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In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ(2)O:O'], [CuCl2(C5H9NO2)]n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d(9) Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a Cu(II) centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter (i.e. a). The O:O'-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for Cu(II); the vast majority of amino acid derivatives of this cation are characterized by N,O-chelation.

Reactions of calcium bromide with enantiopure and racemic proline in aqueous solution lead to two solids in which the zwitterionic amino acid acts as a bridging ligand between neighbouring cations. Depending on the chirality of the amino acid, topologically very different products are obtained. With racemic proline, bromide acts as a simple uncoordinated counter-anion for the cationic heterochiral chains in catena-poly[[aquacalcium(II)]-μ-aqua-μ3-DL-proline-μ2-DL-proline], {[Ca(C5H9NO2)2(H2O)2]Br2}n. In agreement with chemical intuition, only carboxylate and aqua O atoms coordinate the alkaline earth cation in a low-symmetry arrangement. In contrast, L-proline affords the two-dimensional network poly[dibromidobis(μ2-L-proline)calcium(II)], [CaBr2(C5H9NO2)2]n, with an unexpected CaBr2 unit in a more regular coordination sphere.

Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions.

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2 O: O′], [CuCl2(C5H9NO2)] n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter ( i.e. a). The O: O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N, O-chelation. [ABSTRACT FROM AUTHOR]

In catena-poly[copper(II)-di-μ-chlorido-μ-proline-κ2 O: O′], [CuCl2(C5H9NO2)] n, two symmetry-independent metal cations adopt distorted octahedral coordination, typical for d9 Jahn-Teller systems. Each chloride bridge is involved in both a short and a very long interaction with a CuII centre. The centrosymmetric crystal structure contains homochiral chains of opposite handedness which extend along the shortest lattice parameter ( i.e. a). The O: O′-bridging coordination mode of proline, although a common motif for such complexes in general, is remarkable for CuII; the vast majority of amino acid derivatives of this cation are characterized by N, O-chelation. [ABSTRACT FROM AUTHOR]

Reactions of manganese(II) chloride, bromide and iodide with proline as an enantiopure and racemic ligand result in six crystalline solids for which diffraction experiments have been performed at 100 K. For two of these compounds, crystal structures at ambient temperature had been reported previously. The most surprising outcome of our systematic comparison lies in the role of chirality: with enantiopure proline three different coordination polymers have been obtained, whereas racemic proline yields isomorphous mononuclear complexes under the same reaction conditions. [ABSTRACT FROM AUTHOR]