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 SO32- 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 SO32- also contributes to the observed
structural diversity. In compounds 1−3, Zn2+ sites alternate with trigonal pyramidal SO32- 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.