scholarly journals Thermally induced intra-molecular transformation and metalation of free-base porphyrin on Au(111) surface steered by surface confinement and ad-atoms

2020 ◽  
Vol 2 (7) ◽  
pp. 2986-2991
Author(s):  
Dipayan Sen ◽  
Piotr Błoński ◽  
Bruno de la Torre ◽  
Pavel Jelínek ◽  
Michal Otyepka
Keyword(s):  
Dft Calculations ◽  
Chemical Transformations ◽  
Free Base ◽  
Thermally Induced ◽  
Gold Adatoms ◽  
Surface Confinement

We investigated chemical transformations of a fluorinated free-base porphyrin, 5,10,15,20-tetrakis(4-fluorophenyl)-21,23H-porphyrin under a Au(111) surface confinement and including gold adatoms by using an experiment and DFT calculations.

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

2019 ◽  
Author(s):  
Alejandra Gomez-Torres ◽  
J. Rolando Aguilar-Calderón ◽  
Carlos Saucedo ◽  
Aldo Jordan ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Thiophene Ring ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Thermally Induced ◽  
Titanium Complex

<p>The masked Ti(II) synthon (<sup>Ket</sup>guan)(<i>η</i><sup>6</sup>-Im<sup>Dipp</sup>N)Ti (<b>1</b>) oxidatively adds across thiophene to give ring-opened (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti[<i>κ</i><sup>2</sup>-<i>S</i>(CH)<sub>3</sub><i>C</i>H] (<b>2</b>). Complex <b>2</b> is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate <b>1</b> – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from <b>2</b>. Finally, pressurizing solutions of <b>2 </b>with H<sub>2</sub> (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti(S) (<b>3</b>) and butane. </p>

scholarly journals Synthesis, characterization and modeling of self-assembled porphyrin nanorods

2019 ◽  
Vol 23 (11n12) ◽  
pp. 1346-1354 ◽  
Author(s):  
Danielle Laurencin ◽  
Pascal G. Yot ◽  
Christel Gervais ◽  
Yannick Guari ◽  
Sébastien Clément ◽  
...  
Keyword(s):  
Solid State ◽  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
Powder Diffraction ◽  
Solid State Nmr ◽  
Molecular Level ◽  
Ion Association ◽  
Free Base ◽  
X Ray ◽  
Solid State Nmr Spectroscopy

Porphyrin nanorods were prepared by ion-association between free-base meso 5,10,15,20-tetrakis-(4-[Formula: see text]-methylpyridinium)porphyrin cations and tetraphenylborate anions. The nanorods have variable lengths (up to a few micrometers long) and diameters ([Formula: see text]50–500 nm). Their structure at the molecular level was elucidated by combining multinuclear solid state NMR spectroscopy, synchrotron X-ray powder diffraction and DFT calculations.

2,5-Bridged 1-Carba-arachno-pentaborane(10) Derivatives – Intermediates on the Way to Pentaalkyl-1,5-dicarba-closo-pentaboranes(5)

2015 ◽  
Vol 70 (10) ◽  
pp. 741-745 ◽  
Author(s):  
Bernd Wrackmeyer ◽  
Hans-Joerg Schanz
Keyword(s):  
Nmr Spectroscopy ◽  
Low Temperature ◽  
Thermal Degradation ◽  
Dft Calculations ◽  
Large Excess ◽  
Thermally Induced ◽  
Independent Synthesis ◽  
Induced Decomposition ◽  
C Nmr

AbstractStimulated by a report from (R. Köster, G. Benedikt, M. A. Grassberger, Liebigs Ann. Chem. 1968, 719, 187.) on a carbaborane, for which the structure of 2,3,4,5,-tetraethlyl-1-methyl-2,5-μ-(ethyl-1′,1′-diyl)-1-carba-arachno-pentaborane(10) 1 was proposed, an independent synthesis was developed. Diethyl(ethynyl)borane was generated in situ in the presence of a large excess of “Et2B–H” (hydride bath) by ethynyl/H exchange, using ethynyl(trioctyl)tin to react in a mixture with diethyl(vinyl)borane at low temperature. Hydroboration and Et2B–H-catalysed condensation afforded 1, as shown by 11B, 13C NMR spectroscopy and DFT calculations. Thermal degradation of 1 gave 2,3,4-triethyl-1,5-dimethyl-1,5-dicarba-closo-pentaborane(5), whereas the pentaethyl-1,5-dicarba-closo-pentaborane(5) resulted from thermally induced decomposition of other suitably substituted arachno carbaboranes.

Thermally induced mineral and chemical transformations in calcareous mudstones around a basaltic dyke (Perthus Pass, southern Massif Central, France). Possible implications as a natural analogue of nuclear waste disposal

Clay Minerals ◽  
2007 ◽  
Vol 42 (2) ◽  
pp. 213-231 ◽  
Author(s):  
C. Henry ◽  
J.-Y. Boisson ◽  
A. Bouchet ◽  
A. Meunier
Keyword(s):  
Theoretical Calculations ◽  
Heat Diffusion ◽  
Large Temperature ◽  
Chemical Transformations ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
Retention Capacity ◽  
Massif Central ◽  
Thermally Induced ◽  
X Ray

AbstractA mixed-layer illite-smectite, illite-rich calcareous mudstone intruded by a basaltic dyke at the Perthus Pass (southern Massif Central, France) allows us to study the transformation of clays subjected to a brief thermal gradient. X-ray diffraction, scanning electron microscopy, electron microprobe and atomic absorption spectroscopy analyses were performed on samples at variable distances from the mudstone-dyke contacts.A roughly similar evolution is seen on both sides of the dyke: quartz, calcite, kaolinite and illite disappear; Ca-silicates, albite and saponite-beidellite form, late meteoric halloysite crystallizes in open fractures.Chemical and mineralogical transformations are related to heat diffusion from the dyke. Theoretical calculations highlight the influence of the dyke orientation. The mineralogical reactions observed in rocks are similar to those observed in experimental conditions. The formation of new swelling phases with a high retention capacity linked to a short duration, large-temperature increase, should constitute a positive process for Repository Performance Assessment.

Overcrowded aminophospanitrenes: a case study

2017 ◽  
Vol 72 (11) ◽  
pp. 865-871
Author(s):  
Jürgen Tirrée ◽  
Alexander V. Ruban ◽  
Martin Nieger ◽  
Claudia Li ◽  
László Nyulászi ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Ring System ◽  
Thermally Induced ◽  
Induced Decomposition

AbstractIn a search for stable phosphinonitrenes generated by thermally induced decomposition of the azidophosphines 8a, b, different cyclodiphosp(V)azene products were generated. While in the case of 8a the expected phosphinonitrene dimer 10 could be obtained, from 8b, which has the sterically more demanding TMP substituents, product 11, was obtained and characterized. DFT calculations have revealed that the primarily formed phosphinonitrene 9b is unstable against loss of TMP˙, and the resulting radical dimerizes to the biradicaloid 1,3-diaza-2,4-diphosphetane-2,4-diyl 13. Compound 13 then dimerizes after ring opening, yielding in the ring system, which provides the final product upon reaction with the starting azidophosphine.

scholarly journals Structures of Self-Assembled n-Alkanethiols on Gold by Reflection High-Energy Electron Diffraction

2020 ◽  
Author(s):  
Mithun Ghosh ◽  
Ding-Shyue Yang
Keyword(s):  
Electron Diffraction ◽  
High Energy ◽  
Energy Electron ◽  
High Energy Electron ◽  
Thermally Induced ◽  
Alkyl Chains ◽  
Major Species ◽  
Multiple Orders ◽  
Gold Adatoms ◽  
Deposited Films

<div>TThe structures of long-chain alkanethiols (C<sub>18</sub>H<sub>37</sub>SH) chemisorbed on an Au(111) single crystal were investigated using reflection high-energy electron diffraction (RHEED). The primary (√3x√3)R30° structure observed as a major species in the as-deposited films contains gold adatoms below the sulfur headgroups. Between the small ordered domains with the alkyl chains tilting toward six directions are azimuthally disorderly packed regions, with a similar average tilt of 30.2°. In contrast, a significant reduction in the coverage of gold adatoms is found in the thermally-induced (2√3x3)<sub>rect</sub> phase. This superlattice is shown to contain a mixture of two sulfur arrangements, both of which exhibit a small S‒S distance, and the pairing of the aliphatic chains. A microscopic picture is then given for the structural transition. These findings demonstrate how the RHEED technique may be used to resolve structures of nanometer-thick thin films with multiple orders at the interfaces.</div>

[(η5-C5Me5)Ru]+ fragments ligated to polyaromatic hydrocarbons: an experimental and computational approach to pathways for haptotropic migration

2015 ◽  
Vol 44 (1) ◽  
pp. 316-329 ◽  
Author(s):  
Matias Rioja ◽  
Paul Hamon ◽  
Thierry Roisnel ◽  
Sourisak Sinbandhit ◽  
Mauricio Fuentealba ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Polyaromatic Hydrocarbons ◽  
Activation Energies ◽  
Computational Approach ◽  
High Activation ◽  
Thermally Induced

DFT calculations indicated rather high activation energies for the thermally induced intramolecular inter-ring haptotropic migration of the [(η5-C5Me5)Ru+] moiety.

ABSENCE OF CO DISSOCIATION ON Mo(110): TPD AND DFT STUDY

2010 ◽  
Vol 17 (05n06) ◽  
pp. 469-475 ◽  
Author(s):  
N. V. PETROVA ◽  
V. D. OSOVSKII ◽  
D. YU BALAKIN ◽  
YU G. PTUSHINSKII ◽  
I. N. YAKOVKIN
Keyword(s):  
Dft Calculations ◽  
Density Functional ◽  
Co Adsorption ◽  
Temperature Programmed Desorption ◽  
Thermally Induced ◽  
First Order ◽  
Co Dissociation ◽  
Virgin State ◽  
Temperature Programmed ◽  
Good Agreement

The problem of the CO dissociation on Mo (110) has been addressed by means of temperature-programmed desorption (TPD) and density-functional (DFT) calculations. The TPD spectra show a first-order CO desorption, which indicates the desorption from a "virgin" state, not a recombinative form of desorption. The height of the potential barrier for the dissociation (2.75 eV), estimated from DFT calculations, substantially exceeds the energy of CO chemisorption (2.1 eV), which makes the thermally induced CO dissociation on Mo improbable. Monte Carlo simulations of TPD spectra, performed using estimated chemisorption energies, are in good agreement with experiment and demonstrate that the two-peak shape of the spectra can be explained without involving the CO dissociation. Thus, the results of the present study finally refute the concept of a dissociative form of CO adsorption on Mo surfaces.

scholarly journals Detection and Characterization of Mononuclear Pd(I) Complexes

2020 ◽  
Author(s):  
Jia Luo ◽  
Nigam P. Rath ◽  
Liviu M. Mirica
Keyword(s):  
Dft Calculations ◽  
Chemical Reduction ◽  
Spectroscopic Studies ◽  
Oxidation States ◽  
Chemical Transformations ◽  
X Ray ◽  
Tetradentate Ligands ◽  
The Stability ◽  
X Ray Absorption

<p>Palladium is a versatile transition metal used to catalyze a large number of chemical transformations, largely due to its ability to access various oxidation states (0, I, II, III, and IV). Among these oxidation states, Pd(I) is arguably the least studied, and while dinuclear Pd(I) complexes are more common, mononuclear Pd(I) species are very rare. Reported herein are spectroscopic studies of a series of Pd(I) intermediates generated by the chemical reduction of Pd(II) precursors supported by the tetradentate ligands 2,11-dithia[3.3](2,6)pyridinophane (N2S2) and <i>N,N’</i>-di-<i>tert</i>-butyl-2,11-diaza[3.3](2,6)pyridinophane (<sup>tBu</sup>N4): [(N2S2)Pd<sup>II</sup>(MeCN)]<sub>2</sub>(OTf)<sub>4</sub> (<b>1</b>), [(N2S2)Pd<sup>II</sup>Me]<sub>2</sub>(OTf)<sub>2</sub> (<b>2</b>), [(N2S2)Pd<sup>II</sup>Cl](OTf) (<b>3</b>), [(N2S2)Pd<sup>II</sup>X](OTf)<sub>2</sub> (X = tBuNC <b>4</b>, PPh<sub>3</sub> <b>5</b>), [(N2S2)Pd<sup>II</sup>Me(PPh<sub>3</sub>)](OTf) (<b>6</b>), and [(<sup>tBu</sup>N4)Pd<sup>II</sup>X<sub>2</sub>](OTf)<sub>2</sub> (X = MeCN <b>8</b>, tBuNC <b>9</b>). In addition, a stable Pd(I) dinuclear species, [(N2S2)Pd<sup>I</sup>(m-tBuNC)]<sub>2</sub>(ClO<sub>4</sub>)<sub>2</sub> (<b>7</b>), was isolated upon the electrochemical reduction of <b>4</b> and structurally characterized. Moreover, the (<sup>tBu</sup>N4)Pd<sup>I</sup> intermediates, formed from the chemical reduction of [(<sup>tBu</sup>N4)Pd<sup>II</sup>X<sub>2</sub>](OTf)<sub>2</sub> (X = MeCN <b>8</b>, tBuNC <b>9</b>) complexes, were investigated by EPR spectroscopy, X-ray absorption spectroscopy (XAS), and DFT calculations, and compared with the analogous (N2S2)Pd<sup>I</sup> systems. Upon probing the stability of Pd(I) species under various ligand environments (N2S2 and <sup>tBu</sup>N4), it is apparent that the presence of soft ligands such as tBuNC and PPh<sub>3</sub> significantly improves the stability of Pd(I) species, which should make the isolation of mononuclear Pd(I) species possible.</p>

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