Khaled Bahgat, Nazm Al-Den Jasem, T. El‐Emary
2009
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0
Influential Citations
13
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Journal
Journal of The Serbian Chemical Society
Abstract
The solid phase FT-IR and FT-Raman spectra of 6-amino-3-methyl- -1-phenyl-1H-pyrazolo(3,4-b)pyridine-5-carboxylic acid (PYRPCA) and 6,7-di- hydro-3-methyl-6-oxo-1-phenyl-1H-pyrazolo(3,4-b)pyridine-5-carbonitrile (PYR- PCN) were recorded in the region 4000-400 cm -1 . The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculations based on the density functional theory (DFT) using standard B3LYP, BLYP and ab initio RHF methods with 6-31G basis set and were scaled using a recommended set of scaling factors yielding fairly good agreement between the observed and calculated frequencies. Based on the pre- sent good quality, the scaled quantum mechanical (SQM) force field, a reliable description of the fundamentals of PYRPCA and PYRPCN, was provided. The calculations predicated a predominance of different tautomers in PYRPCA and keto-enol tautomers in PYRPCN. For PYRPCA, the most stable conformer is stabilized by intramolecular hydrogen bonding. The characteristic of the hy- drogen bonding is its strengthening effect on the conjugation of the NH2 and COOH groups with the pyridine ring.