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Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.

The photocatalytic sulfoxidation on TiO2 discovered by Parrino et al. represents a new, interesting and lower energy route for the synthesis of sulfonic acids.

Knowledge of the structure of the electrical double layer in ionic liquids (IL) is crucial for their applications in electrochemical technologies. We report the synthesis and applicability of an imidazolium-based amphiphilic ionic liquid with a perdeuterated alkyl chain for studies of electric potential-dependent rearrangements, and changes in the microenvironment in a monolayer on a Au(111) surface. Electrochemical measurements show two states of the organization of ions on the electrode surface. In situ IR spectroscopy shows that the alkyl chains in imidazolium cations change their orientation depending on the adsorption state. The methylene-d2 stretching modes in the perdeuterated IL display a reversible, potential-dependent appearance of a new band. The presence of this mode also depends on the anion in the IL. Supported by quantum chemical calculations, this new mode is assigned to a second νas (CD2 ) band in alkyl-chain fragments embedded in a polar environment of the anions/solvent present in the vicinity of the imidazolium cation and electrode. It is a measure of the potential-dependent segregation between polar and nonpolar environments in the layers of an IL closest to the electrode.

The reaction of the titanium imido complex 1b with 2-butyne leads to the formation of the titanium azadiene complex 2a at ambient temperature instead of yielding the archetypical [2 + 2] cycloaddition product (titanaazacyclobutene) which is usually obtained by combining titanium imido complexes and internal alkynes. The formation of 2a is presumably caused by an initial propargylic C(sp3)–H activation step and quantum chemical calculations suggest that the outcome of this unexpected reactivity is thermodynamically favored. The previously reported titanaazacyclobutene I (which is obtained by reacting 1b with 1-phenyl-1-propyne) undergoes a rearrangement reaction at elevated temperature to give the corresponding five-membered titanium azadiene complex 2b.

In this work we investigate the mechanism of photodesorption of water from a WO3(001) surface by theoretical calculations, applying an embedded cluster model. Using the CASSCF method, we have calculated both the ground state as well as the energetically preferred charge-transfer state in three degrees of freedom of the water molecule on the surface. The calculated potential energy surfaces were afterwards fitted with a neural network optimized by a genetic algorithm. A final quantum dynamic wave packet study provided insight into the photodesorption mechanism.

The reaction of the titanium imido complex 1b with 2-butyne leads to the formation of the titanium azadiene complex 2a at ambient temperature instead of yielding the archetypical [2 + 2] cycloaddition product (titanaazacyclobutene) which is usually obtained by combining titanium imido complexes and internal alkynes. The formation of 2a is presumably caused by an initial propargylic C(sp3)–H activation step and quantum chemical calculations suggest that the outcome of this unexpected reactivity is thermodynamically favored. The previously reported titanaazacyclobutene I (which is obtained by reacting 1b with 1-phenyl-1-propyne) undergoes a rearrangement reaction at elevated temperature to give the corresponding five-membered titanium azadiene complex 2b., An unexpected reactivity between a titanium imido complex and internal alkynes was unveiled yielding titanaazacyclobutenes instead of the expected [2 + 2] cycloaddition products.

In this work we use different theoretical approaches to investigate the mechanism of water splitting on (001)-WO3. Using an LCAO approach with periodic boundary conditions, hybrid DFT functionals, ...

A combined theoretical approach towards the accurate description of water on anatase-TiO2(101) was pursued in this study. Firstly, periodic slab calculations on the basis of density hybrid functionals (PBE0, HSE06) were performed in order to gain insight into the adsorption sites and geometric structure of the surface. For submonolayer coverage of H2O, the molecular adsorption of water is found to be the most stable one with quite similar energetics in PBE0 and HSE06. Moreover, the transition states towards the less preferred dissociative adsorption forms are predicted to be greater than 0.7 eV. Thus, water will not spontaneously dissociate and based on the Computational Hydrogen Electrode model an overpotential of about 1.71 V is needed to drive the overall oxidation. In addition, to validate our results for molecular adsorption of H2O, an embedded cluster model is carefully evaluated for the a-TiO2(101) surface based on the periodic slab calculations. Subsequent high-level DLPNO-CCSD(T) results are in close agreement with our periodic slab calculations since the interaction is found to mainly consist of electrostatic contributions which are captured by hybrid functionals. Finally, first results on optimized geometries in the excited state based on the photogenerated charge-transfer state are presented.

Nanoporous gold (np-Au) is a catalytically highly active material, prepared by selectively dealloying silver from a gold–silver alloy. It can promote aerobic CO oxidation and a range of other oxida...

In the present manuscript we used atomistic simulation methodsto investigate the adsorption of GGG on the titania rutile-(110)surface. The molecule showed a high adsorption to the surface es-pecially in its bidentate-⊥mode. This configuration was furtherinvestigated both in terms of charge transfer and strain analysis.In the first case a transfer of roughly one electron was observedfrom the functional groups binding to the surface atoms, leavingthe molecule at the phosphate and carboxylic groups. This chargeis distributed into the rutile’s bulk, where it gets then dissipated.To get a hint on the location of the bond break, the strain analysis identified the C-C bond as the major strain location. This presump-tion can not be confirmed in this work. In order to understand pho-tocaltalytic degradation of GGG in further investigations, a clustermodel was developed for TD-DFT simulations. The cluster simu-lations are in good agreement with the DFT simulations in termsof ground state properties (band gap and HOMO-levels) as well as geometrically optimized structures. Here not only the DOS showeda reduction of the band gap upon adsorption, but also the TD-DFTspectrum lied in the same regime. Hence, there is a high likelihoodfor GGG to proceed in a photocatalytic reaction

One of the main tasks of quantum chemistry is to predict total energies for a given system within an almost nonapproximate method for a complete basis set. Unfortunately, although computational power is growing, approximate methods such as MP2 or CCSD(T) still have to be used as higher-level methods such as full CI are computationally too demanding. Nevertheless, when using these approximations, at least an almost-complete basis set should be used in order to avoid errors from basis set superposition or incompleteness. The aim of this work is to introduce a new method to analyze the local basis set superposition error (LBSSE) using local counterpoise corrections in order to converge a basis set for a given compound. Using this approach, we are able to define a basis set composition for a CO molecule adsorbed on rutile(110), which can be regarded as complete. In the presented work, CO adsorbed on rutile(110) and CO2 adsorbed on a model Ti3O9 cluster will be used as case examples. Therefore, in addition to a new LBSSE analysis method, adsorption energies of CO on rutile(110) at the MP2 and CCSD levels of theory are presented.

Successful and cost-effective water splitting could be one of the most interesting energy sources of the future. The modification of the transition metal oxide rutile-TiO 2 as photocatalyst can lead to improved performance in the water splitting process. For that purpose, an accurate description of the interaction potential of a water molecule and the rutile-TiO 2 (110) surface in the ground and electronically excited state after photoexcitation is crucial. The electronic Schrodinger equation for the states involved is solved pointwise for different nuclear configurations within the Born-Oppenheimer approximation, and accurate fits to these energy points are required to obtain an analytic expression for the potential energy surface. This is too computationally expensive for fine-grained surface calculations of quantum chemical models. In this paper, we propose to use state-of-the-art deep learning techniques to provide accurate fits for this problem. Namely, we employ a fully connected variant of ResNet and DenseNet with heavy regularization (L2, RReLU, Dropout, and BatchNormalization). Previous literature applied neural network approaches before, but with unsatisfactory accuracy. In an experimental evaluation we show that the root mean squared error (RMSE) can be 6.8 times lower for the exited state and 12.7 times lower for the ground state compared to former approaches.

Introducing spectator molecules to the surface of supported noble metal nanoparticles is an innovative approach to improve the selectivity of heterogeneous catalysts. Colloidal synthesis of the nanoparticles allows researchers to select the spectator and the nanoparticle size, as well as the subsequent particle loading on different supports under well-defined conditions. However, understanding the interplay of the various effects that spectators can have on the catalytic properties of metal surfaces still requires further development. In this work, dodecylamine (DDA) is used to develop insights into the influence of spectator species on the chemical properties of 1.4-3.7 nm colloidal Pt nanoparticles on different supports (powders of Al2O3, ZnO, and TiO2). DDA deposition results in two chemically distinct spectator species on the Pt surface depending on temperature, as evidenced from X-ray photoelectron spectroscopy (XPS). DDA selectively blocks terrace sites on the Pt nanoparticles at room temperature, as apparent from diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with CO as a surface-sensitive probe molecule. The electron donor effect of the amine group in DDA influences the electron densities of the accessible lower coordinated, reactive Pt adsorption sites as indicated from spectral shifts in DRIFTS and XPS. Furthermore, DDA suppresses CO-induced surface reconstruction of the Pt surface and metal-support interactions, although these effects depend on temperature and support composition. Therefore, spectators may be used to adjust the nature of metal nanoparticle-oxidic support interactions. The experimental findings and mechanistic explanations are supported by density functional theory calculations. These results may build a platform in understanding the fundamental properties of amine spectators in Pt-based catalysis, activating specific sites, enhancing site selectivity, acting as sensors, and directing the metal-support interaction.

The interaction of molecules with low coordinated sites and possible modification of surfaces caused by adsorbates are of crucial importance for an understanding of chemical processes on surfaces. Herein, CO adsorption on a stepped Au(332) surface is investigated by combining infrared spectroscopy and density functional theory calculations. It is shown that infrared spectroscopic characterization of isotopically diluted mixtures allows distinguishing different components. These components exhibit significantly different adsorption energies as well as vibrational characteristics which can be understood with the help of a theoretical analysis based on density functional theory (DFT). In addition, it is shown that CO induces a restructuring of the surface, leading to a significantly more heterogeneous ensemble of adsorption sites and a significant reduction of sites with the highest CO adsorption energy.

Through solving the time-dependent Schrodinger equation for the nuclear motion, quantum dynamical simulations of the water/TiO2-rutile (110) system were performed. Five-dimensional potential energy surfaces (PES) for the electronic ground and an excited state previously calculated on CASSCF (Complete Active Space Self-Consistent Field) level of theory served as the starting point for our investigations [J. Mitschker, T. Kluner, Phys. Chem. Chem. Phys. 17 (2015) 268–275]. Through investigating the motion of the water molecule by a selected series of three- and four-dimensional simulations, a precise picture of the photodissociation mechanism is obtained. Furthermore, calculations of photodissociation probabilities reveal the most favoured pathway for a complete dissociation of the adsorbate including the excitation and relaxation process as well as temperature effects.

The reaction of CO with O2 on bimetallic M(321) surfaces (M = Au, Ag, Cu) is investigated using density functional theory (DFT). On monometallic Au and Ag and on bimetallic gold-rich AuAg surfaces, first an OCOO* intermediate and subsequently CO2 and O* are formed in a two-step mechanism. On silver-rich AgCu(321) with Cu dimers substituting Ag at steps, CO2 and O* are formed in a direct one-step mechanism. The adsorption probability of molecular oxygen increases from gold to silver to copper. By replacing surface atoms with other less noble coinage metals, the adsorption strength of O2 is increased compared to the pure metal. If O2 binds to a pair of Cu impurity atoms in Ag(321), its adsorption strength becomes even higher than on pure Cu(321) due to a strong 3d → 2π* back-donation reinforced by tensile strain.

Nanoporous gold (np-Au) has recently emerged as a highly selective environmentally friendly catalyst for low-temperature applications. Despite the seeming simplicity of this material, which consists of almost pure gold, its surface chemistry turns out to be more complex than anticipated. Interactions among gold, chemisorbed O atoms generated and consumed during catalysis, and trace amounts of Ag impurities present in np-Au lead to complex surface dynamics. In this work, theoretical modeling by means of ab initio molecular dynamics (AIMD) is combined with an Auger electron spectroscopic study to investigate oxygen-driven Ag surface diffusion on Au model surfaces exhibiting structural characteristics of np-Au. AIMD simulations reveal that surface O atoms dynamically form −(Au–O)– chain structures on the stepped Au(321) surface and lead to surface restructuring, but no chain formation is found on the flat Au(111). Ag impurities at low concentration lower the activation barrier for −(Au–O)– chain formation, w...

The reaction of bis(η5 :η1 -pentafulvene)titanium complexes with an allylidenephosphorylide Ph3 P=C(H)- C(H)=CH2 leads to binuclear zigzag hexapentaene titanium complexes (Ti2a, Ti2b). The formation of the central C6 H4 unit can be described as a spontaneous double C-H bond activation process, leading to an R3 P=C=C=CH2 intermediate, as a synthon for a titanabutatriene fragment [(CpR )2 Ti=C=C=CH2 ] (R: 2-adamantyl, CH(p-tol)2 ). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single-crystal X-ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations.

Designing efficient algorithms to apply highly accurate pair correlation methods to large molecules of scientific interest has remained an important field of research for a long period of time. We present a new approach toward fast algorithms, which represents an interesting alternative and extension to currently existing methods. The presented new contraction scheme saves a significant amount of memory and can be easily combined with efficient linear scaling algorithms. Additionally, the extension to orbital optimization and explicitly correlated f12-theory is demonstrated to further improve accuracy and applicablility.

The catalytic behavior of several acidic and alkaline solids was investigated in the heterogeneous dehydration of 2,3-butanediol in the temperature range of 350–800 °C. At low temperatures butanone is the main product for all used catalysts. Its yield decreases with increasing temperatures. The formation of 1,3-butadiene was observed over the whole temperature range. Its maximum formation around 700 °C was explained in term of non-catalytic thermal dehydration. DFT calculations of the dehydration steps were made to explain the results. It was shown, that a hydride shift directs the reaction towards the formation of butanone.

The development of hybrid organic-inorganic perovskite solar cells is one of the most rapidly growing fields in the photovoltaic community and is on its way to challenge polycrystalline silicon and thin film technologies. High power conversion efficiencies can be achieved by simple processing with low cost. However, due to the limited long-term stability and environmental toxicity of lead in the prototypic CH3NH3PbI3, there is a need to find alternative ABX3 constitutional combinations in order to promote commercialization. The Goldschmidt tolerance factor and the octahedral factor were found to be necessary geometrical concepts to evaluate which perovskite compounds can be formed. It was figured out that the main challenge lies in estimating an effective ionic radius for the molecular cation. We calculated tolerance factors and octahedral factors for 486 ABX3 monoammonium-metal-halide combinations, where the steric size of the molecular cation in the A-position was estimated concerning the total charge density. A thorough inquiry about existing mixed organic-inorganic perovskites was undertaken. Our results are in excellent agreement with the reported hybrid compounds and indicate the potential existence of 106 ABX3 combinations hitherto not discussed in the literature, giving hints for more intense research on prospective individual candidates.

Invited for the cover of this issue are Elad Gross, F. Dean Toste, and co-workers at The Hebrew University and UC Berkeley. The image depicts the flexible anchoring geometry of addressable carbene molecules on Au surface, which upon exposure to reducing conditions changed their orientation from a standing into a flat-lying position. Read the full text of the article at 10.1002/chem.201903434.

The Cover Feature shows a quite strict correlation which was found between the redox potential and the spectroscopic properties of asymmetrically derivatized 2,5‐diaminoterephthalates (DAT). This correlation allows for the tuning of the redox and emission behaviors of those dyes, or the observation of effector binding to the chromophore. More information can be found in the Full Paper by A. Markovic et al. on page 1176 in Issue 9, 2019 (DOI: 10.1002/open.201900138).[Image: see text]

The development of chemically addressable N-heterocyclic carbene (NHC) based self-assembled monolayers (SAMs) requires in-depth understanding of the influence of NHC's anchoring geometry on its chemical functionality. Herein, it is demonstrated that the chemical reactivity of surface-anchored NO

The development of chemically addressable N-heterocyclic carbene (NHC) based self-assembled monolayers (SAMs) requires in-depth understanding of the influence of NHC’s anchoring geometry on its chemical functionality. Herein, it is demonstrated that the chemical reactivity of surface-anchored NO2-functionalized NHCs (NO2–NHCs) can be tuned by modifying the distance between the functional group and the reactive surface, which is governed by the deposition technique. Liquid deposition of NO2–NHCs on Pt(111) induced a SAM in which the NO2-aryl groups were flat-lying on the surface. The high proximity between the NO2groups and the Pt surface led to high reactivity, and 85% of the NO2groups were reduced at room temperature. Lower reactivity was obtained with vapor-deposited NO2–NHCs that assumed a preferred upright geometry. The separation between the NO2groups in the vapor-deposited NO2–NHCs and the reactive surface circumvented their surface-induced reduction, which was facilitated only after exposure to harsher reducing conditions.

The formation of flexible self-assembled monolayers (SAMs) in which an external trigger modifies the geometry of surface-anchored molecules is essential for the development of functional materials with tunable properties. In this work we demonstrate that NO2-functionalized N-heterocyclic carbene molecules (NHCs), which were anchored on Au (111) surface, change their orientation from tilted into a flat-lying position following trigger-induced reduction of their nitro groups. DFT calculations identified that the energetic driving force for reorientation was the lower steric hindrance and stronger interactions between the chemically-reduced NHCs and the Au surface. The trigger-induced changes in the NHCs’ anchoring geometry and chemical functionality modified the work function and the hydrophobicity of the NHCs-decorated Au surface, demonstrating the impact of chemically-tunable NHCs-based SAM on the properties of the metal surface.

The reaction of Na2 SO4 and K2 SO4 with fuming sulfuric acid (65 % SO3 ) yielded colorless extremely sensitive crystals of Na[HS3 O10 ] (monoclinic; P21 /n (No. 14); Z=4; a=707.36(2), b=1378.56(4), c=848.10(3) pm; β=94.817(1)°; V=824.09(4)⋅106 pm3 ) and K[HS3 O10 ] (orthorhombic; Pccn (No. 56); Z=4; a=1057.16(3), b=807.81(2), c=897.57(2) pm; V=766.51(3)⋅106 pm3 ). The analogous rubidium compound Rb[HS3 O10 ] (orthorhombic; Pnma (No. 62); Z=4; a=891.43(3), b=1095.34(4), c=839.37(3) pm; V=819.58(5)⋅106 pm3 ) originates from the reaction of Rb2 CO3 and SO3 . All of the different structures contain the hitherto unknown anion [HS3 O10 ]- and are stamped by strong hydrogen bonds linking the anions either to dimers or chains. Theoretical investigations by DFT methods give further insight in the structural characteristics of [HS3 O10 ]- . The preparation of the [HS3 O10 ]- anion can be seen as an important milestone on our way to the still elusive polysulfuric acids.

For the first time tetravalent palladium is detected, coordinated exclusively by simple oxoanions. Stabilization was achieved by formation of the [Pd(S2 O7 )3 ](2-) complex in which three chelating disulfate groups surround the metal atom. The salt K2 [Pd(S2 O7 )3 ] could only be obtained if the reaction of K2 [PdCl6 ] and neat SO3 was performed in the presence of XeF2 .

Erstmalig wurde eine Verbindung synthetisiert, in der Pd4+-Kationen ausschlieslich von einfachen Oxoanionen koordiniert werden. Die Stabilisierung des vierwertigen Palladiums erfolgt durch Bildung des Komplexanions [Pd(S2O7)3]2−, in dem das Metallatom von drei chelatisierenden Disulfatgruppen umgeben wird. Interessanterweise wird das Salz K2[Pd(S2O7)3] nur dann erhalten, wenn die Reaktion von K2[PdCl6] und reinem SO3 in Gegenwart von XeF2 durchgefuhrt wird.

Multinuclear transition metal complexes bridged by ligands with extended π‐electronic systems show a variety of complex electronic transitions and electron transfer reactions. While a systematic understanding of the photochemistry and electrochemistry has been attained for binuclear complexes, much less is known about trinuclear complexes such as hexaphenyl‐5,6,11,12,17,18‐hexaazatrinaphthylene‐tristitanocene [(Cp2Ti)3HATN(Ph)6]. The voltammogram of [(Cp2Ti)3HATN(Ph)6] shows six oxidation and three reduction waves. Solution spectra of [(Cp2Ti)3HATN(Ph)6] and of the electrochemically formed oxidation products show electronic transitions in the UV, visible and the NIR ranges. Density functional theory (DFT) and linear response time‐dependent DFT show that the three formally titanium(II) centers transfer an electron to the HATN ligand in the ground state. The optically excited transitions occur exclusively between ligand‐centered orbitals. The charged titanium centers only provide an electrostatic frame to the extended π‐electronic system. Complete active self‐consistent field (CASSCF) calculation on a structurally simplified model compound, which considers the multi‐reference character imposed by the three titanium centers, can provide an interpretation of the experimentally observed temperature‐dependent magnetic behavior of the different redox states of the title compound in full consistency with the interpretation of the electronic spectra., More complex?! The ground state of the three‐nuclear [(Cp2Ti)3HATN(Ph)6] complex is formed by spin states of different multiplicity and explains the rich electronic transition in the UV‐vis‐NIR ranges in different charge states. Contrary to common notion, IVCT transitions do not play a role in the NIR spectra.

This work establishes a comprehensive analysis of the role of steps and kinks of the Au(3 1 0) surface in the generation of active oxygen species and elucidates the reaction pathway for methanol oxidation to formaldehyde. We have considered two possibilities for the O–O bond splitting in molecular O2: via a dissociative O2 adsorption or a direct reaction of O2 with methanol. Both reaction pathways more favorably take place on the step edges of Au(3 1 0) than on flat Au(1 1 1). Depending on the adsorption positions of O2, different dissociation pathways are possible, where the most favored path shows a substantially lower activation barrier compared to the flat gold surface. Atomic oxygen generated on the surface, prefers to build O–Au–O fragments with stronger binding to the surface than individually adsorbed O. The reaction pathways for methanol reaction with O and O2 have been analyzed and compared. The direct reaction of methanol with molecular oxygen (an associative mechanism) proceeds via a formation of the OOH intermediate and its further dissociation to O and OH. This reaction sequence has low activation barriers of 0.3–0.4 eV and therefore should be preferred over O2 dissociation to atomic O and the following reaction of O with methanol. By analogy, O2 can react with water generating OOH with similarly low activation barriers. We have supported the proposed associative mechanism by microkinetic modeling.

The α-alkylation of amines with alkenes catalyzed by early transition-metal complexes represents an efficient and atom economic method for the synthesis of functionalized amines from simple and easily available starting materials. While the successful use of secondary amines, such as dimethylamine, strongly underlines the enormous industrial potential of this reaction, the analogous intermolecular α-alkylation of primary amines, especially methylamine, remains an unsolved synthetic task to this day. Based on calculated thermodynamic data, these experimental findings can now be explained for the first time, whereby several competing reactions, which are explained in detail, are of crucial importance for the different behavior of primary and secondary amines.

The focus of this study lies in the activation of molecular oxygen and reaction with CO within density functional theory (DFT) and high level CCSD(T) calculations. Therefore, we use M13 and M55 nanoparticles (NPs) and periodic M(321) surfaces as model systems and compare the catalytic activity of gold substrates to Ag and Cu based NP catalysts. In the first step, the adsorption energies of CO were compared for nanoparticles of different sizes for Au, Ag and Cu. The adsorption energies on M(321) and M55 NPs (M = Au, Ag, Cu) are virtually identical. For smaller M13 NPs the adsorption energies differ by ∼0.2 eV for Ag, ∼0.4 eV for Au, and ∼0.6 eV for Cu at the PBE level of theory. This can be explained by size effects, as the M13 NPs show a more molecule-like character. Presumably, CO binds more strongly to these very small NPs at the PBE level of theory. However, a benchmark calculation in the framework of CCSD(T)-theory reveals an adsorption energy of CO on Au13 of −0.88 eV, comparable to the adsorption energies calculated at the PBE level for Au55 and Au(321). For Au55, the adsorption energy calculated at the CCSD(T) level is −0.85 eV. This is in perfect agreement with the PBE result. In addition to adsorption energies, dissociation barriers have been calculated on M(321) surfaces. The dissociation energies of O2 on coinage metal catalysts are high, so that direct CO-oxidation reactions with molecular oxygen should be the dominant reaction mechanism compared to the dissociation and reaction of CO and atomic oxygen at least for silver and copper catalysts.

The theoretical treatment of photoreactions on surfaces are addressed in this article by combining quantum chemical and quantum dynamical methods which allows for a profound insight into adsorption and reaction mechanisms concerning surfaces. Our model system involves the adsorption of water on the titanium dioxide rutile (110) surface and its dissociation induced by photochemistry. Although water splitting in general has been studied intensively in the last decades, still no common understanding of the elementary reaction steps exists. At first, potential energy surfaces of the water molecule in five dimensions that are presumably relevant for the dissociation process for the electronic ground and the excited state will be calculated. These will subsequently be employed in our quantum dynamical calculations based on wave-packet simulations. As a result, two possible photoreactions of the water molecule comprising its desorption and its dissociation will be evaluated on a highly sophisticated level of theory. Furthermore, the calculated photodissociation probabilities will finally reveal the most preferred pathway of the initial step of the water splitting reaction.

Nanoporous gold (np-Au) has recently attracted arising interest due to its potential use in catalysis. This unsupported Au-based material etched from bulk Au–Ag alloys combines overall macroscopic dimensions with open porosity at the nanoscale. Recent studies demonstrated high catalytic activity and selectivity of np-Au in a range of low-temperature aerobic oxidation reactions, such as CO oxidation or oxidative coupling/cross-coupling of alcohols to esters. In particular, partial oxidation of alcohols represents an important class of transformations in modern chemical industry and is one of the greatest challenges of energy-efficient “green” chemistry. We provide an up-to-date overview of the current literature and summarize the mechanistic picture of alcohol oxidation catalyzed by np-Au. We discuss the nanoscale structure, silver residues, and atomic surface oxygen as probable essential ingredients responsible for the catalytic activity of np-Au.

Cyclocondensation of alicyclic and heterocyclic α-hydroxy β-dicarbonyl compounds with dimethyl malonate gives bicyclic butenolide derivatives. The reaction sequence is catalyzed by 4-(N,N-dimethylamino)pyridine and consists of two processes: Knoevenagel condensation followed by transesterification. Depending on the chemical nature of the β-dicarbonyl moiety (oxoester, diketone or α-acetyl lactone or lactam), products with either annulated or spirocyclic constitution are obtained.

The adsorption of oxygen on kinked Au(321) slabs is investigated theoretically on the basis of density functional theory. On-surface, subsurface, and surface-oxide forms of O are analyzed and compared on pure gold and on the surfaces containing silver atoms. At low O coverage (0.1 ML) subsurface O species are shown to be unstable both thermodynamically and kinetically due to a low barrier for conversion to stronger bound on-surface chemisorbed oxygen. The presence of Ag in the near-surface region was shown to increase the binding strength of on-surface as well as subsurface O, but the activation barrier for releasing subsurface O to the surface remains essentially unaffected by the presence of Ag. At oxygen coverage 0.2 ML or higher, the most stable surface arrangements of O atoms are chain-like structures consisting of linear −O–Au–O– fragments. Subsurface O atoms being a part of such chains are significantly stabilized. We examine phase transitions between the clean surface and possible stable oxidized ...

In this paper, we report on our results concerning the interaction of water with titanium dioxide in its rutile modification. The (110) surface is modelled by an embedded Ti9O18Mg7(14+) cluster. We present up to five-dimensional potential energy surfaces for the water molecule on this surface and include the dissociation of one hydrogen atom. The electronic ground state as well as one electronically excited state is included. To deal with the multi-configurational character of the wave function, we use the complete active space self-consistent field (CASSCF) approach. The resulting potential energy surfaces are fitted by means of an artificial neural network. As a first example of quantum dynamical studies based on our potential surfaces, we present results on the photodesorption of water from rutile(110).

The S6 O192- ion was obtained both as rubidium and ammonium salt from the reaction of the respective sulfate with SO3 . It is the largest polysulfate ion known to date and exhibits a chain of six vertex-connected [SO4 ] tetrahedra. The unique compound was comprehensively characterized and the bonding within the anion was elucidated by theoretical investigations.

The reaction of bis(η

The oxidation of elemental palladium at 100 °C in a mixture of fuming nitric acid and a pyridine-SO3 complex leads to the anhydrous nitrate Pd(NO3)2 (monoclinic, P2(1)/n, Z=2, a=469.12(3) pm, b=593.89(3) pm, c=805.72(4) pm, β=105.989(3)°, V=215.79(2) Å(3)). The Pd(2+) ions are in square-planar coordination with four monodentate nitrate groups which are connected to further palladium atoms, leading to a layer structure. The reaction of elemental palladium with a mixture of fuming nitric acid and methanesulfonic acid at 120 °C leads to single crystals of Pd(CH3SO3)2 (monoclinic, P2(1)/n, Z=2, a=480.44(1) pm, b=1085.53(3) pm, c=739.78(2) pm, β=102.785(1)°, V=376.254(17) Å(3)). Also in this structure the Pd(2+) ions are in square-planar coordination with four monodentate anions; however, the connection to adjacent palladium atoms leads to a chain-type structure. The thermal decomposition of the compounds has been investigated by means of DSC/TG measurements. Furthermore, IR and Raman spectra have been recorded, and an assignment of the observed vibrational frequencies has been carried out based on theoretical investigations.

For the first time, direct oxidation of elemental platinum by a mineral acid to its tetravalent state was observed in course of the reaction of platinum with oleum (65 % SO3) in the presence of barium carbonate. The reaction has been carried out in torch-sealed glass ampoules at 160 °C and gave yellow single crystals of Ba[Pt(S2O7)3](H2SO4)0.5(H2S O7)0.5 (triclinic, P1, Z=2, a=992.05(2), b=1069.07(3), c=1114.22(3) pm, α=69.49(7), β=72.96(2), γ=72.93(1)°, V=1033.95(5) Å(3)). The structure of Ba[Pt(S2O7)3](H2SO4)0.5(H2S2O7)0.5 exhibits the unique tris-(disulfato)-platinate anion [Pt(S2O7)3](2-) with three chelating disulfate groups coordinated to the platinum atom. Charge balance is achieved by the Ba(2+) ions, which are coordinated by (S2O7)(2-) groups from the platinate complex and by disordered sulfuric acids and disulfuric acid molecules. Thermal decomposition of the bulk material revealed elemental platinum and barium sulfate as decomposition residual.