Construction of Alkynylplatinum(II) Bzimpy-Functionalized Metallacycles and Their Hierarchical Self-Assembly Behavior in Solution Promoted by Pt⋅⋅⋅Pt and π-π Interactions.

A family of new alkynylplatinum(II) 2,6-bis(benzimidazol-2'-yl)pyridine (bzimpy)-functionalized supramolecular metallacycles with different shapes and sizes have been successfully prepared by coordination-driven self-assembly. The obtained metallacycles showed switchable emission and a strong tendency to form intermolecular Pt⋅⋅⋅Pt and π-π stacking interactions in solution that were not displayed by their individual precursors. Further investigation revealed that the existence of the metallacyclic scaffold at the core could facilitate the formation of intermolecular Pt⋅⋅⋅Pt and π-π stacking interactions of peripheral alkynylplatinum(II) bzimpy units. Moreover, the shapes and sizes of the metallacyclic scaffold have a significant influence on the hierarchical self-assembly behavior. Among the three metallacycles, hexagonal metallacycle A, with a relatively small size, could spontaneously self-assemble into an aromatic guest stimuli-responsive metallogel at room temperature without a heating-cooling process.