Structure, Luminescence Properties, and DFT Theoretical Study of Bidentate Ligand Samarium Complexes

Three new luminescent matrix materials, Sm(oct-ala)3phen, Sm(oct-phe)3phen, and Sm(oct-ser)3phen, were prepared by in-solution synthesis method. The molecular structure, fluorescence properties, and thermal stability of the samarium complex were characterized. The results indicate that the introduction of 1,10-phenanthroline (phen) as the second ligand significantly extends the ultraviolet absorption range of the samarium complexes to 200–350 nm. In addition, the introduction of the phen ligand leads to a 30% increase in the molar extinction coefficient of the samarium complexes, providing a 22-fold improvement in the luminescence lifetime. Further morphological observations under a PLM reveal that Sm(oct-ser)3phen has the characteristics of spherulites, while cubic crystal grains are observed via SEM, which has been rarely reported in the family of amino acid–based rare earth complexes. And it was found that samarium complexes emit light that changes color from orange-red to cyan-blue at high temperatures. Theoretical calculations confirm that Sm–N and Sm–O are weak coordination bonds, and the energy gap of the samarium complexes is 3.5 eV, categorizing them as wide bandgap materials. These samarium complexes have excellent optical and thermal properties, making them very promising for applications in luminescent probes and optoelectronics.