Two unique lanthanide-organic frameworks based on 1H-2-methyl-4,5-imidazole-dicarboxylate and oxalate: Crystal structure, luminescence and magnetic properties

The reactions in mixtures of water-ethanol between lanthanide salts and nitrogen N-hetrocyclic carboxylic acid, in the presence of ammonium oxalate, result in two interesting lanthanide-organic coordination polymers, formulated as, {[Sm-4(Hmimda)(4)(mu(4)-C2O4)(2)center dot 6H(2)O]center dot 8H(2)O}(i) (1), [Eu-4(Hmimda)(4) (mu(4)-C2O4)(2)center dot 6H(2)O]center dot 4H(2)O}(n) (2), (H(3)mimda = 1H-2-methyl-4,5-imidazole-dicarboxylic acid). The polymers 1 and 2 are isostructural, and are both built from zig-zag 1D chains constructed from Ln-Hmimda moieties bridged by oxalate, as the secondary building unit (SBU). The Hmimda ligand further is interconnected the 1D chains to form the 3D framework. Variable-temperature magnetic susceptibility measurements indicate that the mu(4)-k(4) O bridging fashion of oxalate results in the possible antiferromagnetic interactions occurring between the adjacent lanthanide(III) centers. The photo-luminescent and thermalgravimetric analyses of the polymers were also determined. (C) 2012 Elsevier B. V. All rights reserved.