A dispersive QCL-VCD spectrometer for studies on asymmetric catalyst

用于研究不对称催化剂的色散QCL-VCD光谱仪

• 批准号: 389178573
• 负责人: Professor Dr. Christian Merten
• 金额: --
• 依托单位: Organische Chemie II - Physikalisch-Organische Chemie (AG Sander)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/389178573?language=en
• 关键词: dispersive; QCL; VCD; spectrometer; studies

In various studies, we showed that vibrational circular dichroism (VCD) spectroscopy, the chiroptical version of infrared spectroscopy, can give insights into the conformational preferences of asymmetric catalysts and catalyst-substrate complexes. As VCD spectroscopy records the differential absorbance of left- and right-circularly polarized light, spectral regions showing total absorbance cannot be characterized. Such total absorbance occurs regularly, for instance when excess substrate must be added in order to form the catalyst-substrate (small binding constants) or when a highly absorbing solvent must be used. Therefore, our initial studies were limited to isolable stable species, e.g. hydrogen bonded clusters with large binding constants or intermediates generated in situ in high yields. In this project we propose the implementation of a dispersive VCD spectrometer that takes advantage of a quantum cascade laser (QCL) as bright light source. With this instrument, the limitations of total absorbance can be overcome to a large degree. Equipped with a widely tunable QCL, the dispersive QCL-VCD instrument will allow us to characterize asymmetric catalysts at more realistic catalyst-substrate ratios (allowing studies on systems with small binding constants) and in a wider range of solvents (toluene, Et2O, even water becomes possible). The bright QCL-VCD is expected to enable measurements with higher signal-to-noise than FT-VCD, thereby allowing much faster measurements. Reaction monitoring will become possible, so that specialized spectra analysis methods will give access to the VCD spectral signatures of intermediates, that exist only in small yields in complex reactions mixtures.

在各种研究中，我们证明了振动圆二色谱(VCD)，红外光谱的手性版本，可以深入了解不对称催化剂和催化剂-底物络合物的构象择优。由于VCD光谱记录了左、右圆偏振光的不同吸光度，因此无法表征显示总吸光度的光谱区域。例如，当必须添加过量底物以形成催化剂-底物(小结合常数)或必须使用高吸收溶剂时，这样的总吸光度经常发生。因此，我们最初的研究仅限于可分离的稳定物种，例如具有大结合常数的氢键团簇或高产率原位生成的中间体。在这个项目中，我们提出了一种利用量子级联激光器(QCL)作为明亮光源的色散VCD光谱仪的实现。使用该仪器，可以在很大程度上克服总吸光度的局限性。配备了可广泛调节的QCL，分散的QCL-VCD仪器将使我们能够在更真实的催化剂-底物比(允许研究结合常数较小的体系)和更广泛的溶剂(甲苯、Et2O，甚至可能是水)中表征不对称催化剂。明亮的QCL-VCD有望实现比FT-VCD更高的信噪比测量，从而实现更快的测量。反应监测将成为可能，因此专门的光谱分析方法将使人们能够获得中间体的VCD光谱特征，这些特征仅存在于复杂反应混合物中的小产率。