The performance of the M06 family of exchange-correlation potentials for describing the electronic structure and the Heisenberg magnetic coupling constant (J) is investigated using a set of representative open-shell systems involving two unpaired electrons. The set of molecular systems studied has well defined structures, and their magnetic coupling values are known experimentally. As a general...

The pinoresinol unit is one of the principal interunit linkages in lignin. As such, its chemistry and properties are of major importance in understanding the behavior or the polymer. This work examines the homolytic cleavage of the pinoresinol system, representing the initial step in thermal degradation. The bond dissociation enthalpy of this reaction has been evaluated using M06-2X density fun...

We present a new formulation of variational transition state theory (VTST) called multi-structural VTST (MS-VTST) and the use of this to calculate the rate constant for the 1,4-hydrogen shift isomerization reaction of 1-pentyl radical and that for the reverse reaction. MS-VTST uses a multifaceted dividing surface and provides a convenient way to include the contributions of many structures (typ...

Nicotine is widely used in pharmaceutical industries, especially for smoking cessation the form of transdermal patches. gel patches has limitations from nicotine instability and high volatility. Thus, a preservation technique needed. In this study, encapsulation process using methyl-?-cyclodextrin (M?CD) investigated compared with ?-cyclodextrin (?CD) to evaluate skin permeation nicotine. The M...

Abstract Density functional theory (DFT) was performed in the gas phase to investigate tautomerization and transitions efavirenz. The amide imidic tautomers' geometrical parameters are using B3LYP/6-31++G** M06-2X/ cc-pVTZ (-F). results showed that tautomer is more stable than phase. non-linear optical (NLO) properties of tautomers computed. Interestingly, forms may be an attractive compound en...

Ionizing alpha radiation (He2+) is known to adversely affect human DNA, but the biochemical reasoning not clear yet. Relatedly, present computational study was conducted investigating effects of ionizing onto Watson-Crick type DNA base pairs (nucleotides) Adenine-Thymine (AT’) and Guanine-Cytosine (GC’). The long-range cation (He2+)−π interactions were modeled for this purpose. A hybrid DFT fun...

We have investigated the possibility of utilizing various single-walled pristine and doped carbon nanotubes as adsorbents for 1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124) gaseous molecule. Three candidates, including nanotube (CNT), silicon carbide (SiCNT) germanium-doped SiCNT (SiCGeNT) are identified evaluated theoretically. The quantum simulations been performed at density functional theory...

A potential based on a bond dipole representation of electrostatics is reported for peptides. Different from those popular force fields using atom-centered point-charge or point-multipole to express the electrostatics, our peptide uses chemical dipole–dipole interactions electrostatic interactions. The parameters permanent and induced dipoles are derived fitting MP2 three-body interaction energ...

The structural, vibrational and theoretical analyses of N-benzylmaleimide (NBM) having chemical biological significances have been made. four possible conformers their sixty-six dimeric forms linked by the intermolecular C=O···H hydrogen bonding were investigated for stability. conformational structures NBM in gas phase population distributions conformations dimers obtained using Boltzmann dist...

The Gibbs energy of reaction of oxidative addition of ammonia to an iridium complex in diethyl ether was calculated by seven density functional methods, in particular B3LYP, PBE, CAMB3LYP, M05, M06, M06-L, and oB97X. The calculated free energies, based on geometry optimization and frequency calculations in both the gas phase and solution, were compared with the experimental result, 1.3 kcal mol...