Solvent influence on complex formation between Cd2+ and 2-hydroxy-1,4-naphthoquinone in binary mixed nonaqueous solvents at 15–45°C

Abstract

The complexation reaction of Cd²⁺ cation with 2-hydroxy-1,4-naphthoquinone (HNQ) was studied in acetonitrile (AN), 2-PrOH, ethyl acetate (EtOAc), EtOH, dimethylformamide (DMF) and in binary solutions AN–2-PrOH, AN–DMF, AN–EtOH, and AN–EtOAc using conductometric method at 15–45°C. The conductance data show that the stoichiometry of the Cd²⁺ complex with HNQ in all solvent systems is 1 : 1. In the pure solvents the stability of the complex changes in the order AN > 2-PrOH > EtOH > DMF. The stability of the complex at 25°C in the studied mixtures changes in the following order : AN−EtOAc > AN−2-PrOH > AN−EtOH > AN−DMF. These orders are affected by the nature and composition of the solvent systems and by the temperature. From the temperature dependence data, the thermodynamic functions values (ΔH° and ΔS°) for the complex formation were calculated.