Pt×××Pt and π-π* Interactions in Luminescentσ-Alkynyl Platinum(II) Terpyridine Complexes

Significance

The authors report the formation of gels and liquid crystals induced by Pt×××Pt and π-π* interactions. Syntheses of the pivotal ethynyl platforms are based on gallate-substituted derivatives with methyl, dodecyl (C₁₂H₂₅) or phytol-like (C₂₀H₄₁) substituents. The final complexes were prepared by a cross-coupling reaction under anaerobic conditions between the terminal ethynyl derivatives and [(terpy)PtCl]BF₄ (terpy = 2,2′:6′,6-terpyridine). The reaction is catalyzed by CuI (ca. 6 mol%), and triethylamine is required to quench the nascent HCl. Compound 2b was found to be a good gelator of dodecane. Dark-green gels displaying a thermally reversible sol-gel-phase transition were obtained from hot dodecane solutions. The Pt×××Pt interactions were identified based on unique absorption and emission features and further confirmed by X-ray data of the columnar liquid crystal.