Ternary complexes of niobium(V) with nitroderivatives of catechol and tetrazolium salts. Extraction-spectro-photometric investigations

Abstract

Te formation and solvent extraction of new ion-association complexes between an-ionic chelates of niobium(V) with nitroderivatives of catechol {NDC: 3,5-dinitrocatechol (3,5-DNC) and 4-nitrocatechol (4-NC)} and tetrazolium cations {2,3,5-triphenyl-2H-tet-razolium (TT +) and 3,3'-[3,3'-dimetoxy(1,1'-biphenyl)-4,4'-diyl]-bis[2,5-diphenyl-2H-tetrazolium] (Blue Tetrazolium, BT 2+)} were studied. Niobium(V) forms two complexes with 4-NC and BT 2+ and one complex with 3,5-DNC and TT + with suggested formulae (BT 2+) [NbO(OH)(4-NC) 2] (I), (BT 2+) 3[NbO(4-NC) 3] 2 ( II), and (TT +) 2[NbO(OH)(3,5-DNC) 2] (III). Te optimum conditions for the extraction of II and III (organic solvent, extraction time, acidity of the aqueous phase, concentration of reagents), some key constants {association constant (β), constant of distribution (K D), extraction constant (K ex)} and analytical characteristics were determined. Te molar absorptivities of II and III were calculated to be ε' 415 = 4.6 × 10 4 L mol -1 cm -1 and ε' 400 = 2.5 × 10 4 L mol -1 cm -1, respectively. Beer's law was obeyed for Nb(V) concentrations ranging from 0.42 to 1.6 μg/mL (II) and 0.51 to 2.3 μg/mL (III). © 2012 Lietuvos mokslu̧ akademija.