HIGHLY SUBSTITUTED CYCLAMS - STEREOSELECTIVE SYNTHESIS AND COORDINATION PROPERTIES

We report here a new synthetic route to highly-substituted tetraazamac rocycles. Raney nickel hydrogenation of macrocyclic phenylenediamine-a cetylacetone condensation products gives cyclams in high yield with co mplete all-cis stereo-selectivity. The extensive C-substitution of the cyclam 2a changes its ligand properties markedly. The X-ray structure analyses of Ni-II, CUII, and Zn-II complexes of 2a reveal a deviation of the metal ion coordination geometry from the usual square-planar a rrangement. This may account for the differences in the redox properti es of the Ni-II and Cu-II complexes of 2a compared to 3. The highly-su bstituted structure of the ligand 2a leads to more positive oxidation and reduction potentials compared to the analogous unsubstituted cycla m complexes. While the binding constant between Zn(ClO4)(2) and 2a is lower by a factor of 10(5) compared to cyclam, the subsequent binding of uridine to the zinc-cyclam complexes in methanol/water is slightly stronger in the case of 2a zn(ClO4)(2).