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化学学报
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化学学报 ›› 2009, Vol. 67 ›› Issue (4): 295-299. 上一篇    下一篇

研究论文

亚碘酰苯低聚物的结构与振动光谱18O-同位素效应的理论研究

徐志广*,a 刘海洋*,b

  

  1. (a华南师范大学化学与环境学院 广州 510006)
    (b华南理工大学化学系 广州 510641)

  • 投稿日期:2008-04-16 修回日期:2008-08-27 发布日期:2009-02-28
  • 通讯作者: 徐志广

Theoretical Study on Structure and 18O Isotope Effect on Vibrational Spectra of Iodosylbenzene Oligomer

Xu, Zhiguang *,a Liu, Haiyang *,b   

  1. (a School of Chemistry and Environment, South China Normal University, Guangzhou 510006)
    (b Department of Chemistry, South China University of Technology, Guangzhou 510641)
  • Received:2008-04-16 Revised:2008-08-27 Published:2009-02-28
  • Contact: Xu, Zhiguang

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应用LDA-PWC方法对亚碘酰苯低聚物HO-(PhIO)n-H (n＝1～10)(链末端以羟基结束)共10个模型分子进行了理论研究. 计算结果表明PhIO分子链大致呈“T”形, I—O链的两个I—O键键长非常接近, 同时发现I—O链产生扭转, 整个亚碘酰苯低聚物呈螺旋状结构. 应用B3LYP法得到HO-(PhIO)6-H更为精确的亚碘酰苯低聚物稳定构型, 平均I—O键长为0.2089 nm, 标准偏差为0.0007 nm. 理论计算表明在600～400 cm－1段, PhI18O的吸收峰向低波数方向移动, 与实验观测结果一致. 振动模式分析发现该段吸收峰均涉及氧原子, 18O同位素效应将降低各振动峰值的频率. 峰值移动最大的吸收峰为591/566 cm－1 (16O/18O), 与之对应的理论计算值为590.409/557.788 cm－1 (16O/18O), 属于对称伸缩振动ν(I—O—I). 吸收峰(443/436 cm－1)对应的理论计算值为460.627/439.158 cm－1 (16O/18O), 归属于不对称伸缩振动ν(I—O—I).

关键词: 亚碘酰苯低聚物, 分子构型, 振动光谱, 理论计算

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