Effects of Anion and Bipyridyl Bridging Ligand Identity on the Co(II) Coordination Networks

Abstract

Five new coordination polymers, {[Co(OAc)2(bpe)(H2O)]•0.5(dmf)}n (1), {[Co(bpy)2(H2O)4][Co(tfa)(bpy)2(H2O)3](tfa)3•1.5(bpy)}n (2), [Co(tfa)2(dps)4]n (3), {[Co(tfa)2(bpe)4]•H2O}n (4), and [Co(tfa)2(bpp)4]n (5) (where AcO– = CH3CO2–; tfa– = CF3CO2–; bpy = 4,4′-bipyridine; bpe = 1,2-bis(4-pyridyl)ethane; bpp = 1,3-bis(4-pyridyl)propane; dps = 4,4′-dipyridyl sulfide; dmf = N,N′-dimethylformamide) were synthesized by the reactions of Co(OAc)2•4H2O and Co(tfa)2•4H2O with different dipyridyl ligands and characterized by elemental analysis, IR spectra, and X-ray single-crystal diffraction. Compound 1 exhibits extended two-dimensional (2D) networks through the bridging AcO– and bpe ligands. The polymeric motifs in 2–5 are exclusively based on bipyridine-type ligands and results in 1D cationic chains in 2, similar charge-neutral double tapes in 3 and 4, and a 2D polymeric network in 5. In 2–5, the tfa anions coordinate to the Co(II) center in a monodentate mode. An impact of the anion’s fluorination on coordination modes and supramolecular architectures is registered. Magnetic measurements reveal almost vanishing exchange interactions in the layered materials 1 and 5. The correlation of mechanical properties and crystal structure has been demonstrated for 1.