Tuning energy landscapes and metal-metal interactions in supramolecular polymers regulated by coordination geometry

Abstract

Herein, we exploit coordination geometry as a new tool to regulate the non-covalent interactions, photophysical properties and energy landscape of supramolecular polymers. To this end, we have designed two self-assembled Pt(ii) complexes1and2that feature an identical aromatic surface, but differ in the coordination and molecular geometry (linearvs.V-shaped) as a result of judicious ligand choice (monodentate pyridinevs.bidentate bipyridine). Even though both complexes form cooperative supramolecular polymers in methylcyclohexane, their supramolecular and photophysical behaviour differ significantly: while the high preorganization of the bipyridine-based complex1enables an H-type 1D stacking with short Pt⋯Pt contactsviaa two-step consecutive process, the existence of increased steric effects for the pyridyl-based derivative2hinders the formation of metal-metal contacts and induces a single aggregation process into large bundles of fibers. Ultimately, this fine control of Pt⋯Pt distances leads to tuneable luminescence—red for1vs.blue for2, which highlights the relevance of coordination geometry for the development of functional supramolecular materials.