Structural organization of a {ruthenium[tris(bipyridyl)]}2+ complex by strong π–π stacking of a tethered 1,8-naphthalimide synthon: Impact on electrochemical and spectral properties

The new ligand N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide has been prepared by the reaction of 1,8-naphthalimide, 5-(bromomethyl)-2,2′-bipyridine and potassium carbonate in refluxing acetone. Reaction of this ligand and bis(bipyridyl)ruthenium(II) dichloride in refluxing ethanol followed by anion exchange with ammonium hexafluorophosphate produces {ruthenium[bis(bipyridyl)][N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide]}(PF6)2 (1). In both the solid state (X-ray analysis) and in solution (shown by PGSE-NMR analysis), the 1,8-naphthalimide synthon organizes the cationic metal units into dimers with a strong, directionally oriented (head to tail) π–π stacking interaction. UV–VIS, fluorescence spectroscopy and electrochemical studies indicate that even with the strong interactions of the 1,8-naphthalimide groups, it does not have a significant influence on the properties of the [Ru(bipy)3]2+ core.

Graphical abstractThe {Ru(bipyridyl)2}2+ complex of the new ligand N-(5-methyl-2,2′-bipyridyl)-1,8-naphthalimide, containing both a bipyridyl and 1,8-naphthalimide group, has been prepared and shown to be organized into dimers in both the solid and solution phase by strong, directionally oriented π–π stacking. UV–VIS, fluorescence spectroscopy and electrochemical studies indicate that the 1,8-naphthalimide groups does not have a significant influence on the properties of the [Ru(bipy)3]2+ core.Figure optionsDownload full-size imageDownload as PowerPoint slide