DFT-Assisted Optical Emission Analysis of Green Luminescent Terbium(III) Mononuclear Complexes with BPTD and N-Donor Chelates.

Compounds with common depiction [Tb(BPTD)3.L], (where BPTD represents “1-(4-bromophenyl)-4,4,4-trifluorobutane-1,3-dione”; and L denotes N-donor neutral auxiliary moeities viz. “2,2’-dipyridyl (Bpy, T1), “1,10-phenantroline (Phen, T2), “2,9-dimethyl-1,10-phenanthroline (DMPhen, T3) and 2,9-dibromo-1,10-phenanthroline (DBPhen,” T4). The complexes were synthesized by reaction of Tb(III) chloride salt with BPTD in the occurrence of respective ancillary ligands. The arrangement and molecular structure of the synthesized terbium complexes are established by elemental analysis, IR spectroscopy, chemical analysis such as NMR and thermogravimetric analysis. The wavelength of emission centered at 545 nm, consistent to the 5D4 → 7F5 transition. The influence of different nitrogen-donor ligands on the photophysical behavior of the complexes was systematically investigated, with particular emphasis on the emission intensity and luminescence lifetime of the central Tb³⁺ ion. The thermal stability and degradation performance of all compounds were examined in detail. In addition, the study highlights the applicability of density functional theory calculations in predicting and interpreting key properties of these complexes, including optimized molecular structures, electronic energies and spectroscopic features.