Four new metal–organic frameworks based on cobalt(II) salts and 1,4-diazabicyclo[2.2.2]octane N,N’-dioxide (odabco) were obtained. Their crystallographic formulae are [Co₃(odabco)₂(OAc)₆] (1, OAc⁻ = acetate), [Co(H₂O)₂(HCOO)₂]·odabco (2), [Co₂(H₂O)(NO₃)(odabco)₅](NO₃)₃·3.65H₂O (3), and [Co₂(DMF)₂(odabco)₄](NO₃)₄·3H₂O (4; DMF = N,N-dimethylformamide). Crystal structures of 1–4 were determined by single-crystal X-ray crystallography. Coordination polymer 1 comprises binuclear and mononuclear metal–acetate blocks alternating within uncharged one-dimensional chains, in which odabco acts as a bridging ligand. A layered Co(II) formate 2 contains odabco only as guest molecules located in the interlayer space. Layered compound 3 and three-dimensional 4 have cationic coordination frameworks with 26% and 34% specific void volumes, respectively, unveiling high structural diversity of Co(II)-odabco MOFs based on quite a rare aliphatic moiety. Magnetization measurements were performed for 1, 3, and 4 and the obtained data were interpreted on the basis of their crystal structures. A strong (J/k_B~100 K) antiferromagnetic coupling was found within binuclear metal blocks in 1. Ion exchange experiments revealed a considerable iodide uptake by 3 resulting in an up to 75% guest nitrate substitution within the voids of a coordination framework, found by capillary zone electrophoresis data and confirmed by single-crystal XRD. A preservation of 3 crystallinity during the exchange allowed for the guest I⁻ positions within a new adduct with the formula [Co₂(H₂O)(NO₃)(odabco)₅]I₂(NO₃)·1.85H₂O (3-I) to be successfully determined and the odabco aliphatic core to be revealed as a main adsorption center for quite large and easily polarizable iodide anions. In summary, this work presents a comprehensive study for a series of 1,4-diazabicyclo[2.2.2]octane N,N’-dioxide-based MOFs of cobalt(II) within the framework of magnetic properties and reports the first example of anion exchange in odabco-based coordination networks, supported by direct X-ray structural data. The reported results unveil promising applications of such frameworks bearing ligands with an aliphatic core in the diverse structural design of selective adsorbents and other types of functional materials.

Four new hybrid inorganic–organic salts of 1,4-diazabicyclo[2.2.2]octane N,N’-dioxide (odabco) with the formulae odabco·2HNO₃ (1), odabco·HClO₄ (2), odabco·H₂SO₄ (3) and odabco·2H₂SO₄ (4) were synthesized and characterized by single-crystal x-ray diffraction (XRD), powder XRD and infrared spectroscopy. Compound 1 is based on the isolated (H₂odabco)²⁺ fragments, representing 0D structure. 2 is based on cationic 1D {Hodabco}_nⁿ⁺ hydrogen-bonded chains. Compound 3 comprising a strongly coordinated sulfate anion consists of two-component hydrogen-bonded {-H₂odabco-SO₄₋} fragments forming uncharged 1D helical chains. 4 contains both {-HSO₄-}_n^n– and {-HSO₄-H₂odabco-HSO₄₋} hydrogen bonding motifs, resulting in a 3D polymeric network. A comparative structural analysis of both the obtained and the previously reported cognate structures was performed to rationalize the impact of the degree of odabco protonation and the anion donor ability on the structural features and dimensionalities of odabco-based hydrogen-bonded lattices.

A series of novel salts of protonated 1,4-diazabicyclo[2.2.2]octane (odabco) with halogen-containing anions is obtained. The compounds Hodabco·HCl·H₂O (1), odabco·HBr·0.5H₂O (2), odabco·2HCl (3), odabco·1.5HCl (4), odabco·1.5HBr (5), (Hodabco)I₃·2(dioxane) (6), odabco·2Htca (7; Htca = = trichloroacetic acid), and odabco·3Htca (8) are structurally characterized by single-crystal XRD. It is shown that the nature of the hydrogen-bonded molecular components and the dimensionality of the resulting motifs in the odabco salts depend on the equivalent (molar) acid content in the salt and on the donor ability of the anion. The purity of compounds 1-4 is confirmed by a combination of powder XRD, ¹H NMR, CHN analysis, and IR spectroscopy.