Co(ii) coordination polymers constructed from a bent chiral linker: influencing framework topology using co-ligands

Abstract

A semi-rigid chiral ligand (1R, 2R)-4,4′-(trans-cyclohexane-1,2-diyl)bis(azanediyl)bis(carbonyl) dibenzoic acid (H₂cbba) was combined with various Co(II) salts and dipyridyl co-ligands to obtain four 2D homochiral coordination polymers of composition [Co(cbba)(dipyridyl)]·solvate (dipyridyl = 4,4′-bipyridyl (bipy), bis(4-pyridyl)ethylene (bpe), 1,4-bis(4-pyridyl)benzene (1,4-bpb), 2,5-bis(4-pyridyl)thiazolo [5,4-d]thiazole (2,5-bptztz)) (1–4). The topology of the frameworks is mediated by the length of the co-ligands, with short dipyridyl co-ligands (4,4′-bipy and bpe) resulting in the formation of (4¹³·6²) networks (1–2), while long co-ligands (1,4-bpb and 2,5-bptztz) led instead to (4⁴·6²) (sql) networks that undergo 2D → 2D parallel interpenetration to form a rare example of a homochiral polyrotaxane (3–4). The length of the dipyridyl co-ligand was also found to have an effect on the conformation of the flexible cbba²⁻ ligands and the crystal packing of the networks.