A Thermodynamic Study of Complex Formation between 18-Crown-6 with T1~+,Hg~2+ and Ag~+ Meta Cations in Some Binary Mixed Non-aqueous Solvents Using the Conductometric Method

摘要

The complexation reactions between T1~+,Hg~2+ and Ag`+ metal cations with 18-Crown-6(18C6) were studied in acetonitrile(AN)-methanol(MeOH_) and bezonitrile(BN)-methanol(MeOH)binary mixtures at different temperatures using the conductometric method.The conductance data show that the stoichiometry of the complexes in most cases is 1:1(ML),but in the case of the T1~+ cation,in addition to a 1:1 complex,a 1:2(ML_2) complex is formed in solutions.a non-linear behaviour wasobserved for the variation of logK_f of the complexesvs the composition of the binary mixed solvents.the stability of 18C6 complexes with T1~+,Hg~2+ and Ag~+ cations is sensitive to solvent ocmposition and in some cases,the stability order is changed iwth chaning the composition of the mixed solvents.The values o fthe thermodynamic parameters (DELTAYH~deg_c,DELTAS~deg_c) for formation of 18C6-T1~+,18C6-Hg~+2 and the 18C6-Ag~+ complexeswere obtained from the temperture dependence of the stability constants and the results show that the thermodynamics of the complexation reactions is affected by the nature and composition of the mixed solvents and in most cases,the complexesare enthalpy destabilized but entropy stabilized.