Schmitt Marcel J P, Kruppa Sebastian V, Walg Simon P, Thiel Werner R, Klopper Wim, Riehn Christoph
Department of Chemistry, Rheinland-Pfälzische Technische Universität (RPTU) Kaiserslautern-Landau, Erwin-Schrödinger Str. 53, 67663 Kaiserslautern, Germany.
Institute of Physical Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany.
Phys Chem Chem Phys. 2023 Aug 9;25(31):20880-20891. doi: 10.1039/d3cp03058j.
Binuclear coinage metal phosphine complexes are examined under ion trap isolation in order to elucidate their noncovalent binding, structural properties and intrinsic electronic spectra. Our survey shows an intriguing order of electronic transitions obtained by synthesis and mass-spectrometrically supported UV photodissociation spectroscopy on a series of six isolated homo- and heterobinuclear complexes of type [MM'(dcpm)] (M, M' = Cu, Ag, Au; dcpm = bis(dicyclohexyl-phosphino)methane). This approach provides the unique opportunity to study all possible coinage metal interactions within a fixed ligand framework. A successive blue-shift (33 700-38 500 cm; 297-260 nm) of the lowest-energy bright electronic transition energy in gas phase was observed in the order of Cu < CuAu < CuAg < Au < AgAu < Ag. This order was reproduced by quantum chemical calculations using a scalar-relativistic GW-Bethe-Salpeter-equation (-BSE) approach. Theory ascribes the electronic bands of all complexes to metal-centered MC(dσ*-pσ) transitions revealing a strengthening of metal-metal' (M-M') binding upon excitation, in agreement to mass spetrometric results. A test of the correlation of transition energies with M-M' distance by quantum chemical calculations of single point energies as a function of intermetallic distance indicates qualitative agreement with experimental results. However, the experimentally observed high sensitivity of spectroscopic shifts towards metal composition cannot be accounted for solely by M-M' distance variation. The differences in electronic transitions are qualitatively rationalized by the varying ( + 1)s ( = 3, 4, 5) orbital contributions (increase from Cu CuAu/CuAg to Au/AgAu/Ag) within the nd( + 1)s/p-hybridization for the ground electronic state of the different complexes, whereas the excited state (of ( + 1)p orbital character) shows significantly less variation in energy. In particular, the observed spectroscopic and mass spectrometric sequence for the Ag/Au complexes is traced back to the interplay of Pauli repulsion and variation in metal-ligand bond strength within the orbital hybridization model.
对双核硬币金属膦配合物进行离子阱分离研究，以阐明其非共价键合、结构性质和固有电子光谱。我们的研究表明，通过合成和质谱支持的紫外光解离光谱法，对一系列六种[MM'(dcpm)]型（M、M' = Cu、Ag、Au；dcpm = 双（二环己基膦基）甲烷）的同核和异核双核配合物进行研究，得到了有趣的电子跃迁顺序。这种方法提供了一个独特的机会，来研究固定配体框架内所有可能的硬币金属相互作用。在气相中，观察到最低能量的明亮电子跃迁能量依次为Cu < CuAu < CuAg < Au < AgAu < Ag，出现连续蓝移（33700 - 38500 cm⁻¹；297 - 260 nm）。使用标量相对论GW - 贝塞耳 - 萨尔彼得方程（-BSE）方法进行的量子化学计算重现了这一顺序。理论将所有配合物的电子能带归因于以金属为中心的MC(dσ* - pσ)跃迁，表明激发时金属 - 金属'（M - M'）键合增强，这与质谱结果一致。通过将单点能量作为金属间距离的函数进行量子化学计算，测试跃迁能量与M - M'距离的相关性，结果表明与实验结果定性一致。然而，实验观察到的光谱位移对金属组成的高敏感性不能仅由M - M'距离变化来解释。不同配合物基态的nd( + 1)s/p杂化中，( + 1)s（ = 3、4、5）轨道贡献不同（从Cu到CuAu/CuAg再到Au/AgAu/Ag增加），这在定性上解释了电子跃迁的差异，而激发态（具有( + 1)p轨道特征）的能量变化明显较小。特别是，观察到的Ag/Au配合物的光谱和质谱顺序可追溯到轨道杂化模型中泡利排斥和金属 - 配体键强变化的相互作用。
