Guided ion beam and theoretical study of the reactions of Au+ with H2, D2, and HD

Abstract

Reactions of the late third-row transition metal cation Au(+) with H(2), D(2), and HD are examined using guided ion beam tandem mass spectrometry. A flow tube ion source produces Au(+) in its (1)S (5d(10)) electronic ground state level. Corresponding state-specific reaction cross sections for forming AuH(+) and AuD(+) as a function of kinetic energy are obtained and analyzed to give a 0 K bond dissociation energy of D(0)(Au(+)-H) = 2.13 ± 0.11 eV. Quantum chemical calculations at the B3LYP∕HW+∕6-311+G(3p) and B3LYP∕Def2TZVPP levels performed here show good agreement with the experimental bond energy. Theory also provides the electronic structures of these species and the reactive potential energy surfaces. We also compare this third-row transition metal system with previous results for analogous reactions of the first-row and second-row congeners, Cu(+) and Ag(+). We find that Au(+) has a stronger M(+)-H bond, which can be explained by the lanthanide contraction and relativistic effects that alter the relative size of the valence s and d orbitals. Results from reactions with HD provide insight into the reaction mechanism and indicate that ground state Au(+) reacts largely via a direct mechanism, in concordance with the behavior of the lighter group 11 metal ions, but includes more statistical behavior than these metals as well.

Communication: Theoretical exploration of Au++H2, D2, and HD reactive collisions

“…The H-Au-H angle in the entrance well is 27.2 • in very good agreement with that given in Ref. 22. These plots also show that the linear configuration with Au + in between the two H atoms is not stable.…”

“…1 and is very similar to that reported in Ref. 22 of 0.87 eV. Also, in the right top panel, the potential for the two diatomic species is shown, showing the large difference of dissociation energies, D e , equal to the endothermicity of the Au + + H 2 → AuH + + H reaction, when the zero-point energy of the diatomic fragments are not taken into account.…”

“…21 The 0 K dissociation energies of H 2 for H 2 and 2.13 ± 0.11 for AuH + , 22 where the latter value is slightly higher than the lower limit obtained from reaction with CH 4 (>1.94 ± 0.08) eV. 25 We can then conclude that the present calculations are of sufficient accuracy to describe the PES.…”

“…21 The PES of the ground state presents a potential well high in energy, considered as a precursor of the chemisorption well appearing in gold nanoparticles and originating from several curve crossings. Particularly interesting is the recent experimental study 22 of the Au + + H 2 → AuH + + H reaction, and its isotopologues, HD and D 2 . This system provides a good benchmark to analyze the effect of the positive charge in this reaction from a theoretical point of view.…”

“…2 and compared with the experimental ones of Ref. 22 (obtained under single collision conditions) in absolute units. The agreement is good, but the theoretical cross sections show a threshold at higher energy, such that they are narrower as well.…”