Density Functional Theory Studies of the Electronic Structure and Muon Hyperfine Interaction in [Au₂₅(SR)₁₈]⁰ and [Au₂₅(SeR)₁₈]⁰ Nanoclusters

Abstract

Density functional theory computational investigation was performed to study the electronic structures, muon sites, and the associated hyperfine interactions in [Au 25 (SR) 18 ] 0 and [Au 25 (SeR) 18 ] 0 where R is phenylethane. The calculated electronic structures show inhomogeneous spin density distribution and are also affected by different ligands. The two most stable muon sites near Au atoms in the thiolated system are MAu11 and MAu6. When the thiolate ligands were replaced by selenolate ligands, the lowest energy positions of muons moved to MAu6 and MAu5. Muons prefer to stop inside the Au12 icosahedral shell, away from the central Au and the staple motifs region. Muonium states at phenyl ring and S/Se atoms in the ligand were found to be stable and the Fermi contact fields are much larger as compared to the field experienced by muons near Au atoms.

Density Functional Theory Study of 12mer Single-Strand Guanine Oligomer and Associated Muon Hyperfine Interaction

“…Thus, C8-G-B5 is made as the reference and its relative energy is set to be 0 eV. Relative energy of other Mu sites was calculated by subtracting the total energy of C8-G-B5 Mu sites from their respective total energy. , The relative energies of the 96 sites lie in the range of 1.891 eV. The Mu site with the highest energy is N3-G-B11.…”

“…Thus, in a 12mer ssG oligomer, there is a total of 96 possible Mu trapping sites that were all investigated in this work. A hydrogen atom with the mass of Mu was used in this study to determine possible Mu trapping sites. , The stabilization of a Mu site and the associated muon hyperfine interaction is sensitive to the relaxation effect of the atoms around Mu . Thus, after a Mu was introduced into the host system, we performed further geometry optimization that allowed Mu and all atoms in the particular guanine base where Mu was trapped to relax to new positions.…”

Origins of the pH-Responsive Photoluminescence of Peptide-Functionalized Au Nanoclusters

“…To explore and characterize the AuNC–biomolecular interface, theoretical and computational modeling approaches complement experimental findings and are an indispensable tool able to provide (sub)­molecular scale information difficult to achieve experimentally . The prototypical Au 25 (SR) 18 cluster is fundamental to many computational studies since predicted properties can be directly compared to available experimental data and its small size is ideal for first-principles calculations (albeit mostly in vacuum or implicit solvent environments). − Quantum mechanical (QM) approaches, such as all-electron (ab initio) and density functional theory (DFT) methods, are vital for elucidating accurate structural, electronic, and optical properties of AuNCs; however, they can be computationally prohibitive for representing biologically relevant conditions. − To reduce computational cost, QM studies often use truncated, simplified ligands that are water-insoluble (e.g., R = H, CH 3 , CH 2 CH 3 , benzene), neglect or approximate solvent effects, and/or perform local geometry optimizations at absolute zero temperature (0 K), disregarding thermal fluctuations and conformational mobility of the ligands. In contrast, classical approaches based on molecular dynamics (MD) simulations can explore AuNC conformational ligand dynamics and thermodynamic properties in more realistic biological environments; − however, commonly used methodologies ignore electronic polarization effects by requiring molecules to have static protonation states that are based on preassigned partial atomic charges.…”