordinate [Sm(fod)3(impy)] (3) and [Sm(fod)3(tppo)2] (4) complexes is similar. However, the splitting pattern of 3 and 4 is distinctively different from the nine- [Sm(fod)3(tptz)] (1) and seven-coordinate [Sm(fod)3(indazole)] (2) complexes. The intensity of the hypersensitive transition and stark splitting of magnetic dipole transition changes significantly upon change in the ligand environment around the Sm (III). The bright luminescence from these complexes reflects efficient energy transfer from the selected sensitizers to Sm (III) ion. It is worth mentioning that the lifetime for 4G5/2 → 6H9/2 transition of complex 3 in solid state is 269 μs which is higher than the lifetime of this transition noted for most of the tris(β-diketonate)Sm(III) reported so for. The emission colour from chloroform solution of [Sm(fod)3(tppo)2] (4) changes from parrot green to orange red upon change in excitation wavelengths. Of the selected sensitizers, the impy is most efficient since the emission from its complex is most intense.