Prototype rhenium metallocavitand with four exocyclic cavities for small molecules

Tuning the Size and Geometry of Pd(II)-Based Metallacalixarenes by Varying the N-Containing Ligands: Synthesis, Structure, and Sensing Properties

“…Calixarene-shaped molecules constructed with phenol as building blocks and methylene as linkers have attracted persistent interest owing to their peculiar structural features and wide practical applications. − Compared with calixarenes, both organic units and inorganic metal centers included calixarene-like metallacalixarenes are under-explored. ,− By employing coordination interactions between the inorganic metal centers and organic compounds as ligands via metal-directed self-assembly, metallacalixarenes exhibit diverse structural potential as well as magnetic, gas adsorptive/separative, electrochemical, and catalytic functionality. ,− It is noteworthy that the metallacalixarenes are capable of encapsulating metal cations, inorganic anions, or neutral molecules because of their calixarene-shaped cavities, ,− which is attracting growing interest from chemists and material scientists. − …”

Rhenium(I)-Based Neutral Coordination Cages with a Spherical Cavity for Selective Recognition of Fluoride

“…The design, synthesis, and functional studies of coordination cages and metallocycles have been continuously getting immense interest because of their potential applications in wide areas. − Cavity-containing cages can act as hosts for suitable molecules and ions. The shape, size, and nature of the cavity in the coordination cages depend on the metal cores and organic building motifs.…”

“…It is important to mention that self-assembly approaches for neutral metallocycles and cages using various metal ions with organic ligands are well-known. Among the available metal-ion sources, the fac -[Re­(CO) 3 ]-core-directed synthetic route is one such approach for self-assembling diverse shapes and sizes of metallocycles and cages without counterions. − The inner cavity present in the supramolecules is often suitable for accommodating organic guest molecules. However, the design of coordination cages as receptors for anions is challenging because of the various shapes, sizes, and diffused charges of the anions.…”

“…Fluoride recognition is of the utmost importance because of applications in the medical and biological fields. − Designing rhenium coordination cages with a small inner cavity having an electronic environment that complements fluoride is a challenge because of the difficulty in organizing the organic frameworks spherically via coordination to the orthogonally arranged three vacant sites of the fac -[Re­(CO) 3 ] core. Recently, we and Lu et al reported the design principles for capped metallocalix[3]­arene-shaped cages by using flexible benzimidazolyl-based tripodal ligands . These cages have preorganized cavities, one small endocavity, one small exocavity, and three exocyclic clefts.…”

“…The framework of the endocavity consists of three electron-deficient heterocyclic motifs, three symmetrically arranged electron-deficient C–H donors, and a phenyl motif. Although the cages are suitable for encapsulating fluoride, the portal of the cavity is blocked by methyl and fused arene groups . We envision that choosing the tripodal N-donor-containing central unsubstituted phenyl motif and imidazole as an anionic heterocyclic core, in principle, may lead to a neutral cage with a guest-accessible endocavity.…”