Showing papers by "Natalya V. Chizhova published in 2004"

Equilibrium of cadmium complexing with porphyrazines in the H2P-Cd(Ac)2-HClO4-(CH3)2SO system at 298 K

Abstract: For porphyrazine and its octaphenyl and octa(4-nitrophenyl)derivatives (H 2 P), the H 2 P ? HP - + H + and HP - ? P 2 - + H + equilibria of the H 2 P-(K[222])OH-(CH 3 ) 2 SO system and the H 2 P + Cd 2 + CdP + 2H + equilibrium of the H 2 P-Cd(Ac) 2 -HClO 4 -(CH 3 ) 2 SO system at 298 K were studied using a spectropotentiometric method. Constants for these equilibria were determined. From the expression K e = K a 1 K a 2 /K s t , Cd 2 + + P 2 - ? CdP equilibrium constants were calculated. The pK e value is independent of the structure of the porphyrazine ligand. A linear correlation log K s t = (0.99 ′ 0.02)(pK a 1 + pK a 2 ) + (3.9 ′ 0.3) was found with a coefficient of 0.9997; from this, it follows that the energy of CdP formation compensates for the energy consumed in H 2 P ionization.