Thermodynamic Studies of Co(II) Complexation with Schiff Base Ligands in Different Nonaqueous Solvents

Authors : Khaled Muftah Elsherif, Abdulfattah Mohamed Alkherraz, Hana Shawish, Salima Abajja, Awatif Al-arbash
Pages : 71-78
Doi:10.51435/turkjac.1606841
View : 48 | Download : 104
Publication Date : 2025-05-31
Article Type : Research Paper
Abstract :This study investigates the synthesis and characterization of two novel Schiff base ligands, L1 and L2, and their complexation behavior with Co(II) ions in non-aqueous media. Ligand L1 was synthesized using o-hydroxyacetophenone and salicylaldehyde with ethylenediamine, while L2 was prepared with 2,3-dihydroxybenzaldehyde and ethylenediamine. Conductometric measurements in ethanol, acetonitrile, and a 1:1 mixture of these solvents at temperatures ranging from 25°C to 40°C determined the stability constants of the Co(II) complexes. Results showed distinct temperature-dependent stability trends: L1 complexes decreased in stability with increasing temperature in all solvents, indicating exothermic reactions, while L2 complexes showed varied behavior, suggesting endothermic reactions in acetonitrile and the mixed solvent. The solvent environment significantly influenced complex stability, with acetonitrile showing the highest stability, followed by the 1:1 solvent mixture and ethanol. L2 exhibited higher stability constants than L1, attributed to additional hydroxyl groups in L2 enhancing Lewis basicity, while the methyl group in L1 caused steric hindrance, reducing stability. Thermodynamic analysis revealed negative ΔG° values (-27.9 to -32.1 kJ/mol) for all reactions, indicating spontaneity. Enthalpy changes (ΔH°) varied, with negative values (-27.6 to -195 kJ/mol) for exothermic and positive values (7.37 and 42.3 kJ/mol) for endothermic reactions. Entropy changes (ΔS°) varied, reflecting differences in molecular organization and solvent-ligand interactions. This study provides insights into factors affecting metal-ligand complexation in non-aqueous environments, with implications for designing coordination compounds for various applications in chemistry
Keywords : İletkenlik Ölçümü, Schiff Bazları, Kobalt Kompleksleri, Kararlılık Sabitleri, Susuz Çözücüler, Termodinamik Parametreler

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