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

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 (4)G(5/2) -> H-6(j) (J = 5/2, 7/2, 9/2, 11/2, 13/2, 15/2), F-6(j) (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 F-4(3/2) energy level to the (4)G(5/2) one and reversible energy transfer from the Sm3+ excited states to the triplet (T-3(1)) state of phosphinate ligand. AJudd-Ofelt analysis was performed to estimate PL quantum efficiency (QE), branching ratios (beta) and induced-emission cross section (sigma(em)) of the compounds obtained. It was found that the Judd-Ofelt parameter Omega(2) of 1 is significantly greater than that of 2. This feature is responsible for large values of beta (50.98%) and sigma(em) (4.29 x 10(-21) cm(2)) which suggest 1 as a good candidate for the development of samarium doped polymethylmethacrylate (PMMA) laser medium acting on the (4)G(5/2) -> H-6(9/2) transition at 645 nm. The estimated room-temperature PL QE of 1 and 2 equals to 1.9 and 0.17%, respectively. (C) 2016 Elsevier B.V. All rights reserved.