Phase-separated hydrogen-bonded chloride ion-water-oxonium ion sheets and protonated 4 '-(4-bromophenyl)-2,2 ':6 ',2 ''-terpyridine stacks, and condensation products of 2-acetylpyridine and benzaldehydes revisited

During attempts to produce layered materials involving protonated 4'-(4-bromophenyl)-2,2':6',2 ''-terpyridine (1) and tetrahalometallate anions, we have serendipitously crystallized the doubly protonated ligand in the form of [H(2)1][H3O]Cl-3 center dot 3H(2)O. In the solid state, the components of this hydrate separate into two well defined domains: rows of stacks of hydrogen bonded {[H(2)1]Cl}(+) units interspersed by puckered (6,3) sheets of hydrogen bonded chloride ions, water molecules and oxonium ions. Without careful control of the conditions during the preparations of 1 and 4'-(4-cyanophenyl)-2,2':6',2 ''-terpyridine (2), cyclohexanol-based condensation products 3 and 4 are observed. Single crystal structures of these racemates confirm a (1SR,2RS,3SR,4SR,5SR)-stereochemistry. While racemic 4 crystallizes in the centrosymmetric space group P-1, 3 center dot CHCl3 crystallizes in the noncentrosymmetric space group Fdd2, and the consequences on the packing of molecules are described.