Synthesis, crystal structure and magnetic properties of an octanuclear cerium(III) complex of pyridine-2,6-dicarboxylate

An octanuclear compound of cerium(III), $[$Ce${}_8$(Pydc)${}_{10}$(HPydc)${}_4$.22H${}_2$O$]$.11H${}_2$O (1) (Pydc=pyridine-2,6-dicarboxylate anion) was prepared under mild solvothermal conditions and its crystal structure was determined by single-crystal X-ray diffraction. Three kinds of coordination environments are observed, which include: $[$Ce(Pydc)${}_3$$]$, $[$Ce(Pydc)(H${}_2$O)${}_4$(O,O)$]$, and $[$Ce(H${}_2$O)${}_7$(O,O)$]$. Each cerium atom in 1 is nine-coordinated but two different geometries are found. The Ce1 and Ce2 atoms exhibit a nearly tricapped trigonal prismatic CeN${}_3$O${}_6$ geometry, while Ce3 and Ce4 possess CeNO${}_8$ and CeO${}_9$ coordination polyhedra, which approximate to slightly distorted mono-capped square antiprisms having 12 triangular faces. The Pydc ligands adopt tri-, tetra-, and penta-coordination modes through tridentate chelating and, ${\mu }_2$ and ${\mu }_3$-bridging modes, respectively. The clusters are joined by O-H$\cdots$O hydrogen bonds to generate 3D supramolecular network. Magnetic susceptibility measurements for 1 indicate that the ${\chi }_m$ values obey the Curie-Weiss law. The overall magnetic behavior is typical for the presence of antiferromagnetic exchange coupling interactions between the cerium(III) ions.