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VIBRATIONAL AND ELECTRONIC SPECTRAL CHARACTERISATION OF SEVERAL PHARMACOLOGICALLY IMPORTANT ARALKYL DERIVATIVES OF THE PYRIDINIUM CATION

Pyridinium or bispyridinium oxime derivatives are known as potent acetylcholinesterase reactivators used for the prophylaxis and treatment of intoxications with organophosphorous compounds such as nerve agents and pesticides. Some 1-phenacylpyridinium salts have interesting antifungal and amebacidal properties while 1-benzoylethylpyridinium and 1-benzoylethylpyridinium-4-aldoxime salts act as possible protectors of human blood cholinesterase due to their capability to reversibly inhibit this enzyme. The spectrophotometric studies on the coordination ability of the selected aralkyl derivatives of the pyridinium cation (Table 1) to the pentacyanoferrate(II) moiety have shown considerable differences concerning their stability and reactivity in aqueous solutions. These findings encouraged us to perform a comparative FT IR and FT Raman spectroscopic study of the solid compounds focused on their structural features. Table 1. The examined derivatives of pyridinium chloride Name R1 R2 1-Phenacylpyridinium chloride -CH2- -H 1-Phenacyl-2-methylpyridinium chloride -CH2--CH3 1-Phenacylpyridinium-4-aldoxime chloride-CH2- -C=N-OH 1-Benzoylethylpyridinium chloride -CH2CH2- -H 1-Benzoylethylpyridinium-4-aldoxime chloride -CH2CH2- -C=N-OH The characteristic vibrational frequencies will be discussed in correlation to their predominant keto-enol form, acido-basic properties, and in comparison with the electronic spectra of the ligands themselves and their pentacyanoferrate(II) complexes.

FT IR and Raman spectroscopy; UV-VIS spectroscopy; 1-Phenacyl- and 1-Benzoylethylpyridinium derivatives

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