Selective Co‐Encapsulation Inside an M₆L₄ Cage

Abstract

There is broad interest in molecular encapsulation as such systems can be utilized to stabilize guests, facilitate reactions inside a cavity, or give rise to energy‐transfer processes in a confined space. Detailed understanding of encapsulation events is required to facilitate functional molecular encapsulation. In this contribution, it is demonstrated that Ir and Rh‐Cp‐type metal complexes can be encapsulated inside a self‐assembled M6L4 metallocage only in the presence of an aromatic compound as a second guest. The individual guests are not encapsulated, suggesting that only the pair of guests can fill the void of the cage. Hence, selective co‐encapsulation is observed. This principle is demonstrated by co‐encapsulation of a variety of combinations of metal complexes and aromatic guests, leading to several ternary complexes. These experiments demonstrate that the efficiency of formation of the ternary complexes depends on the individual components. Moreover, selective exchange of the components is possible, leading to formation of the most favorable complex. Besides the obvious size effect, a charge‐transfer interaction may also contribute to this effect. Charge‐transfer bands are clearly observed by UV/Vis spectrophotometry. A change in the oxidation potential of the encapsulated electron donor also leads to a shift in the charge‐transfer energy bands. As expected, metal complexes with a higher oxidation potential give rise to a higher charge‐transfer energy and a larger hypsochromic shift in the UV/Vis spectrum. These subtle energy differences may potentially be used to control the binding and reactivity of the complexes bound in a confined space.

Unexpected Macrocyclic Multinuclear Zinc and Nickel Complexes that Function as Multitasking Catalysts for CO2 Fixations

“…Cyclic carbonates are raw materials of polycarbonates and polyurethanes,a nd N-functionalized amines are intermediates of various chemicals such as drugs. Am ultitask catalyst for these CO 2 fixations have not been reported, and its development presents as ignificant challenge.…”

“…Interestingly, 2 and 3 with only 0.1 mol %loading worked well without ac o-catalyst at 120 8 8Ct op roduce 7a in high yields (70-97 %, entries 9and 10). By contrast, Zn(OAc) 2 and Ni(OAc) 2 hydrates showed no catalytic activity (entries 11 and 12). Furthermore,Z nCl 2 ,Z nBr 2 ,Z nI 2 ,a nd Zn-(OCOCF 3 ) 2 ·H 2 Oa lso showed no activity (not shown).…”

Supramolecular Host-Selective Activation of Iodoarenes by Encapsulated Organometallics

“…Addition of iodobenzene to 3 resulted in new upfield shifts in the 1 H NMR spectrum corresponding to simultaneous encapsulation of the copper complex and iodobenzene ( I , Figure 2b). 20–22 Over the course of 12 h at room temperature, full conversion of the starting material to a new product was observed with concomitant loss of symmetry in both encapsulated 3 and the host (Figure 2c). A 2D NOESY experiment of the product indicated correlation between the aromatic peaks and one set of DMPE methyl peaks.…”

Unexpected Macrocyclic Multinuclear Zinc and Nickel Complexes that Function as Multitasking Catalysts for CO2 Fixations

“…Artificial metallosupramolecular architectures have been actively investigated, and various macrocycles, [1] cages, [2] and helicates [3] have been synthesized from simple ligands and metal ion sources.L arge but ordered multinuclear metal complexes can be constructed by self-assembly.R ecently, several metallosupramolecules with catalytic activities have been reported. [4] CO 2 is apromising C1 building block as an alternative to petroleum-based chemicals,a nd catalysts for CO 2 fixations have been developed extensively.…”

“…By contrast, Zn(OAc) 2 and Ni(OAc) 2 hydrates showed no catalytic activity (entries 11 and 12). By contrast, Zn(OAc) 2 and Ni(OAc) 2 hydrates showed no catalytic activity (entries 11 and 12).…”