Monoribbed-functionalized iron(II) clathrochelates with optically active and/or terminal biorelevant group(s): synthesis, single-crystal X-ray diffraction and quantum-chemical characterization, and their inherent versus protein-induced chirality

Novel monoribbed-functionalized iron(II) cage complexes with optically active and/or terminal biorelevant group(s) were designed and prepared by two-step nucleophilic substitution of their mono- and dichloroclathrochelate precursors. The single-crystal XRD structures of all of them and those of known leader iron(II)-centered cage bioeffector and of its reactive monochloroclathrochelate precursor were solved. These experimental data were used for theoretical quantum-chemical calculations of electrostatic potentials for their 3D-shaped molecules. This allowed to localize the peripheral (exterior) biorelevant group(s), which are responsible for supramolecular binding of thus designed clathrochelate guests to globular proteins as the hosts. Host—guest binding in aqueous solutions between the unfolded protein macromolecules and all the aforementioned iron(II) complexes was studied by the circular dichroism method. An inherent chirality of the metalloclathrochelates with optically active ribbed substituent and a metal-centered chirality of all the prepared macrobicyclic compounds, induced by their supramolecular clathrochelate-to-protein binding, were observed.