scholarly journals Density functional studies of molecular structures of N-methyl formamide, N,N-dimethyl formamide, and N,N-dimethyl acetamide

2000 ◽  
Vol 112 (1) ◽  
pp. 35-42 ◽  
Author(s):  
V. Renugopalakrishnan ◽  
G. Madrid ◽  
G. Cuevas ◽  
A. T. Hagler
Keyword(s):  
Density Functional ◽  
Molecular Structures ◽  
Dimethyl Formamide ◽  
Functional Studies ◽  
Dimethyl Acetamide

scholarly journals Atmospheric Chlorine Reaction with N-Methyl-2-Pyrrolidinone (NMP)

2021 ◽  
Author(s):  
S. Samai ◽  
A. Ferhati
Keyword(s):  
Density Functional ◽  
Rate Coefficients ◽  
Dimethyl Formamide ◽  
Functional Theory ◽  
Dimethyl Acetamide ◽  
Chlorine Reaction ◽  
Structure Reactivity Relationship ◽  
High Level ◽  
Kinetics Of ◽  
Cl Atom

Abstract Density functional theory (DFT) and Complete Basis Scale methods (CBS-QB3, G3B3) are used to investigate the reactivity, the mechanism, structure-reactivity relationship and the kinetics of N-methyl-2-pyrrolidinone (NMP) with Cl atom. To obtain rate constants of the reaction, the RRKM theory is employed at atmospheric pressure and temperature range 273–380 K. This study provides the rate coefficients and detailed H-abstraction mechanism for the reaction of Cl with NMP at high level of theoretical methods. The obtained rate constant ~ 0.92 x 10− 10 to 8.98 × 10− 10cm 3 molecule− 1s− 1 at 298 K agreed with those obtained previously for N,N-dimethyl formamide (DMF) and N,N-dimethyl acetamide (DMA). The study shows that the reaction mechanism of Cl with NMP goes favorably through an H-abstraction from N-methyl groups and adjacent CH2. The rates constants obtained for the three amides confirm our prediction regarding the structure-reactivity relationship where 1000/T.

Computational Investigation of the Asymmetry in Photosynthetic Reaction Center Models from First Principles

2020 ◽  
Author(s):  
Denis Artiukhin ◽  
Patrick Eschenbach ◽  
Johannes Neugebauer
Keyword(s):  
Spin Density ◽  
Reaction Center ◽  
Density Functional ◽  
Photosynthetic Reaction Center ◽  
Chem Phys ◽  
Molecular Structures ◽  
Error Characteristic ◽  
Molecular Systems ◽  
Density Distributions ◽  
The Asymmetry

We present a computational analysis of the asymmetry in reaction center models of photosystem I, photosystem II, and bacteria from <i>Synechococcus elongatus</i>, <i>Thermococcus vulcanus</i>, and <i>Rhodobacter sphaeroides</i>, respectively. The recently developed FDE-diab methodology [J. Chem. Phys., 148 (2018), 214104] allowed us to effectively avoid the spin-density overdelocalization error characteristic for standard Kohn–Sham Density Functional Theory and to reliably calculate spin-density distributions and electronic couplings for a number of molecular systems ranging from dimeric models in vacuum to large protein including up to about 2000 atoms. The calculated spin densities showed a good agreement with available experimental results and were used to validate reaction center models reported in the literature. We demonstrated that the applied theoretical approach is very sensitive to changes in molecular structures and relative orientation of molecules. This makes FDE-diab a valuable tool for electronic structure calculations of large photosynthetic models effectively complementing the existing experimental techniques.

scholarly journals 1,3,5-Triaza-7-Phosphaadamantane (PTA) as a 31P NMR Probe for Organometallic Transition Metal Complexes in Solution

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1390 ◽  
Author(s):  
Ilya G. Shenderovich
Keyword(s):  
Chemical Shift ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
Molecular Structures ◽  
Basis Sets ◽  
Functional Theory ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Due to the rigid structure of 1,3,5-triaza-7-phosphaadamantane (PTA), its 31P chemical shift solely depends on non-covalent interactions in which the molecule is involved. The maximum range of change caused by the most common of these, hydrogen bonding, is only 6 ppm, because the active site is one of the PTA nitrogen atoms. In contrast, when the PTA phosphorus atom is coordinated to a metal, the range of change exceeds 100 ppm. This feature can be used to support or reject specific structural models of organometallic transition metal complexes in solution by comparing the experimental and Density Functional Theory (DFT) calculated values of this 31P chemical shift. This approach has been tested on a variety of the metals of groups 8–12 and molecular structures. General recommendations for appropriate basis sets are reported.

scholarly journals Ultrafast proton release reaction and primary photochemistry of phycocyanobilin in solution observed with fs-time-resolved mid-IR and UV/Vis spectroscopy

2021 ◽  
Author(s):  
Maximilian Theiß ◽  
Merten Grupe ◽  
Tilman Lamparter ◽  
Maria Andrea Mroginski ◽  
Rolf Diller
Keyword(s):  
Density Functional ◽  
Transient Absorption ◽  
Vibrational Analysis ◽  
Density Functional Theory Calculations ◽  
Chem Phys ◽  
Molecular Structures ◽  
Ir Absorption ◽  
Time Resolved ◽  
Time Constants ◽  
Vis Spectroscopy

AbstractDeactivation processes of photoexcited (λex = 580 nm) phycocyanobilin (PCB) in methanol were investigated by means of UV/Vis and mid-IR femtosecond (fs) transient absorption (TA) as well as static fluorescence spectroscopy, supported by density-functional-theory calculations of three relevant ground state conformers, PCBA, PCBB and PCBC, their relative electronic state energies and normal mode vibrational analysis. UV/Vis fs-TA reveals time constants of 2.0, 18 and 67 ps, describing decay of PCBB*, of PCBA* and thermal re-equilibration of PCBA, PCBB and PCBC, respectively, in line with the model by Dietzek et al. (Chem Phys Lett 515:163, 2011) and predecessors. Significant substantiation and extension of this model is achieved first via mid-IR fs-TA, i.e. identification of molecular structures and their dynamics, with time constants of 2.6, 21 and 40 ps, respectively. Second, transient IR continuum absorption (CA) is observed in the region above 1755 cm−1 (CA1) and between 1550 and 1450 cm−1 (CA2), indicative for the IR absorption of highly polarizable protons in hydrogen bonding networks (X–H…Y). This allows to characterize chromophore protonation/deprotonation processes, associated with the electronic and structural dynamics, on a molecular level. The PCB photocycle is suggested to be closed via a long living (> 1 ns), PCBC-like (i.e. deprotonated), fluorescent species.

Density functional studies on the adsorption and decomposition of SO2 on Cu(100)

2001 ◽  
Vol 115 (1) ◽  
pp. 454-465 ◽  
Author(s):  
José A. Rodriguez ◽  
Josep M. Ricart ◽  
Anna Clotet ◽  
Francesc Illas
Keyword(s):  
Density Functional ◽  
Functional Studies

scholarly journals Density functional studies of the dipole polarizabilities of the linear polyacenes benzene through nonacene

2005 ◽  
Vol 3 (2) ◽  
pp. 361-369 ◽  
Author(s):  
Alan Hinchliffe ◽  
Beatrice Nikolaidi ◽  
Humberto Soscún Machado
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Correlation Coefficients ◽  
Statistical Correlation ◽  
Tensor Component ◽  
Dipole Polarizability ◽  
Functional Studies ◽  
Absolute Agreement ◽  
Different Levels ◽  
Dipole Polarizabilities

AbstractWe report Ab Initio studies of the electric dipole polarizability of the linear polyacene series benzene through nonacene. A number of Ab Initio studies were done at different levels of theory for benzene, with all remaining Ab Initio calculations being at the B3LYP/6-311G(2d, 1p)//B3LYP/6-311+G(2d, 1p) level of theory. We find that the NN tensor component shows a constant increment of 20 atomic units per ring. AM1 and QSAR-quality empirical calculations show poor absolute agreement with the Ab Initio results but given excellent statistical correlation coefficients with the Ab Initio values. This implies that the results of such cheaper calculations can be suitably scaled for predictive purposes.

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