Molecular structures of two E-azobenzocrown ethers

The structures of the E-isomers of two 13- and 16-membered azobenzocrown ethers (compounds 1 and 2) have been determined by single crystal X-ray crystallography. The crystals of the compounds are monoclinic. In the unit cells there are two independent molecules 1A and 1B or 2A and 2B. Both compounds display conformational flexibility of the oxyethylene chain. Comparison of the conformations of the free macrocycles with their metal complexes indicates that the conformational changes of the free molecules to adapt to the metal coordination are more pronounced for the larger homologue.