Interpenetration Phenomena via Anion Template Effects in Fe(II) and Co(II) Coordination Networks with a Bis-(1,2,4-triazole) Ligand.

Seven new coordination networks, Fe(tbbt) (), Co(tbbt) (), Fe(tbbt) (), Co(tbbt) (), [Fe(NCS)(tbbt)] (), [Co(NCS)(tbbt)] (), and [Fe(HO)(tbbt)]Br·2HO (), were synthesized with the linker 1,1'-(-2-butene-1,4-diyl)bis-1,2,4-triazole (tbbt) and structurally investigated. The structure of complexes - is composed of three interpenetrating, symmetry-related 3D networks. Each individual 3D network forms a primitive, nearly cubic lattice () with BF or ClO anions present in the interstitial spaces. The structure of compounds and is composed of two-dimensional layers, which are parallel to each other in the AB stacking type. These layers are interpenetrated by one-dimensional chains, both having the same formula unit, [M(NCS)(tbbt)] (M = Fe, Co). The structure of compound consists of parallel, two-dimensional layers in the ABCD stacking type. The interpenetration in - is not controlled by π-π-interactions between the triazole rings or C=C bonds, as could have been expected, but by (triazole)C-H⋯FB, C-H⋯OCl, and C-H⋯SCN anion hydrogen bonds, which suggests a template effect of the respective non-coordinated or coordinated anion for the interpenetration. In , the (triazole)C-H⋯Br anion interactions are supplemented by O-H⋯O and O-H⋯Br hydrogen bonds involving the aqua ligand and crystal water molecules. It is evident that the coordinated and non-coordinated anions play an essential role in the formation of the networks and guide the interpenetration. All iron(II) coordination networks are colorless, off-white to yellow-orange, and have the metal ions in the high-spin state down to 77 K. Compound stays in the high spin state even at temperatures down to 10 K.