Raman optical activity (ROA) spectroscopy exhibits significant potential in the study of (bio)molecules as it encodes information on their molecular structure, chirality, and conformations. Furthermore, the method reveals details on excited electronic states when applied under resonance conditions. Here, we present a combined study of the far from resonance (FFR)-ROA and resonance ROA (RROA) of a single relatively small molecular system. Notably, this study is the first to employ the density functional theory (DFT) analysis of both FFR-ROA and RROA spectra. This is illustrated for cobalamin derivatives using near-infrared and visible light excitation. Although the commonly observed monosignate RROA spectra lose additional information visible in bisignate nonresonance ROA spectra, the RROA technique acts as a complement to nonresonance ROA spectroscopy. In particular, the combination of these methods integrated with DFT calculations can reveal a complete spectral picture of the structural and conformational differences between tested compounds.

中文翻译：

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为什么要测量共振拉曼光学活性？强谐振与远非谐振条件下测量的独特案例

拉曼旋光 (ROA) 光谱在（生物）分子研究中表现出巨大的潜力，因为它编码有关分子结构、手性和构象的信息。此外，该方法揭示了在共振条件下应用时激发电子态的细节。在这里，我们对单个相对较小的分子系统的远距离共振（FFR）-ROA和共振ROA（RROA）进行了综合研究。值得注意的是，这项研究首次采用密度泛函理论 (DFT) 分析 FFR-ROA 和 RROA 光谱。使用近红外和可见光激发的钴胺素衍生物说明了这一点。尽管常见的单信号 RROA 光谱丢失了双信号非共振 ROA 光谱中可见的附加信息，但 RROA 技术可作为非共振 ROA 光谱的补充。特别是，这些方法与 DFT 计算的结合可以揭示测试化合物之间结构和构象差异的完整光谱图。