Synthesis and Equilibrium Studies of Mixed‐Ligand Complexes of Co(II), Ni(II), and Cu(II) with Some Aliphatic Dicarboxylic Acids and Creatinine

Abstract

Ternary mixed‐ligand metal complexes [M(L¹)(L²)₂](H₂O) _n , where M = Co(II), Ni(II), or Cu(II), L¹ = the dianion of succinic, malic, or tartaric acid, and L² = creatinine, were synthesized and characterized using microchemical and thermal analyses, molar conductance, infrared, and electronic spectral measurements. A square–planar structure is suggested for the Co(II) and Cu(II) ternary complexes, whereas Ni(II) ternary complexes have tetrahedral stereochemistry. Formation constants of the binary and ternary complexes in such systems were determined by pH‐metric titrations at 25 ± 0.1 °C and at a constant ionic strength I = 0.1 M (KNO₃). The stability of the various complexes was discussed in terms of the nature of both the ligands and metal ions. The thermodynamic functions (ΔH, ΔG ^o, and ΔS ^o) associated with the complex formation of [Cu(II) + aliphatic acids + creatinine] were also determined and examined.

Keywords:

• Mixed‐ligand complex
• Creatinine
• Aliphatic acids
• Complex formation