scholarly journals Understanding Trends in Molecular Bond Angles

2020 ◽  
Vol 124 (7) ◽  
pp. 1306-1311
Author(s):  
Gerrit-Jan Linker ◽  
Piet Th. van Duijnen ◽  
Ria Broer
Keyword(s):  
Bond Angles ◽  
Molecular Bond

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.

scholarly journals Dynamical strengthening of covalent and non-covalent molecular interactions by nuclear quantum effects at finite temperature

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huziel E. Sauceda ◽  
Valentin Vassilev-Galindo ◽  
Stefan Chmiela ◽  
Klaus-Robert Müller ◽  
Alexandre Tkatchenko
Keyword(s):  
Finite Temperature ◽  
Electrostatic Interactions ◽  
Zero Point ◽  
Quantum Effects ◽  
Van Der Waals Interactions ◽  
Interatomic Distances ◽  
Point Energy ◽  
Molecular Bond ◽  
Energy Surfaces ◽  
Nuclear Quantum Effects

AbstractNuclear quantum effects (NQE) tend to generate delocalized molecular dynamics due to the inclusion of the zero point energy and its coupling with the anharmonicities in interatomic interactions. Here, we present evidence that NQE often enhance electronic interactions and, in turn, can result in dynamical molecular stabilization at finite temperature. The underlying physical mechanism promoted by NQE depends on the particular interaction under consideration. First, the effective reduction of interatomic distances between functional groups within a molecule can enhance the n → π* interaction by increasing the overlap between molecular orbitals or by strengthening electrostatic interactions between neighboring charge densities. Second, NQE can localize methyl rotors by temporarily changing molecular bond orders and leading to the emergence of localized transient rotor states. Third, for noncovalent van der Waals interactions the strengthening comes from the increase of the polarizability given the expanded average interatomic distances induced by NQE. The implications of these boosted interactions include counterintuitive hydroxyl–hydroxyl bonding, hindered methyl rotor dynamics, and molecular stiffening which generates smoother free-energy surfaces. Our findings yield new insights into the versatile role of nuclear quantum fluctuations in molecules and materials.

Bond equilibrium theory for Te-rich liquid Tl–Te alloys

1977 ◽  
Vol 55 (11) ◽  
pp. 1930-1936 ◽  
Author(s):  
Melvin Cutler
Keyword(s):  
Free Energy ◽  
Good Description ◽  
Hole Concentration ◽  
Enthalpy Of Mixing ◽  
Dangling Bond ◽  
Fermi Model ◽  
Bond Model ◽  
Independent Information ◽  
Molecular Bond ◽  
Rich Liquid

Recent work has provided independent information about the behavior of the hole concentration c in TlxTe1−x as a function of temperature T and composition x in the range 0.2 ≤ x ≤ 0.6. This makes possible a critical reexamination of a molecular bond model for the structure of the alloy, in which holes are generated by broken Te—Te bonds. The earlier theory is revised to formulate an unrestricted independent bond model (ibm), for which the equations are simple and have obvious physical interpretations. This provides a good description of c(T) but only a qualitatively correct c(x). Using a Thomas–Fermi model for the screening interaction between holes and the acceptor ions, it is shown that the equilibrium constant can be expected to increase rapidly with c at large enough values. A modification in which the free energy of a dangling bond is decreased by proximity to a Tl—Te bond is found to significantly improve the result for c(x). The thermochemical behavior is derived. The entropy of mixing is in fair agreement with experiment, but the enthalpy of mixing is grossly wrong. This reflects the neglect of intermolecular interactions in the theory, which, it seems, can easily account for the remaining discrepancies in the predicted behavior of c.

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.

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
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