AM1 and single-crystal X-ray diffraction study of the conformational properties of chlorinated diphenyl ethers

Abstract

Structural and conformational properties of 11 polychlorinated diphenyl ethers (PCDEs)1–11 and thyroxine derivative 12 were studied by the semiempirical AM1 method. In addition, the molecular structures of six PCDEs 1-6 were solved by X-ray crystallography. Conformational analyses for diphenyl ethers 1–12 were performed and the resulting conformational energy maps obtained. The calculated energy minima of PCDEs were obtained, and the structural parameters were compared with the X-ray structures. The X-ray-determined geometries were found to be inside the low-energy regions close to the global energy minima except for compound 2, whose X-ray structure deviates considerably from the global minima. The X-ray structures of PCDE were non-planar, with dihedral angles between two benzene rings ranging from 59.0° to 99.7°.