scholarly journals Exploring Cu/Al cluster growth and reactivity: from embryonic building blocks to intermetalloid, open-shell superatoms

2021 ◽  
Author(s):  
Max Schütz ◽  
Christian Gemel ◽  
Maximilian Muhr ◽  
Christian Jandl ◽  
Samia Kahlal ◽  
...  
Keyword(s):  
Closed Shell ◽  
Building Blocks ◽  
Open Shell ◽  
Cluster Growth ◽  
Powerful Technique

Cu/Al cluster growth reactions leading to open- and closed-shell superatoms are investigated. Therein, LIFDI-MS is presented as a powerful technique for the in situ detection of cluster identities and reactivity patterns.

Laboratory and in-situ analysis of comet dust

1988 ◽  
Vol 46 ◽  
pp. 8-9
Author(s):  
D.E. Brownlee ◽  
A.L. Albee
Keyword(s):  
Electron Microscopy ◽  
Solar System ◽  
Laboratory Study ◽  
Isotopic Analysis ◽  
Building Blocks ◽  
Sem Analysis ◽  
Early Solar System ◽  
Cometary Material ◽  
Comet Dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

Transalkylierung und protonenkatalysierte C-C-Spaltung bei n-Butyl-und n-Pentylbenzol in der Gasphase / Transalkylation and Proton Catalyzed C-C-Cleavage of Gaseous n-Butyl and w-Pentyl Benzenes

1979 ◽  
Vol 34 (3) ◽  
pp. 495-501 ◽  
Author(s):  
C. Wesdemiotis ◽  
H. Schwarz ◽  
C. C. Van de Sande ◽  
F. Van Gaever
Keyword(s):  
Hydrogen Exchange ◽  
Closed Shell ◽  
Open Shell ◽  
Molecular Ions ◽  
Exchange Reactions ◽  
Intramolecular Exchange ◽  
Carbon Carbon Bond ◽  
Exchange Processes ◽  
Reaction Channels ◽  
Alkyl Benzenes

Abstract The investigation of several 13carbon and deuterium labelled n-butyl and n-pentyl benzenes demonstrate that chemical ionization (reagent gas: methane) induces specific carbon-carbon bond cleavages of the alkyl group. The extent of competing reaction channels as for instance direct alkene elimination versus dealkylation/reprotonation is analyzed. Partial hydrogen exchange processes between reagent ions and substrate molecules are restricted to the phenyl ring. Intramolecular exchange reactions between the side chain and the aromatic ring which are typical for the open shell molecular ions of alkyl benzenes are not observed for analogous closed shell cations.

Stresses and Deformations of Toroidal Shells of Elliptical Cross Section: With Applications to the Problems of Bending of Curved Tubes and of the Bourdon Gage

1952 ◽  
Vol 19 (1) ◽  
pp. 37-48
Author(s):  
R. A. Clark ◽  
T. I. Gilroy ◽  
E. Reissner
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Practical Interest ◽  
Closed Shell ◽  
Open Shell ◽  
Elliptical Cross Section ◽  
Axially Symmetric ◽  
Elliptical Cross ◽  
Two Parameters ◽  
Toroidal Shells

Abstract This paper is concerned with the application of the theory of thin shells to several problems for toroidal shells with elliptical cross section. These problems are as follows: (a) Closed shell subjected to uniform normal wall pressure. (b) Open shell subjected to end bending moments. (c) Combination of the results for the first and second problems in such a way as to obtain results for the stresses and deformations in Bourdon tubes. In all three problems the distribution of stresses is axially symmetric but only in the first problem are the displacements axially symmetric. The magnitude of stresses and deformations for given loads depends in all three problems on the magnitude of the two parameters bc/ah and b/c where b and c are the semiaxes of the elliptical section, a is the distance of the center of the section from the axis of revolution, and h is the thickness of the wall of the shell. For sufficiently small values of bc/ah trigonometric series solutions are obtained. For sufficiently large values of bc/ah asymptotic solutions are obtained. Numerical results are given for various quantities of practical interest as a function of bc/ah for the values 2, 1, 1/2, 1/4 of the semiaxes ratio b/c. It is suggested that the analysis be extended to still smaller values of b/c and to cross sections other than elliptical.

Symmetrical tetra-β″-sulfoleno-meso-aryl-porphyrins — synthesis, spectroscopy and structural characterization

2014 ◽  
Vol 18 (01n02) ◽  
pp. 115-122 ◽  
Author(s):  
Srinivas Banala ◽  
Klaus Wurst ◽  
Bernhard Kräutler
Keyword(s):  
Metal Complexes ◽  
Crystal Structures ◽  
Structural Characterization ◽  
Building Blocks ◽  
Cycloaddition Reactions ◽  
One Pot

We report here the preparation (in "one-pot") of a tetra-β″-sulfoleno-meso-aryl-porphyrin in about 80% yield by using an optimized modification of Lindsey's variant of the Adler–Longo approach. The Zn ( II )-, Cu ( II )- and Ni ( II )-complexes of the symmetrical porphyrin were prepared and characterized spectroscopically. Crystal structures of the fluorescent Zn ( II )- and of the non-fluorescent Ni ( II )-tetra-β″-sulfoleno-meso-aryl-porphyrinates showed the highly substituted porphyrin ligands to be nearly perfectly planar. The Zn ( II )-complex of this porphyrin has been used as a thermal precursor of a reactive diene, and — formally — of lateral and diagonal bis-dienes, of a tris-diene and of a tetra-diene, which all underwent [4 + 2]-cycloaddition reactions in situ with a range of dienophiles. Thus, the tetra-β″-sulfoleno-meso-aryl-porphyrin and its metal complexes represent reactive building blocks, "programmed" for the syntheses of symmetrical and highly functionalized porphyrins.

Changes in Electronic Properties of Polymeric One-Dimensional {[M(CN)2]−}n(M = Au, Ag) Chains Due to Neighboring Closed-Shell Zn(II) or Open-Shell Cu(II) Ions

2011 ◽  
Vol 50 (1) ◽  
pp. 231-237 ◽  
Author(s):  
François Baril-Robert ◽  
Xiaobo Li ◽  
Michael J. Katz ◽  
Andrew R. Geisheimer ◽  
Daniel B. Leznoff ◽  
...  
Keyword(s):  
Electronic Properties ◽  
Closed Shell ◽  
Open Shell ◽  
One Dimensional

scholarly journals Ligand-Mediated Spin State Changes in a Cobalt-Dipyrrin-Bisphenol Complex

2020 ◽  
Author(s):  
Nicolaas P. van Leest ◽  
Wowa Stroek ◽  
Maxime A. Siegler ◽  
Jarl Ivar van der Vlugt ◽  
Bas de Bruin
Keyword(s):  
Cobalt Complex ◽  
Closed Shell ◽  
Open Shell ◽  
Triplet Ground State ◽  
Redox Active Ligand ◽  
Redox Active ◽  
Square Planar ◽  
Amine Adducts ◽  
Meso Position ◽  
Electronic Ground

ABSTRACT: The influence of a redox-active ligand on spin changing events induced by coordination of exogenous donors is investigated within the cobalt complex <b>[Co<sup>II</sup>(DPP<sup>•2‒</sup>)]</b>, bearing a redox-active <b>DPP<sup>2‒</sup></b> ligand (DPP = dipyrrin-bis-(<i>o,p</i>-di-tert-butylphenolato) with a pentafluorophenyl moiety on the meso-position. This square planar complex was subjected to coordination of THF, pyridine, tBuNH<sub>2</sub> and AdNH<sub>2</sub> (Ad = 1‑adamantyl), and the resulting complexes were analyzed with a variety of experimental (XRD, NMR, UV-Vis, HRMS, SQUID, Evans’ method) and computational (DFT, NEVPT2-CASSCF) techniques to elucidate the respective structures, spin states and orbital compositions of the corresponding octahedral bis-donor adducts, relative to <b>[Co<sup>II</sup>(DPP<sup>•2‒</sup>)]</b>. This starting species is best described as an open-shell singlet complex containing a <b>DPP<sup>•2‒</sup></b> ligand radical that is antiferromagnetically coupled to a low-spin (S = ½) cobalt(II) center. The redox-active <b>DPP<sup>n‒</sup></b> ligand plays a crucial role in stabilizing this complex, and in its facile conversion to the triplet THF-adduct <b>[Co<sup>II</sup>(DPP<sup>•2‒</sup>)(THF)<sub>2</sub>]</b> and closed-shell singlet pyridine and amine adducts <b>[Co<sup>III</sup>(DPP<sup>3‒</sup>)(L)<sub>2</sub>]</b> (L = py, tBuNH<sub>2</sub> or AdNH<sub>2</sub>). Coordination of the weak donor THF to <b>[Co<sup>II</sup>(DPP<sup>•2-</sup>)]</b> changes the orbital overlap between the <b>DPP<sup>•2‒</sup></b> ligand radical π-orbitals and the cobalt(II) metalloradical d-orbitals, which results in a spin-flip to the triplet ground state without changing the oxidation states of the metal or <b>DPP<sup>•2‒</sup></b> ligand. In contrast, coordination of the stronger donors pyridine, tBuNH<sub>2</sub> or AdNH<sub>2</sub> induces metal-to-ligand single-electron transfer, resulting in formation of low-spin (S = 0) cobalt(III)-complexes <b>[Co<sup>III</sup>(DPP<sup>3‒</sup>)(L)<sub>2</sub>]</b> containing a fully reduced <b>DPP<sup>3‒</sup></b> ligand, thus explaining their closed-shell singlet electronic ground states.

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