1. General Considerations

The following main criteria for the formation of a cage complex with encapsulated species [organic or inorganic anion(s), cation(s), and neutral molecule(s)] have been provided [1]. They include “(1) the presence of three-dimentional cavity in either covalent, or coordination, or supramolecular caging ligand (capsule) and (2) encapsulation of the above guest anion(s), cation(s) or neutral molecule(s), or their combination within this cavity via formation of intracavitary donor–acceptor (coordination) or supramolecular (hydrogen, electrostatic dipole–dipole, van der Walls etc.) bonds” [1]. On the other hand, the term “clathrochelate” (derived from Latin “cläthrätus,” to furnish with lattice, encaged), introduced by D. H. Busch [2], suggests the formation of a complex with an encapsulated metal ion in which (1) a three-dimensional cavity in its macropolycyclic ligand is present, and (2) the metal ion coordinates heteroatoms of this ligand within its cavity, isolating such encapsulated ion from the external factors.