Imaging Photoelectron Circular Dichroism in the Detachment of Mass-Selected Chiral Anions

Photoelectron Circular Dichroism (PECD) is a forward-backward asymmetry in the photoemission from a non-racemic sample induced by circularly polarized light. PECD spectroscopy has potential analytical advantages for chiral discrimination over other chiroptical methods due to its increased sensitivity to the chiral potential of the molecule. The use of anions for PECD spectroscopy allows for mass-selectivity and provides a path to simple experimental schemes that employ table-top light sources. Evidence of PECD for anions is limited, and insight into the forces that govern PECD electron dynamics in photodetachment is absent. Here, we demonstrate a PECD effect in the photodetachment of mass-selected deprotonated 1-indanol anions. By utilizing velocity map imaging photoelectron spectroscopy with a tunable light source, we determine the energy-resolved PECD over a wide range of photon energies. The observed PECD reaches up to 11 %, similar to what has been measured for neutral species.

Comparison of Conventional and Nonconventional Hydrogen Bond Donors in Au- Complexes

Although gold has become a well-known nonconventional hydrogen bond acceptor, interactions with nonconventional hydrogen bond donors have been largely overlooked. In order to provide a better understanding of these interactions, two conventional hydrogen bonding molecules (3-hydroxytetrahydrofuran and alaninol) and two nonconventional hydrogen bonding molecules (fenchone and menthone) were selected to form gas-phase complexes with Au^-. The Au^-[M] complexes were investigated using anion photoelectron spectroscopy and density functional theory. Au^-[fenchone], Au^-[menthone], Au^-[3-hydroxyTHF], and Au^-[alaninol] were found to have vertical detachment energies of 2.71 ± 0.05, 2.76 ± 0.05, 3.01 ± 0.03, and 3.02 ± 0.03 eV, respectively, which agree well with theory. The photoelectron spectra of the complexes resemble the spectrum of Au^- but are blueshifted due to the electron transfer from Au^- to M. With density functional theory, natural bond orbital analysis, and atoms-in-molecules analysis, we were able to extend our comparison of conventional and nonconventional hydrogen bonding to include geometric and electronic similarities. In Au^-[3-hydroxyTHF] and Au^-[alaninol], the hydrogen bonding comprised of Au^-···HO as a strong, primary hydrogen bond, with secondary stabilization by weaker Au^-···HN or Au^-···HC hydrogen bonds. Interestingly, the Au^-···HC bonds in Au^-[fenchone] and Au^-[menthone] can be characterized as hydrogen bonds, despite their classification as nonconventional hydrogen bond donors.