From the theoretical point of view, by considering the position of double bond (C2=C3) with respect to the plane of the hetrocyclic ring and with respect to ph groups, two isomer can be drawn for benzo[f]chromenes. The calculated total electronic energies, the relative stabilities isomers and the conformers calculated at difference levels. The isomer E2 at all levels calculated has been between 4- 5kcal/mol more stable isomer E1. The fully optimized geometrical parameters and the averaged geometrical parameters of isomers E1 and E2 for 1,3-diarylbenzo[ f]chromenes shows that isomer E2 is more stable from isomer E1. These factors appropriate conditions to establish resonance between hetrocyclic ring and phenyl group. Furthermore NMR analyses were performed for two isomer at B3lyp/6-311G** level of theory and compared with the experimental findings.

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