Chiral versus racemic building blocks in supramolecular chemistry: tartrate salts of organic diamines

In the 1:1 adducts C12H10N2.C4H6O6 formed between 1,2-bis(4' -pyridyl)ethene and racemic tartaric acid [(I), triclinic P (1) over bar 1, Z' = 1] and (2R,3R)-tartaric acid [(II), triclinic P1, Z' = 2], the ionic components are linked by hard hydrogen bonds into single sheets, which are further linked by C-H...O hydrogen bonds. In the analogous adducts C10H18N2.C4H6O6 formed by 4,4'-bipyridyl with racemic tartaric acid [(III), triclinic P (1) over bar, Z' = 1] and the chiral acid [(IV), monoclinic P2(1), Z' = 1], the hard hydrogen bonds generate bilayers which are again linked by C-H...O hydrogen bonds. Piperazine forms a 1:1 salt [{(C4H10N2)H-2}(2+)] . [(C4H4O6)(2-)] with (2R,3R)-tartaric acid [(V), monoclinic P21] sheets, which are linked by the cations to form a pillared-layer framework. In each of the 1:2 salts formed by racemic tartaric acid with piperazine [(VI), monoclinic P2(1)/n, Z' = 0.5] and 1,4-diazabicyclo[2.2.2]octane (DABCO) [(VII), monoclinic P2(1)/n, Z' = 0.5], the cation lies across a centre of inversion, with the [{HN(CH2CH2)(3)NH}(2+)] cation disordered over two sets of sites: in both (VI) and (VII) the anions form a three-dimensional framework encapsulating large voids which accommodate the cations. The salt formed between DABCO and (2R,3R)-tartaric acid [(VIII), orthorhombic P2(1)2(1)2(1), Z' = 1] has 3:4 stoichiometry and contains four different types of ion, [{HN(CH2CH2)(3)NH}(2+)](2).- [N(CH2 CH2)(3)NH](+) . 3(C4H5O6)(-) . C4H4O62-: the hard hydrogen bonds generate a three-dimensional framework.