A. Topacli

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.

Ab initio calculations and vibrational structure of sulfanilamide

A complete infrared spectrum analysis of the sulfanilamide is performed in this paper. Observed frequencies for normal modes are compared with those calculated from normal mode coordinated analysis carried out on the basis of ab initio force fields using the 3-21G basis set theoretical optimized geometry. Assignment of all vibrational bands has been performed taking into account the results of the ab initio vibrational analysis.

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.

Infrared studies on Co and Cd complexes of sulfamethoxazole.

In this study, the new Co and Cd complexes of sulfamethoxazole (SMX) (drug substance) [4-amino-N-(5-methyl-3-isoxazolyl) benzenesulfonamide] have been prepared for the first time and their infrared spectra have been investigated. The infrared spectra of the samples were recorded in the range 4000-400 cm(-1) and their fundamental vibrational wave numbers were obtained. The vibrational assignments were determined by using the group frequency tables and compared with the wave numbers of SMX found in the literature. The SMX wave numbers observed in the infrared spectra of the metal complexes were compared with those of free SMX. Investigations of the infrared spectra of the metal complexes indicated the vibrations due to the amino and sulfonamido groups are shifted with respect to the free molecule in line with their coordination to the metal. In the cadmium complex, the active binding sites of SMX are the sulfonamide nitrogen and sulfonic oxygen; in cobalt compound, the metal atom coordinates through the sulfonamide and amino nitrogens. The low energy calculations were also carried out by using geometry optimization. It is shown that the proposed structure for the metal complexes of SMX derived from the infrared spectra are consistent with the theoretical results.

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.

INVESTIGATION ON SULFANILAMIDE AND ITS INTERACTION WITH SOME METALS AND LINCOMYCIN BY INFRARED SPECTROSCOPY

In this work, the new cobalt and cadmium complexes of sulfanilamide were prepared and investigated by infrared spectrocopy. Their infrared spectra were compared with x-ray powder diffraction patterns of the complexes. The vibrations due to the anilino and sulfonamido groups are shifted with respect to the free sulfanilamide molecule in line with their coordination to the metal atoms. In addition, the low energy calculations were also carried out by using geometry optimization. The proposed structure for the complexes derived from the infrared spectra are consistent with the x-ray powder diffraction measurements and theoretical calculations. Among the studies, drug compounds, sulfanilamide-lincomycine interaction was obtained in methanol solution. The predicted structure of the product was given as a result of infrared studies.

An interaction of caffeine and sulfamethoxazole: studied by IR spectroscopy and PM3 method

Abstract IR studies were performed to determine the interaction of caffeine and sulfamethoxazole (SMX). The observed changes in spectral position and shape of characteristic IR bands of caffeine and SMX in the IR spectrum of interacted compound were compared with those of free caffeine and SMX molecules. Investigations of the infrared spectrum of interacted compound indicated that the vibration due to the NH stretching of sulfonamido group is shifted toward a lower wave number when compared with free SMX molecule. To explain the observed changes in IR spectrum of interacted compound upon interaction between caffeine and SMX molecules semi-empirical PM3 calculations on the samples have also been carried out. The results showed that SMX do not complex with caffeine strongly and the weak hydrogen bonding interaction between imidazole ring of caffeine and sulfonamido group of SMX. The X-ray diffraction studies also showed that there is an interaction between caffeine and SMX molecules.

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.

PM3 semi-empirical IR spectra simulations for metal complexes of schiff bases of sulfa drugs

Abstract The molecular structures and infrared spectra of Co, Ni, Cu and Zn complexes of two schiff base ligands, viz N -( o -vanillinidene)sulfanilamide ( o VSaH) and N -( o -vanillinidene)sulfamerazine ( o VSmrzH) are studied in detail by PM3 method. It has been shown that the proposed structures for the compounds derived from microanalytical, magnetic and various spectral data were consistent with the IR spectra simulated by PM3 method. Coordination effects on ν (CN) and ν (C–O) modes in the schiff base ligands are in close agreement with the observed results.

Semi-empirical infrared spectra simulations of metal complexes of sulfanilamide

Abstract The infrared spectra for Co and Cd complexes of sulfanilamide are studied by PM3 method. It has been found that the proposed structures for these compounds derived from IR spectra and X-ray powder diffraction patterns are consistent with the IR spectra simulated by PM3 method. The band assignments on the basis of the 3D dynamic image of the vibrations corresponding to significant modes have also given. Coordination effects on vibrational modes of anilino and sulfonamido groups of sulfanilamide are in close agreement with the observed results.