scholarly journals Calculations of optical rotation: Influence of molecular structure

2012 ◽  
Vol 77 (7) ◽  
pp. 887-898
Author(s):  
Jia Yu ◽  
Yu Cao ◽  
Hang Song ◽  
Xianlong Wang ◽  
Shun Yao
Keyword(s):  
Molecular Structure ◽  
Nitrogen Atom ◽  
Density Functional ◽  
Optical Rotation ◽  
Cyclic Compound ◽  
Polarizable Continuum Model ◽  
Basis Sets ◽  
Dft Methods ◽  
Hartree Fock ◽  
Chiral Compounds

Ab initio Hartree-Fock (HF) method and Density Functional Theory (DFT) were used to calculate the optical rotation of 26 chiral compounds. The effects of theory and basis sets used for calculation, solvents influence on the geometry and values of calculated optical rotation were all discussed. The polarizable continuum model, included in the calculation, did not improve the accuracy effectively, but it was superior to ?s. Optical rotation of five or sixmembered of cyclic compound has been calculated and 17 pyrrolidine or piperidine derivatives which were calculated by HF and DFT methods gave acceptable predictions. The nitrogen atom affects the calculation results dramatically, and it is necessary in the molecular structure in order to get an accurate computation result. Namely, when the nitrogen atom was substituted by oxygen atom in the ring, the calculation result deteriorated.

THEORETICAL STUDY OF GLYCINE CONFORMERS

2008 ◽  
Vol 07 (04) ◽  
pp. 889-909 ◽  
Author(s):  
HONG-WEI KE ◽  
LI RAO ◽  
XIN XU ◽  
YI-JING YAN
Keyword(s):  
Potential Energy Surfaces ◽  
Density Functional ◽  
Polarizable Continuum Model ◽  
Basis Sets ◽  
Dft Methods ◽  
Solvent Interactions ◽  
Solvation Effects ◽  
Moller Plesset ◽  
Energy Surfaces ◽  
Polarizable Continuum

Glycine conformers were investigated with three density functional theory (DFT) methods (B3LYP, PBE1PBE, X3LYP), and the second order Møller–Plesset perturbation theory (MP2) combined with basis sets of 6-31+G*, aug-cc-pVDZ, and aug-cc-pVTZ. Solvation effects were considered by using polarizable continuum model. Results from B3LYP and X3LYP were in generally good agreement with those of MP2, while PBE1PBE was shown to be inferior for the description of conformational potential energy surfaces. Conformers Ip, IIp, IIn, IIIp, IIIn, and IVn were all found to be low-lying states within 2.0 kcal/mol, with Ip being the global minimum in gas phase. Solvation effects can significantly change the nature of the conformational surfaces of glycine. A proper description of conformational equilibrium demands for a good treatment of both long-range and short-range solute–solvent interactions.

THEORETICAL CHARACTERIZATION OF A HIGHLY ELECTROPHILIC CARBENE

2005 ◽  
Vol 04 (03) ◽  
pp. 823-832 ◽  
Author(s):  
JUAN F. VAN DER MAELEN URÍA ◽  
JAVIER RUIZ ◽  
SANTIAGO GARCÍA-GRANDA
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Basis Set ◽  
Basis Sets ◽  
Singlet Ground State ◽  
X Ray Diffraction ◽  
Dft Methods ◽  
Hartree Fock ◽  
Experimental Complex ◽  
Experimental Geometry

The experimental geometry obtained from single-crystal X-ray diffraction data for a metalladiphosphanyl carbene precursor is compared with the results of theoretical calculations made at the ab initio level by using Hartree–Fock (HF) and Density Functional Theory (DFT) methods over the carbene itself. Theoretical geometry optimizations for the singlet ground state of [ Mn(CO)4(PH2)2C: ]+ have been performed with several hybrid functionals and basis sets. Calculated geometries showed a perfect C 2v symmetry in the highest levels of calculation and were somewhat relaxed when compared with the experimental ones; for instance, with the largest basis set, the P–C–P angle found was 124.8°, whereas C–P bond distances were both 1.667 Å, compared to 103.5(3)° and 1.718(5) Å, respectively, from the experimental data. The absence of a ligand attached to the C : atom in the calculated structure, which is present in the form of iodine in the experimental complex, is probably responsible, to a certain extent, for the discrepancies. In addition to the structural computations, in order to theoretically quantify the highly electrophilic character expected for the carbene, electron affinities were calculated and found to be between 6.24 eV and 6.97 eV at different DFT levels of calculation, which confirmed the expectations. In this respect, a comparison with the analogous [Ru(CNH)4(PH2)2C:]2+ carbene is also made, showing the possibility of experimentally trapping the manganese carbene.

scholarly journals Hirshfeld surface and theoretical studies of 2,2,2-trichloro-N,N-bis(2-(2,2,2-trichloroacetamido)phenyl)acetamide compound

2019 ◽  
Vol 10 (4) ◽  
pp. 323-335
Author(s):  
Immihan Sezen Aydogdu ◽  
Ilkay Gumus ◽  
Hakan Arslan
Keyword(s):  
Surface Analysis ◽  
Density Functional ◽  
Crystal Packing ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Basis Sets ◽  
Dft Methods ◽  
Hartree Fock ◽  
Intermolecular Contacts

The vibrational frequencies, atomic charges and the related properties of the 2,2,2-trichloro-N,N-bis(2-(2,2,2-trichloroacetamido)phenyl)acetamide (H2LNNN) were investi-gated by Ab-initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods such as BLYP, B3LYP, B3PW91 and mPW1PW91 functionals with 6-31G(d,p) and 6-311G(d,p) basis sets. The experimentally determined parameters were compared with those calculated theoretically and they were found to complement each other with a very good correlation. The theoretical vibrational spectrum of H2LNNN molecule was interpreted by means of potential energy distributions using the SQM 2.0 program. The Hirshfeld surface analysis was carried out to discuss the role of the hydrogen bonds and other intermolecular contacts in crystal lattice. Hirshfeld surface analysis revealed the occurrence of Cl⋯H, Cl⋯Cl, Cl⋯C, H···H, O⋯H, C···H and Cl···π interactions that display an important role on the crystal packing stabilization of the compound.

scholarly journals Theoretical Study of Copper Complexes: Molecular Structure, Properties, and Its Application to Solar Cells

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Jesus Baldenebro-Lopez ◽  
Norma Flores-Holguin ◽  
Jose Castorena-Gonzalez ◽  
Jorge Almaral-Sanchez ◽  
Daniel Glossman-Mitnik
Keyword(s):  
Molecular Structure ◽  
Solar Cells ◽  
Density Functional ◽  
Copper Complexes ◽  
Chemical Reactivity ◽  
Polarizable Continuum Model ◽  
Basis Sets ◽  
The Density Functional Theory ◽  
Potential Applications ◽  
Implicit Approach

We present a theoretical investigation of copper complexes with potential applications as sensitizers for solar cells. The density functional theory (DFT) and time-dependent DFT were utilized, using the M06 hybrid meta-GGA functional with the LANL2DZ (D95V on first row) and DZVP basis sets. This level of calculation was used to find the optimized molecular structure, the absorption spectra, the molecular orbitals energies, and the chemical reactivity parameters that arise from conceptual DFT. Solvent effects have been taken into account by an implicit approach, namely, the polarizable continuum model (PCM), using the nonequilibrium version of the IEF-PCM model.

Density Functional Theory and ab initio Hartree-Fock Calculations of Molecular Structure and Vibrational Spectra of Anilinium Nitrate

2008 ◽  
Vol 63 (10-11) ◽  
pp. 712-720 ◽  
Author(s):  
Davut Avcı ◽  
Adil Başoğlu ◽  
Yusuf Atalay
Keyword(s):  
Molecular Structure ◽  
Density Functional Theory ◽  
Density Functional ◽  
Molecular Geometry ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Dft Methods ◽  
Functional Theory ◽  
Hartree Fock ◽  
Infrared Intensities

The molecular geometry, vibrational frequencies, infrared intensities, Raman scattering activities and several thermodynamic parameters of anilinium nitrate in the ground state have been calculated by both Hartree-Fock (HF) and three density functional theory (DFT) methods (B3LYP, BLYP and B3PW91) using the 6-31G(d) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray structure. The optimized geometric bond lengths are described very well by the HF method while bond angles are reproduced more accurately by the DFT methods. Comparison between the observed fundamental vibrational frequencies of anilinium nitrate and the results of DFT and HF methods indicates that B3LYP is superior to the scaled HF, BLYP and B3PW91 approaches for molecular vibrational problems. The computed vibrational frequencies are used to determine the types of molecular motions associated with each of the experimental bands observed. In addition, calculated results are related to the linear correlation plot of computed data versus experimental geometric parameters and IR data.

Theoretical and Experimental Investigations of Fullerene Derivatives: C60H2, C60H4, C70H2, AND C60(CH2)2

1994 ◽  
Vol 349 ◽  
Author(s):  
S. Joshua Jacobs ◽  
Kenneth T. Gillen ◽  
Paul A. Cahill ◽  
Craig C. Henderson ◽  
Celeste M. Rohlfing
Keyword(s):  
Density Functional ◽  
Energy Difference ◽  
Basis Sets ◽  
Pt Catalyst ◽  
Energy Separation ◽  
Experimental Investigations ◽  
Level Energy ◽  
Dft Methods ◽  
Fullerene Derivatives ◽  
Hartree Fock

ABSTRACTHydroboration of C70 in toluene yields a 2:1 mixture of 1,9-C70H2 and 7,8-C70H2. Equilibration of these two isomers in the presence of a Pt catalyst reveals a free energy difference of 1.4 ± 0.2 kcal/mol. Whereas semiempirical calculations have been found to predict the energy ordering of many fullerene derivatives incorrectly, ab initio Hartree-Fock (HF) calculations have been found to yield quantitative predictions of experiment. The HF/6-31G* level energy separation of l,9-C70H2 and 7,8-C70H2 of 1.3 kcal/mol is in excellent agreement with experiment. Relative stabilities of isomers of bis(methano)fullerenes were found to parallel those of analogous C60H4 isomers. Density functional theory (DFT) methods have been tested and are equivalent in accuracy to HF methods if similar basis sets are used. C60H2 and C60H4 can be efficiently produced on larger (≥ 50 mg) scales with diimide generated from potassium azodicarboxylate and acetic acid in o-dichlorobenzene.

scholarly journals Role of Exchange and Correlation in High-Harmonic Generation Spectra of H2, N2 and CO2: Real-Time Time-Dependent Electronic-Structure Approaches

2020 ◽  
Author(s):  
Emanuele Coccia ◽  
Eleonora Luppi ◽  
Carlo Federico Pauletti
Keyword(s):  
Real Time ◽  
Harmonic Generation ◽  
Density Functional ◽  
High Harmonic ◽  
High Harmonic Generation ◽  
Time Dependent ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Exchange And Correlation

<p>This study arises from the attempt to answer the following question: how different descriptions of electronic exchange and correlation affect the high-harmonic generation (HHG) spectroscopy of H2, N2 and CO2 molecules? We compare HHG spectra for H2, N2 and CO2 with different ab initio electronic structures methods: real-time time-dependent configuration interaction (RT-TDCIS) and real-time time-dependent density functional theory (RT-TDDFT) using truncated basis sets composed of correlated wave functions expanded on Gaussian basis sets. In the framework of RT-TDDFT, we employ PBE and LC-ωPBE functionals. We study HHG spectroscopy by disentangling the effect of electronic exchange and correlation. We first analyse the electronic exchange alone and in the case of RT-TDDFT with LC-ωPBE, we use ω = 0.3 and ω = 0.4 to tune the percentage of long-range Hartree-Fock exchange and of short-range exchange PBE. Then, we added the correlation as described by PBE functional. All the methods give very similar HHG spectra and they seem not to be particularly sensitive to the different description of exchange and correlation or to the correct asymptotic behaviour of the Coulomb potential. Despite this general trend, some differences are found in the region connecting the cutoff and the background. Here, the harmonics can be resolved with different accuracy depending on the theoretical schemes used. We believe that the investigation of the molecular continuum and its coupling with strong fields merits further theoretical investigations in the next future. </p>

The fragment molecular orbital method combined with density-functional tight-binding and the polarizable continuum model

2016 ◽  
Vol 18 (32) ◽  
pp. 22047-22061 ◽  
Author(s):  
Yoshio Nishimoto ◽  
Dmitri G. Fedorov
Keyword(s):  
Molecular Structure ◽  
Molecular Orbital ◽  
Continuum Model ◽  
Density Functional ◽  
Tight Binding ◽  
Polarizable Continuum Model ◽  
Orbital Method ◽  
Molecular Orbital Method ◽  
Polarizable Continuum ◽  
Structure Of Proteins

The electronic gap in proteins is analyzed in detail, and it is shown that FMO-DFTB/PCM is efficient and accurate in describing the molecular structure of proteins in solution.

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