Molecular spectroscopy, solvent effect, and DFT studies of azithromycin solvate

Area of Science:

• Solid-state chemistry
• Computational chemistry
• Spectroscopy

Background:

• Azithromycin ethanol solvate monohydrate (AZM-MH-EtOH) is a crystalline form of azithromycin.
• Understanding its stability and properties in different environments is crucial for formulation and application.

Purpose of the Study:

• To synthesize and characterize AZM-MH-EtOH.
• To investigate the electronic and vibrational properties of AZM-MH-EtOH under various conditions (aqueous, ethanolic, vacuum).
• To evaluate the influence of solvation effects on its chemical stability and spectral characteristics.

Main Methods:

• Synthesis via slow evaporation.
• Characterization using powder X-ray diffraction, Raman, and infrared (IR) spectroscopy.
• Theoretical investigation using density functional theory (DFT) with implicit solvation and solute electron density models.
• Electronic structure calculations and UV-vis spectroscopy.

Main Results:

• AZM-MH-EtOH exhibits greater chemical stability in ethanolic and aqueous solvents compared to vacuum conditions.
• UV-vis measurements confirm higher stability in ethanol than in water.
• Experimental vibrational spectra (Raman and IR) show better agreement with DFT calculations that include solvation effects, particularly concerning hydrogen bonding.
• DFT calculations reveal a stronger affinity of AZM-MH-EtOH for water and ethanol than predicted under vacuum.

Conclusions:

• Solvation significantly influences the electronic and vibrational properties of AZM-MH-EtOH.
• The compound demonstrates enhanced stability in ethanolic and aqueous media.
• DFT calculations incorporating solvation effects provide a more accurate representation of the experimental spectral data.