Emissive Ruthenium–Bisdiimine Complexes with Chelated Thioether Donors

The photophysical properties of ruthenium(II) complexes of bidentate 2‐[(alkylthio)methyl]pyridine (N,S) ligands have been systematically investigated. The co‐ligands in the heteroleptic complexes were diimines (N,N ligands, e.g., bpy, phen) or tripodal tetradentate tris(2‐pyridylmethyl)amine (tpa). Their X‐ray structures revealed little variation in the Ru–S (2.31–2.33 Å) and Ru–N (2.06–2.11 Å) bond lengths. Despite this, considerable variation can be observed in the electrochemistry and spectroscopy measurements. The presence of the thioether sulfur donor results in a shift to a more positive potential of the Ru 2+ /Ru 3+ process, and the absorption maxima are consequently blueshifted in [Ru(N,N) 2 (N,S)] 2+ complexes compared with the [Ru(N,N) 3 ] 2+ analogues. The [Ru(N,N) 2 (N,S)] 2+ complexes display strong room‐temperature emission from 3 MLCT states, governed by the N,N donors. This is corroborated by low‐temperature steady‐state emission studies, which revealed typical 3 MLCT emission profiles and excited‐state lifetimes of around 5–10 µs.