Metal−Organic Frameworks from Zinc Sulfite Clusters, Chains, and Sheets: 4-Connected, (3,4)-Connected 3-D Frameworks and 2-D Arrays of Catenane-Like Interlocking Rings

Even though open-framework solids have been made in a variety of compositions such as silicates, phosphates,
germanates, borates, and phosphites, few are known that are based on trigonal-pyramidal sulfite anions. We report
here the first synthetic and structural studies of metal−organic framework materials in the zinc sulfite composition.
It is demonstrated here that Zn2+ and SO32- can form various neutral inorganic subunits that can be 0-D clusters,
1-D chains, or 2-D sheets. These inorganic subunits of different dimensionality can subsequently be connected
into extended frameworks of higher dimensionality through bifunctional ligands. In (ZnSO3)2en, infinite corrugated
ZnSO3 layers are pillared by ethylenediamine (en) molecules into a 3-D network that can be classified as a (3,4)-connected net based on tetrahedral Zn nodes and trigonal-pyramidal S nodes. In (ZnSO3)pip, infinite ZnSO3 chains
are cross-linked with piperazine molecules into a 3-D framework that can be classified as 4-connected net based
on tetrahedral Zn nodes only. In (ZnSO3)2(TMDPy)2, (ZnSO3)2 dimers are doubly bridged by trimethylenedipyridine
molecules into an infinite chain with a string of circles. Each circle along the chain is interlocked with another circle
from a chain in the perpendicular direction, creating a 2-D pattern with an infinite-square array of catenane-like
units.