Theoretical and experimental studies of the interactions between Au2(-) and nucleobases.

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-HAu or C-HAu nonconventional hydrogen bonds. The nucleobase-Au2(-) cluster anions have relatively weak N-HAu hydrogen bonds and strong C-HAu hydrogen bonds compared to those of nucleobase-Au(-) anions.