Two-dimensional Lanthanide Coordination Polymers Constructed from Ce3+/Pr3+ Cation, Imidazole-4,5-dicarboxylate and in situ Generated Oxalate Anions

Two new lanthanide coordination polymers [Ln(C5H2N2O4)(H2O)(2)(C2O4)(0.5)](n)center dot nH(2)O (Ln = Ce-III (1) or Pr-III (2); C5H2N2O4 = imidazole-4,5-dicarboxylate anion; C2O4 = oxalate anion) have been synthesized and structurally characterized by single-crystal X-ray diffraction, elemental analyses and IR spectrum. Both compounds crystallize in monoclinic, space group P2(1)/c with a = 7.5225(3), b = 17.2416(6), c = 8.6089(3) angstrom, beta = 110.9610(10)degrees, V = 1042.68(7) angstrom(3), Z = 4, C6H8N2O9Ce, M-r = 392.26, D-c = 2.499 g/cm(3), mu(MoK alpha) = 4.414 mm(-1), F(000) = 752, the final R = 0.0167 and wR = 0.0412 for 1; a = 7.4973(3), b = 17.2113(8), c = 8.5729(4) angstrom, beta = 110.9440(10)degrees, V = 1033.14(8) angstrom(3), Z = 4, C6H8N2O9Pr, M-r = 393.05, D-c = 2.527 g/cm(3), mu(MoK alpha) = 4.764 mm(-1), F(000) = 756, the final R = 0.0192 and wR = 0.0455 for 2. X-ray diffraction analyses reveal that the lanthanide cations in compound 1 or 2 are linked by imidazole-4,5-dicarboxylate and in situ generated oxalate anions via Ln-O and Ln-N covalent bonds to form two-dimensional layered networks. The successful synthesis of compound 1 or 2 also indicates a. crystallographic confirmation for the decomposition of curcumin to form oxalate anion under solvothermal conditions.