Features of spectral properties of Sm3 + complexes with dithia- and diselenophosphinate ligands

Abstract

The samarium complexes Sm(S2PPh2)3(THF)2 (1) and Sm(Se2PPh2)3(THF)2 (2) with soft-donor dithia- and diselenophosphinate ligands were synthesized and their photophysical properties were studied in detail. Both complexes displayed the metal-centered photoluminescence (PL) in visible and NIR regions corresponding to 4G5/2→6HJ (J=5/2, 7/2, 9/2, 11/2, 13/2, 15/2), 6FJ (J=1/2, 3/2, 5/2, 7/2, 9/2, 11/2) f–f transitions of Sm3+. Luminescence decay curves exhibit an initial short build-up region and can be described by double or triple exponential function owing to multiphonon relaxation from the 4F3/2 energy level to the 4G5/2 one and reversible energy transfer from the Sm3+ excited states to the triplet (3T1) state of phosphinate ligand. A Judd–Ofelt analysis was performed to estimate PL quantum efficiency (QE), branching ratios (β) and induced-emission cross section (σem) of the compounds obtained. It was found that the Judd–Ofelt parameter Ω2 of 1 is significantly greater than that of 2. This feature is responsible for large values of β (50.98%) and σem (4.29×10−21cm2) which suggest 1 as a good candidate for the development of samarium doped polymethylmethacrylate (PMMA) laser medium acting on the 4G5/2→6H9/2 transition at 645nm. The estimated room-temperature PL QE of 1 and 2 equals to 1.9 and 0.17%, respectively.