Vibrational (FT-IR, Raman) and DFT analysis on the structure of labile drugs. The case of crystalline tebipenem and its ester

Abstract

A tebipenem is active form of the first, oral carbapenem antibiotic – tebipenem pivoxyl. The optimized conformations of tebipenem pivoxyl and tebipenem were determinated by quantum-chemical calculations performed with the use of B3LYP functional and 6-31G(d,p) as a basis set. For the most stable conformations of tebipenem and its ester were established theoretical Raman and FT-IR spectra. The theoretical approach in significant part was support for identification of experimental Raman (400–4000 cm−1) and FT-IR (100–4000 cm−1) of tebipenem and tebipenem pivoxil. The geometric structure of molecules, HOMO and LUMO orbitals and molecular electrostatic potential were also determined. The benefits of applying FT-IR and Raman scattering spectroscopy for characterization of tebipenem and its ester consisted in demonstrating differences in their spectral properties.