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

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.