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

1989 ◽  
Vol 42 (1) ◽  
pp. 1 ◽  
Author(s):  
RM Ellis ◽  
JD Quilligan ◽  
NH Williams ◽  
JK Yandell
Keyword(s):  
Exchange Rate ◽  
Cytochrome C ◽  
Rate Constant ◽  
Order Rate Constant ◽  
The Self ◽  
Transfer Reactions ◽  
Solution Properties ◽  
Cobalt Iron ◽  
Exchange Rate Constant ◽  
Kinetics Of

Tris picolinate complexes of CO111 and RU111 have been synthesized, and their standard potentials measured (432 �10, 403 �2 mV) at 25�C 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 ΔH+ 19.9 �0.9 kJ mol-1 and ΔS+ -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.

Electron transfer reactions of nickel complexes of 1,4,7-triazacyclodecane

1985 ◽  
Vol 63 (11) ◽  
pp. 2983-2989 ◽  
Author(s):  
M. G. Fairbank ◽  
A. McAuley ◽  
P. R. Norman ◽  
O. Olubuyide
Keyword(s):  
Electron Transfer ◽  
Exchange Rate ◽  
Proton Transfer ◽  
Electrochemical Oxidation ◽  
Rate Constant ◽  
Aqueous Media ◽  
Nickel Complexes ◽  
Outer Sphere ◽  
The Self ◽  
Transfer Reactions

The preparation of [Ni(1,4,7-triazacyciodecane)2]3+, (Ni(10-aneN3)23+) is described. The existing procedure has been modified leading to good yields of the ligand trihydrochloride. The nickel(II) analogue (reported previously) is oxidised in a facile manner, either by Co3+aq in acidic aqueous media or by NO+ in CH3CN. Since the octahedral NiN6, chromophore is retained upon electron transfer, outer sphere reactions both of the Ni(II) and Ni(III) species have been studied. Rates of oxidation by various nickel(III) macrocycles have been measured and details are provided. Electrochemical oxidation of the Ni(II) complex is consistent with E0(Ni(10-aneN3)23+/2+) = 0.997 V (vs. NHE). The data have been used in a Marcus correlation, leading to the self-exchange rate k11 for the couple (Ni(10-aneN3)23+/2+) = (2 ± 1) × 104 M−1 s−1. This value is compared with other data derived using octahedral Ni(II)/Ni(III) centres. The oxidation of the Ni(II) complex by Co(III)aq has been studied in both protonated and deuterated media. There is no evidence for any proton transfer (from the N—H) being coupled to the electron transfer step. The observed rate constant for the reaction of Co3+ with Ni(II)(10-aneN3)22+ (550 M−1 s−1) may be compared with the calculated outer sphere rate (270 M−1 s−1). An estimate of k11 (CoOH2+/+) ~ 3 M−1 s−1 for the CoOH2+/+ exchange is discussed.

Electron transfer in non-oxovanadium(IV) and (V) complexes: Kinetic studies of an amavadin model

2009 ◽  
Vol 81 (7) ◽  
pp. 1241-1249 ◽  
Author(s):  
Jeremy M. Lenhardt ◽  
Bharat Baruah ◽  
Debbie C. Crans ◽  
Michael D. Johnson
Keyword(s):  
Electron Transfer ◽  
Exchange Rate ◽  
Rate Constant ◽  
Exchange Process ◽  
Kinetic Studies ◽  
Electron Transfer Reaction ◽  
The Self ◽  
Synthetic Analog ◽  
Vanadium Complex ◽  
Exchange Rate Constant

Electron-transfer reactions of the eight-coordinate vanadium complex, bis-(N-hydroxyiminodiacetate)vanadium(IV) [V(HIDA)2]2–, a synthetic analog of amavadin with ascorbic acid and hexachloroiridate(IV), have been studied. The self-exchange rate constant for this analog has been calculated from oxidation and reduction cross-reactions using Marcus theory and directly measured using 51V NMR paramagnetic line-broadening techniques. The average self-exchange rate constant for the bis-HIDA vanadium(IV/V) couple equals 1.5 × 105 M–1 s–1. The observed rate enhancements are proposed to be due to the small structural differences between the oxidized and reduced forms of the HIDA complex and inner-sphere reorganizational energies. The electron-transfer reaction of this synthetic analog is experimentally indistinguishable from amavadin itself, although significant differences exist in the reduction potential of these compounds. This suggests that ligand modification effects the thermodynamic driving force and not the self-exchange process.

The oxidation of hydrogen peroxide by tris(polypyridine) complexes of osmium(III), iron(III), ruthenium(III), and nickel(III) in aqueous media

1986 ◽  
Vol 64 (9) ◽  
pp. 1936-1942 ◽  
Author(s):  
Donal H. Macartney
Keyword(s):  
Hydrogen Peroxide ◽  
Exchange Rate ◽  
Rate Constant ◽  
Aqueous Media ◽  
Activation Parameters ◽  
Exchange Rate Constant ◽  
Oxidation Of Hydrogen ◽  
Polypyridine Complexes ◽  
Ph Range ◽  
Kinetics Of

The stoichiometry and kinetics of the oxidation of hydrogen peroxide by tris(2,2′-bipyridine) and tris(4,4′-dimethyl-2,2′-bipyridine) complexes of osmium(III), iron(III), ruthenium(III), and nickel (III) were studied in acidic and neutral aqueous media at 25 °C and I = 0.50 M (LiCF3SO3). The reaction 2M(bpy)33+ + H2O2 → 2M(bpy)32+ + O2 + 2H+ is observed with quantitative yields of dioxygen gas. The observed rate constants displayed an inverse acid dependence over the pH range 6.0–8.5; kobsd = k1 + k2K1/[H+], attributed to the oxidations of H2O2(k1) and HO2− (k2). An application of the Marcus theory relationship to the cross-reaction data gave a self-exchange rate constant of 10−2–10−1 M−1 s−1 for the HO2−/HO2 couple. The electron exchange rate constant is evaluated in terms of the inner-sphere and solvent reorganizational barriers and is compared to values reported for other small molecule couples. Rate and activation parameters for the reduction of the nickel(III) complexes by the hydroxide ion have been determined and are compared with the corresponding values for other metal tris(poly pyridine) complexes.

Sign in / Sign up

Export Citation Format

Share Document