Bond angles in silyl compounds and (p→d)π-bonding

1966 ◽  
Vol 0 (15) ◽  
pp. 530-531 ◽  
Author(s):  
E. A. V. Ebsworth
Keyword(s):  
Bond Angles

Seeking Magneto-Structural Correlations in Easily Tailored Pentagonal Bipyramid Dy(III) Single-Ion Magnets

2019 ◽  
Author(s):  
Guo-Zhang Huang ◽  
Ze-Yu Ruan ◽  
Jie-Yu Zheng ◽  
Yan-Cong Chen ◽  
Si-Guo Wu ◽  
...  
Keyword(s):  
Single Molecule ◽  
Structural Engineering ◽  
Magnetic Hysteresis ◽  
Sweep Rate ◽  
Coordination Bond ◽  
Pentagonal Bipyramid ◽  
Single Molecule Magnets ◽  
Crystal Field Theory ◽  
Bond Angles ◽  
Axial Coordination

<p><a></a>Controlling molecular magnetic anisotropy via structural engineering is delicate and fascinating, especially for single-molecule magnets (SMMs). Herein a family of dysprosium single-ion magnets (SIMs) sitting in pentagonal bipyramid geometry have been synthesized with the variable-size terminal ligands and counter anions, through which the subtle coordination geometry of Dy(III) can be finely tuned based on the size effect. The effective energy barrier (Ueff) successfully increases from 439 K to 632 K and the magnetic hysteresis temperature (under a 200 Oe/s sweep rate) raises from 11 K to 24 K. Based on the crystal-field theory, a semi-quantitative magneto-structural correlation deducing experimentally for the first time is revealed that the Ueff is linearly proportional to the structural-related value S2<sup>0</sup> corresponding to the axial coordination bond lengths and the bond angles. Through the evaluation of the remanent magnetization from hysteresis, quantum tunneling of magnetization (QTM) is found to exhibit negative correlation with the structural-related value S<sub>tun</sub> corresponding to the axial coordination bond angles.<br></p>

Computational modeling of open framework silicates: the case of ferrierite reveals intriguing links between mineralogy, material science, and applications

2019 ◽  
Author(s):  
Federica Trudu ◽  
gloria tabacchi ◽  
Ettore Fois
Keyword(s):  
Computational Modeling ◽  
Material Science ◽  
Text File ◽  
Main Text ◽  
Bond Angles ◽  
Open Framework ◽  
Data Files

1) main text file of the paper: "Computational modeling of open framework silicates: probing straight bond angles in ferrierite reveals intriguing links between mineralogy, nanomaterial science and technological applications"<div>by F. Trudu, G. Tabacchi, E. Fois (pdf file)</div><div>2) supporting information (pdf file)</div><div>3) zip folder containing relevant data files in cif format</div><div><br></div><div>Twitter handle of the submitting author:</div><div>@BL76276</div>

Organic chemistry lecture course and exercises based on true scale models

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Felix Lederle ◽  
Eike G. Hübner
Keyword(s):  
Organic Chemistry ◽  
Bond Length ◽  
3D Models ◽  
Poly Lactic Acid ◽  
X Ray ◽  
Bond Angles ◽  
Chemical Structures ◽  
Scale Models ◽  
Hands On ◽  
Scaled Models

Abstract3D models of chemical structures are an important tool for chemistry lectures and exercises. Usually, simplified models based on standard bond length and angles are used. These models allow for a visualized discussion of (stereo)chemical aspects, but they do not represent the true spatial conditions. 3D-printing technologies facilitate the production of scale models. Several protocols describe the process from X-ray structures, calculated geometries or virtual molecules to printable files. In contrast, only a few examples describe the integration of scaled models in lecture courses. True bond angles and scaled bond lengths allow for a detailed discussion of the geometry and parameters derived therefrom, for example double bond character, aromaticity and many more. Here, we report a complete organic chemistry/stereochemistry lecture course and exercise based on a set of 37 scale models made from poly(lactic acid) as sustainable material. All models have been derived from X-ray structures and quantum chemical calculations. Consequently, the models reflect the true structure as close as possible. A fixed scaling factor of 1 : 1.8·108 has been applied to all models. Hands-on measuring of bond angles and bond length leads to an interactive course. The course has been evaluated with a very positive feedback.

Synthesis and Crystal Structures of Three Carboxylate- Bridged Tetranuclear Copper(II) - Lanthanide(III) Complexes of Ph3P+CH2CH2CO2−

1999 ◽  
Vol 52 (10) ◽  
pp. 983 ◽  
Author(s):  
Yang-Yi Yang ◽  
Seik Weng Ng ◽  
Xiao-Ming Chen
Keyword(s):  
Oxygen Atom ◽  
Crystal Structures ◽  
Triclinic Space Group ◽  
Coordination Environment ◽  
Space Group ◽  
Bond Angles ◽  
Bond Lengths ◽  
Metal Atoms ◽  
Apical Site

Three tetranuclear copper(II)–lanthanide(III) complexes of triphenylphosphoniopropionate (Ph3P+CH2CH2CO2−,tppp), namely [Cu2Ln2(tppp)8(H2O)8](ClO4)10·2H 2 O [Ln = EuIII, NdIII or CeIII], were synthesized and characterized by crystallography. The EuIII complex crystallizes in the triclinic space group P1 – with a 16.249(7), b 17.185(11), c 17.807(11) Å, α 69.750(10), β 89.230(10), γ 84.070(10)˚, V 4639(5) Å3, Z 1. In the crystal structures, four tppp ligands bridge a pair of CuII and tetraaquo-EuIII atoms (Cu···Eu 3.527(2) Å) through their µ2-carboxylato ends to form a dinuclear subunit; two of these subunits are additionally linked by one of the CuII -bonded carboxylato oxygen ends, across a centre of inversion, to furnish a dimeric tetranuclear [Cu(tppp)4 Eu(H2O)4]2 species (Cu···Cu 3.323(2) Å). This CuII -bonded oxygen atom occupies the apical site of the square-pyramidal coordination environment of the CuII atom. The EuIII atom is eight-coordinated in a square-antiprismatic geometry. The NdIII and CeIII complexes are isomorphous to the EuIII complex, and only minor differences in bond lengths and bond angles involving the metal atoms are noted.

scholarly journals Crystal structure of 3-benzyl-2-[(E)-2-(furan-2-yl)ethenyl]-2,3-dihydroquinazolin-4(1H)-one and 3-benzyl-2-[(E)-2-(thiophen-2-yl)ethenyl]-2,3-dihydroquinazolin-4(1H)-one from synchrotron X-ray diffraction

2018 ◽  
Vol 74 (1) ◽  
pp. 10-14
Author(s):  
Flavien A. A. Toze ◽  
Vladimir P. Zaytsev ◽  
Lala V. Chervyakova ◽  
Elisaveta A. Kvyatkovskaya ◽  
Pavel V. Dorovatovskii ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Axial Position ◽  
Isatoic Anhydride ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bond Angles ◽  
Pyramidal Geometry ◽  
Three Component Reaction ◽  
Racemic Crystals

The chiral title compounds, C21H18N2O2, (I), and C21H18N2OS, (II) – products of the three-component reaction between benzylamine, isatoic anhydride and furyl- or thienyl-acrolein – are isostructural and form isomorphous racemic crystals. The tetrahydropyrimidine ring in (I) and (II) adopts a sofa conformation. The amino N atom has a trigonal–pyramidal geometry [sum of the bond angles is 347.0° for both (I) and (II)], whereas the amido N atom is flat [sum of the bond angles is 359.3° for both (I) and (II)]. The furyl- and thienylethenyl substituents in (I) and (II) are planar and the conformation about the bridging C=C bond isE. These bulky fragments occupy the axial position at the quaternary C atom of the tetrahydropyrimidine ring, apparently, due to steric reasons. In the crystals, molecules of (I) and (II) form hydrogen-bonded helicoidal chains propagating along [010] by strong intermolecular N—H...O hydrogen bonds.

Ion size effect on chemical bonds of the RBa2Cu2.9Zn0.1Oy system

2018 ◽  
Vol 33 (3) ◽  
pp. 209-215
Author(s):  
R. Benredouane ◽  
C. Boudaren
Keyword(s):  
Single Phase ◽  
Rietveld Method ◽  
Solid State Reaction Method ◽  
X Ray ◽  
Bond Angles ◽  
Bond Valence Sum ◽  
Ion Size ◽  
First Time ◽  
Unique Variation ◽  
Strong Curvature

Single-phase polycrystalline samples of RBa2Cu2.9Zn0.1Oy (R = Y, Nd, Gd, Er, and Tm) (ZnR123) were synthesized using the standard solid-state reaction method. They were characterized by X-ray powder diffraction (XRD) and scanning electron microscope. XRD shows that all samples consist essentially of a single phase and retain the orthorhombic structure. The structure of the samples was refined by the Rietveld method with the help of the bond valence sum method. The variation of the lattice parameters and some meaningful bond angles and lengths with the ionic radius are discussed. In these compounds, the variations of the buckling angles Cu2–O(2,3)–Cu2 and Cu2–Cu2–O(2,3) are unique: the bond angles Cu2–O3–Cu2 and Cu2–Cu2–O2 increase, whereas the bond angles Cu2–O2–Cu2 and Cu2–Cu2–O3 decrease. The variation of these bond angles brings about a strong curvature of the Cu2O plane. Furthermore, we have found tree fixed triangles formed by the Cu2, O2, and O3 atoms in addition to another fixed triangle O1–Ba–O1 observed for the first time. BVS of Cu2 atom shows a specific and unique variation compared with other compounds.

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