Synthesis, characterization, crystal structure determination and computational study of the two new bidentate O, N Schiff bases derived from bromosalicylaldehyde and amines containing alkyl halide pendant groups

Two new Schiff base compounds 2-{(E)-[2-(bromoethyl)imino]methyl}-4-bromophenol (1) and 2-{(E)-[2-(chloroethyl)imino]methyl}-4-bromophenol (2) have been synthesized and characterized by FT-IR and 1H NMR spectroscopy, elemental analysis, thermal studies and single-crystal X-ray diffraction. They crystallize in the triclinic system, space group P−1. Both Schiff base compounds 1 and 2 display a trans configuration with respect to the CN double bond. Quantum theory of atoms in molecules (QTAIM) has been also used to find intramolecular interactions and investigate their chemical nature. The results show that in both of the compounds 1 and 2, there is a hydrogen bonding between nitrogen of imine and oxygen of phenol which is considerably stronger than normal hydrogen bonds. In addition, it has been shown that these hydrogen bonds are partially covalent and partially electrostatic in nature, in contrast to normal hydrogen bonds, which are usually considered as electrostatic interactions.