Stoichiometrically Controlled Revocable Self‐Assembled “Spiro” versus Quadruple‐Stranded “Double‐Decker” Type Coordination Cages

Abstract

The simple combination of Pd(II) with the tris-monodentate ligand bis(pyridin-3-ylmethyl) pyridine-3,5-dicarboxylate, L, at ratios of 1:2 and 3:4 demonstrated the stoichiometrically controlled exclusive formation of the "spiro-type" Pd1L2 macrocycle, 1, and the quadruple-stranded Pd3L4 cage, 2, respectively. The architecture of 2 is elaborated with two compartments that can accommodate two units of fluoride, chloride, or bromide ions, one in each of the enclosures. However, the entry of iodide is altogether restricted. Complexes 1 and 2 are interconvertible under suitable conditions.

Double‐Decker Coordination Cages

“…In a preliminary communication we recently reported on stoichiometrically controlled and revocable self‐assembled “spiro” and quadruple‐stranded “double‐decker”‐type coordination cages . The molecular architectures of the “spiro”‐ and “double‐decker”‐type assemblies could be classified, on the basis of their compositions, into Pd 1 L 2 and Pd 3 L 4 structures, respectively.…”

“…The architecture of a Pd 3 L 4 ‐type double‐decker coordination cage was also originally conceived by McMorran and Steel in 2002, however, they could not realize their design, probably due to limitations in ligand design. In 2014 we successfully demonstrated the construction of this long‐awaited architecture by using a newly designed ligand and named the self‐assembled Pd 3 L 4 ‐type coordination complex a “double‐decker” cage (Figure ) . In addition, Clever and co‐workers utilized a rigid tridentate ligand for the construction of an elegant Pd 3 L 4 ‐type double‐decker in 2015 …”

“…The complexation behaviors displayed by both types of metal components were found to be comparable as well as contrasting depending upon the stoichiometry of the metal and ligand. Stoichiometrically controlled complexation behavior in supramolecular coordination chemistry has not been extensively explored,, which we have sought to address in this work. The coordination chemistry and anion‐binding properties of a double‐decker‐type cage with the composition Pd 3 L 4 is the major focus of this paper.…”

Modular Synthesis of Linear Bis‐ and Tris‐monodentate Fused [6]Polynorbornane‐Based Ligands and their Assembly into Coordination Cages

“…It is quite interesting to compare these rigid trinuclear structures to a recent report by Chand and co‐workers, who synthesized a [Pd 3 L 4 ] cage based on a highly flexible tris‐pyridyl ligand 28. In contrast to our rigid ligands, which do not form butterfly structures at any ratio of M: L, the flexible ligand was indeed able to form butterfly‐type mononuclear complexes when the palladium to ligand ratio was decreased to 1:2.…”

Polyaromatic molecular peanuts

“…1a)13. There have been several synthetic reports on multicomponent nanostructures with two or three open cavities capable of binding relatively small ions and metal complexes, such as Cl − , PF 6 − and cisplatin1415161718. However, imitation of the characteristic core–shell structures has yet to be accomplished on the nanoscale.…”