Solution Equilibria of Ni(II), Cu(II), and Zn(II) Complexes Involving Pyridoxine and Imidazole Containing Ligands: pH Metric, Spectral, Electrochemical, and Biological Studies

Abstract

Solution equilibria and relevant stability constants for M(II)-pyridoxine (PN)(A) [M(II) = Cu(II), Ni(II), and Zn(II)], and M(II)-PN(A)-imidazole containing ligands (B) [B = imidazole (him), benzimidazole (bim), histamine (hist), and l-histidine (his)] in aqueous solution have been determined by a pH metric method at 310 K and I = 0.15 M NaClO4. The complexation model for each system has been established by the MINIQUAD-75 program. The probable binding mode in the binary and ternary species was discussed based upon the derived stability constants. The concentration distributions of various species formed in solution were evaluated. The stability of ternary complexes follows the Irving–Williams order of metal ions, which was quantitatively (Δ log K, log X, and % RS) compared with their corresponding binary complexes. In terms of the ligands (B), the stability of the complexes follows him > bim > hist > his. The molecular geometry of the complexes formed in solution between the ligands and M(II) was determi...