3.9 Article

Stability constants and thermodynamic behaviour of the complex formation of two crown ethers with zinc (II) and copper (II) ions in water plus acetonitrile mixed solvent: a conductivity measurement study

Journal

PHYSICS AND CHEMISTRY OF LIQUIDS
Volume 60, Issue 2, Pages 297-311

Publisher

TAYLOR & FRANCIS LTD
DOI: 10.1080/00319104.2021.1972105

Keywords

18-crown-6; 24-crown-8; conductometry; complex formation; mixed solvents; thermodynamic parameters

Funding

  1. King Saud University, Riyadh, Saudi Arabia [RSP-2021/360]

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The molar conductivity of mixtures of crown ethers and metal ions in a binary solvent system was investigated using conductometric technique. The K-f values of the complexes decreased with temperature increase, showing different stability trends for Zn2+ and Cu2+ complexes. The negative value of ΔG(o) indicated spontaneous complexation between the crown ethers and metal ions.
We have investigated the behaviour of change of molar conductivity of mixtures of two crown ethers (CE) (18-Crown-6; 18C6 and 24-Crown-8; 24C8) and metal ions (Mn+) (Zn2+ and Cu2+) and the complexation between CE and Mn+ in water + acetonitrile binary solvent system (20, 40, 60 and 80%; v/v) at 298.15 K to 328.15 K by conductometric technique. K-f values for all complexes were found to be decreased with enhancement of temperature. Complexes associated with Zn2+ exhibit a trend of K-f: 24C8 + Zn2+ > 18C6 + Zn2+ in 20% solvent composition (water-acetonitrile) and order of 18C6 + Zn2+ > 24C8 + Zn2+ was found for 80% solvent composition. However, logarithm values of K-f for the Cu2+ complexes were found to obey the order of 24C8 > 18C6 almost for all compositions except with a few exceptions. Delta G(o) was found to be negative indicating spontaneous complexation between CE and Mn+.

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