On the Nature of HOPG-Supported PtTiO and its Decomposition of a Nerve Agent Simulant: A Cluster Model of a Single Atom Catalyst Active Site.

Chemical weapons, including hyper lethal nerve agents, are a persistently looming threat across the modern geopolitical landscape. There is a pressing need for the design and development of improved protective materials, which can be substantially aided by the cultivation of a fundamental molecular-level understanding of candidate systems and the corresponding decomposition chemistry. The emergence of the exciting new class of single atom catalyst (SAC) materials has enhanced the prospect of subnanoscale design tailoring in the hopes of optimizing activity and selectivity for a variety of chemical applications.

Anion photoelectron spectroscopy and chemical bonding of ThS2- and ThSO.

Anion photoelectron spectra of ThSO- and ThS2- were recorded using the third (355 nm) harmonic of an Nd-YAG laser; these provided the measured vertical detachment energies of each anion. The experiments are supported by extensive coupled cluster calculations on ThSO, ThSO-, ThS2, and ThS2-, as well as the oxygen congeners ThO2 and ThO2-. The ab initio calculations, which included complete basis set extrapolations, spin-orbit effects using four-component coupled cluster, and higher-order correlation contributions through CCSDT(Q), yielded an adiabatic electron affinity for ThO2 that was within 0.

Designer "Quasi-Benzyne": The Spontaneous Reduction of Ortho-Diiodotetrafluorobenzene on Water Microdroplets.

It has been widely shown that water microdroplets have a plethora of unique properties that are highly distinct from those of bulk water, among which an especially intriguing one is the strong reducing power as a result of the electrons spontaneously generated at the air-water interface. In this study, we take advantage of the reducing power of water microdroplets to reduce ortho-diiodotetrafluorobenzene (o-CFI) into a CFI radical anion. Photoelectron spectroscopy and density functional theory computations reveal that the excess electron in CFI occupies the I-C1-C2-I linkage, which elongates the C-I bonds but surprisingly shortens the C1-C2 bond, making the bond order higher than a double bond, similar to the benzyne molecule, so we named it "quasi-benzyne".

Electronic Structure and Anion Photoelectron Spectroscopy of Uranium-Gold Clusters UAu, = 3-7.

A collaborative effort between experiment and theory toward elucidating the electronic and molecular structures of uranium-gold clusters is presented. Anion photoelectron spectra of UAu( = 3-7) were taken at the third (355 nm) and fourth (266 nm) harmonics of a Nd:YAG laser, as well as excimer (ArF 193 nm) photon energies, where the experimental adiabatic electron affinities and vertical detachment energies values were measured. Complementary first-principles calculations were subsequently carried out to corroborate experimentally determined electron detachment energies and to determine the geometry and electronic structure for each cluster.

Intramolecular Proton Transfer in the Radical Anion of Cytidine Monophosphate Sheds Light on the Sensitivities of Dry vs Wet DNA to Electron Attachment-Induced Damage.

Single-strand breaks (SSBs) induced via electron attachment were previously observed in dry DNA under ultrahigh vacuum (UHV), while hydrated electrons were found not able to induce this DNA damage in an aqueous solution. To explain these findings, crossed electron-molecular beam (CEMB) and anion photoelectron spectroscopy (aPES) experiments coupled to density functional theory (DFT) modeling were used to demonstrate the fundamental importance of proton transfer (PT) in radical anions formed via electron attachment. Three molecular systems were investigated: 5'-monophosphate of 2'-deoxycytidine (dCMPH), where PT in the electron adduct is feasible, and two ethylated derivatives, 5'-diethylphosphate and 3',5'-tetraethyldiphosphate of 2'-deoxycytidine, where PT is blocked due to substitution of labile protons with the ethyl residues.

Effect of a Single Platinum Atom within a Small Metal Oxide Cluster: Reaction of DMMP with Size-Selected PtZrO Supported on HOPG.

Chemical warfare agents (CWAs) are a persistent threat facing civilians and military personnel across the modern geopolitical landscape. The development of the next generation of protective and sensing materials stands to benefit from an improved fundamental understanding of the interaction of CWA molecules with the active components of such candidate materials. The use of model systems in well-controlled environments offers a route to glean such information and has been applied here to investigate the fundamental interaction of a nerve agent simulant molecule, dimethyl methylphosphonate (DMMP), with a small cluster model of a single atom catalyst (SAC) active site.

Spontaneous Reduction by One Electron on Water Microdroplets Facilitates Direct Carboxylation with CO.

Recent advances in microdroplet chemistry have shown that chemical reactions in water microdroplets can be accelerated by several orders of magnitude compared to the same reactions in bulk water. Among the large plethora of unique properties of microdroplets, an especially intriguing one is the strong reducing power that can be sometimes as high as alkali metals as a result of the spontaneously generated electrons. In this study, we design a catalyst-free strategy that takes advantage of the reducing ability of water microdroplets to reduce a certain molecule, and the reduced form of that molecule can convert CO into value-added products.

Water activation and splitting by single anionic iridium atoms.

Mass spectrometric analysis of anionic products that result from interacting Ir with HO shows the efficient generation of [Ir(HO)] complexes and IrO molecular anions. Anion photoelectron spectra of [Ir(HO)], formed under various source conditions, exhibit spectral features that are due to three different forms of the complex: the solvated anion-molecule complex, Ir(HO), as well as the intermediates, [H-Ir-OH] and [H-Ir-O], where one and two O-H bonds have been broken, respectively. The measured and calculated vertical detachment energy values are in good agreement and, thus, support identification of all three types of isomers.

Theoretical and Experimental Study of the Spectroscopy and Thermochemistry of UC.

A combination of high-level calculations and anion photoelectron detachment (PD) measurements is reported for the UC, UC, and UC molecules. To better compare the theoretical values with the experimental photoelectron spectrum (PES), a value of 1.493 eV for the adiabatic electron affinity (AEA) of UC was calculated at the Feller-Peterson-Dixon (FPD) level.

Au as a Surrogate for F: The Case of UAu vs UF.

Here, anion photoelectron spectroscopy and first-principles quantum chemistry are used to demonstrate to what degree Au can act as a surrogate for F in UF and its anion. Unlike UF, UAu exhibits strong ligand-ligand, i.e.

Electronic Properties of UN and UN from Photoelectron Spectroscopy and Correlated Molecular Orbital Theory.

The results of calculations of the properties of the anion UN including electron detachment are described, which further expand our knowledge of this diatomic molecule. High-level electronic structure calculations were conducted for the UN and UN diatomic molecules and compared to photoelectron spectroscopy measurements. The low-lying Ω states were obtained using multireference CASPT2 including spin-orbit effects up to ∼20,000 cm.

Ultrasmall Cluster Model for Investigating Single Atom Catalysis: Dehydrogenation of 1-Propanamine by Size-Selected PtZrO Clusters Supported on HOPG.

The selective dehydrogenation of hydrocarbons and their functionalized derivatives is a promising pathway in the realization of endothermic fuel systems for powering important technologies such as hypersonic aircraft. The recent surge in interest in single atom catalysts (SACs) over the past decade offers the opportunity to achieve the ultimate levels of selectivity through the subnanoscale design tailoring of novel catalysts. Experimental techniques capable of investigating the fundamental nature of the active sites of novel SACs in well-controlled model studies offer the chance to reveal promising insights.

Experimental and Computational Description of the Interaction of H and H with U.

The results of ab initio correlated molecular orbital theory electronic structure calculations for low-lying electronic states are presented for UH and UH and compared to photoelectron spectroscopy measurements. The calculations were performed at the CCSD(T)/CBS and multireference CASPT2 including spin-orbit effects by the state interacting approach levels. The ground states of UH and UH are predicted to be Ι and Λ, respectively.

Electron Binding Energy Spectra of AlPt Clusters─A Combined Experimental and Computational Study.

Results of size-selected electron photo-detachment experiments and density functional theory calculations on anionic AlPt, = 1-7, clusters are presented and analyzed. The measured and calculated spectra of electron binding energies are, overall, in excellent accord with each other. The analysis reveals the general importance of accounting for the multiplicity of structural forms of a given-size cluster that can contribute to its measured spectrum, especially when the clusters are fluxional and/or the conditions of the experiment allow for structural transitions.

Molecular Properties of Thorium Hydrides: Electron Affinities and Thermochemistry.

High-level electronic structure calculations of the ground and low-lying energy electronic states for ThH and ThH for = 2-5 are reported and compared to available anion photoelectron detachment experiments. The adiabatic electron affinities (EAs) are predicted to be 0.82, 0.

Photoelectron Spectroscopic and Computational Study of the Deprotonated Gallic Acid and Propyl Gallate Anions.

Antioxidants play important roles in eliminating reactive oxygen species (ROS), which have been associated with various degenerative diseases, such as cancer, aging, and inflammatory diseases. Gallic acid (GA) and propyl gallate (PG) are well-known antioxidants and have been widely studied in vitro and in vivo. The biological antioxidant abilities of GA and PG are related to the electronic structure of their dehydro-radicals.

ThAu , ThAuO, and ThAuOH anions: Photoelectron spectroscopic and theoretical characterization.

The thorium-gold negative ions ThAu , ThAuO, and ThAuOH have been observed and experimentally characterized by anion photoelectron spectroscopy. These experiments are accompanied by extensive ab initio electronic structure calculations using a relativistic composite methodology based primarily on coupled cluster singles and doubles with perturbative triples calculations. The theoretical electron affinities (EAs) at 0 K agree with the experimental adiabatic EAs to within 0.

Molecular-level electrocatalytic CO reduction reaction mediated by single platinum atoms.

The activation and transformation of HO and CO mediated by electrons and single Pt atoms is demonstrated at the molecular level. The reaction mechanism is revealed by the synergy of mass spectrometry, photoelectron spectroscopy, and quantum chemical calculations. Specifically, a Pt atom captures an electron and activates HO to form a H-Pt-OH complex.

Interaction of Th with H: Combined Experimental and Theoretical Thermodynamic Properties.

High-level electronic structure calculations of the low-lying energy electronic states for ThH, ThH, and ThH are reported and compared to experimental measurements. The inclusion of spin-orbit coupling is critical to predict the ground-state ordering as inclusion of spin-orbit switches the coupled-cluster CCSD(T) ordering of the two lowest energy states for ThH and ThH. At the multireference spin-orbit SO-CASPT2 level, the ground states of ThH, ThH, and ThH are predicted to be the Δ, Φ, and Δ states, respectively.

Metal-Metal Bonding in Actinide Dimers: U and U.

Understanding direct metal-metal bonding between actinide atoms has been an elusive goal in chemistry for years. We report for the first time the anion photoelectron spectrum of U. The threshold of the lowest electron binding energy (EBE) spectral band occurs at 1.

Trapping of H in aluminum hydride, AlH.

Ever since our first experimental and computational identification of AlH as a boron analog [X. Li et al., Science 315, 356 (2007)], studies on aluminum hydrides unveiled a richer pattern of structural motifs.

Photoelectron Spectroscopic Study of Ascorbate and Deprotonated Ascorbate Anions Using an Electrospray Ion Source and a Cryogenically Cooled Ion Trap.

Reactive oxygen species (ROS) in biological systems are formed through a variety of mechanisms. These species are very reactive and have been associated with many diseases, including cancer and cardiovascular disease. One way of removing ROS from the body is through the use of radical scavengers, which are compounds capable of giving up an electron to neutralize the ROS yet form a stable radical species themselves.

Electrophilic Properties of 2'-Deoxyadenosine···Thymine Dimer: Photoelectron Spectroscopy and DFT Studies.

The anion radical of the 2'-deoxyadenosine···thymine (dAT) pair has been investigated experimentally and theoretically in the gas phase. By employing negative-ion photoelectron spectroscopy (PES), we have registered a spectrum typical for the valence-bound anion, featuring a broad peak at the electron-binding energy (EBE) between ∼1.5 and 2.

The electron affinity of the uranium atom.

The results of a combined experimental and computational study of the uranium atom are presented with the aim of determining its electron affinity. Experimentally, the electron affinity of uranium was measured via negative ion photoelectron spectroscopy of the uranium atomic anion, U. Computationally, the electron affinities of both thorium and uranium were calculated by conducting relativistic coupled-cluster and multi-reference configuration interaction calculations.