Monohafnium Oxide Clusters HfO_n^–and HfO_n(n= 1–6): Oxygen Radicals, Superoxides, Peroxides, Diradicals, and Triradicals

Abstract

The electronic and structural properties of monohafnium oxide clusters, HfO(n)(-) and HfO(n) (n = 1-6), are investigated using anion photoelectron spectroscopy and density-functional theory at the B3LYP level. The observed ground-state adiabatic detachment energy is low for HfO(-) (0.5 ± 0.1 eV) and HfO(2)(-) (2.125 ± 0.010 eV), roughly constant for HfO(3)(-) (3.6 ± 0.1 eV), HfO(4)(-) (3.67 ± 0.05 eV), and HfO(5)(-) (3.9 ± 0.1 eV), and substantially higher for HfO(6)(-) (4.9 ± 0.1 eV). Activated oxygen species, such as radical, superoxide, peroxide, diradical, and triradical, are identified in the HfO(n)(-) and HfO(n) clusters. The Hf center is shown to be flexible to accommodate the oxygen species. The sum of formal Hf-O bond orders around the Hf center is equal to four for all of the neutral clusters studied, and five for all of the anions. The O-rich HfO(n)(-) and HfO(n) (n = 3-6) clusters provide well-defined molecular models to understand O(2) adsorption and activation on an Hf center.

Re-print of “Sub-eV Ion Deposition Utilizing Soft-Landing Ion Mobility for Controlled Ion, Ion Cluster, and Charged Nanoparticle Deposition”

“…In all experiments the laser was rastered along the surface of the metal target to ensure a consistent ablation event. This method is consistent with previous experimental reports for the in situ production of hafnium oxide [42][43][44]. Soft-landing was completed in a step-wise fashion over the course of 7 h, with postlanding Raman analyses being conducted at deposition intervals of 15 min for the first hour, and 1 h increments thereafter.…”

Gas-Phase Reaction Studies of Dipositive Hafnium and Hafnium Oxide Ions: Generation of the Peroxide HfO22+

“…12,36 Several neutral and anionic Hf peroxide species have recently been described based on spectroscopy studies. 11,13 Both neutral HfO 2 and anionic HfO 2 − have bent dioxide structures as indicated by spectroscopy and computations. 12 Computational Studies: Geometry and Electronic Structure of HfO 2+ and HfO 2 2+ .…”

Spin‐Selective, Competitive Hydrogen‐Atom Transfer versus CH2O‐Generation from the CH4/[ReO4]+ Couple at Ambient Conditions

“…For example, triplet [Sc 3 O 6 ] − that possesses two oxyl centers activates two n ‐butane molecules via consecutive hydrogen‐atom abstractions (HAT), generating [Sc 3 O 6 H 2 ] − ; another biradical cluster ion [Al 3 O 6 ] − exhibits the same reactivity . In addition, a few other clusters like WO 4 , [VTi 3 O 10 ] − , HfO n ( n= 4–6), and M 2 O 6 (M=Nb, Ta), generated in the gas phase, also exhibit a biradical character; however, their reactivities were not examined. While it is well‐known that metal‐oxide clusters possessing a terminal oxyl radical are capable to abstract one hydrogen atom from methane, it remains to be explored how biradical clusters perform in regard to methane activation.…”