Vibrational spectroscopic studies of N1-ethyl-5′-bromo-7-azaindirubin-3′-oxime and N1-ethyl-indirubin-3′-monooxime

• The title compounds were synthesized and identified.
• These compounds were studied by vibrational spectroscopy.
• Vibrational assignments were suggested based on the previous work and the group characteristic frequencies.
• Thermal analyses were conducted by DSC and temperature variation of IR spectra.

We have prepared N1-ethyl-5′-bromo-7-azaindirubin-3′-oxime due to its potential for being a pharmaceutical. Infrared and Raman spectra have been recorded and vibrational assignments have been suggested based mainly on our previous vibrational investigation of N1-isopropyl-5′-chloro-7-azaindirubin-3′-oxime and on group characteristic frequencies. Temperature variation study has revealed the presence of conformers due to the internal rotation of ethyl group. IR spectra collected for N1-ethyl-7-azaindirubin-3′-oxime have shown rather similar spectral features with that of N1-ethyl-5′-bromo-7-azaindirubin-3′-oxime. IR spectra of these compounds have revealed the association through hydrogen bonding in the solid state. IR spectra recorded for these samples after annealing at high temperatures indicated the thermal conversion temperature to be lowered than 270 °C. Results from thermal analyses have determined the beginning decomposition temperatures to be 250 °C and the decomposition enthalpies to be 94 kJ/mol for both N1-ethyl-5′-bromo-7-azaindirubin-3′-oxime and N1-ethyl-7-azaindirubin-3′-oxime.