Shift from Covalent to Ionic Bonding in Al₂MoO_y (y = 2–4) Anion and Neutral Clusters

Abstract

The electronic and molecular structures of Al2MoO(y) (y = 2-4) anion and neutral complexes were studied using anion photoelectron spectroscopy and density functional theory calculations. The spectra are broad, reflecting significant structural changes in the transition from anion to neutral, and the neutral electron affinities determined from the spectra are similar for all three species. The calculations suggest that the lowest energy isomers of the neutral clusters can be described as predominantly (Al(+))2[MoO(y)(-2)] ionic complexes, in which the Al(+) cations bond with O(2-) anions in a way that minimizes repulsion with the positively charged Mo center. The anion structures for all three complexes favor closer Mo-Al and Al-Al internuclear distances, with the extra negative charge distributed more evenly among all three metal centers. Energetically, the fully occupied 3s orbitals on the Al centers are lower than the Mo-local 4d-like orbitals and above the O-local 2p-like orbitals. In the case of Al2MoO2(-), there is direct Al-Al covalent bonding. The calculated spectroscopic parameters for these species are consistent with the observed spectra, though definitive assignments are not possible due to the broad, unresolved spectra observed and predicted.

Electronic Structure and Chemical Bonding of a Highly Stable and Aromatic Auro–Aluminum Oxide Cluster

“…Since the discovery of the remarkable catalytic activity of supported gold nanoparticles for low-temperature CO oxidation, intensive studies have been carried out to elucidate the mechanisms of gold catalysts. , Even though earlier studies have suggested quantum-size effects may play a key role in gold catalysts, − increasing studies have shown that the cluster–oxide support interface is also critical. − Size-selected gold clusters have been extensively studied to provide insight into the nature of the catalytic effects of nanogold. − Recently, tertiary clusters of Au atoms with Ti x O y clusters have been produced and their reactivity with CO has been studied as possible models to probe the support effects on the reactivity of gold. , Alumina is also an important support for gold catalysts. − Aluminum oxide clusters have been investigated previously as models for oxide catalysts. − More recent studies have included transition metal-doped aluminum oxides − and their chemical reactivities. , But there have been no reports on Au-doped aluminum oxide clusters.…”

Lanthanide Oxides: From Diatomics to High-Spin, Strongly Correlated Homo- and Heterometallic Clusters

“…Our group has conducted numerous studies on the electronic structures of transition metal oxides using anion PE spectroscopy, − in addition to cluster anion reactivity studies. − In general, we observed an increase in cluster EA with oxidation state, which is readily rationalized as the increased energy cost of removing an electron from an increasingly cationic M (2 y –1)/ x + center within an ionic M x O y – system as y is increased. In reactions with water, we have found two main modes of reactivity.…”