Molecular complexing ability of quinoline and its simple derivatives

Electron donor-acceptor complexes for a group of quinolines and naphthalenes with 9-(dicyanomethylene)-2,4,7-trinitrofluorene in 1,2-dichloroethane were studied by optical absorption methods. Association constants, molar absorptivities, and charge-transfer transition energies were evaluated for each system, together with theoretically calcualted orbital energies and complex geometries. In contrast to the association constants and structures reported for N-heterocycle-halogen complexes, these studies indicate that, with a moderately large pi-electron acceptor, quinolines function as pi-rather then n-(lone-pair) donors. These results support intercalation models for drug-receptor interactions involving the quinoline moiety.