Isomerism in calcium and strontium complexes of six-nitrogen-donor macrocyclic ligands with peripheral methyl substituents, and crystal structure of [Sr(CF3SO3)2(C26H30N6)]

Complexes of Ca(II) and Sr(II) with six-nitrogen-donor macrocyclic ligands carrying a methyl group at each diimine side-chain were synthesized by the metal-templated condensation of 2,6-diacetylpyridine with R-, S-, or R,S-1,2-diaminopropane. The complexes exist as stereoisomers as well as constitutional isomers, which can be identified by 1H NMR spectra and separated by fractional crystallization. The molecular structure of the eight-coordinate complex [Sr(CF3SO3)2(C24H30N6)] was established by X-ray crystallography. © 2001 Elsevier Science Ltd. All rights reserved. Keywords: Calcium complexes; Strontium complexes; Macrocyclic ligands; 2,6-Diacetylpyridine; 1,2-Diaminopropane