Multiple Metal-Metal Bond or No Bond? The Electronic Structure of V2 O2

Vanadium Oxide: Phase Diagrams, Structures, Synthesis, and Applications

Vanadium oxides with multioxidation states and various crystalline structures offer unique electrical, optical, optoelectronic and magnetic properties, which could be manipulated for various applications. For the past 30 years, significant efforts have been made to study the fundamental science and explore the potential for vanadium oxide materials in ion batteries, water splitting, smart windows, supercapacitors, sensors, and so on. This review focuses on the most recent progress in synthesis methods and applications of some thermodynamically stable and metastable vanadium oxides, including but not limited to V₂O₃, V₃O₅, VO₂, V₃O₇, V₂O₅, V₂O₂, V₆O₁₃, and V₄O₉. We begin with a tutorial on the phase diagram of the V-O system. The second part is a detailed review covering the crystal structure, the synthesis protocols, and the applications of each vanadium oxide, especially in batteries, catalysts, smart windows, and supercapacitors. We conclude with a brief perspective on how material and device improvements can address current deficiencies. This comprehensive review could accelerate the development of novel vanadium oxide structures in related applications.

Structural and bonding properties of Cu3O3- and Cu3O4- clusters: anion photoelectron spectroscopy and density functional calculations

The structural and electronic properties of Cu3O3- and Cu3O4- were investigated using mass-selected anion photoelectron spectroscopy in combination with density functional theoretical calculations. The vertical detachment energies of Cu3O3- and Cu3O4- were measured to be 3.48 ± 0.08 and 3.54 ± 0.08 eV, respectively. Their geometrical structures were determined by comparison of the theoretical calculations with the experimental results. The most stable structure of Cu3O3- can be characterized as a C3v symmetric six-membered ring structure with alternating Cu-O bonds, in which the plane of the three O atoms is slightly above that of the three Cu atoms. The most stable structure of Cu3O4- can be viewed as a Cs symmetric seven-membered ring with a peroxo unit. The bond order and molecular orbital analyses indicate that the Cu-Cu interactions in Cu3O3- and Cu3O4- are weak. The calculated NICS(0) and NICS(1) values of Cu3O3- are -25.0 ppm and -19.2 ppm, respectively, and those of Cu3O4- are -18.6 ppm and -10.5 ppm, respectively, indicating that they both are significantly aromatic.

Metal Cluster Models for Heterogeneous Catalysis: A Matrix-Isolation Perspective

Metal cluster models are of high relevance for establishing new mechanistic concepts for heterogeneous catalysis. The high reactivity and particular selectivity of metal clusters is caused by the wealth of low-lying electronically excited states that are often thermally populated. Thereby the metal clusters are flexible with regard to their electronic structure and can adjust their states to be appropriate for the reaction with a particular substrate. The matrix isolation technique is ideally suited for studying excited state reactivity. The low matrix temperatures (generally 4-40 K) of the noble gas matrix host guarantee that all clusters are in their electronic ground-state (with only a very few exceptions). Electronically excited states can then be selectively populated and their reactivity probed. Unfortunately, a systematic research in this direction has not been made up to date. The purpose of this review is to provide the grounds for a directed approach to understand cluster reactivity through matrix-isolation studies combined with quantum chemical calculations.