Kinetics Studies of the Reaction of Co(bpb) with the Azide Ion in Binary Methanol-Water Mixtures
Co(bpb) [bpbH2 is N,N'-o-phenylenebis(pyridine-2-carboxamide), C18H12N4O2] complex has active axial sites like a porphyrin complex. We studied the coordination of azide ion (N-3) to Co(bpb) in binary methanol-water mixtures by spectrophotometric method at the temperature range of 283-303 K. From the temperature dependence of the rate constant, activation parameters (Ea, △H#, △S#, and △G#) were obtained. An isokinetic temperature at about 302 K was observed at which the formation rate of Co(bpb)-N-3 was more or less independent of the solvent composition. The resulting △H against T△S plot showed a good linear correlation, indicating the existence of enthalpy-entropy compensation in azide complexation process. Under optimum conditions and based on the absorbance of Co(bpb)-N-3 produced through complex formation, a spectrophotometric method for the determination of N-3 in solution was developed.Alinear relationship between the absorbance and N-3 concentration was obtained in the range of (0.85-5.00)×10-4 mol·L-1 (3.6-21.0 μg·mL-1). The detection limit was 2.5×10-5 mol·L-1 (1.0 μg·mL-1). The proposed method was applied to the determination of N-3 anion in real water samples.
Document Type: Research Article
Publication date: 2009-06-15
- Acta Physico-Chimica Sinica, founded in 1985, is sponsored by the Chinese Chemical Society and organized by the College of Chemistry and Molecular Engineering, PekingUniversity. Since 1997, Acta Physico-Chimica Sinica has been indexed in SCI of ISI (US). Acta Physico-Chimica Sinica is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, and material physical chemists. Manuscripts that are essentially reporting data, applications of data, or reviews of the literature are not suitable for publication in Acta Physico-Chimica Sinica.
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