Thermodynamic study of the interaction between some recently synthesized benzo-substituted macrocyclic diamides with some pyridinium ion derivatives in acetonitrile solution

The formation of pyridinium, 2-methyl pyridinium, 2,4-dimethyl pyridinium and 2,4,6-trimethyl pyridinium complexes with the some recently synthesized benzo-substituted macrocyclic diamides was investigated conductometrically in acetonitrile solution at various temperatures. The formation constants of the resulting 1:1 complexes were determined from the computer fitting of the molar conductance-mole ratio data. In all cases studied, the stability of complexes decreases in the order Py(+) > 2m-Py(+) > 2,4dim-Py(+) > 2,4,6trim-Py(+). The enthalpy and entropy of complexation reaction were determined from the temperature dependence of the formation constants. In all cases, the complexes were enthalpy stabilized but entropy destabilized.