AMPHIPHILIC COPPER(II) COMPLEXES MODELED AFTER THE METAL-COMPLEXATIONSUBUNIT OF BLEOMYCIN ANTIBIOTICS

A series of lipophilic ligands, structurally related to Bleomycins (BL Ms) metal-binding subunit, have been synthesized. They comprise a 4-al koxypyridine substituted in the 2- and B-positions with methylhistamin e or methylethylenediamine moieties. With respect to native BLMs, pyri dine replaces the pyrimidine ring and the amide function in one of the two sidearms has been reduced to amine. Long hydrocarbon chains in th e alkoxy moiety provide lipophilicity. Hydrophilic ligands were also s ynthesized to get insight on the effect of micellization upon protonat ion and complex formation. All ligands form 1:1 complexes with Cu-II i ons, and those of the lipophilic ligands form micellar aggregates (met allomicelles) with critical micelle concentrations (cmc) in the 9 x 10 (-5)-1.4 x 10(-4) M concentration interval. Micellization affects acid /base and coordination equilibria as well, as suggested by titration, H-1 NMR, and UV-vis spectroscopic investigations, but does not affect the geometry of coordination. The information obtained indicates that, upon micellization, the amines become less basic although the differe nce in basicity between aggregate and nonaggregate systems tends to di sappear with the proceeding of the protonation. Micellization affects the pH at which the complexes switch from tetra-to pentacoordinate: th is explains the pH and aggregation-dependence of the redox potential o f the Cu-II/Cu-I couple we have previously reported (Langmuir 1996, 12 , 5188) for these systems.