ION-TRANSFER CURRENT-SCAN POLAROGRAPHIC STUDIES OF METAL EXTRACTANTS WITH ASCENDING WATER ELECTRODE - MANGANESE(II)-1,10-PHENANTHROLINE AND RELATED LIGAND SYSTEMS

The mechanism of transfer of Mn2+ ion from an aqueous to a dichloroethane (DCE) solution of a phenanthroline derivative (Phen); 1,10-phenanthroline (phen), 4,7-dimethyl-1,10-phenanthroline (4,7-DMP), 4,7-diphenyl-1,10-phenanthroline (4,7-DPP) and 2,9-dimethyl-1,10-phenanthroline (2,9-DMP), was investigated by current scan polarography with the ascending water electrode. The transfer process involves (a) diffusion of Phen to the aqueous/DCE interface, (b) formation of 1:1 Mn2+-Phen complex, whose kinetics are sufficiently slow to influence but not entirely control the polarographic process, (c) transfer of the 1:1 complex from the aqueous into the DCE phase and (d) further reaction of this complex with two additional Phen molecules at the interfacial area in DCE phase. The apparent reaction rates of step (b) were determined in the dimension of the ordinary electrode reaction rate; 8.2 x 10(-2), 5.5 x 10(-2) and 9.3 x 10(-3) dm M-1 s-1 for phen, 4,7-DMP and 4,7-DPP, respectively. The rate for Mn2+-2,9-DMP complex was too slow to be determined.