The weak-link approach (WLA) to supramolecular assemblies allows for the design of multimetallic two- and three-dimensional arrays, host-guest architectures, sensors, catalysts, switches, and signal amplification devices. This Account describes the course of our investigations in this area beginning with the development of a chemical tool kit of building blocks consisting of multiple metals and ligands. These building blocks can be rationally mixed and matched to provide structures with a wide range of properties that have been used to develop functional supramolecular architectures, including chemical sensors and allosteric catalysts.

The advent of methods for the construction of supramolecular assemblies provides a route to exploring the benefits of artificial allosteric catalysts. To expand our ability to control reactions using supramolecular catalysts capable of changing shape in response to chemical input signals, we report the development and high yield syntheses of multidomain modular supramolecular catalysts. These structures can be chemically interconverted between relatively inactive and catalytically active states depending on their shape. Furthermore, this class of supramolecular catalysts can be made to respond to a range of analytes via the introduction of specific structure control elements responsible for binding analyte molecules. Herein, we describe several of these catalysts and their ability to regulate acyl transfer reactions allosterically. In addition, the generality of this approach to signal amplification and detection is examined by incorporating the acyl transfer reaction into a small molecule detection scheme consisting of (i) analyte binding to structure control sites of the catalytic supramolecular assemblies, (ii) enhanced catalytic activity turned on by the resulting shape change, thereby allowing for signal amplification of the binding event, and (iii) signal detection by analysis of the products of the catalytic reaction.

The weak-link approach has been employed to synthesize a series of bimetallic Cu(I) macrocycles in high yield. Addition of phosphinoalkylether or -thioether ligands to [Cu(MeCN)4]PF6 produces "condensed" intermediates, [mu-(1,4-(PPh2CH2CH2X)2Y)2Cu2][PF6]2 (X = S, O; Y = C6H4, C6F4), containing strong P-Cu bonds and weaker O-Cu or S-Cu bonds. The weak bonds of these intermediates can be cleaved through ligand substitution reactions to generate macrocyclic structures, [mu-(1,4-(PPh2CH2CH2X)2Y)2(Z)nCu2][PF6]2 (X = S, O; Y = C6H4, C6F4; Z = pyridine, acetonitrile, diimines, isocyanide) in nearly quantitative yields. The incorporation of tetrahedral Cu(I) metal centers into these macrocycles provides a pathway to complexes that differ from analogous d8 square planar macrocycles generated via this approach in their increased air stability, small molecule reactivity, and ability to form multiple structural isomers. Solid-state structures, as determined by single-crystal X-ray diffraction studies, are presented for condensed intermediates and an open macrocycle

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