Sevgi Haman Bayarı

Coordination behaviour of nicotinamide: an infrared spectroscopic study

Abstract A series of Hofmann-type complexes containing two nicotinamide(nia) molecules attached to transition metal (II) (M) tetracyanonickelate frame with the formula: M(nia) 2 Ni(CN) 4 (where M=Mn, Co, Ni, Cu or Cd) have been synthesised for the first time. Metal (II) halide complexes of nicotinamide complexes of the type [M(nia) 2 X 2 (M=Cd, Ni, Cu, Hg; X=Cl, Br) and Ni(nia) 4 Br 2 nia=nicotinamide] have also synthesised. The FTIR spectra are reported in the 4000–400 cm −1 region. Vibrational assignments are given for all the observed bands. The analysis of the vibrational spectra indicates that there are some structure–spectra correlations. A pronounced change was observed in the N–H stretching frequencies of the NH 2 group. It is proposed that the amide NH 2 group influence by the intramolecular hydrogen bond in the complexes. The coordination effect on the nicotinamide modes is analysed.

Normal coordinate analysis of 4-aminopyridine. Effect of substituent on pyridine ring in metal complexes of 4-substituted pyridines

The normal coordinate analysis has been performed for 4-aminopyridine (4-apy) assuming C2v molecular symmetry. A Urey-Bradley force field has been used. The force constants are adjusted to fit the observed frequencies for 4-apy and its deuterated species. The vibrational assignment has been made on the basis of the calculated frequencies and potential energy distributions. The calculated frequencies were in good agreement with the observed frequencies. The substituent effect upon the M-nitrogen (ligand) (L = 4-methlypyridine, 4-ethylpyridine, 4-vinylpyridine. 4-aminopyridine and 4-cyanopyridine) and pyridine ring frequencies has also been investigated. The frequency shifts are found to be sensitive to the substituent in the 4-position of the pyridine ring.

Urey-Bradley force field of 4-ethylpyridine

Abstract A normal coordinate analysis is carried out to obtain the Urey-Bradley force constants for 4-ethylpyridine (4-etpy) assuming an under C 2 v point group. These constants are adjusted to fit the observed frequencies for 4-etpy and its deuterated species. The calculated frequencies allowed the vibrational assignments of the normal modes of 4-etpy. These assignments are confirmed by the calculations of the potential energy distributions on 4-etpy. Additional information is obtained from the vibrational spectra of Cd (4-etpy) 2 M (CN) 4 (MCd, Hg) and calculated wavenumbers of metal (Cd) bonded 4-etpy. It is shown that the ring vibrations in pyridine are to be effected upon metal substitution. These results have also provided certainty for the vibrational assignments.

Structural alterations in rat liver proteins due to streptozotocin-induced diabetes and the recovery effect of selenium: Fourier transform infrared microspectroscopy and neural network study

The relation between protein structural alterations and tissue dysfunction is a major concern as protein fibrillation and/or aggregation due to structural alterations has been reported in many disease states. In the current study, Fourier transform infrared microspectroscopic imaging has been used to investigate diabetes-induced changes on protein secondary structure and macromolecular content in streptozotocin-induced diabetic rat liver. Protein secondary structural alterations were predicted using neural network approach utilizing the amide I region. Moreover, the role of selenium in the recovery of diabetes-induced alterations on macromolecular content and protein secondary structure was also studied. The results revealed that diabetes induced a decrease in lipid to protein and glycogen to protein ratios in diabetic livers. Significant alterations in protein secondary structure were observed with a decrease in α-helical and an increase in β-sheet content. Both doses of selenium restored diabetes-induced changes in lipid to protein and glycogen to protein ratios. However, low-dose selenium supplementation was not sufficient to recover the effects of diabetes on protein secondary structure, while a higher dose of selenium fully restored diabetes-induced alterations in protein structure.

An infrared and Raman spectroscopic study of Td-type 4,4′-bipyridylcadmium(II) tetracyanometallate (II) benzene (1/2) clathrates: Cd(C10H8N2)Cd(CN)4 · 2C6H6 and Cd(C10H8N2)Hg(CN)4 · 2C6H6

Two new benzene clathrates of the form Cd(4,4′-bipyridyl)M(CN)4 · 2C6H6, (M=Cd or Hg) have been prepared in powder form. Their spectral data were compared with those of the corresponding host complexes and found to be consistent with the host structure found in Td-type clathrates.

An infrared spectroscopic study on Hofmann-type complexes of dimethyl sulfoxide

Abstract The infrared spectra of M(DMSO) 2 NI(CN) 4 (M = Mn, Co, Fe, Cu; DMSO = dimethyl sulfoxide) and M(DMSO)(py)Ni(CN) 4 , (M = Mn, Ni; py = pyridine) complexes are reported. In all the complexes, the SO stretch is shifted to a lower frequency than in the free molecule, indicating coordination through oxygen. Several modes of the pyridine in the M(DMSO)(py) Ni(CN) 4 complexes have upward shifts in frequency compared to those in the free molecule, indicating that the molecule does not act as a guest molecule in the M(DMSO) 2 Ni(CN) 4 host lattice, but is bonded directly to the metal (M) together with dimethyl sulfoxide.

Fourier transform infrared spectra and molecular structure of 5-methoxytryptamine, N-acetyl-5-methoxytryptamine and N-phenylsulfonamide-5-methoxytryptamine

5-Methoxytryptamine (5-MT) is a potent antioxidant and has radioprotective action. N-acetyl-5-methoxytryptamine (melatonin, NA-5-MT) is a free radical scavenger and antioxidant, which protects against oxidative damage due to a variety of toxicants. The infrared spectra of 5-MT, NA-5-MT and new synthesized N-phenylsulfonamide-5-methoxytryptamine (PS-5-MT) were investigated in the region between 4000 and 400 cm(-1). Vibrational assignments of the molecules have been made for fundamental modes on the basis of the group vibrational concept, infrared intensity and comparison with the assignments for related molecules. X-ray powder diffraction patterns of molecules were also recorded. In order to optimize the geometries of the molecules, molecular mechanic calculations (MM3) were performed. Conformational analysis of 5-MT, NA-5-MT and PS-5-MT was also established by the using PM3 method.

The Infrared and Raman Spectra of 4-Phenylpyridine and Its Hofmann Type Complexes.

Abstract The Infrared and Raman spectra of 4-Phenylpyridine are reported for the first time in the 4000-400cm−1 range. Vibrational assignments have been made for fundamental modes on the basis of frequency shifts of coordinated legend, infrared and Raman band contours and comparisons with the assignments for related molecules. The infrared spectra of M (4-Phenylpyridine) Ni(CN)4 complexes (M=Mn, Ni or Cd) are reported. Their structure consists of polymeric layers of [M-Ni(CN)4]∞ with the 4-phenylpyridine molecules bound to metal (M), similar to the structure found in Hoffmann type host complexes.

Theoretical study of ofloxacin: geometrical parameters and vibrational wavenumbers

Abstract Molecular modeling of ofloxacin was performed using MM+molecular mechanics, AM1, PM3, MNDO, MINDO3, ZINDO/1, TNDO semi-empirical methods, as well as Model Builder. The calculated geometries have been compared to the corresponding X-ray structure of ofloxacin perclorate. The FT-IR spectrum of ofloxacin was recorded. The assignments are based on the concept of group frequencies, band intensities and taking into account the results of the semi-empirical vibrational analysis.

Methylparaben isolated in solid argon: structural characterization and UV-induced conversion into methylparaben radical and isomeric ketenes.

Methylparaben (methyl p-hydroxybenzoic acid; MP) is a widely used antimicrobial preservative, being the most frequently used antimicrobial preservative in cosmetics. The generalized use of MP has become controversial, with several recent reports of dangerous side effects. For example, the presence of MP in human breast tumors and its harmful effects on human skin exposed to the sunlight have been demonstrated. In spite of the important practical relevance of the compound and of the controversy about its practical use, its structural and photochemical characterization had not been undertaken hitherto. To fill this gap, in the present study, MP was isolated in solid argon (T = 15 K) and structurally characterized by a combined infrared spectroscopy/quantum chemistry approach. The potential energy surface (PES) of the molecule was investigated in detail, revealing the existence of two almost isoenergetic (ΔE(0) = 0.37 kJ mol(-1)) s-cis carboxylic ester low-energy conformers, with an estimated population ratio in the gas phase at room temperature (∼298 K) of ca. 0.83. The calculations also predicted the existence of two high-energy (ΔE(0) = ∼50 kJ mol(-1)) s-trans carboxylic ester conformers of MP. Upon isolation of the compound in an argon matrix, only the lowest energy conformer was found to survive, due to occurrence of extensive conformational cooling during matrix deposition. The infrared spectrum of this conformer was obtained and interpreted. In addition, the chemical processes resulting from in situ irradiation of the matrix-isolated MP with a broadband UV source (λ > 234 nm) were investigated, revealing extensive conversion of MP into highly reactive methylparaben radical and isomeric ketenes. These observations support the recent concerns regarding uses of MP, in particular when the compound has to be exposed to UV light.