Synthesis, structure and luminescence properties of binary and ternary complexes of lanthanide (Eu3+, Sm3+ and Tb3+) with salicylic acid and 1,10-phenanthroline

A series of binary and ternary complexes of lanthanide (Eu3+, Sm3+ and Tb3+) with salicylic acid (Hsal) and 1,10-phenanthroline (phen) were synthesized, and characterized by element analysis, coordination titration analysis, IR, UV and TG-DTA. Their compositions were (NH4)[Ln(sal)4(H2O)2] (Ln=Eu (1), Sm (2), Tb (3)) and (NH4)[Ln(sal)4(phen)2] (Ln=Eu (4), Sm (5), Tb (6)), respectively. In particular, the ternary complex of Eu3+, 4, was characterized by X-ray diffraction, and luminescence intensities of binary and ternary complexes were compared. In case of Eu3+ and Sm3+ complexes, ternary complexes emitted stronger luminescence than corresponding binary complexes of salicylic acid and Ln3+. On the other hand, the ternary Tb3+ complex had weaker luminescence than the binary complex because of back energy transfer from Tb3+ to phen. The CIE coordinates of 1-6 were calculated as (0.65, 0.35), (0.52, 0.48), (0.33, 0.59), (0.67, 0.33), (0.62, 0.38) and (0.36, 0.58), respectively, which enable these complexes to be promising candidates for red, green, or yellow component in OLEDs.