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    Experimental and theoretical research on -irradiated 7-methoxy-4-methylcoumarin powder through EPR and DFT methods
    (Taylor & Francis Ltd, 2018) Sarikaya, Ebru Karakas; Ates, Levent; Sayin, Ulku; Ozmen, Ayhan; Dereli, Omer
    In this paper, the effects of gamma irradiation on 7-Methoxy-4-methylcoumarin (7M4MC) molecule, an essential coumarin derivative, which has an inherent variety of biological activities, therapeutic properties and industrial usage were examined. For this purpose, the sample was irradiated with Co-60-gamma ray source for about 100kGy total doses. Theoretical calculations were performed using GAUSSIAN03 program for the possible radicals that were modeled from two stable conformations with lowest energies. In order to get well-resolved spectra and to determine the radical identity experimentally, EPR spectra of the irradiated 7M4MC sample were recorded at several spectrometer conditions. By considering the molecular structure and EPR spectra, alkyl-type radical was assumed to be formed by gamma irradiation. To support the estimations, simulations were done using theoretical EPR parameters as an initial value. The experimental spectra were well matched with the sum of simulated spectra obtained from two same type modeled radicals of two different conformations. As a result of experimental estimations and theoretical calculations, radiation-induced radicals were identified as two neutral alkyl radicals, originated from two stable conformations.
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    Molecule and Radical Structures of Isobutyronitrile
    (Gazi Univ, 2017) Dereli, Omer; Erdogdu, Yusuf; Ates, Levent; Karakas Sarikaya, Ebru; Ozturan, F. Pinar
    Molecule and radical structures of Isobutyronitrile were studied by DFT computations. Results of conformational analysis performed by combination of molecular mechanic and B3LYP/6-311++G(d, p) methods showed that isobutyronitrile inelastic molecule which has only one conformer. Using this structure, radical structure was investigated. Possible radicals were modelled and the experimental Electron Paramagnetic Resonance parameters were calculated. The calculated parameters obtained from B3LYP/TZVP computations were compared with the experimental counterparts which were taken from literature. Determined Molecule and Radical structures were given in this study.
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    Theoretical Calculations of Electron Paramagnetic Resonance Parameters of Succinimide Radical
    (Amer Inst Physics, 2018) Dereli, Omer; Ates, Levent; Erdogdu, Yusuf
    The analysis of the molecular structure and spectral properties of succinimide can be used as a reliable tool in understanding all interactions between this molecule with the other chemicals. For this reason, we first examined the conformational variety of succinimide in free state through an energy minimization calculations using the spartan 08 software. This preliminary calculation confirmed that free succinimide molecule has only one stable conformer at room temperature and the dipole moment and energy values of this conformer are 2.221 Debye and -360.779 Hartree, respectively. The optimized geometry of the conformer was then obtained at B3LYP/6-311++ G(d, p) level of theory by using the Gaussian 03 software. In the next step of the study, eleven radicals were formed from this one conformer of succinimide by removing an hydrogen atom or changing its location in the molecule. For each radical structure, the corresponding Electron Paramagnetic Resonance (EPR) parameters were calculated using the DFT/B3LYP method and TZVP basis set and then they were compared with the corresponding experimental values. The g value (EPR parameter) calculated in this study for the model radical (Rad 6) is 2.00388 and in good agreement with the corresponding experimental value (2,00339) previously reported in the literature for the radical form of succinimide.