Structural characteristics of N, N′-bis(salicylidene)-2,6-pyridinediamine

Abstract

The Schiff base N, N′-bis(salicylidene)-2,6-pyridinediamine has been synthesized and characterized in the solid state and in solution using X-ray analysis, IR, UV/Vis and NMR spectroscopy. Crystal data: C 19H 15N 3O 2, M r=317.34, monoclinic, space group P2 1/c, a=19.313(5), b=5.854(2), c=14.957(6) Å, β=110.45(2)°, V=1584.4(9) Å 3, Z=4, R=0.049, R w=0.095 for 3323 independent reflections with I>2 σ( I). There are two intramolecular hydrogen bonds O–H⋯N between the hydroxyl and imino groups of 2.564(3) and 2.633(3) Å. The enolimino form is found in the solid state and is also the predominant tautomeric form in solution. A tendency of interconversion to ketoamine has been observed only in rather polar solvents, such as methanol and methanol/water mixtures and has been found to be very low: tautomeric constants K t=[ketoamine]/[enolimine] amount to 0.02 and 0.03 in methanol and methanol/water 4/1, respectively.© 1997 Elsevier Science B.V.