Sevim Akyuz

Theoretical study of the vibrational spectra of 2-chloropyridine metal complexes. I. Calculation and analysis of the IR spectrum of 2-chloropyridine

Abstract The force field and the electrooptical parameters of 2-chloropyridine were determined by the refinement of the corresponding parameters of the pyridine molecule, for further use in the metal complexes study. During the refinement procedure, the results of semiempirical (MNDO) and ab initio (4-31G*) calculations were taken into account. Approximate normal coordinate analysis was performed on the basis of different theoretical calculations. Theoretical results predict significant mixing of the ring and CH modes. Nevertheless, there is qualitative agreement between normal mode assignments made upon quantum chemical calculations, force field refinement results and results based on earlier experimental information. Calculation of the IR intensities serves as an additional check of the force field quality. The interpretation of the IR intensities and contribution of various parts of the molecule to the total IR spectra is given.

4,4′-Bipyridyl: vibrational assignments and force field

Abstract A normal coordinate analysis of 4,4′-bipyridyl (4,4′-bipy) is carried out to establish consistent vibrational assignment and to determine a Urey-Bradley force field. The potential energy distribution of 4,4′-bipy is calculated which has provided certainty for the assignments. Additional information is obtained from the vibrational spectra of M (4,4′-bipy)Cl 2 complexes (where M = Zn, Cu or Cd) and calculated wave numbers of complexed 4,4′-bipy. Several vibrational modes of 4,4′-bipy in the IR and Raman spectra of the complexes are found to have upward shifts in frequency compared to those in the free molecule and the shifts are metal dependent. An explanation supported by the normal coordinate analysis is provided in terms of coupling with low frequency vibrations, particularly the M-N stretching frequencies.

Force field and IR intensity calculations of aniline and transition metal(II) aniline complexes

Abstract A complete interpretation of the vibrational spectrum of aniline was carried out on the basis of normal coordinate analysis. The reliable force field and electro-optical parameters of aniline was determined by refinement in order to fit in the calculated wavenumbers and intensities of NH 2 - and ND 2 -aniline molecules with the experimental values. The geometrical parameters of free aniline were taken from experimental results. The initial force field parameters of aniline were refined from the corresponding parameters of benzene molecule. The initial values of bond dipole moments of the molecule were calculated by PM3 method. The force field of transition metal (II) aniline complex was determined by refinement of aniline force field. Coordination effect on aniline modes are interpreted in terms of changes in hybridization about the nitrogen atom.

Calculation and analysis of IR spectrum of 2-aminopyridine

Abstract Normal coordinate analysis of 2-aminopyridine (2AP) and ND 2 -pyridine have been performed in valance force field approximation. 2AP was taken as planar because of the low barrier to amino group inversion. The IR absorption intensities have been calculated and the electro–optical parameters (EOP) were fitted to experimental data in order to produce the experimental relative intensities. The created force field and EOP reproduce the IR spectrum of the molecule studied well.

FT-IR spectroscopic investigation of adsorption of 3-aminopyridine on sepiolite and montmorillonite from Anatolia

Abstract The adsorption of 3-aminopyridine by natural sepiolite and montmorillonite from Eskisehir (Anatolia) was investigated in the temperature range from 20 to 125°C by infrared spectrometry using a variable temperature unit. The spectroscopic results indicate that the 3-aminopyridine molecules adsorbed on sepiolite are coordinated to Lewis acidic sites and/or surface hydroxyls by H-bonding interaction through pyridine ring nitrogen lone pairs. Surface Bronsted acid strength of sepiolite is weak and 3-aminopyridinium is not detected under the conditions applied in this study. It must be noted that the adsorption of aminopyridine affected the hydroxyl group vibrations of sepiolite. The intercalation of 3-aminopyridine within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacing. IR spectroscopy indicates that sorbed 3-aminopyridine molecules by montmorillonite are mostly coordinated to exchangeable cations directly or indirectly through water bridges. The formation of 3-aminopyridinium cation is also detected at elevated temperatures.

Theoretical and experimental studies of IR spectra of 4-aminopyridine metal(II) complexes

Abstract In this study FT-IR spectra of M(L) 2 Ni(CN) 4 {where M=Fe or Zn, L=4-aminopyridine} complexes are reported for the first time in the 400–4000 cm −1 range. The spectral features suggest that the compounds are similar in structure to the Hofmann-type complexes with infinite polymeric layers formed with Ni(CN) 4 −2 ions bridged by M(L) 2 +2 cations. IR frequency shifts, upon formation of coordination compound are reliable indicators of the coordination mode of 4-aminopyridine. It is concluded that the ring nitrogen and not the amino nitrogen is involved in complex formation. In order to investigate metal–ligand coupling peculiarities, the vibrational wavenumbers of free and coordinated 4-aminopyridine have been calculated by a force field refinement method. The results indicated that the force field of free 4-aminopyridine should be altered in complex formation in order to represent the experimental data.

Infrared-spectra and normal-coordinate analysis of quinoline and quinoline complexes

Abstract Normal coordinate analysis was performed on the vibrational spectra data of quinoline and the force field parameters of the free molecule were determined by the refinement of the corresponding parameters of benzene and pyridine molecules. The results of semiempirical (AM1) and ab initio (4-31G∗) calculations were taken into account during the refinement procedure. A partially common and well-transferable force field has been obtained for free quinoline. In order to investigate the coupling peculiarities of the vibrational modes of quinoline by metal–ligand vibrations, the calculated force field parameters of the free ligand were used in calculating the IR spectra of the transition metal (II) quinoline complexes, without any alterations and only force field parameters related to the M–N(Q) bond were introduced. The calculated spectra have been compared with the experimental spectra of the quinoline metal (II) complexes.

Theoretical and experimental IR spectra and assignments of 3-aminopyridine

Abstract A normal mode analysis was carried out for 3-aminopyridine using force field refinement method together with ab-initio (4-31G ∗ ) and semiempirical (AM1) quantum chemical calculations. The initial force field parameters of 3-aminopyridine were refined from the corresponding parameters of pyridine molecule. The results indicate a qualitative agreement in normal modes assignments, which are made upon quantum chemical calculations, force field refinement results and one made earlier upon experimental information.

The FT-IR spectra of transition metal 3-aminopyridine tetracyanonickelate complexes

Abstract FT-IR spectra of M(3apy) 2 Ni(CN) 4 where M = Mn, Fe, Co, Ni, Cu, Zn or Cd; 3apy = 3-aminopyridine complexes are reported for the first time in the 400–4000 cm −1 range. The spectral features suggest that the compounds are similar in structure to the Hofmann-type complexes with infinite polymeric layers formed with Ni(CN) −2 4 ions bridged by M(3apy) +2 2 cations. It is concluded that the ring nitrogen and not the amino nitrogen is involved in complex formation.

Pigment analyses of a portrait and paint box of Turkish artist Feyhaman Duran (1886–1970): The EDXRF, FT-IR and micro Raman spectroscopic studies

The samples obtained from nine different places of Ataturk portrait (oil on canvas, 86 cm×136 cm) by Feyhaman Duran (1886-1970), one of the famous Turkish painters of the 20th century, together with five pigment samples (two different white, two different yellow and blue), obtained as powders from artists paint box, were analysed by EDXRF, FT-IR and micro-Raman spectroscopic methods, in order to characterise the pigments used by the artist. Informative Raman signals were not obtained from most of the samples of the portrait, due to huge fluorescence caused by the presence of impurities and organic materials in the samples, however the Raman spectrum of the sample from skin coloured part of the portrait and the pigment samples obtained from the paint box of the artist were found to be very informative to shed light on the determination of the pigments used. Analysis revealed the presences of chrome yellow (PbCrO4), strontium yellow (SrCrO4) and Cadmium yellow (CdS) as yellow, chromium oxides (Cr2O3 and Cr2O3·2H2O) as green, natural red ochre as red, brown ochre as brown and ivory black or bone black (C+Ca3(PO4)2) and manganese oxides (Mn2O3 and MnO2) as black pigments, in the composition of the Ataturk portrait. Lead white (2PbCO3·Pb(OH)2), calcite (CaCO3), barite (BaSO4), zinc white (ZnO) and titanium white (TiO2) were used as extenders to lighten the colours and/or as for ground level painting. Powder pigment samples, obtained from the paint box of artist, were found to be mixed pigments rather than pure ones.