STABILITY-CONSTANTS OF IMIDAZOLE-COPPER(II) AND ALKYLIMIDAZOLE-COPPER(II) COMPLEXES

The stability constants of imidazole (HIm)- and alkylimidazoles-copper(II) acetate complexes were calculated from the potentiometric titration data with the aid of the SUPERQUAD computer program. The stability constants of ionic species of [CuAl(r)]+ type (A: CH3COO, L: HIm a, 1-CH3.Im b, 2-CH3.HIm c, 4-CH3.HIm d, 2-C2H5.HIm e, 2-(CH3)2CH.HIm f, r = 1, 2, 3, and 4) detected from the complexes were ascertained to be decreased in the order of b(1-substituted) greater-than-or-equal-to d(4-substituted) > c(2-substituted) relating to the position of methyl group bonded to the imidazole ring, and c(2-CH3) > e(2-C2H5) > f(2-(CH3)2CH) relating to the kinds of alkyl group substituted on 2-position, respectively. The stability of these ionic species was discussed from the neutralization effect of the charge and the steric effect of alkyl group or acetate ion. The stability constants of the hydroxo species of [CuL2(OH)2] type indicated the extremely small values, and its order did not indicate a similar tendency with those of ionic species of [CuAl(r)]+ types. The distribution of these complex species was investigated as a function of pH.