Syntheses, Spectroscopy, Thermal Analysis, Antioxidant Activity of Two Novel Schiff bases 3-(m-tolylimino)indolin-2-one and (E)-1- ((m-tolylimino)methyl)naphthalen-2-ol

Reaction of 1H-Indole-2,3-dione (Isatin) and
2-hydroxy-1-naphthaldehyde with m-toluidine provided
the corresponding 3-(m-tolylimino)indolin-2-one (HL1)
and (E)-1-((m-tolylimino)methyl)naphthalen-2-ol (HL2).
IR and 1HNMR spectra demonstrate the Keto-tautomer
in the solid state. The little molar conductance (Ʌm = 0.12
(HL1), 0.24 (HL2)) S m2 mol–1

suggests non-electrolyte
behaviour of the Schiff base in DMF at room
temparature. Differential scanning calorimetry (DSC)
results suggest an irreversible phase transformation
from solid crystals to isotropic liquids and provides
estimates of the thermal stability for HL1 and HL2.
Different analytical techniques including Fourier
transform infrared (FTIR), 1H-NMR, thermal analysis,
electronic spectra, antioxidant testing and molar
conductance techniques were used to characterize the
compounds (HL1) and (HL2).