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

ABSTRACT

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. $\mathrm{\Delta }{G}^o$ was found to be negative indicating spontaneous complexation between CE and Mⁿ⁺.

KEYWORDS:

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

Acknowledgements

Authors are grateful to the Researchers Supporting Project Number (RSP-2021/360), King Saud University, Riyadh, Saudi Arabia.

Disclosure statement

No potential conflict of interest was reported by the author(s).

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Funding

Authors are grateful to the Researchers Supporting Project Number (RSP-2021/360), King Saud University, Riyadh, Saudi Arabia.