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

In the 1:1 adducts C(12)H(10)N(2).C(4)H(6)O(6) formed between 1,2-bis(4'-pyridyl)ethene and racemic tartaric acid [(I), triclinic P1;, 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 C(10)H(18)N(2).C(4)H(6)O(6) formed by 4,4'-bipyridyl with racemic tartaric acid [(III), triclinic P1;, 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 [((C(4)H(10)N(2))H(2))(2+)].[(C(4)H(4)O(6))(2-)] with (2R,3R)-tartaric acid [(V), monoclinic P2(1)] 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(CH(2)CH(2))(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(CH(2)CH(2))(3)NH)(2+)](2).[N(CH(2)CH(2))(3)NH](+).3(C(4)H(5)O(6))(-).C(4)H(4)O(6)(2-): the hard hydrogen bonds generate a three-dimensional framework.