Ten geometries of iodosylbenzene oligomer HO-(PhIO)n-H (n＝1～10) model compounds were investigated by LDA-PWC method. The calculated geometries show that the PhIO unit in iodosylbenzene oligomer has a T-shaped structure, and both I—O bond lengths of I—O chain are nearly equal. Due to the torsion of I—O chain, iodosylbenzene oligomer exhibits a helical geometry. To obtain a more accurate and steady geometry, the structure of HO-(PhIO)6-H was also investigated by B3LYP calculations. Results show that the I—O bond mean length is 0.2089 nm with only 0.0007 nm standard deviation. IR spectral calculation results show that the vibrational frequencies between 600～400 cm－1 will shift to lower frequencies upon the 18O substitution, which is in accordance with the experimental observation. Vibrational mode analysis indicates that these bands are related to oxygen atom vibrations. The observed 18O sensitive IR bands of 591/566 cm－1 and 443/436 cm－1 (16O/18O) correspond to the calculated bands of 590.409/557.788 cm－1 and 460.627/439.158 cm－1 (16O/18O) respectively, and the former was ascribed to the symmetric stretching mode ν(I—O—I) of iodosylbenzene oligomer, and the latter to the absymmetric stretching mode ν(I—O—I).

Key words: iodosylbenzene oligomer, molecular geometry, vibrational spectrum, theoretical calculation