Some ternary phenylmethoxybis(tetrazolium) complexes of vanadium(IV,V) and their constants of association

Abstract

Several liquid-liquid extraction systems containing vanadium {vanadium(IV) or vanadium(V)}, azoderivative of resorcinol {ADR: 4-(2-pyridylazo)-resorcinol (PAR) or 4-(2-thiazolylazo)-resorcinol (TAR)} and (phenylmethoxibis)tetrazolium salts {MBT: 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)-bis(2,5- diphenyl-2H- tetrazolium) chloride (Blue Tetrazolium, BT) or 3,3'-(3,3'-dimetoxy-4,4'- biphenylene)- bis[2,5-di(4-nitrophenyl)-2H-tetrazolium] chloride (Tetranitroblue Tetrazolium, TNBT)} were studied. The optimum operating conditions and compositions of the extracted species were found. The constants of association (β) between MBT 2+ and the anionic V-ADR chelates (Chel n-) were calculated. Previously reported negative linear relationship between log β and the number of nitro groups included in tetrazolium cation (N nitro) was discussed taking into account the obtained results and literature data for V-ADR-MBT complexes of the same class, in which MBT is BT or 3,3'-(3,3'-dimetoxy-4,4'-biphenylene)bis[2-(4- nitrophenyl)-5- phenyl-2H-tetrazolium] chloride (Nitroblue Tetrazolium, NBT).