Structural investigation on phenyl- and pyridin-2-ylamino(methylene)naphthalen-2(3H)-one. Substituent effects on the NMR chemical shifts.
Schiff bases bearing phenyl and pyridyl groups were synthesized by condensation of appropriate amines with 2-hydroxynaphthaldehyde. These Schiff bases were obtained as colored crystalline solids. The proton NMR spectra of these compounds showed a doublet for the NH protons indicating a keto tautomer for these Schiff bases. The pyridyl-substituted Schiff bases containing hydroxyl moiety were found to show the most downfield shift for the NH protons in DMSO solvent, and this was rationalized due to the formation of a six- and five-membered ring using hydrogen bonds for these two compounds. Correspondingly, the olefinic proton of the Schiff bases is also found to be a doublet due to coupling to the amine proton. These Schiff bases exhibited thermochromic properties. Detailed NMR spectral analysis for both the phenyl- and pyridyl-substituted Schiff bases is presented.
Venkatachalam
Taracad K
TK
Centre for Advanced Imaging, The University of Queensland, Brisbane, Queensland 4072, Australia. t.venkatachalam@uq.edu.au
Pierens
Gregory K
GK
Campitelli
Marc R
MR
Reutens
David C
DC
D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D012015:Reference Standards; D012545:Schiff Bases / Q000138:chemical synthesis / Q000737:chemistry*; D013237:Stereoisomerism
D012545:Schiff Bases