Hierarchical helices of helices directed by Pt⋯Pt and π–π stacking interactions: reciprocal association of multiple helices of dinuclear alkynylplatinum(ii) complex with luminescence enhancement behavior

Abstract

A dinuclear alkynylplatinum(II) terpyridine complex containing an amphiphilic binaphthol bridge was designed and synthesized, and was shown to display cylindrical columnar assemblies in aqueous acetonitrile solutions, presumably mediated by the Pt⋯Pt and π–π stacking interactions. The length of the binaphthol bridge was found to have a profound effect on the degree of helicity for hierarchical helices of helices and serves as a critical determinant in the formation of tertiary structures for foldamers. Interestingly, the reciprocal association of multiple helices has led to luminescence enhancement behavior, which provides a luminescence turn-on switch for the reporting of the hierarchical assembly of foldamers into higher-order structures, distinct from that of the pure organic systems. Such a transverse aggregation of multiple helices driven by metallophilic interactions has been studied by electronic absorption, circular dichroism, emission spectroscopy and electron microscopy.