The favored trans( O6) geometry in hexadentate copper(II) complexes of 1,3-propanediamine- N,N′-diacetic- N,N′-di-3-propionic acid. Crystal structure of trans( O6)-Na 2[Cu(1,3-pddadp)]·NaNO 3·2H 2O. Strain analysis and spectral assignments of complexes

Abstract

The octahedral copper(II) complexes of 1,3-propanediamine- N,N′-diacetic- N,N′-di-3-propionic acid (H 41,3-pddadp) prepared in the region of pH 2 to 7 are hexadentates. Only one ( trans( O 6)) of the three geometrical isomers was found to dominate. The trans( O 6)-Na 2[Cu(1,3-pddadp)]·NaNO 3·2H 2O complex crystallizes in the space group P2/ c of the monoclinic crystal system with a=9.231(2), b=11.736(14), c=10.150(2) Å, β=109.33(2)° and Z=2. The conformations of the chelate rings are found to be envelope for the glycinate and skew-boat for the β-alaninate and 1,3-propanediamine rings. The complex is a tetragonally elongated octahedron ( T ∼0.8) with C 2 molecular symmetry. IR (carboxylate region) and electronic absorption spectra are assigned and discussed in relation to the structure of complexes. For hexadentate Cu(II) edta-type complexes of known structures the strain analysis is also discussed.