Novel dioxotetrazamacrocyclic “sandwich” complexes – synthesis and structural characterization

Reaction of 1,4,7,10-tetraazacyclododecane-2,9-dione with copper and cobalt perchlorate in water at 1:1 molar ratio afforded two new crystal-engineered 1:2 ‘sandwich’ type complexes. Both of them are isostructural analogues. Copper complex crystallized in monoclinic space group P21/c with a=9.6888(12), b=12.2956(16), c=10.5661(13), β=104.965(2)°, V=1216.0(3) Å3, and Z=2. The Cu(II) ions are six-coordinated by four nitrogen atoms and two amide oxygen atoms. Their coordination geometry can be described as Jahn–Teller distorted octahedra, with elongated Cu–O distances. (2.310(2) Å) Cobalt complex crystallized in monoclinic space group P21/c with a=9.7560(12), b=12.237(16), c=10.7130(13), β=105.194(3)°, V=1234.2(4) Å3, and Z=2. The Co(II) ions are also six-coordinated by similar atoms as found in copper complex. But the bond lengths of Co–O 2.0881(13) Å are slightly shorter than respective Co–N.