Ulku Sayin

Experimental, theoretical calculations of the vibrational spectra and conformational analysis of 2,4-di-tert-butylphenol

In the present work, we reported a combined experimental and theoretical study on conformational stability, molecular structure and vibrational spectra of 2,4-di-tert-butylphenol (2,4-DTBP). The FT-IR (400-4000cm(-1)) and FT-Raman spectra (50-3500cm(-1)) of 2,4-DTBP were recorded. The molecular geometry, harmonic vibrational frequencies and bonding features of 2,4-DTBP in the ground-state have been calculated by using the density functional BLYP/B3LYP methods. The energy calculated by time-dependent density functional theory (TD-DFT) result complements with the experimental findings. The calculated highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energies show that charge transfer occurs within the molecule. Finally the calculation results were compared with measured infrared and Raman spectra of the title compound which showed good agreement with observed spectra.

Novel copper(II) complexes of p-tert-butylcalix[4]arene diamide derivatives: synthesis, antimicrobial and DNA cleavage activities

In this study, two new Cu(II) complexes of p-tert-butylcalix[4]arene amide derivatives (8, 9) have been synthesised and investigated their DNA cleavage and antimicrobial activities. On the basis of spectral studies, a smaller distortion of square planar geometry has been proposed for both of the copper(II) complexes. The DNA cleavage studies show that the ligands are not efficacious, whereas the complexes have high activity. Futhermore, in order to determine the site of DNA cleavage, the DNA interactions of these compounds were investigated with some restriction enzymes. In addition, all synthesised compounds were screened for antimicrobial activities against some bacteria and for antifungal activities against yeast strains. The results showed that ethyl ester and furfuryl amide derivatives of the calixarenes are more efficient than other compounds against tested bacteria. However, complexes have not been effective. In case of DNA interaction studies, compounds were very effective against plasmid DNA.

ESR Characterization of Two Oxovanadium (IV) Schiff Base Complexes Derived from Tris(2-aminoethyl)amine

The compounds, C21H27N4O3(L1) and C21H27N7(L2), is a tripodal Schiff base that was obtained from the reaction of tris(2-aminoethyl)amine (tren) and furan-2-carbaldehyde and pyrole- 2- carbaldehyde. The tripodal Schiff bases and their oxovanadium complexes have been characterized on the basis of the results of the elemental analysis, magnetic susceptibility measurements and spectroscopic studies FT-IR, 1H-NMR, UV–Vis, ESR, magnetic moment and thermal analysis (TGA). Jobs method of continuous variation shows 3:2 metal to ligand ratio.

Molecular structure and vibrational spectra of alpha-benzoinoxime by density functional method

In the present study, an exhaustive conformational search of the Alpha-benzoinoxime has been performed. The FT-IR spectrum of this compound was recorded in the region 4000–400 cm−1. The FT-Raman spectrum was also recorded in the region 3500–50 cm−1. Vibrational frequences of the title compound were calculated by B3LYP method using 6–311++G(d, p) basis set. The calculated vibrational frequences were analysed and compared with experimental results.

An electron paramagnetic resonance and density-functional theory study on the methyl isotropic hyperfine coupling constants in gamma-irradiated 2,6-di-tert-butyl-4-methylphenol

Single crystal of gammairradiated 2,6-di-tert-butyl-4-methylphenol (BHT) was investigated using an electron paramagnetic resonance (EPR) technique at different orientations in the magnetic field at room temperatures. Taking into consideration the chemical structure and the experimental spectra of the irradiated single crystal of BHT, we assumed that one phenoxyltype paramagnetic species was produced having an unpaired electron localized at the methyl fragment side of the phenyl ring. Depending on this assumption, one possible radical was modeled using the B3LYP/6-311+G(d) level of density-functional theory. EPR parameters were calculated for these modeled radical using the B3LYP/TZVP and B3LYP/EPR-III level. The averaged value of isotropic hydrogen hyperfine coupling constants of rotating methyl functional group of phenoxyl radical is calculated for the first time. Theoretically calculated values of the modeled radical are in reasonably good agreement with the experimental data determined from the spectra (differences in averaged coupling constant values smaller than 5%, and differences in isotropic g values fall into 1 ppt).

EPR of gamma irradiated single crystals of amphi-chloroglyoxime

γ-irradiated single crystals of amphi-chloroglyoxime were investigated by the electron paramagnetic resonance (EPR) between 123 and 400 K temperature. Paramagnetic species produced in the crystals were attributed to the R–HCĊNOH radical and relevant spectra were found to be temperature independent. The g-factor and hyperfine coupling constants of the R–HCĊNOH radical were found to be almost isotropic with the average values g = 2.0009, a CN = 31.89 G, a HC = 23.83 G, a OH = 9.49 G and the spin densities .

Experimental and theoretical research on γ-irradiated 7-methoxy-4-methylcoumarin powder through EPR and DFT methods

ABSTRACT 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 60Co-gamma ray source for about 100 kGy 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.

Investigation of Radiation Effects on Coffee Beans Using ESR Technique

Bu calismada kahve cekirdegi uzerine radyasyonun etkisi Elektron Spin Rezonans (ESR) teknigiyle incelenmistir. Dogal ve 60 Co gama kaynagi ile 0.5 Gy ile 11 kGy doz araliginda farkli dozlarda isinlanmis orneklerin spektrumlari X-band ESR spektrometresiyle kaydedilmis ve olusan paramanyetik merkezlerin radyasyona, ESR mikrodalga gucune ve kavite sicakligina bagli degisimleri arastirilmistir. Doz-cevap ve kinetik calismalar sonucunda kahve cekirdegindeki paramanyetik merkezin radyasyona duyarli ve kararli oldugu belirlenmis, incelenen doz araliginda dozimetrik amacli ve isinlanmis gida dedeksiyonu icin kullanilabilirligi gosterilmistir.

ESR analysis of natural and gamma irradiated coriander (Coriandrum sativum L.) seeds

ABSTRACT Electron spin resonance (ESR) is a powerful technique to detect radicals trapped in cellulosic food products and has been suggested as a useful method for identification of irradiated herbal foodstuffs. Coriander spice which has important medicinal properties was investigated using ESR spectroscopy. Radicals in natural and irradiated coriander samples were determined at room temperature. ESR spectra of natural sample were characterized by a single central signal with value and gamma irradiation produced satellite peaks attributed to cellulose-like radical which is used as a marker for detection of irradiated cellulosic plant products. The spectroscopic splitting values of radicals were determined. Dose dependency and stability of this center were analyzed by dose response and kinetic measurements. The reported results about activation energy, thermal life time and dose response relationship of the cellulose-like radical accurately prove that ESR can be used for identification of irradiated coriander spice seeds.

EPR study of gamma-irradiated 2-Bromo-4′-methoxyacetophenone single crystals

ABSTRACT The gamma-irradiated single crystals of 2-Bromo-4′-methoxyaceto-phenone (2B4MA) were investigated using electron paramagnetic resonance (EPR) technique. Density-functional theory calculations were employed to investigate and identify the radicals that have been assumed to be formed upon irradiation of 2B4MA single crystals. The EPR spectra of 2B4MA were recorded at different orientations in the magnetic field at room temperature. Taking into account the chemical structure and experimental spectra of irradiated single crystal of 2B4MA, it was assumed that at least two different radicals were produced in the sample. Following this assumption, six possible radicals were modeled and EPR parameters were calculated by using the DFT, B3LYP/6-311+G(d), for the modeled radicals individually. The calculated hyperfine coupling constants and g-tensors were used as initial values for simulation studies. The three crystallographic axes on the simulated spectra were well matched with experimental spectra for the two modeled radicals. Thus, we identified the R1 type radical and R4 type radical as paramagnetic species produced in gamma-irradiated 2B4MA.