Density Functional Theory and Single Crystal X-ray Studies on Some Bis-Chalcone Derivatives

The three  bis-chalcone compounds, ( 2E,6E )-2,6-bis(3-chlorobenzylidene)cyclohexanone (1), ( 2E,6E )-2,6-bis(2,3-dichlorobenzylidene)cyclohexanone (2) and ( 2E,5E )-2,5-bis(2,6-dichloro benzylidene) cyclopentanone (3), were studied with theoretical and single-crystal X-ray diffraction (XRD) methods. The molecular geometric parameters, frontier molecular orbitals, MEP, normal mode frequencies and the corresponding vibrational assignments, gauge-including atomic orbital (GIAO) 1 H-NMR, 13 C-NMR chemical shift values of the bis-chalcone compounds in the ground state have been calculated using the density functional  (B3LYP) methods with 6-311G (d,p) basis set. These molecules demonstrate apparently a long and flat shape. Each molecule adopt an ( E) configuration about the central olefinic bonds. The most important feature is stacking mode in the molecules. The calculated results reveal that the optimized geometries can well reproduce the crystal structure. The theoretical vibrational frequencies and 1 H-NMR and 13 C-NMR chemical shift values show good agreement with the experimental data.