We report herein the single crystal structures of 4,4Ј-dicarboxy-2,2Ј-bipyridine, H 2 dcbp, and two complexes it forms with Co(), [Co(dcbp)H 2 dcbp adopts the anti conformation in the solid-state, with a dihedral angle of 148Њ between each pyridyl ring. Face-to-face π ؒ ؒ ؒ π interactions reinforce intermolecular hydrogen bonding (O-H ؒ ؒ ؒ N) involving both carboxylate oxygen and pyridyl nitrogen atoms forming a 2D inter-helical network. Alternate 2D layers are of opposite chirality and are linked into 3D through (C-H ؒ ؒ ؒ O) hydrogen bonds. In both 1 and 2 the ligand is deprotonated giving neutral complexes with 1 : 1 stoichiometry. Although 1 is monomeric, extensive hydrogen bonding between the deprotonated carboxylates, lattice water, and coordinated water molecules results in a 3D network which also contains face-to-face π ؒ ؒ ؒ π interactions between adjacent dcbp ligands. Within 2, pseudo-octahedral coordination about the Cu() centre is furnished by bidentate bipyridyl nitrogens, two monodentate carboxylates (from two adjacent dcbp ligands) and two water molecules. Coordination of dcbp in this instance forms a 2D coordination polymer, which is further linked by extensive hydrogen bonding between carboxylates and water molecules, giving a 3D network.

The role of acid in the formation of hydrogen-bonded networks featuring 4,4'-dicarboxy-2,2'-bipyridine (H 2 dcbp): Synthesis, structural and magnetic characterisation of {[Cu(H 2 dcbp)Cl 2 ]?H 2 O} 2 and [Cu(H 2 dcbp)(NO 3 ) 2 (H 2 O)]

The identity of the metal-organic framework formed by Mn(ii) and 4,4[prime or minute]-dicarboxy-2,2[prime or minute]-bipyridine (H(2)dcbp) depends upon the predominant solvent employed in the synthesis and yields the robust network isomers [[Mn(dcbp)][middle dot]1/2DMF](n), and [[Mn(dcbp)][middle dot]2H(2)O](n), which possess vastly different physical properties: irretrievably binds DMF, whereas reversibly binds water whilst retaining crystallinity.

We report herein the single crystal structures of four metal-organic framework complexes incorporating the 4,4'-dicarboxy-2,2'-bipyridine ligand, H(2)dcbp: alpha-[Co(dcbp)(H(2)O)(2)], 1; beta-[Co(dcbp)(H(2)O)(2)], 2, [Ni(dcbp)(H(2)O)(2)], and [[Mn(dcbp)].1/2DEF], 4 (DEF = diethylformamide). In each complex the ligand is deprotonated giving neutral species with 1:1 stoichiometry that form three-dimensional coordination polymers. Supramolecular isomerism (polymorphism) in 1 and 2 arises from the different ligand connectivity around the octahedral Co(II) centres. The two coordinated water molecules in 1 occupy cis positions, which are trans to the chelating bipyridine nitrogen atoms, leaving the carboxylate oxygen atoms in axial trans positions. In 2 all like donors occupy cis positions. Different modes of carboxylate coordination in 1 and 2 give dissimilar network topologies. A rare example of two interpenetrating 6(4)8(2)-b (quartz-like) chiral networks in 1 results from both dcbp carboxylate groups coordinating in a monodentate fashion to adjacent Co(II) centres, whereas in 2 only one carboxylate group bridges between adjacent Co(II) centres giving rise to a single chiral (10,3)-a net. In 1 and 2 the coordinated water molecules hydrogen bond to the non-coordinated carboxylate oxygen atoms. These interactions give rise to water-carboxylate double helices in , and support the coordination network in 2. Strikingly for a pair of dimorphs the crystal densities of 1 and 2 differ by ca. 0.3 g cm(-3)(1.654 vs. 1.940 g cm(-3), respectively). Compound 3 is isomorphous with 1 and likewise features two chiral interpenetrating nets of quartz topology. In 4, chelating bipyridine nitrogen atoms and four carboxylate oxygen atoms from a total of five adjacent dcbp ligands provide distorted octahedral geometry around Mn(II). The carboxylate groups bridge adjacent Mn(II) centres to produce bis-carboxylato chains which cross-link and generate a 3D network that is perforated with channels. The channels are occupied with disordered DEF molecules. The network topology in 4 is quite different to 1-3 and has a (4.6(2))(4(2).6)(4(3).6(6).8(6)) Schlafli notation. Magnetic susceptibility studies performed on 1, 2, [[Mn(dcbp)].1/2DMF] 5 (DMF = dimethylformamide) and [[Mn(dcbp)].2H(2)O] 6 reveal very weak antiferromagnetic coupling between the metal centres in each case.

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