Phosphorescent nematic hydrogels and chromonic mesophases driven by intra- and intermolecular interactions of bridged dinuclear cyclometalated platinum(ii) complexes

Abstract

A new class of dinuclear cyclometalated platinum(II) complexes with [Pt^II(C^N^N)CNR]⁺ (HC^N^N = 6-phenyl-2,2′-bipyridyl, CNR = 2,6-dimethylphenyl isocyanide) motifs covalently connected by oligo(oxyethylene) chains form luminescent lyotropic chromonic liquid crystals or hydrogels in aqueous dispersions with intra- and intermolecular Pt⋯Pt and π–π interactions as the driving force. Their solution behaviour is modulated by the length of the oligo(oxyethylene) chain connecting the two cyclometalated platinum(II) motifs. One of the dinuclear Pt(II) complexes with a long oligo(oxyethylene) bridge and which does not display intramolecular Pt⋯Pt and π–π interactions can act as an effective ‘gelling stimulus’ for mononuclear [Pt^II(C^N^N)CNR]⁺ complexes in aqueous solutions, resulting in the formation of a nematic hydrogel that is persistent and displays red photoluminescence.