The favored trans(O-6) geometry in hexadentate copper(II) complexes of 1,3-propanediamine-N,N-diacetic-N,N-di-3-propionic acid. Crystal structure of trans(O-6)-Na-2[Cu(1,3-pddadp)]center dot NaNO3 center dot 2H(2)O. Strain analysis and spectral assignments of complexes
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The octahedral copper(II) complexes of 1,3-propanediamine-N,N-diacetic-N,N-di-3-propionic acid (H(4)1,3-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)] . NaNO3 . 2H(2)O 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) Angstrom, beta = 109.33(2)degrees and Z = 2. The conformations of the chelate rings are found to be envelope for the glycinate and skew-boat for the beta-alaninate and 1,3-propanediamine rings, The complex is a tetragonally elongated octahedron (T similar to 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.