Synthesis and structures of cobalt-expanded zirconium- and cerium-oxo clusters as precursors for mixed-metal oxide thin films.

Transforming current complementary metal-oxide-semiconductor (CMOS) technology to fabricate memory chips and microprocessors into environmentally friendlier electronics requires the development of new approaches to resource- and energy-efficient electron transport and switching materials. Metal and multi-metal oxide layers play a key role in high-end technical applications. However, these layers are commonly produced through high-energy and high-temperature procedures. Herein, we demonstrate our first attempts to obtain stimuli-responsive mixed-metal oxide thin films from solution-processed molecular precursors under milder conditions. The molecular compounds of interest were prepared by one-pot reactions of a CoII carboxylate complex, triethylamine (Et3N), N-butyldiethanolamine (H2bda), and a hexanuclear complex [Ce6O4(OH)4(piv)12] (Hpiv = pivalic acid) or [Zr6O4(OH)4(ib)12(H2O)]·3Hib (Hib = isobutyric acid) in acetonitrile solution. The resulting charge-neutral, heterometallic coordination compounds display a ligand-supported pentanuclear {CeIV3CoIII2} core (in 1) and a dodecanuclear {ZrIV6CoII6} core (in 2), exhibiting thermal stability up to ca. 100 °C in air. Compound 2 was deposited and analyzed on Au(111) and SiO2/Si(100) surfaces to explore its potential as a single-molecule precursor for the preparation of atomically precise, complex mixed-metal oxide thin films. The adsorption characteristics of it demonstrate the ability to form stable agglomerates on the investigated surfaces.

(CN3H6)[FeIIFeIII(SO4)3(H2O)3]: A Framework Iron Sulfate with a Mixed S = 2 and S = 5/2 Honeycomb Lattice.

A new guanidinium-templated hydrated iron sulfate, [CN3H6][FeIIFeIII(SO4)3(H2O)3] (1), was prepared from strongly acidic aqueous solutions. Its crystal structure is comprised from FeIIIO6 and FeIIO3(H2O)3 octahedra linked by sulfate bridges forming a [FeIIFeII(SO4)3(H2O)3]- 3D framework with a layer-by-layer ordering of ferric and ferrous cations. The structural topology of the framework is related to the anhydrous rhombohedral mikasaite Fe2(SO4)3. The removal of part of the sulfate tetrahedra and the partial replacement of the Fe3+ cations in the [Fe3+2(SO4)3]0 framework by Fe2+ provide a negative charge and allow the incorporation of the protonated organic species in the voids. The compound 1 has been characterized by single-crystal X-ray diffraction, TG and DSC analyses, UV-vis-NIR spectroscopy, magnetic susceptibility, Mössbauer spectroscopy, IR and Raman spectroscopy, and density functional band-structure calculations. The magnetic behavior of 1 shows an interplay of FeII (S = 2) and FeIII (S = 5/2) sublattices that exhibit different types of antiferromagnetic couplings, one FeIII-FeIII (J1 ∼ 6.1 K) and two FeII-FeIII couplings (J2 ∼ 1 K, J3 ∼ 5.9 K) within corrugated honeycomb layers. These ferrimagnetic layers are coupled antiparallel to each other, resulting in an overall antiferromagnetic order below TN = 31 K.

Parabolic gratings enhance the X-ray sensitivity of Talbot interferograms.

In grating-based X-ray Talbot interferometry, the wave nature of X-ray radiation is exploited to generate phase contrast images of objects that do not generate sufficient contrast in conventional X-ray imaging relying on X-ray absorption. The phase sensitivity of this interferometric technique is proportional to the interferometer length and inversely proportional to the period of gratings. However, the limited spatial coherency of X-rays limits the maximum interferometer length, and the ability to obtain smaller-period gratings is limited by the manufacturing process. Here, we propose a new optical configuration that employs a combination of a converging parabolic micro-lens array and a diverging micro-lens array, instead of a binary phase grating. Without changing the grating period or the interferometer length, the phase signal is enhanced because the beam deflection by a sample is amplified through the array of converging-diverging micro-lens pairs. We demonstrate that the differential phase signal detected by our proposed set-up is twice that of a Talbot interferometer, using the same binary absorption grating, and with the same overall inter-grating distance.

Probing a Hydrogen-π Interaction Involving a Trapped Water Molecule in the Solid State.

The detection and characterization of trapped water molecules in chemical entities and biomacromolecules remains a challenging task for solid materials. We herein present proton-detected solid-state Nuclear Magnetic Resonance (NMR) experiments at 100 kHz magic-angle spinning and at high static magnetic-field strengths (28.2 T) enabling the detection of a single water molecule fixed in the calix[4]arene cavity of a lanthanide complex by a combination of three types of non-covalent interactions. The water proton resonances are detected at a chemical-shift value close to zero ppm, which we further confirm by quantum-chemical calculations. Density Functional Theory calculations pinpoint to the sensitivity of the proton chemical-shift value for hydrogen-π interactions. Our study highlights how proton-detected solid-state NMR is turning into the method-of-choice in probing weak non-covalent interactions driving a whole branch of molecular-recognition events in chemistry and biology.

Hydroxamate based transition metal-organic coordination polymers with semiconductive properties.

In addition to carboxylate and N-donor linkers, hydroxamates are a kind of new emerging ligand to form coordination polymers. However, owing to the difficulty in controlling the reversible formation of strong metal-hydroxamate coordination bonds, reports on ditopic or multitopic hydroxamate coordination polymers are rare. In this work, we combined the ligand H2ONDI, a bis-hydroxamate with a naphthalenediimide (NDI) core and rigid chelating groups, with transition metal ions (Mn2+ and Cd2+) and thus obtained three new hydroxamate coordination polymers. Benefiting from π-π stacking interactions between neighbouring ligands, Mn-ONDI-1 and CdCl-ONDI show interesting electrical conductivities.

Expanded Mercaptocalixarenes: A New Kind of Macrocyclic Ligands for Stabilization of Polynuclear Thiolate Clusters.

The syntheses and properties of expanded 4-tert-butyl-mercaptocalix[4]arenes, in which the methylene linkers are replaced by -CH2 NRCH2 - or -CH2 NRCH2 - and -CH2 NRCH2 CH2 CH2 NRCH2 - units, are described. The new macrocycles were obtained in a step-wise manner, utilizing fully protected, i. e. S-alkylated, derivatives of the oxidation-sensitive thiophenols in the cyclisation steps. Reductive cleavage of the macrobicyclic or macrotricyclic intermediates (6, 7, 11) afforded the free thiophenols (H4 8, H4 9, and H4 12) in preparative yields as their hydrochloride salts. The protected proligands can exist in two conformations, resembling the "cone" and "1,3-alternate" conformations found for the parent calix[4]arenes. The free macrocycles do not show conformational isomerism, but are readily oxidized forming intramolecular disulfide linkages. Preliminary complexation experiments show that these expanded mercaptocalixarenes can serve as supporting ligands for tetranuclear thiolato clusters.

Stable thiolate adducts of Rh2(OAc)4 - assembly of hexametallic Ni4Rh2 complexes.

Thiolate adducts of dirhodium(II) tetraacetate have proven difficult to prepare. We isolated a stable, paramagnetic Ni4Rh2 adduct containing Ni-based metallothiolates bound in axial positions of the Rh24+ core. The adduct formation is accompanied by a change of the magnetic exchange interaction in the dinuclear Ni2 subunits.

Synthesis and Characterisation of Luminescent [CrIII 2 L(µ-carboxylato)]3+ Complexes with High-Spin S=3 Ground States (L=N6 S2 donor ligand).

The synthesis, structure, magnetic, and photophysical properties of two dinuclear, luminescent, mixed-ligand [CrIII 2 L(O2 CR)]3+ complexes (R=CH3 (1), Ph (2)) of a 24-membered binucleating hexa-aza-dithiophenolate macrocycle (L)2- are presented. X-ray crystallographic analysis reveals an edge-sharing bioctahedral N3 Cr(µ-SR)2 (µ1,3 -O2 CR)CrN3 core structure with µ1,3 -bridging carboxylate groups. A ferromagnetic superexchange interaction between the electron spins of the Cr3+ ions leads to a high-spin (S=3) ground state. The coupling constants (J=+24.2(1) cm-1 (1), +34.8(4) cm-1 (2), H=-2JS1 S2 ) are significantly larger than in related bis-µ-alkoxido-µ-carboxylato structures. DFT calculations performed on both complexes reproduce both the sign and strength of the exchange interactions found experimentally. Frozen methanol-dichloromethane 1 : 1 solutions of 1 and 2 luminesce at 750 nm when excited into the 4 LMCT state on the 4 A2 → 2 T1 (ν2 ) bands (λexc =405 nm). The absolute quantum yields (ΦL ) for 1 and 2 were found to be strongly temperature dependent. At 77 K in frozen MeOH/CH2 Cl2 glasses, ΦL =0.44±0.02 (for 1), ΦL =0.45±0.02 (for 2).

Synthesis and crystal structure of a one-dimensional chain-like strontium(II) coordination polymer built of N-methyldi-ethano-lamine and isobutyrate ligands.

The one-dimensional coordination polymer (I) [Sr(ib)2(H2mda)] n (Hib = isobutyric acid, C4H8O2, and H2mda = N-methyldi-ethano-lamine, C5H13NO2), namely, catena-poly[[(N-methyldi-ethano-lamine-κ3 O,N,O')strontium(II)]-di-µ2-isobutyrato-κ3 O,O':O;κ3 O:O,O'], was prepared by the one-pot aerobic reaction of [Zr6O4(OH)4(ib)12(H2O)]·3Hib with Sr(NO3)2 and H2mda in the presence of MnCl2 and Et3N in aceto-nitrile. The use of MnCl2 is key to the isolation of I as high-quality colorless crystals in good yield. The mol-ecular solid-state structure of I was determined by single-crystal X-ray diffraction. Compound I crystallizes in the monoclinic space group P21/c and shows a one-dimensional polymeric chain structure. Each monomeric unit of this coordination polymer consists of a central SrII ion in the NO8 coordination environment of two deprotonated ib- ligands and one fully protonated H2mda ligand. The C and O atoms of the H2mda ligand were refined as disordered over two sets of sites with site occupancies of 0.619 (3) and 0.381 (3). Compound I shows thermal stability up to 130°C in air.

Ethereal Hydroperoxides: Powerful Reagents for S-Oxygenation of Bridging Thiophenolate Functions.

S-Oxygenation of thiophenolate bridges by ethereal hydroperoxides was studied. [NiII2LS(PhCO2)]+ (1), where LS = macrocyclic aminethiolate supporting ligand, is S-oxygenated readily in a mixed methanol/acetonitrile solution with ether/dioxygen at room temperature in the presence of daylight. The reactions were found to depend strongly on the choice of the ether. Uptake of two O atoms occurs in dioxane to give a mixed thiolate/sulfinate complex [NiII2LSO2(PhCO2)]+ (2) containing the rare five-membered Ni(µ1,1-S)(µ1,2-OS)Ni core. In tetrahydrofuran, four O atoms are taken up by 1 to generate the bis(sulfinate) species [NiII2LSO4(PhCO2)]+ (3). A mono-S-oxygenated sulfenate intermediate can be detected by electrospray ionization mass spectrometry. The oxygenation reactions proceed in high yields without complex disintegration and invariably provide µ1,2-bridging sulfinates as established by spectroscopy (IR and UV/vis), X-ray crystallography, and accompanying density functional theory calculations. The oxygenation of the S atoms has a strong impact on the electronic structures of the nickel complexes. The monosulfinate complex 2 has an S = 2 ground state resulting from moderate ferromagnetic exchange coupling interactions (J = +15.7 cm-1; H = -2JS1S2), while an antiferromagnetic exchange interaction in 3 shows the presence of a ground state with spin S = 0 (J = -0.56 cm-1).

Synthesis, Structure, and Surface Adsorption Characteristics of a Polynuclear MnII,IV-YbIII Complex.

The controlled adsorption of polynuclear coordination compounds with specific structural and electronic characteristics on surfaces is crucial for the prospective implementation of molecule-surface interfaces into practical electronic devices. From this perspective, a neutral 3d,4f-coordination cluster [MnII3MnIVYb3O3(OH)(L·SMe)3(OOCMe)9]·2MeCN·3EtOH (1·2MeCN·3EtOH), where L·SMe- is a Schiff base, has been synthesized and fully characterized and its adsorption on two different solid substrates, gold and graphite, has been studied. The mixed-valence compound with a bilayered metal core structure and the structurally exposed thioether groups exhibits a substantially different surface bonding to metallic gold and semimetallic graphite substrates. While on graphite the adsorption takes place only on distinguished attraction points with a locally increased number of potential bonding sites such as terrace edges and other surface defects, on gold the molecules were found to adsorb rather weakly on randomly distributed adsorption sites of the surface terraces. This entirely different behavior provides important information for the development of advanced surface materials that may enable well-distributed ordered molecular assemblies.

Metalloligands based on Robson-type amino-thiophenolato macrocycles for assembly of heterotrimetallic complexes.

The ability of macrocyclic Co and Ni aminothiolate complexes to act as metalloligands towards cuprate ions was established. Adduct formation is enabled by a thiolate-to-Cu+ charge transfer (CT) interaction giving stable heterotrimetallics with magnetic properties.

Deposition of exchange-coupled dinickel complexes on gold substrates utilizing ambidentate mercapto-carboxylato ligands.

The chemisorption of magnetically bistable transition metal complexes on planar surfaces has recently attracted increased scientific interest due to its potential application in various fields, including molecular spintronics. In this work, the synthesis of mixed-ligand complexes of the type [NiII2L(L')](ClO4), where L represents a 24-membered macrocyclic hexaazadithiophenolate ligand and L' is a ω-mercapto-carboxylato ligand (L' = HS(CH2)5CO2- (6), HS(CH2)10CO2- (7), or HS(C6H4)2CO2- (8)), and their ability to adsorb on gold surfaces is reported. Besides elemental analysis, IR spectroscopy, electrospray ionization mass spectrometry (ESIMS), UV-vis spectroscopy, and X-ray crystallography (for 6 and 7), the compounds were also studied by temperature-dependent magnetic susceptibility measurements (for 7 and 8) and (broken symmetry) density functional theory (DFT) calculations. An S = 2 ground state is demonstrated by temperature-dependent susceptibility and magnetization measurements, achieved by ferromagnetic coupling between the spins of the Ni(II) ions in 7 (J = +22.3 cm-1) and 8 (J = +20.8 cm-1; H = -2JS1S2). The reactivity of complexes 6-8 is reminiscent of that of pure thiolato ligands, which readily chemisorb on Au surfaces as verified by contact angle, atomic force microscopy (AFM) and spectroscopic ellipsometry measurements. The large [Ni2L] tail groups, however, prevent the packing and self-assembly of the hydrocarbon chains. The smaller film thickness of 7 is attributed to the specific coordination mode of the coligand. Results of preliminary transport measurements utilizing rolled-up devices are also reported.

Light-controlled self-assembly of non-photoresponsive nanoparticles.

The ability to guide the assembly of nanosized objects reversibly with external stimuli, in particular light, is of fundamental importance, and it contributes to the development of applications as diverse as nanofabrication and controlled drug delivery. However, all the systems described to date are based on nanoparticles (NPs) that are inherently photoresponsive, which makes their preparation cumbersome and can markedly hamper their performance. Here we describe a conceptually new methodology to assemble NPs reversibly using light that does not require the particles to be functionalized with light-responsive ligands. Our strategy is based on the use of a photoswitchable medium that responds to light in such a way that it modulates the interparticle interactions. NP assembly proceeds quantitatively and without apparent fatigue, both in solution and in gels. Exposing the gels to light in a spatially controlled manner allowed us to draw images that spontaneously disappeared after a specific period of time.

Highly precise micro-retroreflector array fabricated by the LIGA process and its application as tapped delay line filter.

We report on the fabrication of a one-dimensional micro-retroreflector array with a pitch of 100 µm. The array was fabricated by x-ray lithography and the lithographie, galvanik und abformung (LIGA) process in a 1 mm thick poly(methyl methacrylate) (PMMA) layer and subsequently covered with Au. The area of the array is 1 mm×10 mm. The high precision of the LIGA-based fabrication process allows one to use the element in spectrometers. Here, it is suggested to apply it to the implementation of a transversal filter for femtosecond pulses. We present a theoretical description of the performance of the retroreflector array as a filtering device and show experimental results.

X-ray grating interferometer for biomedical imaging applications at Shanghai Synchrotron Radiation Facility.

An X-ray grating interferometer was installed at the BL13W beamline of Shanghai Synchrotron Radiation Facility (SSRF) for biomedical imaging applications. Compared with imaging results from conventional absorption-based micro-computed tomography, this set-up has shown much better soft tissue imaging capability. In particular, using the set-up, the carotid artery and the carotid vein in a formalin-fixed mouse can be visualized in situ without contrast agents, paving the way for future applications in cancer angiography studies. The overall results have demonstrated the broad prospects of the existing set-up for biomedical imaging applications at SSRF.

Recombinant human bone morphogenetic protein-2 for treatment of open tibial fractures: a prospective, controlled, randomized study of four hundred and fifty patients.

BACKGROUND: The treatment of open fractures of the tibial shaft is often complicated by delayed union and nonunion. The objective of this study was to evaluate the safety and efficacy of the use of recombinant human bone morphogenetic protein-2 (rhBMP-2; dibotermin alfa) to accelerate healing of open tibial shaft fractures and to reduce the need for secondary intervention. METHODS: In a prospective, randomized, controlled, single-blind study, 450 patients with an open tibial fracture were randomized to receive either the standard of care (intramedullary nail fixation and routine soft-tissue management [the control group]), the standard of care and an implant containing 0.75 mg/mL of rhBMP-2 (total dose of 6 mg), or the standard of care and an implant containing 1.50 mg/mL of rhBMP-2 (total dose of 12 mg). The rhBMP-2 implant (rhBMP-2 applied to an absorbable collagen sponge) was placed over the fracture at the time of definitive wound closure. Randomization was stratified by the severity of the open wound. The primary outcome measure was the proportion of patients requiring secondary intervention because of delayed union or nonunion within twelve months postoperatively. RESULTS: Four hundred and twenty-one (94%) of the patients were available for the twelve-month follow-up. The 1.50-mg/mL rhBMP-2 group had a 44% reduction in the risk of failure (i.e., secondary intervention because of delayed union; relative risk = 0.56; 95% confidence interval = 0.40 to 0.78; pairwise p = 0.0005), significantly fewer invasive interventions (e.g., bone-grafting and nail exchange; p = 0.0264), and significantly faster fracture-healing (p = 0.0022) than did the control patients. Significantly more patients treated with 1.50 mg/mL of rhBMP-2 had healing of the fracture at the postoperative visits from ten weeks through twelve months (p = 0.0008). Compared with the control patients, those treated with 1.50 mg/mL of rhBMP-2 also had significantly fewer hardware failures (p = 0.0174), fewer infections (in association with Gustilo-Anderson type-III injuries; p = 0.0219), and faster wound-healing (83% compared with 65% had wound-healing at six weeks; p =0.0010). CONCLUSIONS: The rhBMP-2 implant was safe and, when 1.50 mg/mL was used, significantly superior to the standard of care in reducing the frequency of secondary interventions and the overall invasiveness of the procedures, accelerating fracture and wound-healing, and reducing the infection rate in patients with an open fracture of the tibia.