Tris(bipyridine)Metal(II)-Templated Assemblies of 3D Alkali-Ruthenium Oxalate Coordination Frameworks: Crystal Structures, Characterization and Photocatalytic Activity in Water Reduction

A series of 3D oxalate-bridged ruthenium-based coordination polymers with the formula of {[Z(II)(bpy)(3)][(MRu)-Ru-I(C2O4)(3)]}(n) (Z(II) = Zn2+ (1), Cu2+ (3, 4), Ru2+ (5, 6), Os2+ (7, 8); M-I = Li+, Na+; bpy = 2,2'-bipyridine) and {[Zn-II(bpy)(3)](H2O)[LiRu(C2O4)(3)]}(n) (2) has been synthesized at room temperature through a self-assembly reaction in aqueous media and characterized by single-crystal and powder X-ray diffraction, elemental analysis, infrared and diffuse reflectance UV-Vis spectroscopy and thermogravimetric analysis. The crystal structures of all compounds comprise chiral 3D honeycomb-like polymeric nets of the srs-type, which possess triangular anionic cages where [Z(II)(bpy)(3)](2+) cationic templates are selectively embedded. Structural analysis reveals that the electronic configuration of the cationic guests is affected by electrostatic interaction with the anionic framework. Moreover, the MLCT bands gaps values for 1-8 can be tuned in a rational way by judicious choice of [Z(II)(bpy)(3)](2+) guests. The 3D host-guest polymeric architectures can be used as self-supported heterogeneous photocatalysts for the reductive splitting of water, exhibiting photocatalytic activity for the evolution of H-2 under UV light irradiation.