Search

This work presents eight coordination assemblies based on divalent metal ions (M = CoII, CuII, ZnII, and CdII), dicyanamide anion (N(CN)2−, dca), and two isomeric bent dipyridyl coligands (L), namely, 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) and 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo). In the resulting crystalline materials, both bpo and dca tectons generally display the bidentate bridging fashion (except in the mononuclear species 5), extending the metal centers to afford diverse one-, two-, and three-dimensional (1-D, 2-D, and 3-D) coordination networks that are not commonly observed in M−dca−L systems. Notably, the inclined polycatenated 2-D → 3-D framework and 3-D polyknotting network with the unique 6-connected (44.611) topology are formed for the CuIIand CdIIspecies with dca and 4-bpo. For the polymeric CoIIand CuIIcomplexes, very weak antiferromagnetic or ferromagnetic interactions are observed between the metal centers due to the μ1,5-bridging mode of dca, and their magneto-structural correlations have been discussed in detail. The ZnIIand CdIIcomplexes show solid-state fluorescent emissions at room temperature. [ABSTRACT FROM AUTHOR]

Two new flexible dipyridyl building blocks, N,N‘-bis(4-picolinoyl)hydrazine (4-bph) and its N-orientation isomer N,N‘-bis(3-picolinoyl)hydrazine (3-bph), have been synthesized as versatile cocrystallizing agents and introduced into the reactions with pyromellitic acid (H4BTA) and fumaric acid (H2Fa). Hydrogen-bonded directed assemblies of two hydrates of bphs and four binary cocrystals were validated by single-crystal X-ray diffraction analysis. With the presence of the reliable hydrogen-bonding donor/acceptor(s) of bph, the crystalline lattices of 4-bph·2H2O (1) and 3-bph·2H2O (4) are managed by N−H···Owaterand O−H···Ocarbonylto afford one-dimensional (1D) arrays, which are further extended to distinct three-dimensional (3D) (for 1) and two-dimensional (2D) (for 4) networks via O−H···Npyridylinteractions. While for the concomitant polymorphs (H2BTA)·(H2-4-bph) (2and 3), charge-assistant bifurcated N−H···O bonds do favor 1D acid−base hydrogen-bonding tapes, which are interlinked to result in a 2D layer in 2and a 3D network in 3through the competition of O−H···Ocarboxyland O−H···Ocarbonylforces. (H3BTA)2·(H2-3-bph)·4H2O (5) is also a charge-transfer organic salt with a 2D bilayered array. Proton transfer from weak H2Fa to 3-bph is not observed, and this leads to the formation of a binary neutral cocrystal (H2Fa)·(3-bph) (6), in which the 2D undulating herringbone pattern is constructed via the expected carboxylpyridyl heterosynthon and amide−amide homosynthon. [ABSTRACT FROM AUTHOR]

A bent dipyridyl compound, 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo), was employed to crystallize with 1,4-cyclohexanedicarboxylic acid (H2chdc), hydroquinone, citric acid (H4ca·H2O), barbituric acid, and ferrocene dicarboxylic acid (H2Fc) under general conditions, affording binary cocrystals [(H2chdc)·(4-bpo)] (1), [(hydroquinone)·(4-bpo)2] (2), [(H4ca)·(4-bpo)] (3), [(barbituric acid)·(4-bpo)] (4), and [(HFc)·(H-4-bpo)] (5) in high yield. X-ray single-crystal structures of these compounds reveal that a supramolecular synthon [%@mt;sys@%R%@sx@%2%@be@%2%@sxx@%%@mx@%(7)] containing classical O−H···N and weak C−H···O interactions, usually observed in organic cocrystals of carboxylic acid and heterocyclic base, is again involved in constructing the hydrogen-bonding networks of 1, 3, and 5. Its ionic analogous synthon [consisting of strong N−H···O and weak C−H···O/C%@mt;sys@%R%@sx@%2%@be@%2%@sxx@%%@mx@%(7)] also appears in the partly charge-transfer salt 5. For 2, only hydroxyl of the hydroquinone component can act as the hydrogen-bonding contributor, giving a strong O−H···N bond with 4-bpo. Multiple hydrogen-bonded donating/accepting sites in compound 3 saline 86.3 +/- 34.3 nmol/L per milligram of tissue per hour;4, another heterosynthon ring [containing strong N−H···N and weak C−H···O/C%@mt;sys@%R%@sx@%2%@be@%2%@sxx@%%@mx@%(7)] is formed due to the presence of the imide functional group. As a consequence, robust hydrogen-bonding interactions in these compounds afford diverse 2-D waved or planar layers (1 or 4), 1-D extended tape (2), 3-D net (3), and 1-D molecular-box type (5) supramolecular architectures. Thermal stability of these compounds has been investigated by thermogravimetric analysis (TGA) of mass loss. [ABSTRACT FROM AUTHOR]

Assembly of pamoic acid (H2PA) with piperazine (PIPO) or 4,4′-bipyridyl (BIPY) results in two distinct supramolecular complexes [(PA)·(H2PIPO)]·3H2O (1) and [(H2PA)·(BIPY)] (2). The former displays triple-helix host arrays via charge-assisted N+−H···O−interactions with the inclusion of helical water chains, whereas the latter represents the first cocrystal of pamoic acid sustaining by the familiar carboxyl-pyridyl H-bonding synthons. Notably, the structure of 1can be dehydrated/rehydrated with retention of crystallinity. [ABSTRACT FROM AUTHOR]