Structural and Chromic Behaviour of Cycloplatinated(II) Complexes Bearing Isocyanide Ligands

Zusammenfassung

Cyclometalated platinum(II) complexes have received extensive attention due to theirproperties, such as long emissive lifetimes, high phosphorescent efficiency and tuneableexcited states. All these characteristics make them attractive candidates for chromicdevices with applications in bioimaging, sensors and optoelectronic devices.[1]In particular, cycloplatinated complexes bearing strong field isocyanide ligands haveattracted a great interest as efficient chromophores with stimuli switching responses. Inthis regard, we have previously reported a family of chloride isocyanide Pt(II) complexeswith remarkable mechanochromic properties.[2]To expand this research, we present the synthesis of a new family of luminescent platinumcomplexes, chloride-isocyanide [Pt(C^N)Cl(CNBut)] (1) and bis-isocyanide [Pt(C^N)(CNBut)2]ClO4 (2), bearing 2-(2,4-difluorophenyl)pyridine (dfppy, a) and 4-(2-pyridyl)benzaldehyde (ppy-CHO, b) as cyclometalating ligands. The characterization andphotophysical properties of all complexes have been studied in detail and rationalizedtogether with TD-DFT calculations.The chloride derivatives exhibit an interesting multi-stimuli behaviour, related to the formation of aggregates through intermolecular Pt···Pt and/or π···π interactions, resulting in a significantly red-shifted luminescence changes that have been analysed by X-ray studies.