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Co(bpb) [bpbH2is N,N′-o-phenylenebis(pyridine-2-carboxamide) ,C18H12N4O2] complex has active axial sites like a porphyrin complex. We studied the coordination of azide ion(N3-) 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,ΔH,ΔS,and ΔG) were obtained. An isokinetic temperature at about 302 K was observed at which the formation rate of Co(bpb) -N3-was more or less independent of the solvent composition. The resulting ΔH against TΔS 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) -N3-produced through complex formation,a spectrophotometric method for the determination of N 3-in solution was developed. A linear relationship between the absorbance and N3-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 N3-anion in real water samples.
(Bpb) [bpbH2is N, N’-o-phenylenebis (C12H12N4O2) complex has active axial sites like a porphyrin complex. We studied the coordination of azide ion (N3-) to Co 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, ΔH, ΔS, and ΔG) were obtained. An isokinetic temperature at about 302 K was observed at which the formation rate of Co (bpb) -N3-was more or less independent of the solvent composition. The resulting ΔH against TΔS 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) -N3-produced through complex formation, a spectrophotometric method for the determination of N 3-in solution was developed. A linear relationship between the absorbance and N3-concentration was obtained in the range of (0.85 The proposed method was 2.5 × 10-5 mol·L-1 (1.0 μg · mL-1). The proposed method was applied to the determination of N3-anion in real water samples.