Non‐covalent Interactions and Charge Transfer between Propene and Neutral Yttrium‐Doped and Pure Gold Clusters

Abstract

The dopant and size‐dependent propene adsorption on neutral gold (Aun) and yttrium‐doped gold (Aun−1Y) clusters in the n=5–15 size range are investigated, combining mass spectrometry and gas phase reactions in a low‐pressure collision cell and density functional theory calculations. The adsorption energies, extracted from the experimental data using an RRKM analysis, show a similar size dependence as the quantum chemical results and are in the range of ≈0.6–1.2 eV. Yttrium doping significantly alters the propene adsorption energies for n=5, 12 and 13. Chemical bonding and energy decomposition analysis showed that there is no covalent bond between the cluster and propene, and that charge transfer and other non‐covalent interactions are dominant. The natural charges, Wiberg bond indices, and the importance of charge transfer all support an electron donation/back‐donation mechanism for the adsorption. Yttrium plays a significant role not only in the propene binding energy, but also in the chemical bonding in the cluster‐propene adduct. Propene preferentially binds to yttrium in small clusters (n<10), and to a gold atom at larger sizes. Besides charge transfer, relaxation also plays an important role, illustrating the non‐local effect of the yttrium dopant. It is shown that the frontier molecular orbitals of the clusters determine the chemical bonding, in line with the molecular‐like electronic structure of metal clusters.

Observation of the Reaction Intermediates of Methanol Dehydrogenation by Cationic Vanadium Clusters

“…Thec hemical bonding was studied based on the energy decomposition and charge transfer analysis (EDA) and interpreted based on the complementary occupied virtual orbitals, [25] which we have recently employed to reveal the gold cluster-propene interactions. [26] Thec alculations show V 7 + to be ad istorted pentagonal bipyramid with one vanadium atom of the pentagon being outside the plane of the other four, consistent with aprevious infrared spectroscopic study, [20] and as imilar structure was computationally predicted for Co 7…”

“…All computations were performed using Q‐Chem 5.3 [23] and Gaussian 16 [24] program packages. The chemical bonding was studied based on the energy decomposition and charge transfer analysis (EDA) and interpreted based on the complementary occupied virtual orbitals, [25] which we have recently employed to reveal the gold cluster‐propene interactions [26] …”

The effect of size, charge state and composition on the binding of propene to yttrium-doped gold clusters

“…44 We reoptimized structures determined in previous publications for neutral and cationic pure gold clusters. [44][45][46][47][48] While the structures of small neutral yttrium doped gold clusters 33,34,36,38 were reported earlier, little information is available about the structure of their cationic states; 35 therefore, we computed the geometric structures of the low-energy cationic isomers using the Particle Swarm Optimization algorithm of CALYPSO [49][50][51] and investigated the growth patterns using the capping method. 52 The obtained low-energy structures were re-optimized using the higher LRC-uPBE/def2-TZVP level of theory 53,54 including the Exchange Dipole Model (XDM) dispersion correction.…”

“…Only for n ¼ 6 and 11, the neutral and cationic clusters have the same geometric structures. Propene binds to the gold atom with the lowest coordination number in Au n + , where one of the low-lying unoccupied orbitals of the bare cluster has a large lobe 27,38 (see orbitals in ESI †). In the case of n ¼ 5, 8, 9 and 13, several energetically low-lying isomers of cationic gold cluster propene adducts were found (geometries are available in the ESI †).…”

“…This is remarkable, as our study on neutral Au nÀ1 Y pointed out that donation from propene to the unoccupied d atomic orbitals of yttrium is an important stabilizing factor. 38 It is known that metal clusters can activate and even break C-H bonds. 8,78,79 We computed the dissociation reaction paths (Fig.…”