Contribution to the Semiempirical Interpretation of the Anisotropy of the 29Si NMR Shielding Tensor in Silicates. II. Influence of Changes in the O-Si-O Bond Angle in SiO44- Ion

1993 ◽  
Vol 58 (6) ◽  
pp. 1255-1268
Author(s):  
Christine Vogel ◽  
Renate Wolff ◽  
Reiner Radeglia
Keyword(s):  
Bond Length ◽  
Silicon Atom ◽  
Bond Angle ◽  
Basis Set ◽  
29Si Nmr ◽  
Shielding Tensor ◽  
Valence Basis Set

The influence of variations in the OSiO bond angle α on the anisotropy of the 29Si shielding tensor of the monosilicate anion SiO44- in C3ν symmetry has been investigated by semiempirical CNDO/2 calculations. In the valence basis set of the silicon atom, no d-orbitals were employed. It could be shown that the terms characterizing the four Si-O bond contributions to ∆σ are of greatest importance for reproducing the experimentally observed trend of anisotropy signs in silicates. Both the increasing O(1)-Si-O(B) bond angle α, and the decreasing Si-O(1) bond length r(Si-O(1)) (and vice versa) exhibit an amplifying geometrical influence on ∆σ.

Conformational prediction for molecules containing vicinal lone pairs: Basis set studies for H2O2

1977 ◽  
Vol 30 (2) ◽  
pp. 231 ◽  
Author(s):  
PG Burton ◽  
BR Markey
Keyword(s):  
Bond Length ◽  
Bond Angle ◽  
State Of The Art ◽  
Basis Set ◽  
Basis Sets ◽  
Conformational Study ◽  
Gaussian Basis Sets ◽  
Lone Pairs ◽  
Polarization Functions ◽  
Bond Functions

The Dunning and Winter1 (DW) conformational study of H2O2 represents accepted state-of-the-art methodology in accurate SCF computation of molecular properties; nevertheless the prediction of a very short O-O bond length and a very large O-O-H bond angle by DW indicates the difficulty in adequately describing molecules with vicinal lone pairs. Consequently we have reexamined H2O2 with several standard Gaussian basis sets, and in addition have investigated the properties of two further basis set prescriptions. While polarization functions are confirmed to be necessary to attaining the correct H2O2 conformation, the situation of s (and p) Gaussian bond functions in mid-bond positions is shown to be an economical and efficacious alternative to traditional polarizing functions.

Clusterization Effect on the 29Si NMR Signal of a Spiro Silicon Atom

2021 ◽  
Author(s):  
Akihiro Tsurusaki ◽  
Hiroyasu Sato ◽  
Soichiro Kyushin
Keyword(s):  
Silicon Atom ◽  
29Si Nmr

scholarly journals Theoretical Study of Solvent Effects on the Electronic and Thermodynamic Properties of Tetrathiafulvalene (TTF) Molecule Based on DFT

2021 ◽  
pp. 42-54
Author(s):  
Rabiu Nuhu Muhammad ◽  
N. M. Mahraz ◽  
A. S Gidado ◽  
A. Musa
Keyword(s):  
Thermodynamic Properties ◽  
Bond Length ◽  
Density Functional ◽  
Theoretical Study ◽  
Energy Gap ◽  
Basis Set ◽  
Basis Sets ◽  
Frontier Molecular Orbital ◽  
Orbital Energy ◽  
Chemical Hardness

Tetrathiafulvalene () is an organosulfur compound used in the production of molecular devices such as switches, sensors, nonlinear optical devices and rectifiers. In this work, a theoretical study on the effects of solvent on TTF molecule was investigated and reported based on Density Functional Theory (DFT) as implemented in Gaussian 03 package using B3LYP/6-31++G(d,p) basis set. Different solvents were introduced as a bridge to investigate their effects on the electronic structure. The HUMO, LUMO, energy gap, global chemical index, thermodynamic properties, NLO and DOS analysis of the TTF molecule in order to determine the reactivity and stability of the molecule were obtained. The results obtained showed that the solvents have effects on the electronic and non-linear-optical properties of the molecule. The optimized bond length revealed that the molecule has strong bond in gas phase with smallest bond length of about 1.0834Å than in the rest of the solvents. It was observed that the molecule is more stable in acetonitrile with HOMO-LUMO gap and chemical hardness of 3.6373eV and 1.8187eV respectively. This indicates that the energy gap and chemical hardness of TTF molecule increases with the increase in polarity and dielectric constant of the solvents. The computed results agreed with the results in the literature. The thermodynamics and NLO properties calculation also indicated that TTF molecule has highest value of specific heat capacity (Cv), total dipole moment () and first order hyperpolarizability () in acetonitrile, while acetone has the highest value of entropy and toluene has a slightly higher value of zero point vibrational energy (ZPVE) than the rest of the solvents. The results show that careful selection of the solvents and basis sets can tune the frontier molecular orbital energy gap of the molecule and can be used for molecular device applications.

Rate of tert-butyl rotation in 2-tert-butyl 1,3-diheteroatomic rings. Roles of bond angle and bond length in a trend reversal

1972 ◽  
Vol 94 (13) ◽  
pp. 4743-4744 ◽  
Author(s):  
Philip E. Stevenson ◽  
Warren G. Anderson ◽  
C. Hackett Bushweller ◽  
Geetha U. Rao
Keyword(s):  
Bond Length ◽  
Bond Angle ◽  
Tert Butyl ◽  
Trend Reversal

Quantitative Structure-Property Relationship (QSPR) Study on the Complex Compounds Formed From Gadolinium(III) with Dibutyl Dithiophosphate Derivatives Ligands Based on Molecular Descriptors

2021 ◽  
Vol 874 ◽  
pp. 171-181
Author(s):  
Nurdeni ◽  
Atje Setiawan Abdullah ◽  
Budi Nurani Ruchjana ◽  
Anni Anggraeni ◽  
Annisa Nur Falah ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Linear Regression ◽  
Bond Length ◽  
Bond Angle ◽  
Linear Regression Analysis ◽  
Multiple Linear Regression Analysis ◽  
Complex Compounds ◽  
Quantitative Structure ◽  
Structure Property ◽  
Structure Property Relationship

A study of the quantitative relationship of structure and property (Quantitative Structure Property Relationship (QSPR) has been carried out on complex compounds formed between gadolinium (Gd) and dibutyldithiophosphate (DBDTP) derivative ligands. This study is a part of our laboratory research program on the development of extractant ligands, including DBDTP in extraction for the separation and purification of rare-earth elements (REEs), specifically Gd. Gadolinium has also been a part of the research program about its use in the synthesis of magnetic resonance imaging (MRI) contrast agents, for the diagnosis of various diseases. This chemical calculation research aims to analyze the effect of descriptors in the form of parameters of the physical-chemical properties of bond lengths, bond angles, and bond energies on the stability of Gd complex compounds with DBDTP derivative ligands. To get descriptors PM7 semi-empirical method was used, while for data analysis, Multiple Linear Regression Analysis was used, assuming the model error is normally distributed with zero mean and constant variance. Furthermore, data processing was done using SPSS software. This research was conducted by involving 28 DBDTP derivative ligands and using multiple linear regression analysis. The regression equation is Y ̂ = - 0.966 + 0.586 V1 - 0.014 V2 + 0.000 V3. From the resulted research data it was found that there are three findings, namely: (1) bond length and bond angle have a significant simultaneous effect on stability of Gd complex compounds with DBDTP derivative ligands; (2) bond length and bond angle have a partially significant effect on stability of Gd complex compounds with DBDTP derivative ligands; (3) bond length proved to have a significant dominant effect on stability of Gd complex compounds with DBDTP derivative ligands.

Nitrido-und Oxochlorokomplexe des Vanadiums(V); die Kristallstruktur von AsPh4 [V0C14] Nitrido and Oxochloro Complexes of Vanadium(V); the Crystal Structure of AsPh4[VOCl4]

1980 ◽  
Vol 35 (5) ◽  
pp. 522-525 ◽  
Author(s):  
Gisela Beindorf ◽  
Joachim Strähle ◽  
Wolfgang Liebelt ◽  
Kurt Dehnicke
Keyword(s):  
Crystal Structure ◽  
Ir Spectra ◽  
Bond Length ◽  
Bond Angle ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
Linear Arrangement ◽  
Space Group ◽  
X Ray ◽  
Complex Anions

The complexes AsPh4[Cl4V = N-Cl] and AsPh4[VOCl4] are prepared by the reaction of AsPh4Cl with Cl3VNCl and VOCl3, respectively. The IR spectra indicate C4v symmetry for the complex anions with multiple VN and VO bonds and a linear arrangement for the VNCl-group. AsPh4[VOCl4] crystallizes in the tetragonal space group P4/n with two formula units in the unit cell. The crystal structure was solved by X-ray diffraction methods (R = 0,062, 1096 observed, independent reflexions). The structure consists of AsPh4+ cations and [VOCl4]- anions with symmetry C4v. The extremely short VO bond length corresponds with a VO triple; its steric requirements cause the relatively large bond angle OVCl of 103.4°.

Structure and Morphology Properties of Nanosized La0.75K0.05Ba0.05Sr0.15MnO3 Manganite

2020 ◽  
Vol 860 ◽  
pp. 106-111
Author(s):  
Dhawud Sabilur Razaq ◽  
Budhy Kurniawan ◽  
Ikhwan Nur Rahman ◽  
Dicky Rezky Munazat
Keyword(s):  
Bond Length ◽  
Crystallite Size ◽  
Sintering Temperature ◽  
Bond Angle ◽  
Sol Gel ◽  
Rhombohedral Structure ◽  
Phase Purity ◽  
X Ray ◽  
Structure And Morphology ◽  
Scanning Electron

Nanosized La0.75K0.05Ba0.05Sr0.15MnO3 manganite have been synthesized using sol-gel method. Afterwards, the samples were sintered at eight different temperature ranging from 650 to 1000 °C. Phase purity, crystal structure and the morphology of the sample have been examined using X-Ray Diffractometer (XRD) and Scanning Electron Microscope. It has been found that different higher sintering temperature greatly affect the phase purity and crystallite size of the sample. Regardless of the sintering temperature, all the samples crystallized in rhombohedral structure with R-3c space group. The crystallite size of the samples is found to increase from 41.59 nm up to 73.42 nm as the sintering temperature increases. Further analysis from XRD result shows that sintering temperature also affect the average Mn-O bond length and Mn-O-Mn bond angle of the sample. The average Mn-O bond length is found to increase while the average Mn-O-Mn bond angle tends to decrease as sintering temperature increases. SEM measurement shows that various grain size ranging from ~100 nm up to ~ 350 nm exists in all the sample regardless the sintering temperature.

Electronic spectrum of D2O+

1987 ◽  
Vol 65 (7) ◽  
pp. 739-752 ◽  
Author(s):  
H. Lew ◽  
R. Groleau
Keyword(s):  
Bond Length ◽  
Ground State ◽  
Simple Formula ◽  
Bond Angle ◽  
Spin Rotation ◽  
Type B ◽  
Infrared Band ◽  
Asymmetric Rotor ◽  
Linear Molecules ◽  
Van Vleck

An analysis of 15 bands of the [Formula: see text] system of D2O+ is given. All assigned lines are tabulated. The rotational structures of the [Formula: see text], 1, and 3 levels of the ground state are fitted to the Watson asymmetric rotor Hamiltonian with added spin-rotation terms. For the upper state, the rotational structures of various substates are expressed: for [Formula: see text], in terms of a simple formula for linear molecules; and for [Formula: see text], 2, and 3, in terms of a modified Hill – Van Vleck formula given by Jungen, Hallin, and Merer. From the rotational constants of the ground state, term values are calculated and a small portion of a Type-B infrared band is derived. Some predicted microwave lines are also given. The bond length and bond angle of the molecule in the ground state (ν = 0) are r0 = 0.9987 ± 0.0002 Å and θ0 = 110.17 ± 0.02 deg.

Neue Chalkogenometallate mit binuklearen Anionen, I: Darstellung und Kristallstruktur von Rb6Sn2S7 / New Chalcogenometallates with Binuclear Anions, I: Preparation and Crystal Structure of Rb6Sn2S7

1999 ◽  
Vol 54 (12) ◽  
pp. 1505-1509 ◽  
Author(s):  
Kurt O. Klepp ◽  
Ferdinand Fabian
Keyword(s):  
Crystal Structure ◽  
Bond Length ◽  
Sulfur Atom ◽  
Bond Angle ◽  
The Mean

Colorless crystals of the new thiostannate Rb6Sn2S7 were obtained by reacting a stoichiometric melt of Rb2S, Sn and S at 700°C. The compound is orthorhombic, oP60, s.g. P212121 (No. 19) with a = 9.982(4), b = 13.45(1), c = 15.20(1) Å; Z = 4. The crystal structure was determined from diffractometer data and refined to a conventional R of 0.043 (1380 Fo's, 137 variables). The crystal structure contains dimeric anions, [Sn2S7]2 -, which are built up by slightly distorted SnS4 tetrahedra sharing a common sulfur atom. The mean Sn-S bond length calculates as 2.384 Å, the bond angle on the bridging S is 110.4°. The structure contains six independent Rb-cations which are coordinated to 5-6 sulfur atoms in irregular configurations.

scholarly journals An Assessment of Computational Methods for Calculating Accurate Structures and Energies of Bio-Relevant Polysulfur/Selenium-Containing Compounds

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3323 ◽  
Author(s):  
Sahar Nikoo ◽  
Paul Meister ◽  
John Hayward ◽  
James Gauld
Keyword(s):  
Inorganic Chemistry ◽  
Bond Length ◽  
Gas Phase ◽  
Electron Correlation ◽  
Negative Charge ◽  
Basis Set ◽  
Proton Affinities ◽  
Selenium Compounds ◽  
Gas Phase Basicities

The heavier chalcogens sulfur and selenium are important in organic and inorganic chemistry, and the role of such chalcogens in biological systems has recently gained more attention. Sulfur and, to a lesser extent selenium, are involved in diverse reactions from redox signaling to antioxidant activity and are considered essential nutrients. We investigated the ability of the DFT functionals (B3LYP, B3PW91, ωB97XD, M06-2X, and M08-HX) relative to electron correlation methods MP2 and QCISD to produce reliable and accurate structures as well as thermochemical data for sulfur/selenium-containing systems. Bond lengths, proton affinities (PA), gas phase basicities (GPB), chalcogen–chalcogen bond dissociation enthalpies (BDE), and the hydrogen affinities (HA) of thiyl/selenyl radicals were evaluated for a range of small polysulfur/selenium compounds and cysteine per/polysulfide. The S–S bond length was found to be the most sensitive to basis set choice, while the geometry of selenium-containing compounds was less sensitive to basis set. In mixed chalcogens species of sulfur and selenium, the location of the sulfur atom affects the S–Se bond length as it can hold more negative charge. PA, GPB, BDE, and HA of selenium systems were all lower, indicating more acidity and more stability of radicals. Extending the sulfur chain in cysteine results in a decrease of BDE and HA, but these plateau at a certain point (199 kJ mol−1 and 295 kJ mol−1), and PA and GPB are also decreased relative to the thiol, indicating that the polysulfur species exist as thiolates in a biological system. In general, it was found that ωB97XD/6-311G(2d,p) gave the most reasonable structures and thermochemistry relative to benchmark calculations. However, nuances in performance are observed and discussed.

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