SPECIFIC SEQUESTERING AGENTS FOR THE ACTINIDES .29. STABILITY OF THE THORIUM(IV) COMPLEXES OF DESFERRIOXAMINE B (DFO) AND 3 OCTADENTATE CATECHOLATE OR HYDROXYPYRIDINONATE DFO DERIVATIVES - DFOMTA, DFOCAMC, ANDDFO-1,2-HOPO - COMPARATIVE STABILITY OF THE PLUTONIUM(IV) DFOMTA COMPLEX

The metal complex stability constants of Th(TV) with desferrioxamine B (DFO) and three octadentate derivatives [N-(2,3-dihydroxy-4-carboxybe nzoyl)desferrioxamine B (DFOCAMC), hydroxy-2-oxopyridin-6-yl)carbonyl) desferrioxamine B (DFO-1,2-HOPO) and 3-dihydroxy-4-(methylamido)benzoy l)desferrioxamine B (DFOMTA)] have been determined. The formation cons tant of the Pu(IV)/DFOMTA complex has also been determined, and the fo rmation constants have been estimated for the other Pu(IV) complexes o f octadentate DFO derivatives. The DFO derivatives form 1:1 complexes with Th(IV) in aqueous solution. The solution chemistry of the Th(IV) complexes has been studied by spectrophotometric, potentiometric and p roton NMR titrations. The Th(IV) formation constants are as follows (l og K-f values and esd's): DFO, 26.6(1); DFOMTA, 38.55(5); DFOCAMC, 37. 2(3); DFO-1,2-HOPO, 33.7(4). The Pu(IV)/DFOMTA formation constant, det ermined by competitive spectrophotometric titration is (log K-f value) 41.7(2). The estimation of the other Pu(IV) formation constants are a s follows (log K-f values): DFOCAMC, 40.4; DFO-1,2-HOPO, 36.9. The sel ectivity of DFO and the three derivatives for actinide(IV) ions is dis cussed.