二甲基亚砜溶剂中All-trans-astaxanthin的拉曼和红外光谱

Raman and Infrared Spectra for All-trans-astaxanthin in Dimethyl Sulfoxide Solvent

基于实验和理论研究了二甲基亚砜溶剂（DMSO）中all—trans—astaxanthin（AXT）的拉曼和红外光谱．拉曼光谱的密度泛函理论预示了AXT的u1带分离为v1—1和v1—2两个成分．拉曼实验光谱中光谱带分离的缺失归因于AxT主链上两个对称C=C伸展振动之间的竞争．v1带对激发波长非常敏感，即共振激发激励较高频v1-2振动模，非共振动激发导致较低频v1—1振动模．AXT／DMSO体系中C=O和NO-H之间分子内氢键的分析揭示了：激发态相对基态而言，C4=O1…H1-O3之间的氢键加强，而C4’=O2…H2-O4之间的氢键减弱．研究结果表明了AXT在不同电子态分子结构的明显变化．

The Raman and infrared spectra of all-trans-astaxanthin （AXT） in dimethyl sulfoxide （DMSO） solvent were investigated experimentally and theoretically. Density functional cal-culations of the Raman spectra predict the splitting of the υ1 band into υ1-1 and υ1-2 compo-nents. The absence of splitting in Raman experimental spectra is ascribed to the competition between the two symmetric C=C stretching vibrations of the backbone chain. The υ1 band is very sensitive to the excitation wavelength： resonance excitation stimulates the higher-frequency υ1-2 mode, and off-resonance excitation corresponds to the lower-frequency υ1-1 mode. Analyses of the intramolecular hydrogen bonding between C=O and O-H in the AXT/DMSO system reveal that the C4=O1...H1-O3 and C4＇=O2...H2-O4 bonds are strengthened and weakened, respectively, in the electronically excited state compared with those in the ground state. This result reveals significant variations of the AXT molecular structure in different electronic states.