Protonated bis(quinuclidine) included in layered bis(urea)–bromide and -iodide hosts: new ternary urea inclusion compounds

Abstract

The synthesis, crystal structure, and properties of novel ternary inclusion compounds formed by the insertion of protonated bis(quinuclidine) guests into urea–bromide and urea–iodide anionic hosts are reported. (Urea₂[quinuclidine₂H]⁺Br⁻), 1, and (urea₂[quinuclidine₂H]⁺I⁻), 2, are monoclinic, space group C2. The cell parameters for 1 are a = 19.323(8), b = 7.145(3), c = 8.566(4), β = 112.19(3), d_calc = 1.284 and Z = 4, considering 472 reflections; for 2 they are a = 20.51(11), b = 7.34(3), c = 8.17(4), β = 111.81(8), d_calc = 1.369, Z = 4, considering 716 reflections. In the two structures each urea molecule interacts with adjacent urea molecules via N–H⋯O hydrogen bonds forming a ribbon-like arrangement. The ribbons are linked through halide ions by N–H⋯X hydrogen bonds forming layered structures. The distances between the layers are 10.301 Å for 1 and 8.566 Å for 2. The compounds may be described as commensurate species. Conductivity values determined for 1 and 2 at room temperature are 1.19 × 10⁻⁵ and 8.66 × 10⁻⁷ (Ω cm)⁻¹, and they increase with temperature. Aspects of the thermal stability of the products are discussed.