Synthesis and stereochemistry of long-chain quinoxaline metallocyclophanes

Condensation of 1,2-diamino-4,5-bis(n-alkoxy)arenes with an oligopyridyl-type alpha-diketone afforded a series of long-chain pyridine-quinoxaline hybrids. These were evaluated for their ability to self-assemble with tetrahedral Cu(I) and Ag(I) to form dimeric, double-decker amphiphillic complexes having a flattened metallocyclophane topology. Detailed NOESY and T-1 relaxation time experimentation showed that the configuration of the dicoppper (I) complexes corresponds to inversion (meso) symmetry, which leads to an extended molecular shape, wherein the alkoxy chains of the individual ligand components lie on opposite sides of the metallocyclophane core, as opposed to the same side. Preliminary measurements show that the disilver(I) complexes having (C12H25)-C-n and (C18H37)-C-n chains exhibit reversible melting processes and undergo two endothermic transitions each, at 189/237 and 59/80 degrees C, respectively.