Complex Formation in a Liquid-Liquid Extraction System Containing Vanadium(IV/V), 2,3-Dihydroxynaphtahlene and Thiazolyl Blue

Abstract

Liquid-liquid extraction systems for VIV/V containing 2,3-dihydroxynaphtahlene (DN) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (thiazolyl blue, MTT) were studied. The optimum conditions for VIV and VV extraction were found. VIV is extracted in chloroform as a 1:2:2 complex (V:DN:MTT) with lmax = 570 nm and e570 = 2.9´104 dm3 mol–1 cm–1. However, this wavelength was found unsuitable for precise spectrophotometric measurements due to time dependent absorbance changes. VV forms predominantly a 1:1:1 complex with lmax = 335 nm. The calibration graph for this oxidation state is linear in the range of 0.06–1.5 mg cm–3. The molar absorptivity, Sandell’s sensitivity and limit of detection were calculated to be 1.6 ´ 104 dm3 mol–1 cm–1, 3.2 ng cm–2 and 0.02 mg cm–3, respectively. The ground-state equilibrium geometries of the anionic parts of the extracted ion-associates, [VIVO(DN2-)2]2-and [VVO2(DN2-)]-, were optimized at the BLYP/6-31++G* level of theory.

Keywords

• vanadium(IV/V)
• 2,3-dihydroxynaphtahlene
• ternary complex
• liquid-liquid extraction
• spectrophotometry
• DFT calculations