Tetrahedral-atom zincophosphate structures: synthesis and structural characterization of two novel anionic eight-ring frameworks containing cationic 1,4-diazabicyclo[2.2.2]octane guests

Abstract

The synthesis and structures of two new microporous, anionic zincophosphates whose channels contain cationic organic cations are described.

Zn₂(HPO₄)₃·H₂N₂C₆H₁₂(ZnPO/dab-A) crystallizes in the triclinic space group P with a= 9.933(2)Å, b= 9.966(2)Å, c= 9.518(2)Å, α= 98.022(3)°, β= 114.805(3)°, γ= 107.696(3)°, V= 775.0 ų and Z= 2, with R(F)= 3.94% for 3417 observed reflections, according to the criterion I > 3σ(I).

Zn₄(PO₄)₂(HPO₄)₂·3H₂O·H₂N₂C₆H₁₂(ZnPO/dab-B) is also centric triclinic, P, with a= 9.515(2)Å, b= 12.297(2)Å, c= 9.461(2)Å, α= 91.030(4)°, β= 98.658(4)°, γ= 93.714(4)°, V= 1091.7 ų, Z = 2, with R(F)= 6.38% for 4150 observed reflections [I > 3σ(I)].

Both these new phases consist of a three-dimensional network of ZnO₄ and PO₄ tetrahedra, linked through oxygen vertices, to form two different open structures containing one-dimensional eight-ring channels, occupied by cationic, protonated diazabicyclo[2.2.2]octane, or dabco [(H₂N₂C₆H₁₂)²⁺] molecules and water. Some of the zinc and phosphorus polyhedra contain ‘hanging’ OH₂ and OH groups: guest–framework and framework–framework hydrogen-bonds are a key structural feature of these new phases. These new phases are briefly compared with other open-framework topologies.