Identification of Intermediate Au22(SR)4(SR')14 Cluster on Ligand-Induced Transformation of Au25(SR)18 Nanocluster

Anu George; Anusree Sundar; Akhil S Nair; Manju P Maman; Biswarup Pathak; Nitya Ramanan; Sukhendu Mandal

doi:10.1021/acs.jpclett.9b01856

Identification of Intermediate Au₂₂(SR)₄(SR')₁₄ Cluster on Ligand-Induced Transformation of Au₂₅(SR)₁₈ Nanocluster

J Phys Chem Lett. 2019 Aug 15;10(16):4571-4576. doi: 10.1021/acs.jpclett.9b01856. Epub 2019 Jul 30.

Authors

Anu George¹, Anusree Sundar¹, Akhil S Nair², Manju P Maman¹, Biswarup Pathak², Nitya Ramanan³, Sukhendu Mandal¹

Affiliations

¹ School of Chemistry , Indian Institute of Science Education and Research Thiruvananthapuram , Maruthamala PO, Trivandrum 695551 , India.
² Discipline of Chemistry, School of Basic Sciences , Indian Institute of Technology , Indore 453552 , India.
³ Alba Synchrotron , Carrer delallum 2-26 , Cerdanyola del valles, 08290 Barcelona , Spain.

PMID: 31339731
DOI: 10.1021/acs.jpclett.9b01856

Abstract

We report the ligand-exchange-induced transformation from an icosahedral Au₂₅(SR)₁₈ cluster (where SR = 2-phenylethanethiol (PET)) to a bitetrahedral Au₂₂(SR)₄(SR')₁₄ cluster (where SR' = 4-tert-butylbenzenethiol (TBBT)). This partial exchange of the ligands was achieved by controlling the concentration of the incoming TBBT ligand. Being a bulky and aromatic ligand, TBBT can efficiently distort the atomic structure of the Au₂₅PET₁₈ cluster, resulting in Au₂₂(PET)₄(TBBT)₁₄, which is highly stable and considered to be an intermediate with a bitetrahedral structure. Time-dependent mass spectrometry and optical spectroscopy revealed the dissociation of the parent cluster and gave a deep insight on the ligand-exchange mechanism. Theoretical calculations and extended X-ray absorption fine structure studies confirm the formation of the Au₂₂ structure. Identifying the atomic structure of the intermediate species opens a new avenue to study the transformation of one cluster to another.