DFT Studies of Solvation Effects on the Nanosize Bare, Thiolated, and Redox Active Ligated Au₅₅ Cluster

Abstract

The structural and electronic properties of the bare Au 55 cluster, and of the model thiol passivated Au 55 (SCH 3 ) 42 , the redox active ligated Au 55 S(CH 2 ) 2 CO 2 (CH 2 ) 10 bpy • 2Cl and Au 55 (SCH 3 ) 41 (S(CH 2 ) 2 CO 2 (CH 2 ) 10 bpy) • 2Cl (bpy ) N-methyl-4,4′-bipyridinium) complexes are studied at the DFT level in the gas phase and with an explicit water layer. For all complexes, neutral, positive, and negative charge states are investigated. The thiol ligation distorts the outer layer of the approximate icosahedral geometry of the bare cluster and induces a charge transfer from the gold core to the ligand shell. The anchoring of a single redox active ligand on the bare Au 55 leads to the formation of a cavity around the S-Au bond. We show that this cavity formation is prevented by the thiol ligands in Au 55 (SCH 3 ) 41 (S(CH 2 ) 2 CO 2 (CH 2 ) 10 bpy) • 2Cl. The vertical addition of one electron to the [Au 55 S(CH 2 ) 2 CO 2 (CH 2 ) 10 bpy • 2Cl] 0 cluster is followed by a charge transfer from the Au 55 core to the bpy 2+ ligand, which is accompanied by a mechanical motion of the redox active bpy arm driven by electrostatic interactions. The presence of a solvent shell does not alter the structure but significantly decreases the computed charging energies of the clusters, making them comparable with experimental values. The computed redox potential differences are in good agreement with the experimental values. † Part of the special issue "Protected Metallic Clusters, Quantum Wells and Metallic Nanocrystal Molecules".

Tuning the electronic and optical properties of graphene and boron-nitride quantum dots by molecular charge-transfer interactions: a theoretical study

“…Also, as it is known that the chemical reactivity of a molecule is dependent on the H-L gap in an inverse manner, if the gap is larger, lower would be the reactivity. 42 As is well known, chemically reactive systems would transfer charges more, and we find that our results on charge-transfer also reflect the same -the higher the H-L gap, the stronger would be the chemical reactivity leading to the larger chargetransfer. In fact, it can be qualitatively seen by comparing the columns 3/4 and 5 of Table 2.…”

“…Finally, it is known that the chemical reactivity of a molecule is dependent on the H-L gap in an inverse manner-that is, higher the gap, lower the reactivity. 41 Assuming that the charge-transfer will occur only when a system is chemically reactive, we find that our results on charge-transfer also reflects the same -larger the H-L gap, greater the chargetransfer (please compare columns 2/3 and 4 of table 3) -though, not quantitatively. find that the spin-polarized H-L gap of TCNQ-GQD complex has an origin in the spinpolarized charge-transfer from GQD to TCNQ.…”

Probing structural relaxation in nanosized catalysts by combining EXAFS and reverse Monte Carlo methods

“…Parameter FEFFIT H [12] FEFFIT QH [12] Since in this particular case EXAFS spectrum alone does not contain sufficient information, one can use the findings from other methods to distinguish between the two possible geometries. In particular, as was mentioned before, both DFT simulations [12] and our modelling using Sutton-Chen potential suggest that icosahedral geometry is more likely for Au147 (and smaller [59]) gold nanoparticles. Therefore, to conclude our discussion on the structure of Au147 nanoparticles, in Table 4 we list the values of structure parameters, obtained from our RMC/EA simulations for Au147 nanoparticles with icosahedral ge-ometry.…”

MALDI Mass Analysis of 11 kDa Gold Clusters Protected by Octadecanethiolate Ligands

“…In our previous study, we speculated that 32 thiolates are bound to the facet of the Au 55 core having an icosahedral or cuboctahedral motif, similar to the case of Au 55 (PR 3 ) 12 Cl 6 , which has a cuboctahedral Au 55 core . A recent computational study performed at the density functional theory (DFT) level on Au 55 (SCH 3 ) 32 revealed that this cluster has a local minimum structure in which a deformed icosahedral Au 55 core is coordinated with 32 RS ligands via Au−SR single bonds . However, with the Au core−RS shell structure model, we cannot explain why Au 54 (SC 18 H 37 ) 30 and Au 55 (SC 18 H 37 ) 31 prefer the Au 54 core and 31 thiolate ligands, respectively.…”