On the complexation of copper(II) ion with 2-hydroxybenzamide

The complexation of the Cu2+ ion with 2-Hydroxybenzamide (salicylamide, HL) has been studied, at 25 degrees C, by potentiometric measurements with a glass electrode in NaClO4 media for ionic strength ranging from 0.5 to 3 mol/dm(3). The data are consistent with the formation of the complexes CuH-1(HL)(+), CuH-2(HL)(2), Cu2H-2(HL)(2)(2+) and CuH-2(HL). The minor species, CU2H-2(HL)(2)(+) and CuH-2(HL), amount to at least 20% of the total copper. Elaboration of the data according to the Specific Interaction Theory yields the constants valid in the infinite dilution reference state: HL reversible arrow L- + H+ log (degrees)beta(011) = -8.27 +/- 0.03 Cu2+ + HL reversible arrow CuH-1(HL)(+) + H+ log (degrees)beta(111) =-3.06 +/- 0.05 Cu2+ + 2 HL reversible arrow CuH-2 (HL)(2) + 2 H+ log (degrees)beta(122) = -7.72 +/- 0.05 2Cu(2+) + 2HL reversible arrow Cu2H-2(HL)(2)(2+) + 2H(+) log (degrees)beta(222) = -5.5 +/- 0.1 Cu2+ + HL reversible arrow CuH-2(HL) + 2 H+ log (degrees)beta(121) = -10.9 +/- 0.1 and the interaction coefficients (kg/mol) of complex species with medium ions: b(L-,Na+) = 0.11 +/- 0.03; b(CuH-1(HL)(+),NaClO4) = 0.17 +/- 0.05; b(CuH-2(HL)(2),NaCLO4) = 0.11 +/- 0.05; b(Cu2H-2)(HL)(2)(2+),NaClO4) = 0.2(7) +/- 0-1; b(CuH-2(HL),NaClO4) = - 0-0(3) +/- 0-1.