Novel triiodide ion-selective polymeric membrane electrodes based on some transition metal–Schiff base complexes

We studied Mn(II) and copper(II) complexes of Schiff bases (with different spacers between the two nitrogens in bis-N,O-bidentate Schiff base) as ionophores in polymeric membranes of anion selective electrodes. The potentiometric selectivity of the ion selective electrodes (ISEs) based on metalloSchiff bases was significantly dependent on both the nature of the central atom and the spacer between two nitrogens in imine groups. The electrode based on a N,N′-1,2-propylene-bis-(5-methyl salicylidene iminato) copper(II) complex, A1, exhibited a near Nernstian response of 61.4 mV decade−1 to I3− ions over the activity range 4.0 × 10−5 to 0.7 × 10−1 mol l−1 with a limit of detection 1.0 × 10−5 mol l−1. The response time of the electrode was short (<15 s) and the membrane could be used for 2 months without any significant divergence in response. The potentiometric selectivity coefficients were evaluated and displayed the anti-Hofmeister behavior. The electrode based on A1 revealed comparatively good selectivity with respect to lipophilic anions such as, iodide (I−), thiocyanate (SCN−) and perchlorate (ClO4−) was used as an indicator electrode in direct and indirect potentiometric titration in real samples.