Density Functional Theory Studies on Structure, Ligand Exchange, and Optical Properties of Ligand-Protected Gold Nanoclusters: Thiolate versus Selenolate

Abstract

Atomically precise thiolate-protected Au nanoclusters (NCs), i.e. Au m (SR) n , have attracted intensive research interest during the past few years. Recently, the synthesis and isolation of selenolate-protected gold clusters (Au m (SeR) n ) via the ligand exchange of thiolate with selenol were achieved, which demonstrated identical compositions to those of thiolate-protected Au NCs. In this study, we perform a comprehensive theoretical study on the structure, electronic structure, and electronic optical absorption properties of 11 selenolate-protected gold clusters on the basis of density functional theory (DFT) calculations. Our results propose that the selenolate-protected Au NCs with framework structure identical to the thiolated ones are stable local minima. The ligand effect is proposed to understand the distinct geometrical structures of Au24(SeR)20 and Au24(SR)20 NCs. In addition, the optical absorption properties of thiolate- and selenolate-protected Au NCs are compared via the time-dependent density functional theory (TD-DFT). The results indicate that two types of Au NCs possess similar shape of electronic optical absorption spectra and electronic structure. The excitation wavelength dependent intermolecular electron transfer between the Au25(ER)− (E = S and Se) and O2 is revealed as well.

Metal Nanoclusters Stabilized by Selenol Ligands

“…Based on DFT calculations, Pei and co‐workers theoretically compared the electronic structures of Au 10 (ECH 3 ) 10 , Au 12 (ECH 3 ) 9 , Au 20 (ECH 3 ) 16 , Au 23 (ECH 3 ) 16 , Au 24 (ECH 3 ) 18 , Au 25 (ECH 3 ) 18 , Au 28 (ECH 3 ) 20 , Au 36 (ECH 3 ) 24 , Au 38 (ECH 3 ) 24 , and Au 44 (ECH 3 ) 28 nanoclusters (E = S/Se) ( Figure ) . Calculated results demonstrated that the selenol‐protected Au nanoclusters with framework identical to the thiolated ones were stable local minima—all reaction energies (△ H ) for exchanging one S‐CH 3 ligand on thiolated nanoclusters into a Se‐CH 3 were negative (Figure ).…”

“…Calculated results demonstrated that the selenol‐protected Au nanoclusters with framework identical to the thiolated ones were stable local minima—all reaction energies (△ H ) for exchanging one S‐CH 3 ligand on thiolated nanoclusters into a Se‐CH 3 were negative (Figure ). Accordingly, the reactions of Au m (SCH 3 ) n + n [HSeCH 3 ] → Au m (SeCH 3 ) n + n [HSCH 3 ] were all exothermic reactions, and thus such Au m (SeCH 3 ) n nanoclusters were more stable than their thiolated analogues …”

Thiolate‐protected gold nanoclusters: structural prediction and the understandings of electronic stability from first principles simulations

“…Besides, the PBE functional with and without van der Waals correction were employed to calculate the relative energies of the isomer structures. 77,78 Both the PBE and PBE-D energies proposed that the thiolated Au 24 nanocluster favors configuration B when the substituent groups are CH 3 and CH 2 Ph-t Bu. Moreover, the predicted energy orders of configuration A and B for Au 24 (SCH 2 CH 2 Ph) 20 and Au 24 (SPh) 20 were found to be different, depending on the PBE or PBE-D functional used for calculations.…”

Understanding and Designing the Gold–Bio Interface: Insights from Simulations

“…However, it has been shown that a plasmon‐like response may be produced by AuNCs with as few as 23 Au atoms by changing the nature of the ligand . Further investigation is therefore required to establish the characteristics of this transition for different thiol and other functionalized ligands (e.g., selenoate groups), and it is through structural studies like these that our knowledge regarding the origin of the intrinsic size‐dependent properties of gold grows.…”

“…In addition to static structure determination, QM methods may also be used to investigate the dynamics of AuNP formation, including aspects such as self‐assembly/aggregation, doping, metal oxidation, ligand exchange,[16a,39,51] and the binding of small molecules to gold surfaces and nanoclusters …”