Tuning the Coordination Environment of Ru(II) Complexes with a Tailored Acridine Ligand.

A novel tridentate ligand featuring an acridine core and pyrazole rings, namely 2,7- di-butyl-4,5-di(pyrazol-1-yl)acridine, , was designed and used to create two ruthenium(II) complexes: [Ru](PF) and [Ru(tpy)](PF). Surprisingly, the ligand adopted different coordination modes in the complexes: facial coordination for the homoleptic complex and meridional coordination for the heteroleptic complex. The electronic absorption and electrochemical properties were evaluated. Although both complexes exhibited favorable electronic properties for luminescence, neither emitted light at room temperature nor at 77 K. This study highlights the complex interplay between ligand design, coordination mode, and luminescence in ruthenium(II) complexes.