Crystal structure and theoretical studies of the keto-enol isomerism of N,N′-bis(salicylidene)-o-phenylenediamine (salophen)

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2012-12, Vol.99, p.110-115
• Main Authors: Mota, Vinicius Z., de Carvalho, Gustavo S.G., Corbi, Pedro P., Bergamini, Fernando R.G., Formiga, André L.B., Diniz, Renata, Freitas, Maria C.R., da Silva, Adilson D., Cuin, Alexandre
• Format: Article
• Language: English
• Subjects: DFT; o-Phenylenediamine; Salicylaldehyde; Salophen; Tautomerism
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2012.09.002

[Display omitted] ► Synthesis and structural characterization of salophen are presented. ► The compound crystallizes in the monoclinic system with Z=4. ► Tautomerism of salophen was studied by calculations using DFT. ► Experimental and simulated IR data support the presence of salophen 1 in the solid sample. The Schiff base N,N′-bis(salicylidene)-o-phenylenediamine (salophen) was prepared by the condensation of salicylaldehyde with o-phenylenediamine in ethanol solution. The compound was characterized by elemental analysis, infrared (IR), 1H, 13C and 1H15N HMBC nuclear magnetic resonance (NMR) spectroscopic measurements, and also by X-ray diffraction. The tautomerism of salophen was also studied by calculations using density functional theory (DFT). Two of the three tautomers were shown to coexist. A comparison of the DFT data of the three tautomers has shown that the most stable one is salophen 1, which is in accordance with experimental X-ray crystallographic data.