Electrogenerated nitro radical anions -: A comparative kinetic study using scanning electrochemical microscopy

The use of scanning electrochemical microscopy (SECM) cyclic voltammetry (CV) in tip generation/substrate collection mode is proposed as a new alternative for measuring the kinetics of the chemical coupled reactions of the nitro radical anions generated from nitrocompounds. We have applied the theory developed by Bard and co-workers to obtain the homogeneous rate constant for the dimerization of electrogenerated nitro radical anions from PA-824 (a new antituberculosis agent) and metronidazole (MTZ, a well-known bactericidal agent) in dimethylsulfoxide. Using SECM we have obtained k(2,dim) values of 2.15 +/- 0.73 X 10(4) [M X s](-1) and 332 +/- 74 [M X s](-1) for PA-824 and MTZ, respectively. For comparative purposes, we have obtained k(2,dim) values of 2.58 +/- 0.61 X 10(4) [M X s](-1) and 222 +/- 38 [M X s](-1) for PA-824 and MTZ, respectively, but using the CV methodology. The agreement between the results obtained from the well-proved CV methodology and the recently developed SECM methodology support the validity of this new approach. Thus, this work reveals the first approach wherein the SECM technique is applied to the study of the nitro radical anion electrogenerated from nitrocompounds of biological significance. (C) 2004 The Electrochemical Society.