M(II)(H2O)2 (5,5′-dimethyl-2,2′-bipyridine)(fumarato) [M = Co and Zn] complexes bearing a unique distorted trigonal-prismatic geometry and displaying 2D supramolecular structures

Novel M(II)(H2O)2(dbpy)(fum) complexes, M = Co (1) and M = Zn (2); where: dbpy = 5,5′-dimethyl-2,2′-bipyridine, fum = fumarato; were obtained by simple one-pot solution reactions at ambient conditions, and structurally characterized by elemental analysis, IR spectroscopy and X-ray single crystal diffraction. In both complexes, the Co(II) and Zn(II) ions exhibit an uncommon six-coordinated distorted trigonal-prismatic geometry, especially for complexes having mono-dentate and bi-dentate innocent ligands. These are the first examples of metaprism complexes with aqua ligands in their coordination spheres. Moreover, the η1:η1 non-bridging coordination mode of fumarato ligand appears for the first time in these type of mononuclear complexes. In addition, the solid-state self-assembly of the mononuclear structures of 1 and 2, mainly throughout hydrogen bonding, give rise to 2D supramolecular wrinkle-sheet type frameworks. These extended structures seem to be the driving force for the unusual coordination geometry obtained in both complexes. Magnetic properties measurements reveal that complex 1 exhibits weak antiferromagnetic ordering with θ(C–W) = −14 K and an E1 = 0.24 cm−1 according to Curie–Weiss model and Rueff phenomenological approach, respectively; whereas, complex 2 displays blue fluorescence in the solid-state.

Unique distorted trigonal-prismatic Co and Zn complexes bearing aqua and η1:η1 – fumarato ligands exhibiting 2D-supramolecular arrays.Figure optionsDownload as PowerPoint slide