Crystal structure,physical, and photophysical properties of a ruthenium(II) bipyridine diazafluorenone complex

The complex Ru(bpy)₂(dafo)](PF₆)₂, where bpy is 2,2-bipyridine and dafo is diazafluorenone crystallizes in the space group P2₁/n witha=9.505(3) Å,b=14.002(4) Å andc=25.783(8) Å. The coordination geometry of the Ru atom is that of a distorted octahedron with a RuN₆ core. The two Ru-N bond distances to the dafo ligand are 2.13(1) and 2.15(1) Å; the four Ru-N bond distances to the bipyridine ligands are 2.03(1), 2.05(1), 2.06(1), and 2.07(1) Å. The three shortest Ru-N distances aretrans to the three longest Ru-N distances. The complex is oxidized and reduced reversibly at 1.41 and –0.65 V vs. SSCE, respectively. It displays absorptions at 438 nm (1.6×10⁴), 285 nm (6.2×10⁴), and 240 nm (4.1×10⁴) and a broad emission centered at 626 nm in water at room temperature. The emission lifetime is 420 ns and the emission quantum yield is 5.3×10^–4.