Complexation equilibrium between iron ( III ) and N , N ’ - bis ( 2 - hydroxyphenylmethyl ) - N , N ’ - bis ( 2 - pyridylmethyl ) - 1 , 2 - ethanediamine

Complexation equilibrium between iron(III) and N,N’-bis(2-hydroxyphenylmethyl)-N,N’-bis(2-pyridylmethyl)-1,2ethanediamine (H2bbpen), a colorless hydrophobic divalent hexadentate ligand, and potential use of the ligand for the spectrophotometric determination of iron(III) in aqueous solution was investigated. In the pH range 2.0 − 3.0, Fe(III) forms stable 1:1 complex with H2bbpen, and Fe(III) can be determined selectively as the purple Fe(bbpen)+ complex (λmax = 560 nm, ε = 4.3 × 103 dm3 mol−1 cm−1, log β1 = 32.6 ± 0.1). In this system, linear calibration range of Fe(III) was 5 × 10−6 − 2 × 10−4 mol dm–3 (0.3 − 12 μg cm−3) and detection limit was 3 × 10−6 mol dm−3 (0.2 μg cm−3). Furthermore, most of foreign metal cations did not influence largely the determination of Fe(III).