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When spin-orbit-entangled d electrons reside on a honeycomb lattice, rich quantum states are anticipated to emerge, as exemplified by the d^{5} Kitaev materials. Distinct yet equally intriguing physics may be realized with a d-electron count other than d^{5}. The magnetization, ^{7}Li-nuclear magnetic resonance (NMR), and inelastic neutron scattering measurements, together with the quantum chemistry calculation, indicate that the layered ruthenate Ag_{3}LiRu_{2}O_{6} with d^{4}Ru^{4+} ions at ambient pressure forms a honeycomb lattice of spin-orbit-entangled singlets, which is a playground for frustrated excitonic magnetism. Under pressure, the singlet state does not develop the expected excitonic magnetism, but two successive transitions to other nonmagnetic phases were found in ^{7}Li-NMR, neutron diffraction, and x-ray absorption fine structure measurements, first to an intermediate phase with moderate distortion of honeycomb lattice and eventually to a high-pressure phase with very short Ru-Ru dimer bonds. While the strong dimerization in the high-pressure phase originates from a molecular orbital formation as in the sister compound Li_{2}RuO_{3}, we argue that the intermediate phase represents a spin-orbit-coupled singlet dimer state which is stabilized by the admixture of upper-lying J_{eff}=1-derived states via a pseudo-Jahn-Teller effect. The emergence of competing electronic phases demonstrates rich spin-orbital physics of d^{4} honeycomb compounds, and this finding paves the way for realization of unconventional magnetism.

The interplay of spin-orbit coupling with other relevant parameters gives rise to the rich phase competition in complex ruthenates featuring octahedrally coordinated Ru 4+ . While locally, spin-orbit coupling stabilizes a nonmagnetic J eff = 0 state, intersite interactions resolve one of two distinct phases at low temperatures: an excitonic magnet stabilized by the magnetic exchange of upper-lying J eff = 1 states or Ru 2 molecular orbital dimers driven by direct orbital overlap. Pyrochlore ruthenates A 2 Ru 2 O 7 ( A = rare earth, Y) are candidate excitonic magnets with geometrical frustration. We synthesized In 2 Ru 2 O 7 with covalent In─O bonds. This pyrochlore ruthenate hosts a local J eff = 0 state at high temperatures; however, at low temperatures, it forms a unique nonmagnetic ground state with nearly linear Ru─O─Ru molecules, in stark contrast to other A 2 Ru 2 O 7 compounds. The disproportionation of covalent In─O bonds drives Ru 2 O molecule formation, quenching not only the local spin-orbit singlet but also geometrical frustration.

A combination of high-level ab initio 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. The lowest vertical detachment energy (VDE) is predicted to be 1.500 eV compared to the experimental value of 1.487 ± 0.035 eV. A shoulder to lower energy in the experimental PD spectrum with the 355 nm laser can be assigned to a combination of low-lying excited states of UC - and excited vibrational states. The VDEs calculated for the low-lying excited electronic states of UC at the SO-CASPT2 level are consistent with the observed additional electron binding energies at 1.990, 2.112, 2.316, and 3.760 eV. Potential energy curves for the Ω states and the associated spectroscopic properties are also reported. Compared to UN and UN + , the bond dissociation energy (BDE) of UC (411.3 kJ/mol) is predicted to be considerably lower. The natural bond orbitals (NBO) calculations show that the UC 0/+/- molecules have a bond order of 2.5 with their ground-state configuration arising from changes in the oxidation state of the U atom in terms of the 7s orbital occupation: UC (5f 2 7s 1 ), UC - (5f 2 7s 2 ), and UC + (5f 2 7s 0 ). The behavior of the UN and UC sequence of molecules and anions differs from the corresponding sequences for UO and UF.

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 -1 . At the Feller-Peterson-Dixon (FPD) level, the adiabatic electron affinity (AEA) of UN is estimated to be 1.402 eV and the vertical detachment energy (VDE) is 1.423 eV. The assignment of the UN excited states shows good agreement with the experimental results with a VDE of 1.424 eV. An Ω = 4 ground state was obtained for UN - which is mainly associated with the 3 H ΛS state. Thermochemical calculations estimate a bond dissociation energy (BDE) for UN - (U - + N) of 665.9 kJ/mol, ∼15% larger than that of UN and UN + . The NBO analysis reveals U-N triple bonds for the UN, UN - , and UN + species.

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 4 Ι 9/2 and 5 Λ 6 , respectively. The spectroscopic parameters T e , r e , ω e , ω e x e , and B e were obtained, and potential energy curves were calculated for the low energy Ω states of UH. The calculated adiabatic electron affinity is 0.468 eV in excellent agreement with an experimental value of 0.462 ± 0.013 eV. The lowest vertical detachment energy was predicted to be 0.506 eV for the ground state, and the adiabatic ionization energy (IE) is predicted to be 6.116 eV. The bond dissociation energy (BDE) and heat of formation values of UH were obtained using the IE calculated at the Feller-Peterson-Dixon level. For UH, UH - , and UH + , the BDEs were predicted to be 225.5, 197.9, and 235.5 kJ/mol, respectively. The BDE for UH is predicted to be ∼20% lower in energy than that for ThH. The analysis of the natural bond orbitals shows a significant U + H - ionic component in the bond of UH.

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 2 - . The threshold of the lowest electron binding energy (EBE) spectral band occurs at 1.0 eV, which corresponds to the electron affinity (EA) of U 2 , whereas the vertical detachment energy of U 2 - is found at EBE ∼ 1.2 eV. Electronic structure calculations on U 2 and U 2 - were carried out with state-of-the-art theoretical methods. The computed values of EA(U 2 ) and EA(U) and the difference between the computed dissociation energies of U 2 and U 2 - are found to be internally consistent and consistent with experiment. Analysis of the bonds in U 2 and U 2 - shows that while U 2 has a formal quintuple bond, U 2 - has a quadruple bond, even if the effective bond orders differ only by 0.5 unit instead of one unit. The resulting experimental-computational synergy elucidates the nature of metal-metal bonding in U 2 and U 2 - .

Elucidating the multifaceted processes of molecular activation and subsequent reactions gives a fundamental view into the development of iridium catalysts as they apply to fuels and propellants, for example, for spacecraft thrusters. Hydroxylamine, a component of the well-known hydroxylammonium nitrate (HAN) ionic liquid, is a safer alternative and mimics the chemistry and performance standards of hydrazine. The activation of hydroxylamine by anionic iridium clusters, Ir n - ( n = 1-5), depicts a part of the mechanism, where two hydrogen atoms are removed, likely as H 2 , and Ir n (NOH) - clusters remain. The significant photoelectron spectral differences between these products and the bare clusters illustrate the substantial electronic changes imposed by the hydroxylamine fragment on the iridium clusters. In combination with DFT calculations, a preliminary reaction mechanism is proposed, identifying the possible intermediate steps leading to the formation of Ir(NOH) - .

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. The experimentally determined value of the electron affinity of the uranium atom was determined to be 0.309 ± 0.025 eV. The computationally predicted electron affinity of uranium based on composite coupled cluster calculations and full four-component spin-orbit coupling was found to be 0.232 eV. Predominately due to a better convergence of the coupled cluster sequence for Th and Th - , the final calculated electron affinity of Th, 0.565 eV, was in much better agreement with the accurate experimental value of 0.608 eV. In both cases, the ground state of the anion corresponds to electron attachment to the 6d orbital.

Mass spectrometric analysis of the anionic products of interaction between palladium hydride anions, PdH - , and carbon dioxide, CO 2 , in a reaction cell shows an efficient generation of the PdHCO 2 - intermediate and isolated formate product. Multiple isomers of the PdHCO 2 - intermediates are identified by a synergy between negative ion photoelectron spectroscopy and quantum-chemical calculations. It is shown that a direct mechanism, in which the H atom in PdH - directly activates and hydrogenates CO 2 , leads to the formation of the formate product. An indirect mechanism, on the other hand, leads to a stable HPdCO 2 - structure, where CO 2 is chemisorbed onto the Pd atom.

Mass spectrometric analysis of the anionic products of interaction between bimetallic palladium-copper tetrahydride anions, PdCuH 4 - , and carbon dioxide, CO 2 , in a reaction cell shows an efficient generation of the PdCuCO 2 H 4 - intermediate and formate/formic acid complexes. Multiple structures of PdCuH 4 - and PdCuCO 2 H 4 - are identified by a synergy between anion photoelectron spectroscopy and quantum chemical calculations. The higher energy PdCuH 4 - isomer is shown to drive the catalytic hydrogenation of CO 2 , emphasizing the importance of accounting for higher energy isomers for cluster catalytic activity. This study represents the first example of CO 2 hydrogenation by bimetallic hydride clusters.

We discovered superconductivity at 4.8 K in the hexagonal layered compound La 2 IRu 2 comprising a triangular lattice of the La and a honeycomb lattice of the Ru atoms. First-principles calculations reveal a two-dimensional band structure made up of La 5 d and Ru 4 d electrons and formal oxidation states +1.5 for the La and the uncommon oxidation state -1 for the Ru atoms. The temperature dependence of the specific heat indicates fully gapped superconductivity. Nevertheless, the upper critical field of this compound violates the Pauli limit. We argue that the high upper critical field is ascribed to an antisymmetric spin-orbit coupling in the unique multilayer structure.

The design and realization of a torque magnetometer is reported that reads the deflection of a membrane by optical interferometry. The compact instrument allows for low-temperature measurements of tiny crystals less than a microgram with a significant improvement in sensitivity, signal-to-noise ratio as well as data acquisition time compared with conventional magnetometry and offers an enormous potential for further improvements and future applications in different fields. Magnetic measurements on single-molecule magnets demonstrate the applicability of the membrane-based torque magnetometer.

We report the synthesis and magnetic and photomagnetic behaviour of a novel valence tautomeric cobalt complex, [Co(3,5-dbbq)2(μ-bpym)] (1) (3,5-dbbq = 3,5-di-tert-butyl-1,2-benzoquinone and μ-bpym = 2,2'-bipyrimidine). The synthesis is performed by reacting Co2(CO)8 and μ-bpym in the presence of the ligand 3,5-dbbq in a mixed solvent under inert atmosphere. The magnetic behavior clearly shows the presence of electron transfer from the catecholate ligand to the cobalt center, producing valence tautomers of [Co(II)(SQ)2] with a transition temperature (T1/2) of 215 K. Photomagnetic studies, performed via both SQUID magnetometry and X-band electron paramagnetic resonance, show the clear presence of photoinduced valence tautomerism, at temperatures considerably higher than previous systems. A metastable charge distribution is observed, strengthening previous investigations on the character of mixed valence ligands. Entropy-driven valence tautomeric interconversion is observed, and drives the transition to the most stable charge distribution. The complex has the ability to coordinate and can be used as a photoswitchable building block, with the photomagnetic characterisation evidencing a metastable state lifetime of the photo-induced valence tautomeric process of ca. 2.9 × 10(4) s below 20 K. The observed yields are higher than ones in similar systems, showing that tiny changes in the molecular structures may have a huge impact.

Hypofrontality and decreased lateralization have been two major, albeit controversial, results from functional neuroimaging studies of schizophrenia. We used fMRI to study cortical activation during a verbal and spatial working memory (WM) task (2-back) in 15 inpatients acutely ill with schizophrenia and 15 matched control subjects. We hypothesized (i) hypofrontality in patients in both tasks and (ii) decreased lateralization of prefrontal activation in patients under the assumption that, in controls, left prefrontal cortex (PFC) is engaged preferentially in the verbal task (verbal domain dominance) and the right prefrontal cortex is engaged preferentially in the spatial task (spatial domain dominance). Our results showed no significant differences in frontal activation between controls and patients, i.e. no hypofrontality in patients, even at a very liberal threshold (p<0.01). This may be explained by the fact that nearly all patients studied received atypical neuroleptics. Nonetheless, we found evidence for more subtle, domain-related prefrontal dysfunction. Whereas controls showed verbal WM domain dominance in left inferior frontal cortex and spatial WM domain dominance in right prefrontal cortex, these domain dominance effects were absent in the patient group, i.e. there were no lateralization effects. Finally, only patients showed an inverse correlation between performance and right prefrontal activation in verbal WM. We conclude that the finding of hypofrontality may depend on the medication of the patients and that there is prefrontal dysfunction even in the absence of hypofrontality.

Purpose: 31P MR spectroscopic imaging (31P SI) was evaluated in a clinical study as a method for monitoring presurgical devascularization of meningiomas. The aim was to assess noninvasively metabolic alterations in tumor and in healthy brain tissue before and after embolization., Methods: Localized 31P MR spectra of the brain were obtained by means of 2D-SI (voxel size: 36 cm3) using a 1,5-T whole-body MR tomograph., Results: Eleven of 19 patients with intracranial meningiomas examined in this study underwent preoperative embolization therapy; eight patients were examined before and after treatment. After embolization, alterations of pH and of the concentrations of high-energy phosphates (nucleoside-5' triphosphate = NTP, phosphocreatine = PCr), inorganic phosphate (Pi), and membrane constituents were observed in the tumors. A tendency of [Pi] increase and decrease of [NTP], [PCr], and pH predominated, which is explained by ischemic processes after tumor devascularization., Conclusion: 31P SI is applicable in clinical studies and detects alterations of phosphate metabolism in a meningioma after embolization.