Theoretical Investigations and Comparisons of the Amorphous Structures of Adamantane-like Cluster Materials Utilizing Molecular Dynamics Simulations.

Cluster materials of the composition AdR (Ad = adamantane, R = organic substituent) and [(RT)E] (R = organic substituent; T = Si, Ge, Sn; and E = S, Se, Te) exhibit directional white light emission or produce second harmonics when irradiated with a continuous wave infrared laser source. The nature of the nonlinear optical properties correlates with the macroscopic structures of the cluster materials. The desired white light emission predominantly occurs in amorphous materials.

From Lithium and Sodium Superoxides to Singlet-Oxygen - Insights into the Mechanism of Dissociation Using SHARC-MD.

The formation of highly reactive singlet oxygen from alkaline superoxides presents an important reactivity of this component class. Investigations of the reaction paths such as disproportionation of LiO and NaO have been presented. Furthermore, the dissociation of these superoxide systems have been discussed as an alternative reaction channel that also allows the formation of singlet oxygen.

Development of a multi-step screening procedure for redox active molecules in organic radical polymer anodes and as redox flow anolytes.

Benzo[d]-X-zolyl-pyridinyl (XO, S, NH) radicals represent a promising class of redox-active molecules for organic batteries. We present a multistep screening procedure to identify the most promising radical candidates. Experimental investigations and highly correlated wave function-based calculations are performed to determine benchmark redox potentials.

Deciphering the Mechanism of On-Surface Dehydrogenative C-C Coupling Reactions.

On-surface synthesis has proven to be a powerful approach for fabricating various low-dimensional covalent nanostructures with atomic precision that could be challenging for conventional solution chemistry. Dehydrogenative C-C coupling is one of the most popular on-surface reactions, of which the mechanisms, however, have not been well understood due to the lack of microscopic insights into the intermediates that are fleetingly existing under harsh reaction conditions. Here, we bypass the most energy-demanding initiation step to generate and capture some of the intermediates at room temperature (RT) via the cyclodehydrobromination of 1-bromo-8-phenylnaphthalene on a Cu(111) surface.

Development of Novel Redox-Active Organic Materials Based on Benzimidazole, Benzoxazole, and Benzothiazole: A Combined Theoretical and Experimental Screening Approach.

Sustainability is one of the hot topics of today's research, in particular when it comes to energy-storage systems such as batteries. Redox-active molecules implemented in organic batteries represent a promising alternative to lithium-ion batteries, which partially rely on non-sustainable heavy metal salts. As an alternative, we propose benzothiazole, -oxazole and -imidazole derivatives as redox-active moieties for polymers in organic (radical) batteries.

How Adsorption Affects the Energy Release in an Azothiophene-Based Molecular Solar-Thermal System.

Molecular solar-thermal (MOST) systems combine solar energy conversion, storage, and release within one single molecule. To release the energy, different approaches are applicable, e.g.

Insights into molecular cluster materials with adamantane-like core structures by considering dimer interactions.

A class of adamantane-like molecular materials attracts attention because they exhibit an extreme non-linear optical response and emit a broad white-light spectrum after illumination with a continuous-wave infrared laser source. According to recent studies, not only the nature of the cluster molecules, but also the macroscopic structure of the materials determines their non-linear optical properties. Here we present a systematic study of cluster dimers of the compounds AdR and [(RT) S ] (T = Si, Ge, Sn) with R = methyl, phenyl or 1-naphthyl to gain fundamental knowledge about the interactions in the materials.

Cluster-Glass for Low-Cost White-Light Emission.

The development of efficient and high-brilliance white-light sources is an essential contribution to innovative emission technologies. Materials exhibiting strong nonlinear optical properties, in particular second-harmonic generation (SHG) or white-light generation (WLG), have therefore been investigated with great activity in recent times. While many new approaches have been reported until now, the processability of the compounds remains a challenge.

Bonding character of intermediates in on-surface Ullmann reactions revealed with energy decomposition analysis.

On-surface synthesis has become a thriving topic in surface science. The Ullmann coupling reaction is the most applied synthetic route today, but the nature of the organometallic intermediate is still under discussion. We investigate the bonding nature of prototypical intermediate species (phenyl, naphthyl, anthracenyl, phenanthryl, and triphenylenyl) on the Cu(111) surface with a combination of plane wave and atomic orbital basis set methods using density functional theory calculations with periodic boundary conditions.

Influence of the PON structural units on the formation energies and transport properties of lithium phosphorus oxynitride: a DFT study.

The potential of mobile applications for digital networking is constantly increasing. A key challenge is to ensure a reliable and long-term power supply. One possible solution is the use of all-solid-state thin-film lithium batteries which use amorphous lithium phosphorus oxynitride (LIPON) as solid electrolyte.

Singlet Oxygen in Electrochemical Cells: A Critical Review of Literature and Theory.

Rechargeable metal/O batteries have long been considered a promising future battery technology in automobile and stationary applications. However, they suffer from poor cyclability and rapid degradation. A recent hypothesis is the formation of singlet oxygen (O) as the root cause of these issues.

Uncertainty of exchange-correlation functionals in density functional theory calculations for lithium-based solid electrolytes on the case study of lithium phosphorus oxynitride.

Amorphous lithium phosphorus oxynitride (LIPON) has emerged as a promising solid electrolyte for all-solid-state thin-film lithium batteries. In this context, the use of theoretical modeling to characterize, understand, or screen material properties is becoming increasingly important to complement experimental analysis or elucidate features at atomistic level that are difficult to obtain through experimental studies. Density functional theory (DFT) is the method of choice for quantum mechanical material modeling at the atomistic scale.

Mechanism of Heterogenization of Dirhodium Catalysts: Insights from DFT Calculations.

Dirhodium(II) complexes such as [Rh(TFA)] bound to a functionalized mesoporous SBA-15 carrier material have proven to be valuable candidates for heterogeneous catalysis in the field of pharmaceutical synthesis. However, the mechanistic steps of immobilization by linker molecules containing carboxyl or amine functionalities remain the subject of discussion. Here we present a theoretical study of possible mechanistic binding pathways for the [Rh(TFA)] complex through model representations of synthetically investigated linkers, namely -butylamine and -butyric acid.

Surface-controlled reversal of the selectivity of halogen bonds.

Intermolecular halogen bonds are ideally suited for designing new molecular assemblies because of their strong directionality and the possibility of tuning the interactions by using different types of halogens or molecular moieties. Due to these unique properties of the halogen bonds, numerous areas of application have recently been identified and are still emerging. Here, we present an approach for controlling the 2D self-assembly process of organic molecules by adsorption to reactive vs.

Towards Understanding the Reactivity and Optical Properties of Organosilicon Sulfide Clusters.

We report the extension of the class of organotetrel sulfide clusters with further examples of the still rare silicon-based species, synthesized from RSiCl with R=phenyl (Ph, I), naphthyl (Np, II), and styryl (Sty, III) with Na S. Besides known [(PhSi) S ] (IV), new compounds [(NpSi) S ] (1) and [(StySi) S ] (2) were obtained, the first two of which underwent reactions with [AuCl(PPh )] to form ternary complexes. DFT studies of cluster dimers helped us understand the differences between the habit of {Si S }- and {Sn S }-based compounds.

Pathways to Triplet or Singlet Oxygen during the Dissociation of Alkali Metal Superoxides: Insights by Multireference Calculations of Molecular Model Systems.

Recent experimental investigations demonstrated the generation of singlet oxygen during charging at high potentials in lithium/oxygen batteries. To contribute to the understanding of the underlying chemical reactions a key step in the mechanism of the charging process, namely, the dissociation of the intermediate lithium superoxide to oxygen and lithium, was investigated. Therefore, the corresponding dissociation paths of the molecular model system lithium superoxide (LiO ) were studied by CASSCF/CASPT2 calculations.

New insights into the origin of unstable sodium graphite intercalation compounds.

The thermodynamically unstable binary graphite intercalation compounds (GICs) with Na remain a main drawback preventing the implementation of Na-ion batteries in the market. In order to shed some light on the origin of Na-GICs instability, we investigate the structure and the energetics of different alkali metal (AM)-GICs by means of density functional theory (DFT) calculations with dispersion correction. We carefully consider different stages of AM-GICs for various AM concentrations and compare the results for Li, Na and K intercalation into graphite.

Comparative study of density functionals for the description of lithium-graphite intercalation compounds.

The lack of description of van der Waals interactions in layered materials such as graphite and binary graphite intercalation compounds remains a main drawback of conventional density functional theory. Two fundamentally different approaches to overcome this issue are the employment of semiempirical dispersion correction scheme such as Grimme dispersion correction or nonlocal density functionals. We carefully compare these two approaches for the description of the geometric structure and the thermodynamic stability of pure graphite and Li-GICs at different lithium concentrations and stages.

Adsorption of Mono- and Divalent 4-(Dimethylamino)pyridines on Gold Surfaces: Studies by Surface-Enhanced Raman Scattering and Density Functional Theory.

The adsorption thermodynamics of 4-(dimethylamino)pyridine (DMAP) and its five divalent derivatives di-DMAP- n (2 ≤ n ≤ 6) with gradually increasing methylene-spacer lengths n binding to planar gold surfaces has been studied by surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT). SERS intensities of the totally symmetrical breathing mode of the pyridine ring at approximately 1007 cm are used to monitor the surface coverage of the DMAP and di-DMAP- n ligands on gold surfaces at different concentrations. The equilibrium constant as a measure of the binding affinity is obtained from these measurements by using a modified Langmuir isotherm.

Bond-Level Imaging of the 3D Conformation of Adsorbed Organic Molecules Using Atomic Force Microscopy with Simultaneous Tunneling Feedback.

The chemical structure and orientation of molecules on surfaces can be visualized using low temperature atomic force microscopy with CO-functionalized tips. Conventionally, this is done in constant-height mode by measuring the frequency shift of the oscillating force sensor. However, this method is unsuitable for analyzing 3D objects.

Adsorption Structure of Mono- and Diradicals on a Cu(111) Surface: Chemoselective Dehalogenation of 4-Bromo-3″-iodo- p-terphenyl.

Selectivity is a key parameter for building customized organic nanostructures via bottom-up approaches. Therefore, strategies are needed that allow connecting molecular entities at a specific stage of the assembly process in a chemoselective manner. Studying the mechanisms of such reactions is the key to apply these transformations for the buildup of organic nanostructures on surfaces.

Critical Role of the Crystallite Size in Nanostructured LiTiO Anodes for Lithium-Ion Batteries.

Lithium titanate LiTiO (LTO) is regarded as a promising alternative to carbon-based anodes in lithium-ion batteries. Despite its stable structural framework, LTO exhibits disadvantages, such as the sluggish lithium-ion diffusion and poor electronic conductivity. To modify the performance of LTO as an anode material, nanosizing constitutes a promising approach and the impact is studied here by a systematical experimental approach.

Synthesis of an Iron(IV) Aqua-Oxido Complex Using Ozone as an Oxidant.

The iron(IV) oxido complex [(tmc)Fe=O(OTf)]OTf with the macrocyclic ligand 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclo-tetradecane (tmc) has been synthesized using ozone as an oxidant. By adding water to this compound the complex [(H O)(tmc)Fe=O)](OTf) could be prepared. This complex is important in regard to a better understanding of the reactivity of Fe oxido complexes.