Interactions between Ultrastable Na4Ag44(SR)30 Nanoclusters and Coordinating Solvents: Uncovering the Atomic-scale Mechanism

Abstract

We report the mechanism on the ultrahigh stability of Na<sub>4</sub>Ag<sub>44</sub>(SR)<sub>30</sub> by uncovering how coordinating solvents interact with the Na<sub>4</sub>Ag<sub>44</sub>(SR)<sub>30</sub> nanocluster at the atomic scale. Through synchrotron X-ray experiments and theoretical calculations, it was found that strongly coordinating aprotic solvents interact with surface Ag atoms, particularly between ligand bundles, which compresses the Ag core and relaxes surface metal-ligand interactions. Furthermore, water was used as a cosolvent to demonstrate that semi-aqueous conditions play an important role in protecting exposed surface regions and can further influence the local structure of the silver nanocluster itself. Notably, under semi-aqueous conditions, aprotic coordinating solvent molecules preferentially remain on the metal surface while water molecules interact with ligands, and ligand bundling persisted across the varied solvation conditions.

Utilizing an Improved EXAFS Structure Analysis Method to Reveal Site-Specific Bonding Properties of Ag44(SR)30 Nanoclusters

“…The detailed description of the sample preparation for XAS measurement has been reported previously. 18 The fitting of EXAFS spectra were performed by Artemis and Athena. 29 The amplitude reduction factor (S0 2 ) was fixed at 0.90, which was determined from a Ag foil reference.…”

“…In order to get detailed structural information from fitting the FT-EXAFS spectra of Ag44(SR)30, the site-specific bonding in the NCs was first analyzed. 18,20,26 using the structure that was experimentally measured by single-crystal X-ray diffraction. 6 As shown in Scheme 1, the https://doi.org/10.26434/chemrxiv-2023-1pz58 ORCID: https://orcid.org/0000-0003-3603-0175 Content not peer-reviewed by ChemRxiv.…”

“…[14][15][16][17] The extended X-ray absorption fine structure (EXAFS) is the region of XAS about 50 eV above the edge, which is useful for investigating the element-specific local structural environment of thiolate protected NCs under different conditions. [18][19][20][21][22] It has already been applied to study temperature effect on 25-atom NCs. 20,21 Generally, a thiolate protected NC has several different coordination environments, and the bond distances can be grouped into distinct shells.…”

Utilizing an Improved EXAFS Structure Analysis Method to Reveal Site-Specific Bonding Properties of Ag44(SR)30 Nanoclusters

“…The detailed description of the sample preparation for XAS measurement has been reported previously. 18 The fitting of EXAFS spectra were performed by Artemis and Athena. 29 The amplitude reduction factor (S 0 2) was fixed at 0.90, which was determined from a Ag foil reference.…”

“…33 In order to get detailed structural information from fitting the FT-EXAFS spectra of Ag 44 (SR) 30 , the site-specific bonding in the NCs was first analyzed. 18,20,26 using the structure that was experimentally measured by single-crystal X-ray diffraction. 6 As shown in Scheme 1, the structure can be broken down into a hollow icosahedral Ag 12 inner metal core, a dodecahedral Ag 20 cage, and six Ag 2 (SR) 5 mount motifs.…”