Polymeric lanthanide acetates with peripheral cymantrenecarboxylate groups – Synthesis, magnetism and thermolysis

Abstract

By means of exchange reactions between Ln acetates and CymCO2H (Cym=(η5-C5H4)Mn(CO)3) in H2O–THF–MeOH media, the following isomorphous complexes, having polymeric structures based on tetradentate acetate groups connecting three Ln3+ ions, were obtained: [Ln(CymCO2)2(OAc)(MeOH)]n (Ln=Nd (1), Gd (2) and Dy (3)). In H2O–THF–i-PrOH media, the same reaction results in polymers containing aqua ligands, [Nd(CymCO2)2(OAc)(H2O)2]n·0.5n(i-PrOH)·nH2O (4), [Gd(CymCO2)2(OAc)(H2O)2]n·2nH2O (5) and [Dy(CymCO2)2(OAc)(H2O)]n·0.55nTHF·0.45n(i-PrOH)·0.45nH2O (6). In all cases, the CymCO2 groups are situated at the periphery of the chain and play chelate, monodentate or bridging roles. The reactions with Ho, Er and Tm acetates give the isomorphous binuclear complexes [Ln2(μ2-O2CCym)2(η2-O2CCym)2(η2-OAc)2(H2O)4]·5H2O (Ln=Ho (7), Er (8) and Tm(9)), regardless of which alcohol is present in the reaction mixture. Crystallization of complex 8 from methanol results in the polymeric complex 10, isomorphous with 1–3 (Ln=Er). Magnetic studies of the Gd complexes indicate weak antiferromagnetic interactions between the Gd3+ ions in 2 (J=−0.0374cm−1) and ferromagnetic ones in 5 (J=0.0148cm−1). Thermolysis of the complexes was studied by means of TG and DSC in the 30–900°C temperature range under air and Ar atmosphere; in the first case it affords LnMn2O5 phases which have interesting magnetic properties.