Subcomponent Self-Assembly of Covalent Metallacycles Templated by Catalytically Active Seven-Coordinate Transition Metal Centers

Coordination
geometries of transition metals play vital roles in
the self-assembly process of supramolecular coordination complexes.
Herein, seven-coordinate 3d metal ions were applied as templates and
catalytically active sites for subcomponent self-assembly that resulted
in a new category of covalent metalla­­cycles. Single-crystal
structures showed that the sizes, configurations, and functionalization
of covalent metalla­cycles could be tuned by the selection of
rigid dihydrazide, transition metal ions, and prefunctionalized subcomponents,
respectively. Moreover, metalla­cycles decorated with carboxylic
groups could be employed as precursors to prepare aerogels through
hierarchical self-assembly, which also exhibited high catalytic activity
for cycloaddition of CO2 into cyclic carbonates.