Lead(II) complexes with some SNO and ONO tridentate Schiff base ligands and their evaluation as lead(II) sensors

New Pb(II) complexes of the general formula PbL2 where HL = 2-acetylthiophene benzoylhydrazone, 2-acetylfuran benzoylhydrazone, 2-carboxaldehydethiophene benzoylhydrazone and 2-carboxaldehydefuran benzoylhydrazone were synthesized by reaction of lead(II) acetate with the ligands in methanol in lead to ligand ratio of 1: 2. The complexes are insoluble in common organic solvents but soluble in DMF and DMSO. The measured molar conductance values in DMF indicate that, the complexes are non-electrolytes in nature. In view of analytical and spectral (IR, UV–vis and NMR) studies, it has been concluded that, all the metal complexes possess octahedral geometry in which the ligand is coordinated to lead(II) through azomethine nitrogen, benzoyl oxygen and thiophene sulfur or furan oxygen atom via deprotonation. These complexes were tested as ionophores for lead(II) determination. Pb(ATBH)2 gave the best response with two plasticizers Doph and DOS were fully characterized. Their detection limit were 3.9 × 10− 7 mol L− 1, 7.9 × 10− 7 mol L− 1, concentration range 5.9 × 10− 7 ــ1.0 × 10− 2 mol L− 1, 9.1 × 10− 7–1.0 × 10− 2 mol L− 1 response time ~ 8–10 sec and pH range 6.2–7.8. The proposed sensors show a reasonable discrimination ability towards Pb(II) in comparison to some alkali, alkaline earth, transition heavy metal ions. The modified electrodes were applied as an indicator electrode and successfully used to determine Pb(II) in synthesized polluted water samples giving satisfactory results.

► Preparation and characterization of lead complexes of some SNO and NNO tridentate ligands.
► New chemically modified carbon paste electrodes (CMCPEs) for lead(II) were designed.
► Lead complexes were used as sensing material in preparation of lead-CMCPEs.
► Modifies carbon paste electrodes are unique in surface renewal and ease of use.
► These electrodes are useful in determination of lead(II) in polluted water samples.