23852-07-5Relevant academic research and scientific papers
Cobalt(I) polypyridine complexes. Redox and substitutional kinetics and thermodynamics in the aqueous 2,2′-bipyridine and 4,4′-dimethyl-2,2′-bipyridine series studied by the pulse-radiolysis technique
Schwarz, Harold A.,Creutz, Carol,Sutin, Norman
, p. 433 - 439 (2008/10/08)
Pulse radiolysis was used to study Co(I) produced by eaq- reduction of Co(II) in aqueous solutions containing 2,2′-bipyridine (bpy) or 4,4′-dimethyl-2,2′-bipyridine (dmb) and a hydroxyl radical scavenger. Six equilibria between CoLn+ and CoLn2+ pairs were characterized. The absorption maxima and stability constants (log K) of the CoLn+ species are as follows: Co(bpy)3+, 610 nm, 6.9; Co(bpy)2+, 570 nm, 7.6; Co(bpy)+, 670 nm, ≥12; Co(dmb)3+, 610 nm, 7.3; Co(dmb)2+, 500 nm, 8.0; Co(dmb)+, 660 nm, ≥12. The reduction potentials vs. NHE, based on E°(Co(bpy)32+/+) = -0.95 V and E°(Co(dmb)32+/+) = -1.07 V, were as follows: Co(bpy)22+/+, -1.09 V; Co(bpy)2+/+, -1.23 V; Co(dmb)22+/+, -1.17 V; Co(dmb)2+/+, -1.29 V; Co2+/+, ≤-1.6 V. Stability constants were also measured for the Co(II) species in 0.1 M chloride. The log K values are 5.95, 5.27, and 4.60 for Co(bpy)2+, Co(bpy)22+, and Co(bpy)32+, respectively, and 6.38, 5.92, and 5.25 for Co(dmb)2+, Co(dmb)22+, and Co(dmb)32+, respectively. The (CH3)2COH and CO2-·radicals, produced by ·OH oxidation of 2-propanol and formate, react slowly (k ～ 106 to 4 × 107 M-1 s-1) with the Co(II) complexes to yield Co(I) and radical-addition products in parallel.
