Preparation, characterization and crystal structure of some imino Schiff bases

Bis[2-N(methyleneimino)ethylbutanoate] [(eaa)2en] (1), 2-[1-(2-hydroxypropylimino)ethyl]phenol [ohap-1-a-2-pn] (2), and 3-(2-hydroxyethylimino)-1-phenylbutan-1-one [bzacmea] (3) were isolated from the condensation reactions between the corresponding ketone and amine at 303 K. The single crystal XRD analyses revealed that the packing of the molecules in the crystal structure of compounds (1), (2) and (3) are stabilized through hydrogen bonding interactions. Compounds (2) and (3) are zwitter ions. Thermal decomposition kinetics has been studied using model free evaluation techniques. The Friedman technique gave average activation energy (Ea) of 79, 78, and 73 kJ mol−1 for the non-isothermal decomposition of (1), (2), and (3) in nitrogen environment. The average activation energy of (1) was found to be 88, and 86 kJ mol−1, which are derived by Kissinger and Flynn–Wall techniques from non-isothermal TG plots at different heating rates.