Organically templated inorganic–organic hybrid metal (Zn and Cd) Sulfite–oxalates with layered and three-dimensional structures

Abstract

We report single crystal X-ray investigations of three d¹⁰ metal based oxalate–sulfite inorganic–organic hybrid open framework materials, namely [Zn₂(SO₃)₂(C₂O₄)_0.5(C₆N₂H₁₃)]·(H₂O)₂, 1, [C₄N₂H₁₂]_0.5[Zn₂(SO₃)₂(C₂O₄)_0.5(H₂O)₂], 2 and [C₄N₂H₁₂][Cd₂(SO₃)₂(C₂O₄)(H₂O)]·H₂O, 3 which show layered and three dimensional structures with different organic templates. These materials were synthesized under hydrothermal conditions and characterized by techniques such as single crystal X-ray diffraction, dipole moment calculations, FTIR, powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The common feature for 1 and 2 is the interconnection of embedded zinc-sulfite chains via oxalate anions in the framework and in 3, cadmium-oxalate chains are interconnected via sulfite anions. The coordination geometries of metal(II) ions vary significantly resulting in a ladder-like layered structure in the case of 1, a 3D framework in case of 2 and a layered structure with an embedded one-dimensional channel in 3. The observed structures can also be partly attributed to the influence exerted by the presence of different structure directing agents (SDA) in the lattice. The dipole moments for metal polyhedra 1, 2 and 3 were calculated from bond valence analyses and are 2.39 D for Zn(1)O₄N polyhedra and 1.66 D for Zn(2)O₄ polyhedra in 1, 24.90 D for Zn(1)O₆ and 29.52 D for Zn(2)O₄ in 2 and 5.82 D for Cd(1)O₇ and 2.90 D for Cd(2)O₆ in 3.