The mechanism of Ce(IV) water oxidation catalyzed by [Ru(tpy)(bpm)(OH(2))](2+) (tpy = 2,2':6',2''-terpyridine; bpm = 2,2'-bipyrimidine) and related single-site catalysts has been determined by a combination of mixing and stopped-flow experiments with spectrophotometric monitoring. The mechanism features O---O coupling by water attack on Ru(V)=O(3+) and three peroxidic intermediates that have been characterized by a combination of spectroscopy and DFT calculations.

Copper electrocatalysts have been shown to selectively reduce carbon dioxide to hydrocarbons. Nevertheless, the absence of a systematic study based on time-resolved spectroscopy renders the functional agent-either metallic or oxidative Copper-for the selectivity still undecidable. Herein, we develop an operando seconds-resolved X-ray absorption spectroscopy to uncover the chemical state evolution of working catalysts. An oxide-derived Copper electrocatalyst is employed as a model catalyst to offer scientific insights into the roles metal states serve in carbon dioxide reduction reaction (CO 2 RR). Using a potential switching approach, the model catalyst can achieve a steady chemical state of half-Cu(0)and-half-Cu(I) and selectively produce asymmetric C 2 products-C 2 H 5 OH. Furthermore, a theoretical analysis reveals that a surface composed of Cu-Cu(I) ensembles can have dual carbon monoxide molecules coupled asymmetrically, which potentially enhances the catalyst's CO 2 RR product selectivity toward C 2 products. Our results offer understandings of the fundamental chemical states and insights to the establishment of selective CO 2 RR.

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We present an approach to calculate the free energy profile along a condensed-phase reaction path based on high-level electronic structure methods for the reactive region. The bulk of statistical averaging is shifted toward less expensive descriptions by using a hierarchy of representations that includes molecular mechanics, density functional theory, and coupled cluster theories. As an application of this approach we study the reaction of CHCl3 with OH- in aqueous solution.

Ion-molecule complexes of the form Mg(H2O)Ar(n)+ (n = 1-8) are produced by laser vaporization in a pulsed-nozzle cluster source. These complexes are mass-selected and studied with infrared photodissociation spectroscopy in the O-H stretch region. The spectra are interpreted with the aid of ab initio calculations on the n = 1-5 complexes, including examination of various isomeric structures. The combined spectroscopic and theoretical studies reveal the presence of multiple isomeric structures at each cluster size, as the argon atoms assemble around the Mg(+)(H2O) unit. Distinct infrared resonances are measured for argon-on-metal, argon-on-OH and argon-on-two-OH isomers.

Tin perovskite nanomaterial is one of the promising candidates to replace organic lead halide perovskites in lighting applications. Unfortunately, the performance of tin-based systems is markedly inferior to those featuring toxic Pb salts. In an effort to improve the emission quantum efficiency of nanoscale 2D layered tin iodide perovskites through fine-tuning the electronic property of organic ammonium salts, we came to unveil the relationship between dielectric confinement and the photoluminescent properties of tin iodide perovskite nanodisks. Our results show that increasing the dielectric contrast for organic versus inorganic layers leads to a bathochromic shift in emission peak wavelength, a decrease of exciton recombination time, and importantly a significant boost in the emission efficiency. Under optimized conditions, a leap in emission quantum yield to a record high 21% was accomplished for the nanoscale thienylethylammonium tin iodide perovskite (TEA 2 SnI 4 ). The as-prepared TEA 2 SnI 4 also possessed superior photostability, showing no sign of degradation under continuous irradiation (10 mW/cm 2 ) over a period of 120 h.

The interaction and mechanism for CO oxidation on the Mn/ CeO 2 (111) surface have been studied by using periodic density functional theory calculations corrected with the on-site Coulomb interaction via a Hubbard term (DFT + U). It is found that the Mn dopant facilitates oxygen vacancy formation, while the Mn adatoms may restrain oxygen vacancy formation. In addition, physisorbed CO, physisorbed CO 2 ,and chemisorbed CO (carbonite, CO 2 − ) species are observed on the Mn-doped CeO 2 (111) surface, in contrast, only physisorbed CO is found on the pure CeO 2 (111) surface. The vibrational frequency calculations as well as the calculated adsorption energies are carried to characterize these species. The Mn dopant promotes CO oxidation without any activation energy leading to O vacancy formation and CO 2 desorption. The Bader charge analysis is carried to characterize the oxidation state of Mn ions along the catalytic cycle.

The redox states of Ru(OH(2))(Q)(tpy)(2+) (Q = 3,5-di-tert-butyl-1,2-benzoquinone, tpy = 2,2':6',2''-terpyridine) are investigated through experimental and theoretical UV-vis spectra and Pourbaix diagrams. The electrochemical properties are reported for the species resulting from deprotonation and redox processes in aqueous solution. The formal oxidation states of the redox couples in the various intermediate complexes are systematically assigned using electronic structure theory. The controversy over the electronic assignment of ferromagnetic vs. antiferromagnetic coupling is investigated through comparison of ab initio methods and the broken-symmetry density functional theory (DFT) approach. The various pK(a) values and reduction potentials, including the consideration of proton-coupled electron-transfer (PCET) processes, are calculated, and the theoretical version of the Pourbaix diagram is constructed in order to elucidate and assign several previously ambiguous regions in the experimental diagram.