A conductometric study on the effect of solvent upon complex formation between kryptofix22dd with Ho3+ metal cation in organic solvents
The complexation reaction between Ho3+ cation with macrocyclic ligand kryptofix22DD was studied in ethyl acetate (EtOAC), methanol (MeOH), propylene carbonate (PC), tetrahydrofuran (THF) at different temperatures by coductometric method. Kryptofix22DD forms a 1:1 complex with Ho3+ cation. The stability of (kryptofix22DD.Ho)3+ complex changes with the type of the organic solvents and also with temperature. The stability constant of the complex in the non-aqueous solvents varies in order: EtOAC ≥ THF > PC ≥ MeOH. By plotting the van’t Hoff diagrams, the values of standard thermodynamic parameters such as enthalpy (∆H°c), entropy (∆S°c) and Gibbs free energy (ΔG°C), for formation of (kryptofix22DD.Ho)3+ complex were obtained. The results showed that the entropy and enthalpy of complexation reaction between kryptofix22DD with Ho3+ metal cation depend on the nature of the solvents.
KEY WORDS: Kryptofix22DD, Ho3+ cation, Organic solvents, Complexation, Conductometry
Bull. Chem. Soc. Ethiop. 2019, 33(2), 277-284.