Luminescence from a highly asymmetric nine-coordinate tricapped trigonal prismatic Sm(III) complex

Abstract

The nine-coordinate complexes of tris(dibenzoylmetanato)La(III) and Sm(III) with tptz were synthesized and thoroughly characterized. The 1H NMR spectrum of [La(dbm)3(tptz)]∙CH3CN is consistent with the coordination of three dbm and one tptz. The tricapped trigonal prism geometry of [Sm(dbm)3(tptz)]∙CH3CN complex is revealed by single crystal X-ray diffraction analysis. The shape 2.1v analysis authenticates the tricapped trigonal prism geometry of [Sm(dbm)3(tptz)]∙CH3CN complex. The Sm(III) is coordinatively saturated by the coordination of six oxygen atoms from dbm units and two pyridyl and one triazine nitrogen atoms from tptz moiety. The steady-state and time resolved photoluminescence of the solid [Sm(dbm)3(tptz)]∙CH3CN and its PMMA hybrid films of different concentration are investigated and discussed. The complex has only one emitting center since the decay times are fitted by mono-exponential function. The higher PL intensity of 4G5/2 → 6H7/2 (ΔJ = 1, magnetic-dipole transition) transition compared to 4G5/2 → 6H9/2 (ΔJ = 2, electric-dipole transition), in the case of 3% (w/w) PMMA hybrid film is the result of strong vibrionic coupling. Although the PL intensity of two transition are different even then the decay times of the transition are roughly similar in magnitude. The stark splitting of electric-dipole 4G5/2 → 6H9/2 transition in the spectrum of 3% film is interesting and leads to believe a strong coupling between states of f-electrons and electric fields of the surrounding ligands.