Synthesis and structural studies of 5,12-dioxocyclams capped by 4-substituted pyridines across the amine nitrogens.

A series of 4-substituted pyridine-capped 5,12-dioxocyclams was synthesized and fully characterized. The 4-substituent varied from electron-withdrawing groups (NO2, NO, CN) to electron-donating groups (NHCbz, NH2). The most versatile substituent was the 4-bromo group, which could be replaced by a variety of groups using Stille, Sonogashira, or Buchwald-Hartig palladium-catalyzed chemistry. Copper complexes of a majority of these capped dioxocyclams were synthesized and characterized as well.