Dimensional Control and Morphological Transformations of Supramolecular Polymeric Nanofibers Based on Cofacially-Stacked Planar Amphiphilic Platinum(II) Complexes

Square-planar platinum(II) complexes often stack cofacially to yield supramolecular fiber-like structures with interesting photophysical properties. However, control over fiber dimensions and the resulting colloidal stability is limited. We report the self-assembly of amphiphilic Pt(II) complexes with solubilizing ancillary ligands based on polyethylene glycol [PEGn, where n = 16, 12, 7]. The complex with the longest solubilizing PEG ligand, Pt-PEG16, self-assembled to form polydisperse one-dimensional (1D) nanofibers (diameters <5 nm). Sonication led to short seeds which, on addition of further molecularly dissolved Pt-PEG16 complex, underwent elongation in a “living supramolecular polymerization” process to yield relatively uniform fibers of length up to ca. 400 nm. The fiber lengths were dependent on the Pt-PEG16 complex to seed mass ratio in a manner analogous to a living covalent polymerization of molecular monomers. Moreover, the fiber lengths were unchanged in solution after 1 week and were therefo...