Organopalladium(II) Complexes as Ionophores for Thiocyanate Ion-Selective Electrodes
نویسندگان
چکیده
A thiocyanate poly(vinyl chloride) (PVC) membrane electrode based on [1,2-bis(diphenylphosphino)ethane]dihalopalladium(II), [(dppe)PdX2, X = Cl (L), X = I (L)] as active sensor has been developed. The diiodopalladium complex, [(dppe)PdI2](L) displays an anti-Hofmeister selectivity sequence: SCN‒ > I‒ > ClO4‒ > Sal‒ > Br‒ > NO2‒ > HPO4‒ > AcO‒ > NO3‒ > H2PO4‒ > CO32‒. The electrode exhibits a Nernstian response (-59.8 mV/decade) over a wide linear concentration range of thiocyanate (1.0 × 10 to 5.0 × 10 M), low detection limit (1.1 × 10 M), fast response (t90% = 24 s), and applicability over a wide pH range (3.5∼11). Addition of anionic sites, potassium tetrakis[p-chlorophenyl]borate (KTpClPB) is shown to improve potentiometric anion selectivity, suggesting that the palladium complex may operate as a partially charged carrier-type ionophore within the polymer membrane phase. The reaction mechanism is discussed with respect to UV-Vis and IR spectroscopy. Application of the electrode to the potentiometric titration of thiocyanate ion with silver nitrate is reported.
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