Interconversion between Superatomic 6-Electron and 8-Electron Configurations of M@Au₂₄(SR)₁₈ Clusters (M = Pd, Pt)

Abstract

The exceptional stability of thiolate-protected Au25 clusters, [Au25(SR)18](-), arises from the closure of superatomic electron shells, leading to a noble-gas-like 8-electron configuration (1S(2)1P(6)). Here we present that replacing the core Au atom with Pd or Pt results in stable [MAu24(SR)18](0) clusters (M = Pd, Pt) having a superatomic 6-electron configuration (1S(2)1P(4)). Voltammetric studies of [PdAu24(SR)18](0) and [PtAu24(SR)18](0) reveal that the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps of these clusters are 0.32 and 0.29 eV, respectively, indicating their electronic structures are drastically altered upon doping of the foreign metal. Density functional investigations confirm that the HOMO-LUMO gaps of these clusters are indeed smaller, respectively 0.33 and 0.32 eV, than that of [Au25(SR)18](-) (1.35 eV). Analysis of the optimized geometries for the 6-electron [MAu24(SR)18](0) clusters shows that the MAu12 core is slightly flattened to yield an oblate ellipsoid. The drastically decreased HOMO-LUMO gaps observed are therefore the result of Jahn-Teller-like distortion of the 6-electron [MAu24(SR)18](0) clusters, accompanying splitting of the 1P orbitals. These clusters become 8-electron [MAu24(SR)18](2-) clusters upon electronic charging, demonstrating reversible interconversion between the 6-electron and 8-electron configurations of MAu24(SR)18.

A gold superatom with 10 electrons in Au13(PPh3)8(p-SC6H4CO2H)3

“…13,14 Au superatoms with n * values smaller than 8 have been synthesized by electrochemical and aerobic oxidation, doping with other elements, and deformation of the spherical core into a lower symmetry morphology. [15][16][17][18][19][20][21][22][23][24][25] For example, open electron configuration for Au 13 (7e) was verified by SQUID 24 and electron paramagnetic resonance (EPR) measurements. 16,21 Closure of two 1P subshells in Au 13 (6e) and MAu 12 (6e) (M = Pt and Pd) due to Jahn-Teller distortion was illustrated by voltammetric measurement and density functional theory (DFT) calculation.…”

“…Similarly, Jahn-Teller distortion of the Au 13 (6e) and MAu 12 (6e) (M = Pt and Pd) structures induces the splitting of triply degenerated 1P superatomic orbitals and two of the 1P orbitals thus stabilized accommodate 4 electrons to form a singlet state. 23,24 These results suggest that Hund's rule cannot be applied in the construction of the periodic table of superatoms because of the structural fluxionality. Figure 3(a) compares the optical absorption spectra of 1, 2, and Au 11 (PPh 3 ) 7 (SPy) 3 having the Au 11 (10e), Au 11 (8e), and Au 11 (8e) cores, respectively.…”

“…16,21 Closure of two 1P subshells in Au 13 (6e) and MAu 12 (6e) (M = Pt and Pd) due to Jahn-Teller distortion was illustrated by voltammetric measurement and density functional theory (DFT) calculation. 23,24 However, to the best of our knowledge, Au 11 /Au 13 superatoms with n * values larger than 8 have not been synthesized up to now.…”

Characterization of floating-gate memory device with thiolate-protected gold and gold-palladium nanoclusters

“…Tables I and II show redox potentials of each nanocluster obtained by the electrochemical measurement reported previously. 47,48 The work function of an Au electrode is estimated to be 5. The results show that it is possible to control the floating-gate behavior with the size-and composition-dependencies of precisely synthesized metal nanoclusters.…”

In situ thermolysis of Pt-carbonyl complex to form supported clean Pt nanoclusters with enhanced catalytic performance

“…Nanoclusters with a high volume/surface ratio and quantum effect have been proven to be efficient catalysts in various useful reactions. To date, several synthetic approaches have been developed to fabricate these small nanoparticles, including solution-phase reduction, gas-phase synthesis, and the ligand-assisted approach [25][26][27][28][29]. However, the fabrication of small nanoparticles is still challenging because of their severe aggregation, wide size distribution, low output, and low activity.…”