Propellers and Planes: Phosphorescent PtII σ‐Acetylides from Polyaromatic Ligands

This article details the preparation, photophysical and electrochemical investigation of four novel polyaromatic square‐planar platinum(II) bis(acetylide) complexes, incorporating either a planar hexa‐ peri ‐hexabenzocoronene ( L 2 ) or its uncyclised ethynyl‐hexaphenylbenzene precursor ( L 1 ). Complexes in both cis and trans geometries ( cis ‐[Pt( L ) 2 (dppe)] [ C 1 , C 2 ; dppe = 1,2‐bis(diphenylphosphanyl)ethane] and trans ‐[Pt( L ) 2 (PPh 3 ) 2 ] ( T 1 , T 2 ) were successfully prepared and fully characterised. The low‐energy bands of the UV/Vis absorption spectra for the uncyclised family ( L 1 , C 1 , T 1 ) and for the cyclised family ( L 2 , C 2 , T 2 ) exhibit a redshift in the order trans > cis > ligand, indicating enhanced π‐conjugation along the molecular axis in trans configuration. Each Pt II complex is dual luminescent and possesses a high‐energy ligand‐centred fluorescence and a lower energy emission with significant phosphorescent character facilitated by the high spin‐orbit coupling of the heavy platinum metal centre. Notably, cis ‐ and trans ‐ L 2 complexes exhibit remarkably long lifetimes in degassed CH 2 Cl 2 at room temperature ( trans : 30.9 μs; cis : 18.3 μs) for sharp phosphorescence at λ = 578 nm.