A study of complexation Kryptofix 5 with La3+ cation in several individual and binary non-aqueous solvents using a conductometric method

Complexation of the La3+ cation with 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix5) was studied in pure solvents acetonitrile (AN), methanol (MeOH), nitrobenzene (NB), tetrahydrofuran (THF), Methyl acetate (MeOAC) and in various binary solvent mixtures of AN-MeOH, AN-NB, AN-THF and AN-MeOAC systems at different temperatures using the conductometric method [1]. The stoichiometry of the complex was found to be 1:1 (ML). In all cases, the variation of the log kf with composition of the solvent was non-linear. This bahaviour is probably due to a change in the structure of these binary mixed solvents as the compostion of the medium is varied [2-4].The stability order of the complex in pure non-aqueous solvents at 25°C increases in the order: AN THF MeOAC MeOH NB. The values of thermodynamic data (〖∆H〗_c^°,〖∆S〗_c^°) formation of (Kryptofix5.La)3+ complex are definitely solvent dependent.