Pascher Tobias F, Ončák Milan, van der Linde Christian, Beyer Martin K
Institut für Ionen und Angewandte Physik, Universität Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
J Chem Phys. 2020 Nov 14;153(18):184301. doi: 10.1063/5.0030034.
We investigate the structure of copper formate and deuterated copper formate clusters using infrared multiple photon dissociation in combination with quantum chemical calculations. Symmetric and asymmetric C-O stretching vibrations along with C-H/C-D stretching vibrations were characterized. Fermi interactions between the C-H stretch and likely a C-O combination band and/or the overtone of a C-H in-plane bending motion have been confirmed by deuteration. The spectra reveal a strong dependence on the monodentate or bidentate binding motif of the formate ligands. Many minima are energetically accessible on the potential energy surface through rotation of the monodentate formate ligands into several almost isoenergetic local minima. While the C-H/C-D stretching vibration is heavily influenced by the charge distribution in the cluster, the C-O vibrations are largely unaffected. The C-H stretch region is not very diagnostic due to a variety of possible Fermi resonances, which also depend on the charge distribution at the formate ligand. Deuteration yields unperturbed spectra in the C-D stretch region and reveals characteristic shifts of the C-D stretching mode for the different binding motifs, with a strong dependence of the band position on the oxidation state of the copper center. The observed bands are compared with formate adsorbed on copper surfaces from the literature.
我们结合量子化学计算，利用红外多光子解离研究了甲酸铜和氘代甲酸铜团簇的结构。对对称和不对称的C-O伸缩振动以及C-H/C-D伸缩振动进行了表征。通过氘代证实了C-H伸缩与可能的C-O组合带和/或C-H面内弯曲运动的泛音之间的费米相互作用。光谱显示出对甲酸根配体的单齿或双齿结合模式有强烈依赖性。通过将单齿甲酸根配体旋转到几个几乎等能量的局部极小值，在势能面上有许多能量上可及的极小值。虽然C-H/C-D伸缩振动受团簇中电荷分布的影响很大，但C-O振动基本不受影响。由于存在各种可能的费米共振，C-H伸缩区域的诊断性不强，这些共振也取决于甲酸根配体上的电荷分布。氘代在C-D伸缩区域产生未受扰动的光谱，并揭示了不同结合模式下C-D伸缩模式的特征性位移，其谱带位置强烈依赖于铜中心的氧化态。将观察到的谱带与文献中吸附在铜表面的甲酸进行了比较。
