KINETICS AND MECHANISM OF FORMATION AND DECOMPOSITION OF COPPER(II) COMPLEXES WITH A BINUCLEATING HEXAAZAMACROCYCLE

The kinetics of formation and decomposition of mono- and binuclear cop per(II) complexes of the macrocycle 15)]triaconta-1(29),11(30),12,14,2 5(26),27-hexaene (L) has been studied at 25 degrees C and 1.0 M ionic strength under a variety of conditions. All reactions occur in the sto pped-flow time-scale and results indicate that upon addition of a larg e excess of H+ binuclear complexes convert rapidly into mononuclear sp ecies in which some nitrogens of the ligand are uncoordinated. The kin etics of decomposition of the resulting mononuclear species is interme diate between that of complexes with linear polyamines and those with mononucleating macrocycles. On the other hand, the formation of Cu-II complexes at high concentrations of OH- occurs essentially through rea ction of Cu(OH)(3)(-) with the unprotonated form of the ligand, at a r ate similar to that observed for reactions with simpler ligands. Coord ination of the second Cu-II is very rapid under these conditions. Copy right (C) 1996 Elsevier Science