Synthesis, NMR and optical features of intense green color terbium(III) complexes

Abstract

The paper reports the three highly green luminescent terbium(III) complexes functionalized with 1,1,1,5,5,6,6,6-octafluorohexane-2,4-dione (L) as main ligand, 1,10-phenanthroline (phen) and2,2′-bipyridyl (bipy) as ancillary ligands. These complexes were characterized by means of IR, 1H-NMR, elemental analysis, UV–vis, TG-DTG and photoluminescence (PL) spectroscopy. In 1H-NMR spectra, large highfield and lowfield shifts are noticed in these paramagnetic complexes. The proton resonances of phen and bipy have been shifted to highfield, while, the resonance of methine proton in main ligand has been shifted to lowfield. In this way, all the proton signals are resolved as revealed in NMR spectra. The photoluminescent features clearly indicate that the substitution of solvent molecules by ancillary ligand in the coordination sphere enhance the emission intensity and decay time of the complexes. Furthermore, the intramolecularenergy transfer mechanism shows that an efficient transfer of energy from triplet level of ligands to the emitting level of terbium(III) ion takes place in the complexes. In this manner, main ligand and ancillary ligands sensitize the terbium(III) ion yielding the intense and characteristic green luminescence in the complexes. The CIE color coordinates of Tb(L)3bipy complex exactly matches with standard pure green color (x = 0.21, y = 0.71) of NTSC (National Television Standard Committee) which makes them pure green promising component for potencial application as luminescent materials. The beauty of complexes is that these acts as NMR shift reagent as well as these are of great interest in the field of emitting material and display devices.