C. Li et al., GROUND-STATE INTERACTIONS BETWEEN RUTHENIUM(II)-DIIMINE COMPLEXES ANDPHENOL AND MONOCHLOROPHENOLS IN AQUEOUS-SOLUTION, Inorganic chemistry, 37(12), 1998, pp. 3078-3082
Ground-state interactions between Ru(bpy)(3)(2+) (bpy = 2,2'-bipyridin
e) or Ru(bpz)(3)(2+) (bpz = 2,2'-bipyrazine) and phenol (PhOH) or mono
chlorophenols (ClPhOH) have been investigated in aqueous (D2O) solutio
n by NMR. The upfield shifts of the resonances and the NOE difference
spectra of the complexes in the presence of the phenols indicate the p
resence of offset face-to-face pi-stacking interactions between the ph
enol and the aromatic ligands. Electron withdrawal from the phenol rin
g by the monochloro substituent and less effective solvation by aqueou
s (compared to acetonitrile) media favor the interaction. The formatio
n constant for the 1:1 Ru(bpy)(3)(2+)-PhOH complex is estimated to be
similar to 0.01 M-1; K is smaller for Ru(bpz)(3)(2+) than for Ru(bpy)(
3)(2+), and it increases for both complexes in the order PhOH < 4-ClPh
OH < 3-CIPhOH < 2-CIPhOH.