Encapsulation versus Aggregation of Metal–Organic Cages Controlled by Guest Size Variation

Abstract

The strength and mode of binding (inside vs outside) of bisanionic guest molecules to a cationic, self-assembled metal-organic cage depend on their size and the stoichiometry of the addition. Herein we show that the composition of the solid/liquid phase of a heterogeneous system can be kinetically controlled by the order of the addition of two different guest compounds.

Interpenetrated Cage Structures

“…The highest binding affinities were found for bis‐sulfonate guests with the best match between the guest's size and the Pd⋅⋅⋅Pd separation. Besides this, the authors also showed that addition of a second equivalent of a bis‐anionic guest resulted in the formation of an insoluble salt due to guest‐mediated ionic interaction between two neighboring cages . Moreover, this host was found to be capable of encapsulating various other guest molecules, notably including metal‐based guests such as the hexamolybdate anion [Mo 6 O 19 ] 2−[36] or even the coencapsulation of two different guest species of the Magnus’ salt type .…”

Stacked Platinum Complexes of the Magnus’ Salt Type Inside a Coordination Cage

“…[11] Fujita and co-workers were the first to apply this principle to the selfassembly of discrete stacks of square-planar coordinated M II complexes (M = Pd, Pt, Cu, or Ni) showing metal-metal d-d contacts [12] and spin-spin interaction phenomena [13] inside an organic-pillared coordination box.Recently, we introduced a new supramolecular coordination cage 1 consisting of four rigid, concave ligands and two square-planar coordinated d 8 metal ions, such as Pd II (1 a) or Pt II (1 b), sitting on oppositely arranged poles of a globular structure. [14] The ability of this cage to bind bis(anionic) guest compounds in its interior was studied systematically [15] and led to pH-switchable (pseudo)rotaxanes [16] and a system capable of light-triggered crystallization. [17] We herein report the first example of the rational preparation of a short stretch of pentanuclear stacked platinum compounds of the Magnus salt type, in the form of a discrete host-guest compound based on cage 1 in solution and in the solid state Figure 1).The derivatives of Magnus salt having the formula {[PtY 4 ][PtX 4 ]} n (X = Cl À or Br À ; Y= neutral N-donor ligands, NH 3 , NH 2 R, or pyridine) are characterized by an alternate, face-to-face stack of the dicationic and dianionic complexes.…”

“…Recently, we introduced a new supramolecular coordination cage 1 consisting of four rigid, concave ligands and two square-planar coordinated d 8 metal ions, such as Pd II (1 a) or Pt II (1 b), sitting on oppositely arranged poles of a globular structure. [14] The ability of this cage to bind bis(anionic) guest compounds in its interior was studied systematically [15] and led to pH-switchable (pseudo)rotaxanes [16] and a system capable of light-triggered crystallization. [17] We herein report the first example of the rational preparation of a short stretch of pentanuclear stacked platinum compounds of the Magnus salt type, in the form of a discrete host-guest compound based on cage 1 in solution and in the solid state Figure 1).…”

Self-Assembled M2L4 Nanocapsules: Synthesis, Structure and Host-Guest Recognition Toward Square Planar Metal Complexes

“…Fujita and co-workers reported, for example, metal-metal d-d interaction through the discrete stacking of square planar complexes within a M 4 L 6 coordination cage [30]. Clever and coworker described the ability of a M 2 L 4 cage to bind bis(anionic)guest compounds or to form a discrete stack of platinum complexes of the Magnus’ salt type [31–32]. Moreover Crowley and coworkers recently published the preparation of a dipalladium(II) cage complex using 2,6-bis(pyridin-3-ylethynyl)pyridine ligand, capable of binding two molecules of cis -platin within its cavity [33].…”