Calcium, strontium, and barium complexes of pyridyl-containing macrocyclic Schiff bases

Abstract

Reaction of 2,6-diacetylpyridine, or pyridine-2,6-dicarbaldehyde, with 3,6,9-trioxaundecane-1,11-diamine, 1,5-bis(2-aminophenoxy)-3-oxapentane, or 4,7-diazadecane-1,10-diamine in ethanol in the presence of M[NCS]₂ or M[ClO₄]₂(M = Ca, Sr, or Ba) gives complexes of the type [M(NCS)₂L] or [M(ClO₄)₂L] where L is the corresponding macrocyclic Schiff base. In the absence of the metal salt the macrocycles are formed in very small yield or not at all. Alkali-metal salts are ineffective in promoting the synthesis of the macrocycles, and magnesium only promotes the formation of a macrocycle derived from the tetra-amine.