Samarium (III) complexes with tunable luminescence: efficient sensitization and semiconducting properties for optoelectronic devices

This study synthesizes and characterizes luminescent ternary samarium complexes (S1–S4), formulated as [Sm(L)₃(S)_n], where the variable n ranges from 2 for monodentate ligands to 1 for bidentate ligands. In the formulation, L represents Trifluoroacetylacetone (tfaa) and S signifies various Lewis bases i.e. Tri-n-octylphosphine oxide (TOPO, S1), 1,10-phenanthroline (phen, S2), Neocuproine (NeoC, S3) and Bathocuproine (BathoC, S4). The prepared Sm(III) complexes were characterized through various analytical as well as spectral techniques. The peaks observed at around 415 and 520 cm⁻¹ in FTIR spectra imply the formation of coordination bond between Sm(III) ion and –O and –N atoms of tfaa and neural moieties, respectively. In NMR spectra of complexes, diketone and neutral ligand protons exhibit notable downfield and upfield shifts, reflecting the paramagnetic influence of samarium ion. The complexes exhibit thermal stability upto 240 °C, thereby demonstrating their suitability for utilization in display devices. Photophysical characteristics were assessed through photoluminescence (PL) and excited state lifetime measurements. The complexes exhibited a hyperintense peak at around 648 nm (⁴G_5/2 → ⁶H_9/2) which is sensitive to ligand environment and associated with the characteristic orange-red emission. The comprehensive investigation supports the potential of these complexes in photonic and display devices.