Synthesis, characterization and computational studies of 3-{(E)-[(2-hydroxyphenyl)imino]methyl}benzene-1,2-diol and molecular structure of its zwitterionic form

• Published in: Journal of molecular structure 2018-01, Vol.1152, p.21-28
• Main Authors: Ezeorah, Julius Chigozie, Ossai, Valentine, Obasi, Lawrence Nnamdi, Elzagheid, Mohamed I., Rhyman, Lydia, Lutter, Michael, Jurkschat, Klaus, Dege, Necmi, Ramasami, Ponnadurai
• Format: Article
• Language: English
• Subjects: 2,3-Dihydroxybenzaldehyde; DFT; Schiff base; X-ray crystallography; Zwitterionic
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2017.09.083

The Schiff base 3-{(E)-[(2-hydroxyphenyl)imino]methyl}benzene-1,2-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 π → π ∗, n → π∗ and n-σ∗ 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 CN 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. [Display omitted] •Triclinic crystal systems with space groups of P-1 were obtained for the crystals.•One of the crystals is solvated by methanol.•The crystal structures are zwitterionic.•The spectroscopic studies confirmed the structures of the compounds.•The Compound SB2A has a HOMO-LUMO gap of 3.09 eV.