Molecular complex formation between bridgehead amines and quinones

Abstract

Formation of 1 : 1 complexes occurs between the bridgehead amines triethylenediamine, quinuclidine, and quinuclidin-3-ol and 1,4-quinones. Values of the equilibrium constant (Kc₁), molar absorptivity (ε₁), standard enthalpy, and entropy changes were obtained from optical data for the stronger complexes whilst only the product Kc₁ε₁ could be determined for the weaker complexes. Formation of 2 : 1 complexes was observed for solutions containing chloranil and an excess of triethylenediamine. CNDO/2 calculations show that complex formation should occur at four equivalent positions corresponding to the mid-point between C(1) and C(2). The non-bridgehead amines piperidine and triethylamine do not form complexes in solution under the same conditions.