THERMODYNAMIC STABILITIES OF NI(II), CU(II), CO(II), FE(III), AND U(II) COMPLEXES OF THE OXIMATED DERIVATIVE OF P-TERT-BUTYLCALIX[6]ARENE

The stability constant (log K) of Ni(II), Cu(II), Co(II), Fe(III) and U(II) complexes with the oximated derivative of p-tert-butylcalix[6]ar ene were determined at different ionic strengths (0.012, 0.023 and 0.0 32 M) and at different temperatures (20 degrees, 24 degrees, 28 degree s and 32 degrees C). For each metal-ligand system at each temperature, thermodynamic stability constant, log K degrees, was obtained graphic ally at zero ionic strength from the plot of log K vs ionic strength. The older of thermodynamic stability of the complexes is as follows: U (II)>Fe(III)>Ni(II)>Cu(II)>Co(II). The stability constants were found to be proportional with the ionic strength and inversely proportional to temperature. Thermodynamic parameters such as Delta H degrees, Delt a S degrees were derived from the plot of log K degrees vs T-1 and Del ta G was calculated for each temperature. Based on the negative values of Delta G and Delta H degrees suggest that the metal-ligand interact ion is exothermic.