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Bare versus Protected Tetrairidium Clusters by Density Functional Theory


The tetrairidium (Ir4) clusters are subnanometric systems vastly applied in catalysis, specially, because of the higher activity than mononuclear Ir complexes, intrinsic and controllable stability in relation to the supports, and non-coalescence properties. The main catalytic properties of nanoclusters (activity and selectivity) are directly associated with their size, shape, and interactions with the environment, whose understanding requires a study at the atomistic level. Here, the Ir4 clusters are studied considering the energetic stability for different chemical environments, bare versus protected, using the density functional theory calculations within the generalized gradient approximation with the van der Waals corrections and the spin-orbit coupling, employing the all-electron projected augmented wave method. The square planar isomer is confirmed for bare case as the lowest energy configuration considering semilocal and non-local exchange-correlation functionals, however, for different chemical environments (Ir4 protected by CO, O2, PH3, and SH2 ligands) the energy stability scenario is different, for CO, O2, and PH3 ligands the tetrahedron is the most stable isomer, in agreement with experimental insights, while for SH2 ligands the square motif is the most stable isomer. To improve the understanding of these systems, structural and electronic analysis were performed, in addition to the energy decomposition analysis, to explore the bonding situation at Ir4 compounds. Our results showed an important relationship between the geometrical behavior and the nature and magnitude of Ir2 · · · Ir2 interactions, showing how the chemical environment affects the Ir4 nanoclusters. In general, the compounds with tetrahedron motifs showed a weakening of the σ and π bonds in relation to the square ones.

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Publication details

The article was received on 17 Aug 2018, accepted on 07 Nov 2018 and first published on 07 Nov 2018

Article type: Paper
DOI: 10.1039/C8CP05263H
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Bare versus Protected Tetrairidium Clusters by Density Functional Theory

    M. J. Piotrowski, G. R. Nagurniak, E. H. D. Silva and R. L. T. Parreira, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP05263H

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