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

Abstract

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 [H₂1][H₃O]Cl₃·3H₂O. In the solid state, the components of this hydrate separate into two well defined domains: rows of stacks of hydrogen bonded {[H₂1]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·CHCl₃ crystallizes in the non-centrosymmetric space groupFdd2, and the consequences on the packing of molecules are described.