Experimental and Theoretical Investigation of the Molecular and Electronic Structure of [Zn₄(μ₄-S){μ-S₂As(CH₃)₂}₆] and [Cd₄(μ₄-S){μ-S₂As(CH₃)₂}₆]: Two Possible Molecular Models of Extended Metal Chalcogenide Semiconductors^†

The molecular and electronic structure of hexakis[μ-(dimethylarsinodithioate-S:S‘)]-μ4-thioxotetrazinc has been investigated by combining X-ray diffraction measurements, electrospray mass spectrometry (ESI), UV absorption spectroscopy, and density functional calculations. The polynuclear zinc complex consists of discrete “tetrazinc sulfide” moieties held together by van der Waals interactions. The unit cell contains four independent molecules and four solvent molecules. Each independent unit is characterized by a central μ4-S coordinated to four Zn ions, each of them at the center of an irregular tetrahedron of S atoms. ESI measurements point out that the synthesis of the analogous Cd derivative was successful. Crystal data are as follows:  chemical formula, C12H36As6Cl1.5S13Zn4; monoclinic space group P21/n (no. 14); a = 30.4228(7) Å, b = 18.3720(5) Å, c = 32.3758(8) Å, β = 95.857(1)°; Z = 16. Theoretical calculations indicate that, despite their structural arrangement, neither the Zn nor the Cd complex can be considered molecular models of the extended ZnS and CdS. Nevertheless, the electronic transitions localized in the Zn4(μ4-S) and Cd4(μ4-S) inner cores of the title compounds have the same nature as those giving rise to the maxima in the excitation spectra of the extended Zn4S(BO2)6 and Cd4S(AlO2)6 [Blasse, G.; Dirksen, G. J.; Brenchley, M. E.; Weller, M. T. Chem. Phys. Lett. 1995, 234, 177]

Experimental and Theoretical Investigation of the Molecular and Electronic Structure of [Zn₄(μ₄-S){μ-S₂As(CH₃)₂}₆] and [Cd₄(μ₄-S){μ-S₂As(CH₃)₂}₆]: Two Possible Molecular Models of Extended Metal Chalcogenide Semiconductors^†

The molecular and electronic structure of hexakis[μ-(dimethylarsinodithioate-S:S‘)]-μ4-thioxotetrazinc has been investigated by combining X-ray diffraction measurements, electrospray mass spectrometry (ESI), UV absorption spectroscopy, and density functional calculations. The polynuclear zinc complex consists of discrete “tetrazinc sulfide” moieties held together by van der Waals interactions. The unit cell contains four independent molecules and four solvent molecules. Each independent unit is characterized by a central μ4-S coordinated to four Zn ions, each of them at the center of an irregular tetrahedron of S atoms. ESI measurements point out that the synthesis of the analogous Cd derivative was successful. Crystal data are as follows:  chemical formula, C12H36As6Cl1.5S13Zn4; monoclinic space group P21/n (no. 14); a = 30.4228(7) Å, b = 18.3720(5) Å, c = 32.3758(8) Å, β = 95.857(1)°; Z = 16. Theoretical calculations indicate that, despite their structural arrangement, neither the Zn nor the Cd complex can be considered molecular models of the extended ZnS and CdS. Nevertheless, the electronic transitions localized in the Zn4(μ4-S) and Cd4(μ4-S) inner cores of the title compounds have the same nature as those giving rise to the maxima in the excitation spectra of the extended Zn4S(BO2)6 and Cd4S(AlO2)6 [Blasse, G.; Dirksen, G. J.; Brenchley, M. E.; Weller, M. T. Chem. Phys. Lett. 1995, 234, 177]

An iron(II) diamine diketonate molecular complex: synthesis, characterization and application in the CVD of Fe2O3 thin films

<div>Green open access version of the paper:</div><div><div>An iron(II) diamine diketonate molecular complex: synthesis, characterization and application in the CVD of Fe2O3 thin films</div></div><div><br></div><div>published in:</div><div><div>Inorganica Chimica Acta, 2012, 380, 161–166  </div><div><div>http://dx.doi.org/10.1016/j.ica.2011.10.036</div></div><div>which should be cited to refer to this work</div></div><div><br></div><div>Short non-technical summary of this paper: https://goo.gl/Fpwws7</div><div><br></div><div><div>This contribution was uploaded during the Open Access Week 2016 and is meant to be a little concrete step to put "Open in Action".</div><div><br></div></div

Controlled Growth of Supported ZnO Inverted Nanopyramids with Downward Pointing Tips

High purity porous ZnO nanopyramids with controllable properties are grown on their tips on Si(100) substrates by means of a catalyst-free vapor phase deposition route in a wet oxygen reaction environment. The system degree of preferential [001] orientation, as well as nanopyramid size, geometrical shape, and density distribution, can be finely tuned by varying the growth temperature between 300 and 400 °C, whereas higher temperatures lead to more compact systems with a three-dimensional (3D) morphology. A growth mechanism of the obtained ZnO nanostructures based on a self-catalytic vapor–solid (VS) mode is proposed, in order to explain the evolution of nanostructure morphologies as a function of the adopted process conditions. The results obtained by a thorough chemico-physical characterization enable us to get an improved control over the properties of ZnO nanopyramids grown by this technique. Taken together, they are of noticeable importance not only for fundamental research on ZnO nanomaterials with controlled nano-organization but also to tailor ZnO functionalities in view of various potential applications

<i>Ab Initio</i> and Experimental Studies on the Structure and Relative Stability of the <i>cis</i>-Hydride−η²-Dihydrogen Complexes [{P(CH₂CH₂PPh₂)₃}M(H)(η²-H₂)]⁺ (M = Fe, Ru)

Ab initio calculations (DMOL method) including the estimate of the total energy and the full optimization of the geometrical parameters have been used to study the electronic structures and the coordination geometries of the model systems [{P(CH2CH2PH2)3}M(H)(L)]+ (M = Fe, L = H2, C2H4, CO, N2; M = Ru, L = H2). Single crystal X-ray analyses have been carried out on the complexes [(PP3)Fe(H)(η2-H2)]BPh4·0.5THF (1·0.5THF), [(PP3)Fe(H)(CO)]BPh4·THF (3·THF), and [(PP3)Ru(H)(η2-H2)]BPh4·0.5THF (5·0.5THF) [PP3 = P(CH2CH2PPh2)3]. Crystal data:  for 1·0.5THF, triclinic P1 (No. 2), a = 17.626(3) Å, b = 14.605(3) Å, c = 12.824(4) Å, α = 90.09(2)°, β = 103.87(2)°, γ = 107.46(2)°, Z = 2, R = 0.082; for 3·THF, triclinic P1 (No. 2), a = 12.717(2) Å, b = 14.553(1) Å, c = 17.816(2) Å, α = 72.90(1)°, β = 76.82(2)°, γ = 89.71(1)°, Z = 2, R = 0.067; for 5·0.5THF, monoclinic P2/1a (No. 14), a = 19.490(5) Å, b = 19.438(2) Å, c = 16.873(5) Å, β = 110.96(2)°, Z = 4, R = 0.074. On the basis of theoretical calculations, X-ray analyses, and multinuclear NMR studies, all of the complexes of the formula [(PP3)M(H)(L)]BPh4 [M = Fe, L = H2 (1), C2H4 (2), CO (3), N2 (4); M = Ru, L = H2 (5), C2H4 (6)] are assigned a distorted octahedral structure where the hydride (trans to a terminal phosphorus donor) and the L ligand occupy mutually cis positions. The theoretical calculations indicate that the H2 ligand in the η2-dihydrogen−hydride derivatives 1 and 5 is placed in the P−M−H plane (parallel orientation) and that there is an attractive interaction between the H and H2 ligands. XPS measurements, performed on the iron complexes, show that the Fe → L back-bonding interaction plays a leading role in 3. It is concluded that the stronger metal−H2 bond in the dihydrogen−hydride complex 1, as compared to the Ru analog 5, is due to the greater d(metal) → σ*(H−H) back-donation as well as a more efficient interaction between the terminal hydride and an H of the dihydrogen ligand. This cis effect is suggested to contribute to the relative stability of the iron complexes, which increases in the order C2H4 2 2 < CO

Modeling the first activation stages of a Fe(II) CVD precursor on a heated growth surface

<div>Green open access version of the paper:</div><div>"Modeling The First Activation Stages of the Fe(hfa)2 TMEDA CVD Precursor on a Heated Growth Surface"<br></div><div>published in:</div><div>Ceramic Engineering and Science Proceedings (2016) 36(6):83 - Advanced Processing and Manufacturing Technologies for Nanostructured and Multifunctional Materials II: A Collection of Papers Presented at the 39th International Conference on Advanced Ceramics and Composites (eds T. Ohji, M. Singh and M. Halbig), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9781119211662.ch10<br></div><div>Which should be cited to refer to this work.</div><div><br></div><div>A popular summary of this paper is available at this link: https://goo.gl/MpdOpn</div

Toward the Detection of Poisonous Chemicals and Warfare Agents by Functional Mn₃O₄ Nanosystems

The detection of poisonous chemicals and warfare agents, such as acetonitrile and dimethyl methylphosphonate, is of utmost importance for environmental/health protection and public security. In this regard, supported Mn₃O₄ nanosystems were fabricated by vapor deposition on Al₂O₃ substrates, and their structure/morphology were characterized as a function of the used growth atmosphere (dry vs. wet O₂). Thanks to the high surface and peculiar nano-organization, the target systems displayed attractive functional properties, unprecedented for similar p-type systems, in the detection of the above chemical species. Their good responses, selectivity, and sensitivity pave the way to the fabrication of low-cost and secure sensors for different harmful analytes

Cu(II) Reduction without Reductants: Insights from Theory

<p>A topic issue in sustainable technologies is the production of Cu<i>_x</i>O (<i>x</i>=1,2) nanomaterials with tailored composition and properties. They can be fabricated through bottom-up processes that involve unexpected changes in the metal oxidation state and open intriguing challenges on the copper redox chemistry. How Cu^(II) complexes can lead to Cu^(I) species in spite of the absence of any explicit reducing agent is a question only recently answered by investigating the fragmentation of a Cu^(II) precursor for Cu oxide nanostructures by computer simulations and ESI-MS with multiple collisional experiments (ESI/MS<i>n</i>). Here we show that a Cu-promoted CH bond activation leads to reduction of the metal center and formation of a Cu^I-C-NCCN six-membered ring. Such 6-ring moiety is the structural motif for a new family of cyclic Cu^(I) adducts, characterized by a bonding scheme that may shed unprecedented light on high-temperature Cu chemistry. In particular, in this contribution we describe how collisions with hot atoms may activate Cu^(II) species to a configuration prone to the reduction. Besides its relevance for the fabrication of Cu-oxide nanostructures, the hydrogen-abstraction/proton-delivery/electron-gain mechanism of Cu^(II) reduction described herein could be a general property of copper and might help to understand its redox reactivity.</p><p>Poster presented at the 39th International Conference and Expo on Advanced Ceramics and Composites - Daytona Beach (FL) 25-31 Jan 2015</p

Tailoring Vapor-Phase Fabrication of Mn₃O₄ Nanosystems: From Synthesis to Gas-Sensing Applications

Supported p-type α-Mn₃O₄ nanosystems were fabricated by means of chemical vapor deposition (CVD) on polycrystalline alumina substrates at temperatures of 400 and 500 °C, using Mn­(hfa)₂·TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine) as precursor compound. The structure, chemical composition, and morphology of the obtained deposits were characterized in detail, devoting particular attention to the influence of the used reaction atmosphere (dry O₂ vs O₂ + H₂O) on the system characteristics. For the first time, the gas-sensing performances of the obtained CVD Mn₃O₄ nanomaterials were investigated toward ethanol and acetone vapors, with concentrations ranging from 10 to 50 and from 25 to 100 ppm, respectively. The developed systems showed the best activity ever reported in the literature for Mn₃O₄ chemoresistive sensors in the detection of the target gases, a result that, along with their low detection limits and good selectivity, is an appealing starting point for eventual technological applications