Acta Cryst. (2013). C69, 837-840 [ doi:10.1107/S010827011301768X ]
Synopsis: Transmetallation of a barium [2+2] Schiff base macrocycle with copper(II) results in three successive ring contractions, reducing the ring size from 20 to 16 members. Unusually, the contraction does not appear to result in an improved `fit' for the copper(II) ion.
Copyright © International Union of Crystallography