Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, New York 13244-4100, USA.
J Phys Chem A. 2011 Sep 1;115(34):9467-78. doi: 10.1021/jp111878h. Epub 2011 Mar 29.
Cocrystallized adenine and thymine derivatives, along with the pure monomeric crystals, were investigated by terahertz spectroscopy and solid-state density functional theory (DFT). The methylated nucleobase derivatives crystallize in planar hydrogen-bonded adenine-thymine pairs similar to the manner found in DNA. The spectra obtained for 1-methylthymine, 9-methyladenine, and the 1:1 cocrystal in the range of 10-100 cm(-1) clearly demonstrate that absorptions in this spectral range originate from the uniquely ordered assembly and the intermolecular interactions found in each individual crystal system. The quality of spectral reproduction for the DFT simulations of each system was clearly improved by the inclusion of an empirical correction term for London-type dispersion forces to the calculations. Notably, it was found that these weak dispersion forces in the adenine-thymine cocrystal were necessary to produce a properly converged crystal structure and meaningful simulation of the terahertz vibrational spectrum.
采用太赫兹光谱和固态密度泛函理论（DFT）研究了共结晶的腺嘌呤和胸腺嘧啶衍生物以及纯单体晶体。甲基化碱基衍生物以类似于 DNA 中发现的方式在平面氢键结合的腺嘌呤-胸腺嘧啶对中结晶。在 10-100 cm(-1) 范围内获得的 1-甲基胸腺嘧啶、9-甲基腺嘌呤和 1:1 共晶的光谱清楚地表明，该光谱范围内的吸收源自每个单独晶体系统中独特有序组装和分子间相互作用。通过在计算中包含伦敦型色散力的经验校正项，每个系统的 DFT 模拟的光谱再现质量明显提高。值得注意的是，发现腺嘌呤-胸腺嘧啶共晶中的这些弱色散力对于产生适当收敛的晶体结构和太赫兹振动光谱的有意义的模拟是必要的。
