Lanthanide cymantrenecarboxylate complexes with an Ln:Mn ratio of 1:2 as precursors for LnMn_2O_5 phases. Synthesis, structure, physicochemical properties, and thermal decomposition

摘要

New binuclear rare-earth cymantrenecarboxylate complexes [Ln _2(μ_2-OOCCym)_2(μ-O,η~2- OOCCym)_2(η~2-NO_3)_2(η ~2-DME)_2], Ln = Pr (1), Eu (2), Gd (3), Tb (4a), Dy (5), Ho(6a), Er (7); [Ln_2(μ_2-OOCCym)_4(η ~2-NO_3)_2(η~2-DME)_2], Ln = Tb (4b), Ho(6b,c), Yb (8) and the trinuclear complex [Yb_3(μ-O, η~2-OOCCym)_2(μ_2-OOCCym) _4(η~2-NO_3)_3(η~2- DME)_2(H_2O)_2] (9) (Cym = (η~5- C_5H_4)Mn(CO)_3), DME = CH_3OCH _2CH_2OCH_3) were synthesized and characterized by X-ray diffraction. The magnetic properties of 3 are indicative of antiferromagnetic exchange between the Gd atoms. Complexes 4a and 6a were found to exhibit significant ferromagnetic interactions. It was shown that the luminescence of Eu~(3+) in 2 is efficiently quenched by the cymantrenecarboxylate moiety which determines the luminescent properties of this complex. For complex 4a standard thermodynamic functions were calculated from adiabatic calorimetry data. The thermal decomposition of the complexes in air affords pure LnMn_2O_5 phases as the final products. The magnetic properties of the LnMn_2O_5 phases (Ln = Gd, Ho) prepared by the thermal decomposition of 3 and 6a were studied.