The Influence of Steric Effect, Alkyl Chain Length, and Donor Number of Solvents on the Extraction of Copper(II) Complexes with 1-Alkyl-4-Methylimidazoles

Abstract

The formation of Cu(II) complexes with 1-alkyl-4-methylimidazoles (where alkyl = butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl) has been studied by using the liquid-liquid partition method at 25°C and a fixed ionic strength of the aqueous phase (I = 0.5; (HL)NO₃, KNO₃). 2-Ethylhexanol, dichloromethane, chloroform, p-xylene, and toluene were used as a solvent. Stability constants, β_n, of the complexes in aqueous solution were determined as well as their partition ratios between the organic and aqueous phase. Under the influence of the steric effect, the methyl group in position 4 as well as the length of the alkyl group in position 1 of the ligands and electron-donating properties of solvents, both the polyhedral structure and the co-ordination numbers of the Cu(II) complexes are changed, thus resulting in an increase in the solvent/water partition ratios, P_n, of the complexes and lowering of the pH_1/2 of the extraction.

Keywords:

• Cu(II) complexes
• 1-alkyl-4-methylimidazoles
• stability constants
• partition ratios
• steric effect