Theoretical and experimental studies of the interactions between Au2− and nucleobases

Abstract

Combined anion photoelectron spectroscopy and relativistic quantum chemical studies are conducted on nucleobase–Au₂⁻ cluster anions. The vertical detachment energies of uracil–Au₂⁻ (UAu₂⁻), thymine–Au₂⁻ (TAu₂⁻), cytosine–Au₂⁻ (CAu₂⁻), adenine–Au₂⁻ (AAu₂⁻), guanine–Au₂⁻ (GAu₂⁻) are determined to be 2.71 ± 0.08 eV, 2.74 ± 0.08 eV, 2.67 ± 0.08 eV, 2.65 ± 0.08 eV and 2.73 ± 0.08 eV, respectively, based on the measured photoelectron spectra. Through computational geometry optimizations we have identified the lowest-energy structures of these nucleobase–Au₂⁻ cluster anions. The structures are further confirmed by comparison of theoretically calculated vertical and adiabatic electron detachment energies with experimental measurements. The results reveal that the Au₂⁻ anion remains as an intact unit and interacts with the nucleobases through N–H⋯Au or C–H⋯Au nonconventional hydrogen bonds. The nucleobase–Au₂⁻ cluster anions have relatively weak N–H⋯Au hydrogen bonds and strong C–H⋯Au hydrogen bonds compared to those of nucleobase–Au⁻ anions.