One- and two-dimensional polymers from proline and calcium bromide.

Authors :: Lamberts, Kevin
Şerb, Mihaela-Diana
Englert, Ulli
Source :: Acta Crystallographica Section C: Structural Chemistry; Apr2015, Vol. 71 Issue 4, p311-317, 7p
Publication Year :: 2015
Abstract: 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-μ<subscript>3</subscript>-DL-proline-μ<subscript>2</subscript>-DL-proline], {[Ca(C<subscript>5</subscript>H<subscript>9</subscript>NO<subscript>2</subscript>)<subscript>2</subscript>(H<subscript>2</subscript>O)<subscript>2</subscript>]Br<subscript>2</subscript>}<subscript> n</subscript>. 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(μ<subscript>2</subscript>-L-proline)calcium(II)], [CaBr<subscript>2</subscript>(C<subscript>5</subscript>H<subscript>9</subscript>NO<subscript>2</subscript>)<subscript>2</subscript>]<subscript> n</subscript>, with an unexpected CaBr<subscript>2</subscript> unit in a more regular coordination sphere. [ABSTRACT FROM AUTHOR]