Modular Supramolecular Assembly through Clickable Hemilabile Ligands via the Weak-Link Approach

In an effort to develop a convergent method for synthesizing a wide range of hemilabile ligands suitable for generating allosteric coordination complexes, phosphino-thioether hemilabile ligands bearing pendant alkyne groups were prepared and employed as synthons. These were used to generate four distinct hemilabile ligands with the desired chemical functionalities via Cu(I)-catalyzed azide-alkyne cycloaddition (click chemistry). This click chemistry approach to ligand synthesis enables the rapid preparation of Pt(II) coordination complexes from PtCl₂(1,5-cyclooctadiene). The resulting complexes can be allosterically regulated using chloride (Cl^-) as a small-molecule effector. Proof-of-concept complexes demonstrate that coordination switchability is independent of the ligand's steric bulk and electronics and the solubility of the complex. Both homo- and heteroligated coordination complexes were synthesized using WLA (weak-link approach) coordination-chemistry-based methods and fully characterized in solution. Two of these complexes (the fully chelated homoligated complexes of the benzyl and phenyl derivative ligands) were also characterized in the solid state by single-crystal X-ray diffraction studies. These advances expand the structural diversity of compounds accessible through the WLA and, given the generality and functional group tolerance of click chemistry, facilitate the preparation of allosteric systems with tailored functionalities for applications in catalysis and small-molecule sensing.