Source of materialThe mixture of Ce(NO 3)3 (0.038 g, 0.1 mmol) and 2,3-pyrazinedicarboxylic acid (0.034 g, 0.2 mmol), was stirred into 15 ml water. Then the pH was adjusted to approx. 5with 1.Msolution of NaOH, and 3mlethanol solution of 4,4'-bipyridine (4,4'-bipy, 0.2 mmol) was added. The reaction mixture was heated on awater bath for 10 hat70°C, then filtered. The resulting clear solution was diffused with diethyl ether vapor at room temperature for two weeks. Yellow crystals were obtained (yield, 0.013 g, 36 . %). The products are insoluble in water and common solvents. Elemental analysis -found: C, 20.62.%; H, 2.28.%; N, 7.84 %; calculated for C 6H8CeN2O7:C ,20.01 %; H, 2.24 %; N, 7.76 %. IR data are available in the CIF. DiscussionThe rational design and construction of coordination polymers with unique structural motifs and unique chemical and physical properties have attracted extensive interest in supramolecular and materials chemistry [1][2][3]. In the past decade, plenty of metalorganic hybrids exhibiting fascinating structures have been synthesized [4][5][6]. Some studies on di-and multi-carboxyl ligands or multifunctional carboxyl-containing ligands incorporating other coordination groups, such as N, Sh ave been reported [7,8]. Pyrazine is well-known as abridging ligand, especially in lowdimensional materials. When coordinated to metallic ions, it affords awide variety of polynuclear compounds. Carboxylic acid ligands are also capable of bridging and providing effective magnetic exchange pathway. When the two ligands are combined, such as pyrazinecarboxylic acid, pyrazine dicarboxylic acid and pyrazine teracarboxylic acid, it is very likely to obtain some structurally novel and magnetically interesting complexes. For the lanthanide complexes based on 2,3-pyrazonedicarboxylic acid, just several examples were previously reported [9]. Because the lanthanide ions generally have higher coordination numbers than the d-block metal ions, it is more likely to incorporate ancillary ligands into lanthanide coordination networks. Such ancillary ligands may be removed keeping the lanthanide-organic framework intact, thereby generating porous solids with coordinatively unsaturated lanthanide ions that may have potential catalytic activity. The asymmetric unit of the title complex consists of one Ce(III) cation, one 2,3-pyrazinedicarboxylate ligand, and three coordi- , and their coordination modes are essentially different. Maybe, this is due to the effect of lanthanide contraction [11]. 2,3-Pyrazinedicarboxylate ligand acts as tetra-dentate bridge pillar mode to connect two adjacent Ce1 and Ce1A ions in abridge mode, and thus affords athree connecting node, the carboxylate groups coordinate to the metal atoms in either bridging or chelating fashion. 2,3-Pyrazinedicarboxylate ligand chelate the central ion forming five-and afour-membered ring around the Ce(III). These rings are nearly perpendicular to each other. The bond angles of O2− Ce1−O4, O2−Ce1−N1, O4−Ce1−N1 are 175.9(2)°,1 04.0(2)°a nd 72.0(2)°,r espectively...

Ten new title compounds were synthesized and their crystal structures refined from X-ray powder diffraction data. For the light rare earth (R = La, Ce, Pr, Nd, Sm) compounds, one of the copper sites is only partially occupied while the occupancies of this position are almost ignorable for the rare earth metals heavier than Gd including Y. The unit cell parameters show normal lanthanide contraction. The bonding energy and density of states of the La compounds are calculated. The results show that the La compound with partial Cu occupancy is more stable than that without the extra Cu.

IntroductionThe title crystal structure was published as the crystal structure of acerium compound [1]. During the routine processing and validation of the CIF file for entry into the Cambridge Structure Database (CSD) the editors of the Cambridge Crystallogrphic Data Centre (CCDC) discover some inconsistancies, concerning the interatomic distances of the central cation. More detailed refinement of the occupation parameter for the cation position revealed that not cerium but cadmium may occupy this site. The error happened, because the cadmium sulfate and the cerium sulfate were mixed labled on the small beaker. Here we published the corrected structure data.

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