In search of a structural model for a thiolate-protected Au38 cluster

TL;DR

This paper investigates the structure of the Au38(SR)24 gold cluster using computational methods, proposing a new dimer-dominated model that aligns well with experimental optical spectra and shows improved energetic stability.

Contribution

The study introduces a novel dimer-dominated structural model for Au38(SR)24, differing from previous models by emphasizing staple motifs as dimers and monomers, validated through DFT calculations.

Findings

Dimer-dominated model is 2.6 eV more stable than previous models.

The new model agrees well with experimental optical spectra.

It shows improved energetic stability over earlier models.

Abstract

The structure of thiolate-protected gold cluster Au38(SR)24 has not been determined experimentally and the best available signature is its measured optical spectrum. Using this signature and energetic stability as criteria and SCH3 for SR, we compare four candidate structures: two from others and two we obtained. Our models are distinct from others in that thiolate groups form monomers and dimers of the staple motif (a nearly linear RS-Au-SR bonding unit). We examine the energetics and electronic structures of the four structures with density functional theory (DFT) and compute their optical spectra with time-dependent DFT. We show that our dimer-dominated model is over 2.6 eV lower in energy than the two models from others and 1.3 eV lower than our previous monomer-dominated model. The dimer-dominated model also presents good agreement with experiment for optical absorption.