Eastwood Jonathan B, Procacci Barbara, Gurung Sabina, Lynam Jason M, Hunt Neil T
Department of Chemistry, University of York, York YO10 5DD, U.K.
Department of Chemistry and York Biomedical Research Institute, University of York, York YO10 5DD, U.K.
ACS Phys Chem Au. 2024 Jul 9;4(5):536-545. doi: 10.1021/acsphyschemau.4c00037. eCollection 2024 Sep 25.
The solution phase structure, vibrational spectroscopy, and ultrafast relaxation dynamics of the precatalyst species [Mn(ppy)(CO)] () in solution have been investigated using ultrafast two-dimensional infrared (2D-IR) spectroscopy. By comparing 2D-IR data with the results of anharmonic density functional theory (DFT) calculations, we establish an excellent agreement between measured and predicted inter-mode couplings of the carbonyl stretching vibrational modes of that relates to the atomic displacements of axial and equatorial ligands in the modes and the nature of the molecular orbitals involved in M-CO bonding. Measurements of IR pump-probe spectra and 2D-IR spectra as a function of waiting time reveal the presence of ultrafast (few ps) intramolecular vibrational energy redistribution between carbonyl stretching modes prior to vibrational relaxation. The vibrational relaxation times of the CO-stretching modes of are found to be relatively solvent-insensitive, suggestive of limited solvent-solute interactions in the ground electronic state. Overall, these data provide a detailed picture of the complex potential energy surface, bonding and vibrational dynamics of , establishing a fundamental basis for the next steps in understanding and modulating precatalyst behavior.
利用超快二维红外（2D - IR）光谱研究了预催化剂物种[Mn(ppy)(CO)]（）在溶液中的溶液相结构、振动光谱和超快弛豫动力学。通过将2D - IR数据与非谐密度泛函理论（DFT）计算结果进行比较，我们在测得的和预测的羰基伸缩振动模式的模间耦合之间建立了良好的一致性，该耦合与模式中轴向和赤道配体的原子位移以及参与M - CO键合的分子轨道的性质有关。作为等待时间函数的红外泵浦 - 探测光谱和2D - IR光谱的测量揭示了在振动弛豫之前羰基伸缩模式之间存在超快（几皮秒）的分子内振动能量重新分布。发现的CO伸缩模式的振动弛豫时间对溶剂相对不敏感，这表明在基态电子态中溶剂 - 溶质相互作用有限。总体而言，这些数据提供了的复杂势能面、键合和振动动力学的详细图景，为理解和调节预催化剂行为的下一步奠定了基础。
