Anion exchange during pressing of tablets in IR-spectroscopy practice

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

“…This observation is similar to that of ICAIO, which has a strong IR band at 1568 cm À1 due to the absence of C i symmetry [13]. The very intense central C@C stretch Raman bands have also been observed and assigned for indigoid dye [16], indigo [17][18][19][20], Maya blue [21][22][23][24], isoindigo [25], thioindigo and indirubin [20] in the frequency region from 1557 to 1594 cm À1 . This can be regarded as a characteristic C@C central double bond stretch.…”