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Temperature dependent polymorphism of pyrazinamide: An in situ Raman and DFT study
Poornima Sharma1, Rajib Nandi2, Debraj Gangopadhyay1
1Department of Physics, Institute of Science, Banaras Hindu University, Varanasi, Uttar Pradesh, India; Department of Physics, Lucknow University, Lucknow, Uttar Pradesh, India.
Abstract:
The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature dependent Raman spectroscopic technique. Pyrazinamide is a very useful drug used for the treatment of tuberculosis (TB) and plays a significant role in destroying the dormant tubercle bacilli which are not destroyed by other common TB drugs. Temperature dependent Raman spectra suggest polymorphic phase change from α→γ form of pyrazinamide between 145 and 146°C. In situ Raman spectra of pyrazinamide between 145 and 146°C show the conversion of α→γ form by the shift in CO stretching vibration accompanied by several other changes. The phase change is characterized by the breaking of two linear NH⋯O type hydrogen bonds associated with CO stretching vibration in α dimer and formation of one linear NH⋯N type hydrogen bond along with a weak intramolecular CH⋯O type hydrogen bond in the γ dimer.
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