Terbium-oxalate-pyridinedicarboxylate coordination polymers suggesting the reductive coupling of carbon dioxide (CO2) to oxalate (C2O42−):[Tb2 (3,5-PDC)2(H2O)4(C2O4)]·2H2O and [Tb(2,4-PDC)(H2O)(C2O4)0.5] (PDC = pyridinedicarboxylate)

Under hydrothermal conditions, Tb(NO3)3·5H2O reacted with 3,5-pyridinedicarboxylic acid (3,5-PDCH2) to give a 3-D coordination polymer with the empirical formula of [Tb2 (3,5-PDC)2(H2O)4(C2O4)]·2H2O (1). Tb(NO3)3·5H2O also reacted with 2,4-pyridinedicarboxylic acid (2,4-PDCH2) to give another 3-D coordination polymer [Tb2 (2,4-PDC)2(H2O)2(C2O4)] (2). The structures of both polymers have been determined by X-ray diffraction. X-ray structure analyses show that both polymers contain bridging oxalate (C2O42−) ligands, which might have been formed by the reductive coupling of CO2 molecules released from the PDC2− ligands through the C–C bond cleavage.