Cobalt, Iron and Ruthenium Complexes of Picolinic and Dipicolinic Acids: Syntheses, Solution Properties and Kinetics of Electron Transfer Reactions With Cytochrome C(II) and Some Inorganic Reductants

Tris picolinate complexes of CO111 and RU111 have been synthesized, and their standard potentials measured (432 ±10, 403 ±2 mV) at 25ºC and ionic strength 0.1 mol dm-3. The self-exchange rate constant of Ru ( pic )3O/- was found to be (1 .4 ±0.9)×108 dm3 mol-1 s-l, from reaction with cytochrome C(II), Co( bpy )32+ and ~Co( phen )32+. For the reaction between Fe( dipic )2- and cytochrome ~(II), at 2S260C, pH 5.5 and I 0.1 mol dm-3 (KNO3), the second-order rate constant was (3.2 ±0.l)×105 dm3 mol-1 s-1,with ?H+ 19.9 ±0.9 kJ mol-1 and ?S+ -72.8 ±.7 J K-1 mol-l. The self-exchange rate constant of Fe( dipic )2-/2- was reevaluated as (5.8 ±0.2)×106 dm3 mol-l s-1.