A Reduced‐Symmetry Heterobimetallic [PdPtL₄]⁴⁺ Cage: Assembly, Guest Binding, and Stimulus‐Induced Switching

Abstract

A strategy is presented that enables the quantitative assembly of a heterobimetallic [PdPtL4]4+ cage. The presence of two different metal ions (PdII and PtII) with differing labilities enables the cage to be opened and closed selectively at one end upon treatment with suitable stimuli. Combining an inert PtII tetrapyridylaldehyde complex with a suitably substituted pyridylamine and PdII ions led to the assembly of the cage. 1H and DOSY NMR spectroscopy and ESI mass spectrometry data were consistent with the quantitative formation of the cage, and the heterobimetallic structure was confirmed using single‐crystal X‐ray crystallography. The structure of the host–guest adduct with a 2,6‐diaminoanthraquinone guest molecule was determined. Addition of N,N′‐dimethylaminopyridine (DMAP) resulted in the formation of the open‐cage [PtL4]2+ compound and [Pd(DMAP)4]2+ complex. This process could then be reversed, with the reformation of the cage, upon addition of p‐toluenesulfonic acid (TsOH).

Multi-stimuli Control over Assembly and Guest Binding in Metallo-supramolecular Hosts Based on Dithienylethene Photoswitches

“…It has been shown that interaction of such cages with chemical stimuli, e.g., additional ligands, allows structural rearrangement and guest release. 16 The addition of halide anions to positively charged hosts can trigger the uptake of neutral guest molecules. 17 Guest uptake can also be tuned in redox-responsive systems.…”

The Biologically Inspired Abilities of Metallosupramolecular Architectures

“…Further expanding on this work, Crowley and coworkers used the subcomponent self‐assembly approach to form heterometallic platinum(II)‐palladium(II) cages using a platinum(II) pyridylaldehyde complex and pyridylamine building blocks (Figure 3b middle) [49a] . This heterometallic monocavity cage was shown to bind both 2,6‐diaminoanthraquinone and 5‐fluorouracil.…”

Allosterically Regulated Guest Binding Determines Framework Symmetry for an FeII4L4 Cage

“…These cages have also proven useful across diverse areas, including molecular recognition and sensing, [5] chemical separation, [6] stabilization of otherwise unstable species, [7] and catalytic transformations [8] . The reversible linkages between metal vertices and coordination sites can enable these cages to disassemble and reassemble in response to external stimuli, [9] for instance, temperature, [10] light, [11] redox, [12] and pH [13] …”