Synthesis and spectroscopic studies of some new polyether ligands of the Schiff base type

New polyether ligands of Schiff base type (3-13) were synthesized from the reaction of diethylene glycol bis(2-aminophenyl)ether and triethylene glycol bis(2-aminophenyl)ether with salicylaldehyde, 5-methoxysalicylaldehyde, 5-bromosalicylaldehyde, 5-nitro salicylaldehyde, and 2-hydroxy-1-naphthaldehyde. The products were characterized by elemental analysis, IR, H-1, C-13 NMR, and UV-VIS techniques. The UV-VIS spectra of those Schiff bases with an OH group in the ortho position to the imino group were studied in polar and nonpolar solvents in acidic and basic media. The compounds are in tautomeric equilibrium (enol-imine, O-(HN)-N-... reversible arrow keto-amine, (OH)-H-...-N forms) in solvents, acidic chloroform, and benzene solutions and basic DMSO, chloroform, and benzene solutions. These tautomers were not observed in polar and non-polar solvents and in basic solutions of DMSO, chloroform, and benzene for the Schiff bases 5-10. Tautomer proportions, which were obtained from H-1 NMR and UV-VIS data in DMSO, were compared for compounds 3, 4, 11, and 12.