Amine-Controlled Assembly of Metal-Sulfite Architecture from 1D Chains to 3D Framework

Whereas open-framework materials have been made in a variety of chemical compositions, few are known in which 3-connected SO₃^2- anions serve as basic building units. Here, we report four new metal-sulfite polymeric structures, (ZnSO₃)Py (1, py = pyridine), (ZnSO₃)₂(2,2′-bipy)H₂O (2,2,2′-bipy = 2,2′-bipyridine), (ZnSO₃)₂(TMDPy) (3, TMDPy = 4,4′-trimethylenedipyridine), and (MnSO₃)₂en (4, en = ethylenediamine) that have been synthesized hydrothermally and structurally characterized. In these compounds, low-dimensional 1D and 2D inorganic subunits are assembled into higher 2D or 3D covalent frameworks by organic ligands. In addition to the structure-directing effect of organic ligands, the flexible coordination chemistry of Zn²⁺ and SO₃^2- also contributes to the observed structural diversity. In compounds 1-3, Zn²⁺ sites alternate with trigonal pyramidal SO₃^2- anions to form three types of [ZnSO₃]_n chains, whereas in compound 4, a 2D-corrugated [MnSO₃]_n layer is present. Compound 1 features a rail-like chain with pendant pyridine rings. The π-π interaction between 2,2′-bipy ligands is found between adjacent chains in compound 2, resulting in 2D sheets that are further stacked through interlayer hydrogen bonds. Compound 3 exhibits a very interesting inorganic [(ZnSO₃)2]_n chain constructed from two chairlike subunits, and such chains are bridged by TMDPy ligands into a 2D sheet. In compound 4, side-by-side helical chains permeate through 2D-corrugated [MnSO₃]_n layers, which are pillared by neutral ethylenediamine molecules into a 3D framework that can be topologically represented as a (3,6)-connected net. The results presented here illustrate the rich structural chemistry of metal-sulfites and the potential of sulfite anions as a unique structural building block for the construction of novel open-framework materials, in particular, those containing polymeric inorganic subunits that may have interesting physical properties such as low-dimensional magnetism or electronic properties. © 2007 American Chemical Society.