Selective Catalytic Activation of Acetylene by a Neutral Gold Cluster of Experimentally Known Gas-Phase Geometry

Abstract

The electronic and structural details for the acetylene selective catalytic activation by one of the few small gold clusters whose experimental gas-phase initial geometry in neutral charge state is known, the gold heptamer, are investigated. Doing an exhaustive search of the acetylene−gold heptamer ZORA scalar relativistic PW91/TZ2P configurational space, we determine the main, secondary, and also the unimportant structures relative to the catalytic activation. We found that the leading mechanism of activation consists in the tendency to the disappearance of one of the acetylene π bonds at the expense of the formation of C−Au strong interactions, by the predominant dative interaction of s/d-like gold heptamer molecular orbitals toward a π* orbital of acetylene. This results in adducts having very diminished energy barriers toward processes such as, for example, the selective hydrogenation reaction to ethylene. This activation would occur with a considerable change of the participant species geometries and, with the formation of a frontier single occupied molecular orbital, very localized at carbon atoms region.

Activation and diffusion of ammonia borane hydrogen on gold tetramers

“…These effects are much better considered by the ZORA scalar relativistic method, used in the gradient‐based optimization stage. Our previous studies about the C 2 H 2 Au 7 system yielded excellent results with this combination of computational levels of theory, which were in agreement with several experimental evidences about the systems Au 7 and C 2 H 2 …”

“…We have found that stochastic‐based search of suitable candidate structures for the mutual AB and Au 4 spatial disposition, and their subsequent gradient‐based optimizations, has proven to be a very successful combination of methodologies. Among stochastic‐based methods, ASCEC has demonstrated to be very effective, both for atomic and molecular clusters of diverse nature . ASCEC is a simulated annealing algorithm in which the Metropolis criterion has been modified in such a way that it is possible to ensure exhaustive scans, moving down from high energy areas to areas of the lowest possible energies for the studied adducts.…”

“…In fact, since the discovery of catalytic properties of gold in the form of nanoparticles and small clusters, this noble metal has been one of the most studied as a catalyst. One very interesting property of gold clusters is the structural fluxionality, namely, the interconversion among cluster structures, which, remarkably, can also influence catalytic processes . Gold fluxionality is due to the habitual existence of large amount of structures very close in energy to the global minimum.…”

Reactions involving some gas molecules through sequestration on Al12Be cluster: An electron density based study

“…For the decomposition of CH 3 F/C 2 H 5 F/NH 3 /NO molecules on Al 12 Be, corresponding direct pathways have been considered. For the case of C 2 H 2 hydrogenation reaction, we have explored reaction pathways similar to the one described by Hadad and coworkers . NBO analysis has been carried out to gauge the change in atomic charges on various gas molecules on getting adsorbed on the cluster.…”

“…Therefore, it has been suggested that hydrogenation of C 2 H 2 could be an important step toward the goal of removing C 2 H 2 from the reaction cycle. To this end, Au‐based clusters can achieve this target quite successfully . In this work, we would like to explore whether Al 12 Be can act as a suitable reaction platform for all the aforementioned processes.…”