Evolving Trends in Transition Metal-Modified Receptor Design and Function - Designing Receptors for the Next Generation of Biosensors - page 241

Fig. 4 General strategy of the WLA to macrocyclic coordination complexes. Reprinted with
permission from [ 26 ]. Copyright 2005 American Chemical Society
Since their first report of an allosteric catalyst made possible through supra-
molecular chemistry [ 25 ], Mirkin and coworkers have remained pioneers in the
development of synthetic enzyme mimics using the weak-link approach (WLA) to
macrocyclic coordination complexes [ 26 , 27 ]. The WLA allows one to construct
multimetallic macrocycles with flexible hemilabile ligands that form both strong
and weak coordination bonds with a transition metal center. Specifically, the WLA
approach relies on condensed macrocyclic structures that contain at least two
strategically placed strong (metal-phosphine) and weak (metal-X) bonds (Fig. 4 ).
A critical feature of this approach is that the structural metals that direct the
assembly process are available for further ligand substitution reactions without
compromising the supramolecular structure. Thus, macrocycles can be toggled
between well-defined architectures with different shapes and rigidities through
ligand displacement reactions by selectively and reversibly breaking weak coordi-
nation bonds with small molecule effectors. This inherent property of all weak-link
macrocycles makes the approach well suited for preparing functional systems that
exhibit allosteric control through appropriately designed hemilabile ligands
(i.e., transition metal catalysts, receptors).