The first dinuclear and trinuclear chromium(III) and dinuclear vanadium(III) complexes of N4-R-substituted-3,5-di(2-pyridyl)-1,2,4-triazole (Rdpt) ligands have been prepared by solvothermal complexations under inert atmospheres, and characterized. The reactions of CrIII and VIII with adpt (R = amino) resulted in deamination of the ligand and yielded the dinuclear doubly-triazolate bridged complexes [V2III(dpt−)2Cl4] (1) and [Cr2III(dpt−)2Cl4] (2). In the case of the CrIII complex 2 this bridging results in a rare example of ferromagnetic coupling for a dinuclear CrIII compound. DFT studies confirm that in 2 the ferromagnetic coupling pathways dominate over the antiferromagnetic pathways, whereas in 1 the reverse occurs, consistent with the observed overall antiferromagnetic coupling in that case. It was also found that the use of different additives in the reaction allows the nuclearity of the CrIII product to be manipulated, giving either the dinuclear system, or the first example of a trinuclear circular helicate for a Rdpt complex, [Cr3III(dpt)3Cl6]·1¾MeCN·¼DCM (3). Reaction of N4-pydpt (R = 4-pyridyl) with VIII led to an unusual shift of the pyridyl substituent from N4 to N1 of the triazole, forming the ligand isomer N1-pydpt, and giving a dinuclear doubly-triazole bridged complex, [V2III(N1-pydpt)2Cl6]·2MeCN (4). Reaction with CrIII results in loss of the 4-pyridyl ring and a mixture of the di- and trinuclear complexes, 2 and 3. Interestingly, partial oxidation of the VIII in dinuclear complex 4 to vanadyl VIV=O was identified by crystallographic analysis of partially oxidized single crystals, [(VIVO)0.84(VIII)1.16(N1-pydpt)2Cl5.16]·0.84H2O·1.16MeCN (5).

We present a novel approach to produce a composite of the HKUST-1 metal-organic framework (MOF) and graphene, which is suited for the fabrication of monolithic coatings of solid substrates. In order to avoid the degradation of graphene electrical properties resulting from chemical functionalization (e.g., oxidation yielding graphene oxide, GO), commercial, nonmodified graphene was utilized. The one-pot synthesis of the moldable composite material allows for a controllable loading of graphene and the tuning of porosity. Potentially, this facile synthesis can be transferred to other MOF systems. The monolithic coatings reported here exhibit high surface areas (1156-1078 m2/g). The electrical conductivity was high (a range of 7.6 × 10-6 S m-1to 6.4 × 10-1 S m-1) and was found to be proportional to the graphene content. The ability to readily attain different forms and shapes of the conductive, microporous composites indicates that the MOF@G system can provide a compelling approach to access various applications of MOFs, specifically in electrochemical catalysis, supercapacitors, and sensors.

In the search for new single molecule magnets (SMM), i.e., molecular systems that can retain their magnetization without the need to apply an external magnetic field, a successful strategy is to associate 3d and 4f ions to form molecular coordination clusters. In order to efficiently design such systems, it is necessary to chemically project both the magnetic building blocks and the resultant interaction before the synthesis. Lanthanide ions can provide the required easy axis magnetic anisotropy that hampers magnetization reversal. In the rare examples of 3d/4f SMMs containing CrIII ions, the latter turn out to act as quasi-isotropic anchors which can also interact via 3d-4f coupling to neighbouring Ln centres. This has been demonstrated in cases where the intramolecular exchange interactions mediated by CrIII ions effectively reduce the efficiency of tunnelling without applied magnetic field. However, describing such high nuclearity systems remains challenging, from both experimental and theoretical perspectives, because the overall behaviour of the molecular cluster is heavily affected by the orientation of the individual anisotropy axes. These are in general non-collinear to each other. In this article, we combine single crystal SQUID and torque magnetometry studies of the octanuclear [Cr4Dy4(μ3-OH)4(μ-N3)4(mdea)4(piv)8]·3CH2Cl2 single molecule magnet (piv=pivalate and mdea=N-methyldiethanol amine). These experiments allowed us to probe the magnetic anisotropy of this complex which displays slow magnetization dynamics due to the peculiar arrangement of the easy-axis anisotropy on the Dy sites. New ab initio calculations considering the entire cluster are in agreement with our experimental results.

Silica is the second most abundant biomineral being exceeded in nature only by biogenic CaCO3. Many land plants (such as rice, cereals, cucumber, etc.) deposit silica in significant amounts to reinforce their tissues and as a systematic response to pathogen attack. One of the most ancient species of living vascular plants, Equisetum arvense is also able to take up and accumulate silica in all parts of the plant. Numerous methods have been developed for elimination of the organic material and/or metal ions present in plant material to isolate biogenic silica. However, depending on the chemical and/or physical treatment applied to branch or stem from Equisetum arvense; other mineral forms such glass-type materials (i.e. CaSiO3), salts (i.e. KCl) or luminescent materials can also be isolated from the plant material. In the current contribution, we show the chemical and/or thermal routes that lead to the formation of a number of different mineral types in addition to biogenic silica.

Increasing energy demands and the requirement to reduce carbon dioxide emissions at the same time accelerated the world-wide research on renewable energy sources and energy storage. However, for future applications in personal electronics, electro-mobility and decentralised energy storage, new LIB electrode materials based on light-weight and earth abundant components with superior redox activity, long-term stability and high energy density are urgently required. The concept of using molecular transition metal clusters as active electrode materials for reversible Li ion shuttling opens up a new direction for energy storage.[1] These metal complexes are interesting electrode materials due to the ability of the transition metal ions to exist in several oxidation states and reversibly reacting with Li.[2,3] In this study we introduce LIBs based on molecular cluster systems of the early transition metal ions vanadium and chromium as the cathode active material, in a so-called molecular cluster battery (MCB). Transition metal complexes of different ligand systems were characterised by IR, XRD and SEM techniques. Their Li cycling behaviour was investigated by galvanostatic cycling and cyclic voltammetry (CV). High reversible specific capacities with low capacity loss were found and multi-step redox processes were observed reflecting the various oxidation states of these metal ions. The 2D channels of the crystalline compounds, which are revealed in their crystal packing diagram, are suitable for an easy Li ion transportation trough the structure. The Li ion diffusion coefficients were determined by various electrochemical techniques, such as GITT, CV and EIS to understand the Li ion kinetics of these molecular metal clusters. The various oxidation steps of molecular cluster compounds allow multi-step redox changes making these materials interesting compounds with potentially high specific capacities and allow a study of the kinetics of the lithium ion diffusion pathway. References: [1] H. Yoshikawa, C. Kazama, K. Awaga, M. Satoh, J. Wada, Chem. Commun. 2007, 3169-3170. [2] H. Wang, Z. Zeng, N. Kawasaki, H. Eckert, H. Yoshikawa, K. Awaga, Chemistry, 2013, 19, 34, 11235-40. [3] H. Yoshikawa, S. Hamanaka, Y. Miyoshi, Y. Kondo, S. Shigematsu, N. Akutagawa, M. Sato, T. Yokoyama, K. Awaga, Inorg. Chem., 2009, 48, 19, 9057-9059.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Reactions of the N-substituted diethanolamine ligand N-n-butyldiethanolamine with chromium(II) and lanthanide(III)/rare earth salts (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in the presence of coligands give access to three series of isostructural 1:1 3d(Cr-III)/4f(Ln(III)) coordination cluster compounds that can be designated in terms of octanuclear square-in-square (Ln = La-Tb), hexanuclear triangle-in-triangle (Ln = Dy, Ho, Y) and tetranuclear butterfly or defect dicubane core (Ln = Er-Lu) topologies as revealed by single-crystal X-ray crystallographic analysis. The bulk magnetic properties were also measured. The influences of the various components in the reaction system on the final topology and the role of the ionic radius are discussed.

Reactions of the N-substituted diethanolamine ligand N-n-butyldiethanolamine with chromium(II) and lanthanide(III)/rare earth salts (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in the presence of coligands give access to three series of isostructural 1:1 3d(Cr(III))/4f(Ln(III)) coordination cluster compounds that can be designated in terms of octanuclear "square-in-square" (Ln = La-Tb), hexanuclear "triangle-in-triangle" (Ln = Dy, Ho, Y) and tetranuclear "butterfly" or defect dicubane core (Ln = Er-Lu) topologies as revealed by single-crystal X-ray crystallographic analysis. The bulk magnetic properties were also measured. The influences of the various components in the reaction system on the final topology and the role of the ionic radius are discussed.

Reactions of the N-substituted diethanolamine ligand N-n-butyldiethanolamine with chromium(II) and lanthanide(III)/rare earth salts (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y) in the presence of coligands give access to three series of isostructural 1:1 3d(CrIII)/4f(LnIII) coordination cluster compounds that can be designated in terms of octanuclear "square-in-square" (Ln = La–Tb), hexanuclear "triangle-in-triangle" (Ln = Dy, Ho, Y) and tetranuclear "butterfly" or defect dicubane core (Ln = Er–Lu) topologies as revealed by single-crystal X-ray crystallographic analysis. The bulk magnetic properties were also measured. The influences of the various components in the reaction system on the final topology and the role of the ionic radius are discussed.

The synthesis and characterization of size-separated silicon nanocrystals functionalized with a heteroatom-substituted organic capping group, allylphenylsulfide, via photochemical hydrosilylation are described for the first time. These silicon nanocrystals form colloidally stable and highly photoluminescent dispersions in non-polar organic solvents with an absolute quantum yield as high as 52% which is 20% above that of the allylbenzene analogue. Solutions of the size-separated fractions are characterized over time to monitor the effect of aging in air by following the change of their photoluminescence and absolute quantum yields, supplemented by transmission electron microscopy.

We present highly efficient electroluminescent devices using size-separated silicon nanocrystals (ncSi) as light emitting material. The emission color can be tuned from the deep red down to the yellow-orange spectral region by using very monodisperse size-separated nanoparticles. High external quantum efficiencies up to 1.1% as well as low turn-on voltages are obtained for red emitters. In addition, we demonstrate that size-separation of ncSi leads to drastically improved lifetimes of the devices and much less sensitivity of the emission wavelength to the applied drive voltage.

In this study, we investigate for the first time morphological and compositional changes of silicon quantum dot (SiQD) light-emitting diodes (SiLEDs) upon device operation. By means of advanced transmission electron microscopy (TEM) analysis including energy filtered TEM (EFTEM) and energy dispersive X-ray (EDX) spectroscopy, we observe drastic morphological changes and degradation for SiLEDs operated under high applied voltage ultimately leading to device failure. However, SiLEDs built from size-separated SiQDs operating under normal conditions show no morphological and compositional changes and the biexponential loss in electroluminescence seems to be correlated to chemical and physical degradation of the SiQDs. By contrast, we found that, for SiLEDs fabricated from polydisperse SiQDs, device degradation is more pronounced with three main modes of failure contributing to the reduced overall lifetime compared to those prepared from size-separated SiQDs. With this newfound knowledge, it is possible to devise ways to increase the lifetimes of SiLEDs.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

A contemporary question in the intensely active field of periodic mesoporous organosilica (PMO) materials is how large a silsesquioxane precursor can be self-assembled under template direction into the pore walls of an ordered mesostructure. An answer to this question is beginning to emerge with the ability to synthesize dendrimer, buckyball, and polyhedral oligomeric silsesquioxane PMOs. In this paper, we further expand the library of large-scale silsesquioxane precursors by demonstrating that photoluminescent nanocrystalline silicon that has been surface-capped with oligo(triethoxysilylethylene), denoted as ncSi:(CH2CH2Si(OEt)(3))(n)H, can be self-assembled into a photoluminescent nanocrystalline silicon periodic mesoporous organosilica (ncSi-PMO). A comprehensive multianalytical characterization of the structural and optical properties of ncSi-PMO demonstrates that the material gainfully combines the photoluminescent properties of nanocrystalline silicon with the porous structure of the PMO. This integration of two functional components makes ncSi-PMO a promising multifunctional material for optoelectronic and biomedical applications.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

„Quadrat im Quadrat“: Der erste Cr-Dy-Einzelmolekülmagnet (SMM) mit einer Energiebarriere für die Spinreorientierung von 15 K wird vorgestellt. Die Anisotropie in dieser achtkernigen Verbindung ist auf die Ausrichtung der vier DyIII-Ionen (dunkelblaue Kugeln) zurückzuführen, die in Verbindung mit den Beiträgen der CrIII-Ionen (grüne Kugeln) zu SMM-Verhalten führt. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

"Square-within-a-square": The first Cr–Dy single-molecule magnet (SMM) with an energy barrier to spin reorientation of 15 K is presented. The anisotropy in this octanuclear compound arises from the orientations of the four DyIII centers (dark blue), which, in conjunction with the contributions from the CrIII centers (green), leads to the SMM behavior. Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Wie Superatome mit platonisch-polyedrischer Substruktur ordnen sich [Ga12Ga12(Br18Se2)]⋅12 THF-Einheiten über Se-Se-Wechselwirkungen zu Ketten im Kristall an (siehe Bild). Die Clusterketten können anhand topologischer, spektroskopischer und energetischer Befunde als Modell für die in der Schichtstruktur von GaSe beobachtete Photoleitfähigkeit herangezogen werden. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2001/2007/z701986_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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