scholarly journals Computational Spectroscopy of the Cr–Cr Bond in Coordination Complexes

2021 ◽  
Author(s):  
Toru Shiozaki ◽  
Bess Vlaisavljevich
Keyword(s):  
Spectroscopic Data ◽  
Technological Development ◽  
Vibrational Analysis ◽  
Bond Distance ◽  
Coordination Complexes ◽  
Vibrational Structure ◽  
Complete Active Space ◽  
Computational Spectroscopy ◽  
First Time ◽  
Good Agreement

We report the accurate computational vibrational analysis of the Cr–Cr bond in dichromium complexes using second-order multireference complete active space methods (CASPT2), allowing direct comparison with experimental spectroscopic data both to facilitate interpreting the low-energy region of the spectra and to provide insights into the nature of the bonds themselves. Recent technological development by the authors has realized such computation for the first time. Accurate simulation of the vibrational structure of these compounds has been hampered by their notorious multiconfigurational electronic structure that yields bond distances that do not correlate with bond order. Some measured Cr–Cr vibrational stretching modes, ν(Cr2), have suggested weaker bonding, even for so-called ultrashort Cr–Cr bonds, while others are in line with the bond distance. Here we optimize the geometries and compute ν(Cr2) with CASPT2 for three well-characterized complexes, Cr2(O2CCH3)4(H2O)2, Cr2(mhp)4, and Cr2(dmp)4. We obtain CASPT2 harmonic ν(Cr2) modes in good agreement with experiment at 282 cm−1 for Cr2(mhp)4 and 353 cm−1 for Cr2(dmp)4, compute 50Cr and 54Cr isotope shifts, and demonstrate that the use of the so-called IPEA shift leads to improved Cr–Cr distances. Additionally, normal mode sampling was used to estimate anharmonicity along ν(Cr2) leading to an anharmonic mode of 272 cm−1 for Cr2(mhp)4 and 333 cm−1 for Cr2(dmp)4.

scholarly journals Computational Spectroscopy of the Cr–Cr Bond in Coordination Complexes

2021 ◽  
Author(s):  
Toru Shiozaki ◽  
Bess Vlaisavljevich
Keyword(s):  
Spectroscopic Data ◽  
Technological Development ◽  
Vibrational Analysis ◽  
Bond Distance ◽  
Coordination Complexes ◽  
Vibrational Structure ◽  
Complete Active Space ◽  
Computational Spectroscopy ◽  
First Time ◽  
Good Agreement

We report the accurate computational vibrational analysis of the Cr–Cr bond in dichromium complexes using second-order multireference complete active space methods (CASPT2), allowing direct comparison with experimental spectroscopic data both to facilitate interpreting the low-energy region of the spectra and to provide insights into the nature of the bonds themselves. Recent technological development by the authors has realized such computation for the first time. Accurate simulation of the vibrational structure of these compounds has been hampered by their notorious multiconfigurational electronic structure that yields bond distances that do not correlate with bond order. Some measured Cr–Cr vibrational stretching modes, ν(Cr2), have suggested weaker bonding, even for so-called ultrashort Cr–Cr bonds, while others are in line with the bond distance. Here we optimize the geometries and compute ν(Cr2) with CASPT2 for three well-characterized complexes, Cr2(O2CCH3)4(H2O)2, Cr2(mhp)4, and Cr2(dmp)4. We obtain CASPT2 harmonic ν(Cr2) modes in good agreement with experiment at 282 cm−1 for Cr2(mhp)4 and 353 cm−1 for Cr2(dmp)4, compute 50Cr and 54Cr isotope shifts, and demonstrate that the use of the so-called IPEA shift leads to improved Cr–Cr distances. Additionally, normal mode sampling was used to estimate anharmonicity along ν(Cr2) leading to an anharmonic mode of 272 cm−1 for Cr2(mhp)4 and 333 cm−1 for Cr2(dmp)4.

Theoretical calculation of the low-lying doublet electronic states of the SrF molecule

2014 ◽  
Vol 92 (10) ◽  
pp. 1223-1231 ◽  
Author(s):  
F. Jardali ◽  
M. Korek ◽  
G. Younes
Keyword(s):  
Electronic States ◽  
Electronic Energy ◽  
Harmonic Frequency ◽  
Complete Active Space ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Schrödinger Perturbation ◽  
First Time ◽  
Good Agreement

The potential energy curves of the low-lying doublet electronic states in the representation 2s+1Λ(+/−) of the SrF molecule have been investigated by using the complete active space self-consistent field with multireference configuration interaction and multireference Rayleigh–Schrödinger perturbation theory methods. The harmonic frequency, ωe; the internuclear distance, Re; the dipole moment; and the electronic energy with respect to the ground state, Te, have been calculated for the considered electronic states. The eigenvalues, Ev; the rotational constants, Bv; and the abscissas of the turning points, Rmin and Rmax, have been investigated using the canonical functions approach. The comparison between the values of the present work and those available in the literature for several electronic states shows very good agreement. Nine new electronic states have been investigated here for the first time.

Ab initio calculation of the low-lying electronic states of the ZrN molecule

2012 ◽  
Vol 90 (7) ◽  
pp. 631-639 ◽  
Author(s):  
A. Farhat ◽  
M. Korek ◽  
M.A.L. Marques ◽  
S.N. Abdul-Al
Keyword(s):  
Ab Initio ◽  
Ab Initio Calculation ◽  
Electronic States ◽  
Electronic Energy ◽  
Zirconium Nitride ◽  
Harmonic Frequency ◽  
Complete Active Space ◽  
Self Consistent Field ◽  
First Time ◽  
Good Agreement

An ab initio calculation of the low-lying electronic states of zirconium nitride (ZrN) were performed by using a complete active space self-consistent field with multireference single and double excitation configuration interaction (MRSDCI). The potential energy curves of 21 low-lying electronic states of the ZrN molecule with different spin and spatial symmetries, in the representation 2s+1Λ(+/−) and below 30 000 cm–1, were identified. The harmonic frequency (ωe), the equilibrium internuclear distance (Re), the rotational constants (Be), the electronic energy with respect to the ground state (Te), and the permanent dipole moment (µ) were calculated for the considered electronic states. The comparison of these values with those available in the literature shows a very good agreement with either theoretical or experimental data. Fifteen new electronic states were studied here for the first time.

scholarly journals Dipole Moment and Electronic Structure Calculations of the Electronic States of the Molecule SiC below 97000cm-1

2016 ◽  
Vol 10 (11) ◽  
pp. 192 ◽  
Author(s):  
Karam Hamdan ◽  
Ghassan Younes ◽  
Mahmoud Korek
Keyword(s):  
Dipole Moment ◽  
Excited Electronic State ◽  
Electronic States ◽  
Theoretical Data ◽  
Electronic Energy ◽  
Complete Active Space ◽  
Self Consistent Field ◽  
Experimental Works ◽  
First Time ◽  
Good Agreement

Beside its importance in the astrophysics, the silicon carbide has a great importance in the industry of semiconductors and ceramics. Because of the absence of theoretical data, extensive ab initio calculations of dipole moment and higher excited electronic state have been done for this molecule. These calculations have been performed by using the Complete Active Space Self Consistent Field (CASSCF) with Multireference Configuration Interaction MRCI+Q (singly and doubly excitation with Davidson corrections). The potential energy and the dipole moment curves for the 47 low-lying singlet, triplet and quintet electronic states in the representation 2s+1Λ(+/-) of the molecule SiC have been calculated. The harmonic frequency we, the internuclear distance Re, the electronic energy with respect to the ground state Te, the rotational constants Be and the permanent dipole moment have been obtained for these electronic states. The comparison between the values of the present work and those available in the literature, for several electronic states, shows a good agreement. In the present work thirteen new electronic states have been investigated here for the first time. These new results may leads to more investigation of new experimental works on this molecule.

scholarly journals Dipole Moment and Electronic Structure Calculations of the Electronic States of the molecular ion SiN+

2016 ◽  
Vol 8 (4) ◽  
pp. 1
Author(s):  
Karam Hamdan ◽  
Ghassan Younes ◽  
Mahmoud Korek
Keyword(s):  
Dipole Moment ◽  
Electronic States ◽  
Electronic Energy ◽  
Permanent Dipole Moment ◽  
Molecular Ion ◽  
Complete Active Space ◽  
Self Consistent Field ◽  
First Time ◽  
Structure Calculations ◽  
Good Agreement

<p class="1Body">A theoretical investigation of the lowest electronic states of the molecular ion SiN<sup>+</sup> has been performed via Complete Active Space Self Consistent Field (CASSCF) method with Multi Reference Configuration Interaction MRCI+Q (single and double excitations with Davidson correction) calculations. The potential energy curves of the low-lying 37 electronic states in the representation <sup>2s+1</sup>Λ<sup>(+/-)</sup>, up to 140000 cm<sup>-1 , </sup>have been investigated. The permanent dipole moment, the harmonic frequency ω<sub>e</sub>, the equilibrium internuclear distance R<sub>e</sub>, the rotational constants B<sub>e</sub> and the electronic energy with respect to the ground state T<sub>e</sub> have been calculated for these electronic states. The comparison between the values of the present work and those available in the literature for several electronic states shows a very good agreement. The permanent dipole moment, of the investigated 37 electronic states, have been calculated in the present work for the first time along with the investigation of nine new electronic states that have not been observed yet.</p>

THEORETICAL CALCULATION OF THE LOW-LYING ELECTRONIC STATES OF THE MOLECULE YS

2010 ◽  
Vol 09 (04) ◽  
pp. 757-765 ◽  
Author(s):  
M. KOREK ◽  
A. FARHAT ◽  
S. N. ABDUL-AL
Keyword(s):  
Electronic States ◽  
Electronic Energy ◽  
Basis Sets ◽  
Harmonic Frequency ◽  
Gaussian Basis Sets ◽  
Complete Active Space ◽  
Self Consistent Field ◽  
First Time ◽  
Configuration Interaction Calculations ◽  
Good Agreement

The potential energy curves have been investigated for the 25 lowest electronic states in the 2s+1Λ(±) representation of the molecule YS via complete active space self-consistent field. Multireference configuration interaction calculations (single- and double excitations with Davidson corrections) were performed by using Gaussian basis sets for the two considered atoms. The harmonic frequency ωe, the internuclear distance re, and the electronic energy with respect to the ground state Te have been calculated for 25 electronic states where 21 states have been studied for the first time. The comparison of these values to the theoretical and experimental results available in the literature shows a very good agreement.

Multicanonical Molecular Dynamics Simulation Study of the Liquid-Solid and Solid-Solid Transitions in Lennard-Jones Clusters

2011 ◽  
Author(s):  
Toshihiro Kaneko ◽  
Kenji Yasuoka ◽  
Ayori Mitsutake ◽  
Xiao Cheng Zeng
Keyword(s):  
Molecular Dynamics ◽  
Heat Capacity ◽  
Transition Temperature ◽  
Peak Position ◽  
Temperature Curve ◽  
Dynamics Simulation ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
First Time ◽  
Good Agreement

Multicanonical molecular dynamics simulations are applied, for the first time, to study the liquid-solid and solid-solid transitions in Lennard-Jones (LJ) clusters. The transition temperatures are estimated based on the peak position in the heat capacity versus temperature curve. For LJ31, LJ58 and LJ98, our results on the solid-solid transition temperature are in good agreement with previous ones. For LJ309, the predicted liquid-solid transition temperature is also in agreement with previous result.

Darstellung, Schwingungsspektren und Normalkoordinatenanalyse von Chloro-Bromo-Rhodaten(III) / Preparation, Vibration Spectra and Normal Coordinate Analysis of Chloro-Bromo-Rhodates(III)

1989 ◽  
Vol 44 (10) ◽  
pp. 1221-1227 ◽  
Author(s):  
W. Preetz ◽  
W. Kuhr
Keyword(s):  
Exchange Chromatography ◽  
Trans Isomers ◽  
Normal Coordinate ◽  
Valence Force ◽  
Trans Influence ◽  
Diethylaminoethyl Cellulose ◽  
Point Groups ◽  
First Time ◽  
Ir And Raman ◽  
Good Agreement

The mixed chloro-bromo-rhodates(III) [RhClnBr6-n]3-, n = 1-5, have been separated for the first time by ion exchange chromatography on diethylaminoethyl-cellulose. Due to the stronger trans-effect of Br, as compared with Cl, on treatment of [RhBr6]3- with conc. HCl nearly pure cis/fac-isomers for n = 2, 3, 4 are formed. The reaction of [RhCl6]3- with conc. HBr yields mixtures of the cis/trans-isomers for n = 2, 4, which cannot be separated, but mer-[RhCl3Br3]3 is formed stereospecifically. The IR and Raman spectra of all isolated mixed ligand complexes are completely assigned according to point groups Oh, D3d, C4v, C3v and C2v, supported by normal coordinate analyses based on a general valence force field. The good agreement of calculated and observed frequencies confirms the assignments. Due to the stronger trans-influence of Br as compared to Cl, in all asymmetric Cl—Rh—Br axes the Rh—Br bonds are strengthened and the Rh—Cl bonds are weakened, indicated by valence force constants for Rh—Br approximately 14% higher, for Rh—Cl 10% lower, as compared with the values calculated for symmetric Br—Rh—Br and Cl—Rh—Cl axes, respectively.

Isolation and Structure Determination of a Heat Shock Protein Inducer, Asparagus-Derived Proline-Containing 3-Alkyldiketopiperazines (Asparaprolines), From a Standardized Extract of Asparagus officinalis Stem

2020 ◽  
Vol 15 (3) ◽  
pp. 1934578X2091468
Author(s):  
Shoichiro Inoue ◽  
Jun Takanari ◽  
Keima Abe ◽  
Ayako Nagayama ◽  
Yukinobu Ikeya ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Protein ◽  
Spectroscopic Data ◽  
Asparagus Officinalis ◽  
Hsp70 Mrna ◽  
Mrna Induction ◽  
Natural Amino Acids ◽  
First Time ◽  
Hsp70 Induction

ETAS® has been developed from the stems of Asparagus officinalis L. as a functional ingredient for nutraceuticals. ETAS possesses heat shock protein 70 (HSP70) induction activity and may contribute to maintenance and improvement of health. Here, 3 compounds (1, 2, 3) were isolated from ETAS. The structures of 1, 2, and 3 were deduced by HREIMS and NMR spectroscopic data, and the compounds were identified as cyclo(l-Phe-l-Pro), cyclo(l-Tyr-l-Pro), and cyclo(l-Leu-l-Pro), respectively. Each compound contained a diketopiperazine ring derived from proline with an alkyl group at C-3; thus, we termed them asparagus-derived proline-containing 3-alkyldiketopiperazines (Asparaprolines). In an HSP70 mRNA induction assay in HL-60 cells, Asparaprolines significantly enhanced the expression of HSP70 mRNA compared with a control. To our knowledge, these results demonstrate for the first time that proline-containing diketopiperazines derived from natural amino acids exhibit HSP70 mRNA induction activity.

Antidiabetic and Antioxidant Activities of Major Flavonoids of Cynanchum acutum L. (Asclepiadaceae) Growing in Egypt

2008 ◽  
Vol 63 (9-10) ◽  
pp. 658-662 ◽  
Author(s):  
Ghada A. Fawzy ◽  
Hossam M. Abdallah ◽  
Mohamed S. A. Marzouk ◽  
Fathy M. Soliman ◽  
Amany A. Sleem
Keyword(s):  
Blood Glucose ◽  
Spectroscopic Data ◽  
Methanolic Extract ◽  
Antioxidant Activities ◽  
First Report ◽  
Insulin Levels ◽  
Butanol Fraction ◽  
Aerial Parts ◽  
First Time

Seven flavonoids were isolated from the butanol fraction of the methanolic extract of the aerial parts of Cynanchum acutum L. (Asclepiadaceae). All of which have been isolated for the first time from the genus Cynanchum. Their structures were established as quercetin 3-O-β-galacturonopyranoside (1), quercetin 7-O-β-glucopyranoside (2), tamarixtin 3-O-β-galacturonopyranoside (3), kaempferol 3-O-β-galacturonopyranoside (4), 8-hydroxyquercetin 3-O-β-galactopyranoside (5), tamarixtin 3-O-α-rhamnopyranoside (6), and tamarixtin 7-O-α-arabinopyranoside (7) on the basis of their chromatographic properties, chemical and spectroscopic data. The major isolated flavonoids 1, 2 and 3 were found to exhibit significant antioxidant and antidiabetic activities (by measuring blood glucose and insulin levels). This is the first report about the antioxidant and antidiabetic activities of compounds 1 - 3.

Sign in / Sign up

Export Citation Format

Share Document