Gooden, V.,; Dasgupta, Tara, P.; Gordon, N.; Sadler, Garfield G.
Author Affiliation, Ana.
Chemistry; Faculty of Pure and Applied Sciences
Properties and kinetics of dihydroxy- and diaminoanthraquinone ruthenium bipyridyl dimers
Inorganica Chimica Acta
Date of Publication
Ru (bpy)2C12 (bpy:2,2' -bipyridine) reacts with 1,4-diaminoanthraquinone (1,4-DAAQ) to produce a dimeric complex which precipitates from solution in its mixed-valence form. Redox couples show that the rutheniums are easier to oxidize than those in the corresponding 1,4- DHAQ (1,4-dihydroxyanthraquinone) and 1,4-AHAQ (1-amino-4-hydroyanthraquinone) dimers and give a value of 2.8 x 106 for Kcom. Visible absorbtion bands are broad and may be combinations of transitions. The IT band in acetonitrile shows structure with lmax (log Î) at 845 nm (3.5), 1493 nm (4.44) and 2028 nm (4.04). Preliminary kinetic studies of the S2O82- oxidation of the 1,4-DHAQ, 1,4-AHAQ and 1,4-DAAQ dimers show a faster oxidation of the fully reduced form ([2,2]) followed by a slower oxidation of the mixed-valence form 9[2,3]). No mechanism could be determined for the faster oxidation. However, the slower oxidation appeared to be first order in both dimer and S2O82-, and involved ion pairing. Kip was determined to be 13 for the 3 +,2- ion pair. Values for ket were found to parallel the second ruthenium oxidation potential for the dimers, and were found to be 6 X 10-4, 8 X 10-4 and 1.1 X 10-2 M-1 s-1 for the 1,4-DHAQ, 1,4- AHAQ and 1,4-DAAQ dimers, respectively, at 25°C....