University of Innsbruck, Institute of Analytical Chemistry and Radiochemistry, Innrain 80-82, 6020 Innsbruck, Austria.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Oct 15;279:121438. doi: 10.1016/j.saa.2022.121438. Epub 2022 May 28.
Quantum mechanical calculations are routinely used as a major support in mid-infrared (MIR) and Raman spectroscopy. In contrast, practical limitations for long time formed a barrier to developing a similar synergy between near-infrared (NIR) spectroscopy and computational chemistry. Recent advances in theoretical methods suitable for calculation of NIR spectra opened the pathway to modeling NIR spectra of various molecules. Accurate theoretical reproduction of NIR spectra of molecules reaching the size of long-chain fatty acids was accomplished so far. In silico NIR spectroscopy, where the spectra are calculated ab initio, provides substantial improvement in our understanding of the overtones and combination bands that overlap in staggering numbers and create complex lineshape typical for NIR spectra. This improves the comprehension of the spectral information enabling access to rich and detail molecular footprint, essential for fundamental research and useful in routine analysis by NIR spectroscopy and chemometrics. This review article summarizes the most recent accomplishments in the emerging field with examples of simulated NIR spectra of molecules reaching long-chain fatty acids and polymers. In addition to detailed NIR band assignments and new physical insights, simulated spectra enable innovative support in applications. Understanding of the difference in the performance observed between miniaturized NIR spectrometers and chemical interpretation of the chemometric models are noteworthy here. These new elements integrated into NIR spectroscopy framework enable a knowledge-based design of the analysis with comprehension of the processed chemical information.
量子力学计算通常被用作中红外（MIR）和拉曼光谱的主要支持。相比之下，实际应用的局限性长期以来一直阻碍着近红外（NIR）光谱学和计算化学之间类似协同作用的发展。最近，适合计算近红外光谱的理论方法的进步为各种分子的近红外光谱建模开辟了道路。迄今为止，已经成功实现了达到长链脂肪酸大小的分子的近红外光谱的准确理论再现。基于从头算的计算近红外光谱法在我们对重叠数量惊人的泛音和组合带的理解上提供了实质性的改进，这些泛音和组合带产生了近红外光谱特有的复杂谱线形状。这提高了对光谱信息的理解，使我们能够获取丰富而详细的分子特征，这对于基础研究至关重要，并且在通过近红外光谱和化学计量学进行常规分析时也非常有用。本文总结了这一新兴领域的最新成就，展示了达到长链脂肪酸和聚合物大小的分子的模拟近红外光谱示例。除了详细的近红外带分配和新的物理见解外，模拟光谱还为应用提供了创新性的支持。值得注意的是，这里还包括对小型化近红外光谱仪之间观察到的性能差异的理解以及对化学计量模型的化学解释。这些新元素集成到近红外光谱框架中，使我们能够基于知识设计分析，并理解处理后的化学信息。
