Bio-inspired synthetic approaches: from hierarchical, hybrid supramolecular assemblies to CaCO₃-based microspheres

A bio-inspired synthetic approach to unprecedented hybrid supramolecular assemblies [Ca(Me₂hda)(H₂O)₃]·H₂O (1) and [Ca(C₁₂hda)(H₂O)₂]·H₂O (2), that are stabilized by iminodiacetate-substituted organic ligands is reported. The results of the single-crystal X-ray analysis of 1 further allowed the use of electron microscopy to verify the supramolecular structure of the fibrous assemblies of 2 that incorporate extended alkyl-substituted ligand derivatives. 2 reveals interesting features that distinguish these soft structures from purely inorganic, brittle materials: meshes of nanobelts transform on solid supports to form homogeneous films covering extended, micro-sized areas. The use of the reported ligand system as a habit modifier for CaCO₃ results in hierarchical calcite aggregates. The structure-influencing effects of the ligands and their supramolecular assemblies promote the formation of calcite disks that tessellate into hollow microspheres that contain distinctive openings.