Oxalate-bridged transition-metal supramolecular polymers: syntheses, structures and properties of [Co(im)2(C2O4)] and [Fe2(im)4(C2O4)2]

The hydrothermal reactions of K3[M(C2O4)3] (M=Co, Fe) and imidazole (im) molecule result in the syntheses of two oxalate-bridged transition-metal supramolecular polymers: [Co(im)2(C2O4)] 1 and [Fe2(im)4(C2O4)2] 2. Both exhibit the one-dimensional (1D) zigzag chain structures with the tetradentate oxalato bridges and ancillary im molecules, and are further propagated into a 3D supramolecular network via the interchain weak N–H⋯O hydrogen bonds. The TG behaviors of both are studied and thermally stable up to ca. 180 and 270°, respectively. The third-order non-linear optical properties of both were also studied, and both exhibit the reverse saturable absorption and self-defocusing performance with the γ values of 1.55×10−31 esu for 1 and 1.02×10−31 esu for 2, respectively.