Synthesis, characterization and computational studies of 3-{(E)-[(2-hydroxyphenylimino]methyl}benzene-l,2-diol and molecular structure of its zwitterionic form

The Schiff base 3-{(E)-[(2-hydroxyphenyl)imino]methyl}benzene-l,2-diol was synthesized by the condensation of 2,3-dihydroxybenzaldehyde and 2-aminophenol in water at room temperature. The crystal was grown using two solvents (dry methanol and 60% methanol). The compound was characterized using elemental microanalysis, IR, NMR, UV spectroscopies and single-crystal X-ray diffraction crystallography. The X-ray structure reveals that the Schiff base crystallizes as a methanol solvate in dry methanol with triclinic crystal system, space group P-1 and Z = 2 in the unit cell and as a non-methanol solvate in 60% methanol with triclinic crystal system, space group P-1 and Z = 4 in the unit cell. The compound showed absorption bands at 272,389,473 and 602 nm in DMSO. These bands were assigned as n -> pi*, n -> pi* and n ->pi* transitions. The 473 and 602 nm bands in DMSO reveal that the compound exists in tautomeric forms. The presence of N-H, C-O and C=N stretching vibrations in the IR spectrum indicates that the compound is zwitterionic in the solid state. This study was supplemented using density functional theory method. (c) 2017 Elsevier B.V. All rights reserved.