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Zarei S.A.,Islamic Azad University | Khaledian D.,University of Kurdistan | Akhtari K.,University of Kurdistan | Akhtari K.,Institute of Education Research of Kurdistan Province | Hassanzadeh K.,Islamic Azad University
Molecular Physics | Year: 2015

The experimental fourier transforminfrared (FT-IR) and ultraviolet-visible (UV-Vis) spectra of copper(II) and nickel(II) complexes of the deprotonated tetradentate Schiff base ligandN,N-bis(2-hydroxybenzylidene)-2,2-dimethyl-1,3-propanediamine (H2L) are compared with their corresponding theoretical ones. The applied theoretical method is based on the density functional theory and time-dependent density functional theory at the UPBE0/PBE0 levels using Def2-TZVP basis set. The computational optimised geometric parameters of the complexes are in good agreement with their corresponding experimental data. The FT-IR and UV-Vis spectra of the complexes were reproduced on the basis of their optimised structures. The vibrational assignments of some fundamental modes of the complexes are performed. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies are calculated. The analyses of the calculated electronic absorption spectra of the complexes are carried out to elucidate the electronic transitions assignments and their characters. Second-order nonlinear optical property of the complexes is evaluated by the above-mentioned theoretical method that implies much greater values for the complexes in comparison with the corresponding value of urea. © 2015 Taylor & Francis. Source

Akhtari K.,University of Kurdistan | Akhtari K.,Institute of Education Research of Kurdistan Province | Hassanzadeh K.,Islamic Azad University at Sanandaj Branch | Fakhraei B.,Institute of Education Research of Kurdistan Province | And 7 more authors.
Monatshefte fur Chemie | Year: 2015

The mechanism of thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone) for scavenging peroxide radicals was explicated in gas phase and in liquid phase (benzene, water) using density functional theory approach. The calculated bond dissociation enthalpy, ionization potential, and proton dissociation enthalpy revealed that the H-atoms at positions 2-isopropyl and 5-methyl groups can be readily abstracted. In fact, the 2-isopropyl C-H bond dissociation enthalpy is lower than the 5-methyl C-H dissociation enthalpy. Analysis of spin density distribution indicates that H-atom abstraction in 2-isopropyl site generates more stable radical. The plots of highest occupied molecular orbital of thymoquinone demonstrate that the whole molecule can be easily attacked by electrophilic agents like radicals. In this paper, we studied the interaction of thymoquinone with hydroxyl, hydroperoxyl, and superoxide anion radicals, using potential energy surface scans and natural bond orbital analysis. Calculated potential energy barriers for hydroxyl radical attack (~2.5 kJ/mol) revealed an instant scavenging by thymoquinone. Modeling of the reaction between thymoquinone and lipid peroxyl radical shows a barrier energy around 26.23 kJ/mol. Graphical Abstract: [Figure not available: see fulltext.]. © 2014 Springer-Verlag Wien. Source

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