Characterization of an unusual specific interaction between aromatic cyclic cis-vicinal triketones and cyclic saturated ethers

The nature of an unusual specific interaction between aromatic cyclic cis-v icinal triketone (I, II, III in Fig. 1) and cyclic saturated ethers (tetrah ydrofuran and 2-methyl tetrahydrofuran) in the ground state has been explor ed using detailed AM1 calculation. The experimental values of DeltaH for su ch interaction, determined by the temperature variations of the lowest (1)( n pi*) transition of the triketo compounds match well with the calculated v alues of DeltaH. The solvent shift observed for (1)(n pi*) transition of I, II, III in cyclic saturated ethers compared with that in a non-interacting solvent like dichloromethane supports our theoretical prediction. The poss ibility of such specific interaction in the lowest (1)(n pi*) state of I, I I and III has been discussed. (C) 2001 Elsevier Science B.V. All rights res erved.