Faculty of Life Sciences, University of Copenhagen, Rolighedsvej 23, DK-1958 Frederiksberg C, Denmark.
J Phys Chem B. 2011 Oct 6;115(39):11470-80. doi: 10.1021/jp203910h. Epub 2011 Sep 8.
Structural analysis of plant materials, i.e., lignin, cellulose, hemicellulose, etc., supports the growing interest of their uses, e.g., as sources for biofuels or materials. Lignin is a main polymer formed from three phenolic presursors, containing none, one, or two OMe groups, i.e., H, G, and S units, respectively. Raman spectroscopy gives valuable knowledge on lignin and has a large potential for further developments. Thus in the present work we show how the use of electronic structure theory can support the study of environmental effects on lignin Raman bands. Raman spectra of the lignin model monomer, vanillyl alcohol (G type), dissolved in different solvents were compared to investigate such effects on the Raman band shapes and positions. Density functional theory combined with the polarizable continuum model were applied to assign the observed bands and tested for prediction accuracy. Two ring deformation modes at ∼1600 cm(-1) showed strong dependency on solvent ability to act as hydrogen bond donor, and this has to be considered in addition to substitutional effects on these modes.
植物材料（如木质素、纤维素、半纤维素等）的结构分析支持了其用途的不断增长的兴趣，例如作为生物燃料或材料的来源。木质素是由三种酚类前体形成的主要聚合物，分别含有一个、两个或没有甲氧基（即 H、G 和 S 单元）。拉曼光谱法为木质素提供了有价值的知识，并且具有进一步发展的巨大潜力。因此，在本工作中，我们展示了如何使用电子结构理论来支持对木质素拉曼带环境效应的研究。比较了溶解在不同溶剂中的木质素模型单体香草醇（G 型）的拉曼光谱，以研究这些溶剂对拉曼带形状和位置的影响。应用密度泛函理论结合极化连续体模型对观察到的带进行了归属，并对预测精度进行了测试。两个约 1600 cm(-1) 的环变形模式强烈依赖于溶剂作为氢键供体的能力，除了对这些模式的取代效应外，还必须考虑到这一点。
