The NMR study of hydrogen bond formation in some tris(((-salicylidene)amino)ethyl)amine derivatives in solution and in the solid state

Eight Schiff bases, derived from tris(2-aminoethyl)amine and some aromatic aldehydes have been investigated by heteronuclear NMR methods in solution and in the solid state. Six of those compounds can form intramolecular hydrogen bonds and two remaining imines which do not have hydroxyl substituent in position 2 cannot form such bonds and were chosen as a model compounds for nonbonded structure. The tautomeric equilibrium position of investigated compounds were estimated on the base of nitrogen chemical shifts and nitrogen-proton one bond coupling constants when available. In solution for each compound in all temperatures applied, single symmetrical dynamic averaged structures were found but in the solid state in a few cases mixtures of several nonequivalent or nonsymmetrical structures were observed. Generally at low temperature the –NH– form is more abundant then at room temperature. Similarly in the solid state the proton transfer from oxygen to nitrogen site is more effective in comparison with the solution, except for the 9-formyl-8-hydroxyjulolidine derivative for which different behavior was found. q 2004 Elsevier B.V. All rights reserved