Study of photophysical behaviour of some Sm(III) complexes with 4-oxo-4H-1-benzopyran-3-carboxaldehyde and other N,N′-donor π-conjugated ligands

Trivalent lanthanide ions show interesting optical properties. Keeping this in view, five Sm(III) complexes were synthesized using 4-oxo-4H-1-benzopyran-3-carboxaldehyde (L) as primary ligand along with 1,10-Phenanthroline (Phen); Bipyridine (Bipy); Bathophenanthroline (Bathophen) and Neocuproine (Neo) as secondary ligands. Characterizations of prepared complexes were carried out by means of FTIR, elemental analysis, UV-vis, ESI-MS+, thermal studies, PXRD, FESEM, and luminescence studies. Thermal studies confirmed the good thermal stability of complexes. Sharp peaks in X-ray diffractograms suggest their crystalline nature. The photoluminescence process in complexes has been thoroughly studied and discussed in liquid and powder state. The complexes show (4)G(5/2)-> H-6(j) transitions where j = 5/2, 7/2, and 9/2, analogous to characteristic emission peaks of Sm(III) ion at similar to 566, 601, and 648 nm, respectively. The complexes demonstrate intense emission peaks at similar to 601 in liquid and similar to 648 nm in a powder state, which is responsible for bright orange and red emission, respectively. The synergistic effect of secondary ligands was responsible for longer luminescence lifetime and enhanced emission intensity in ternary complexes. Attractive photoluminescence properties of complexes could play a vital role in electroluminescent devices, bio-assays, liquid lasers, OLEDs, etc. Graphic abstract Five new Sm(III) complexes were synthesized using 4-oxo-4H-1-benzopyran-3-carboxaldehyde (L) and other N,N '-donor pi-conjugated ligands. Results were in favour of the formation of bright orange (in solution) and red (in powder state) luminescent complexes exhibiting sharp Sm(III)-centered emission peaks. Hence, the selected ligands act as efficient sensitizers in transferring their excitation energy towards Sm(III) ion.