Xue-Hua Ding

Proton-transfer supramolecular salts resulting from 3,5-dinitrobenzoic acid and aminomethyl pyridine

Three hydrogen-bonding three-dimensional (3D) networks of ammonium carboxylate salts formed between 3,5-dinitrobenzoic acid and aminomethyl pyridine (2-, 3-, 4-) are described here. During solution crystallization, the hydrogen atom transfers from the carboxylic acid to the amine to yield ammonium carboxylate salts, which feature three charge-separated N+–H⋯O− hydrogen bonds to afford two types of one-dimensional (1D) hydrogen-bonding columns. Of the three structures, ((2-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (1) shows a hydrogen-bonding column which consists of alternating R12(4) and R24(8) rings whereas ((3-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (2) results in a hydrogen-bonding column which comprises repeating R34(10) rings. ((4-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (3) bears a unique shape of Chinese knot among four cations instead of the column constructed by rings. From this we can gather information about the possible position effects of functional groups on the overall packing.

Inorganic anion-assisted supramolecular assemblies of bent dipyridines: effects of anionic geometries on hydrogen-bonding networks

A series of inorganic acids were introduced into the self-assembly with the bent 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo), yielding seven anion-assisted supramolecular salts, i.e. [(4-H2bpo2+)·(NO3−)2]·2H2O (1), (4-H2bpo2+)·(HPO42−) (2), [(4-H2bpo2+)2·(4-Hbpo+)·(I3−)3·(I−)2]·2H2O (3), [(4-Hbpo+)2·(PF6−)2]·H2O (4), [(4-H2bpo2+)·(BF4−)2]·H2O (5), [(4-Hbpo+)·(BF4−)] (6) and (4-H2bph2+)·(SO42−) (7). Structural analyses indicate that different inorganic anions (e.g. spherical, linear, trigonal planar, tetrahedral and octahedral) can induce the formation of diverse supramolecular architectures, influencing the crystallization ratio, the protonated number and the final structure. The anions are hydrogen bonded to the angular dipyridine, which offers a sufficient driving force for the directed assembly of supramolecular hydrogen-bonding frameworks. Thereto, various hydrogen-bonding motifs are observed in all these cases (1–7) and the nitrogen atoms of pyridines are protonated apart from salt 6. Among them, salts 1, 3, 4 and 5 crystallize with water molecules but the others do not. Interestingly, appealing substructures have been generated by anions and water molecules in 1, 3 and 5 but not in 4. HPO42− dimers form in 2 despite there being no assistance from solvent water. BF4− anions facilitate the formation of the helical chain in 6. Unexpectedly, the oxadiazole ring opened via the in situ hydrolysis under hydrothermal conditions during crystallization with H2SO4, producing salt 7.

Di-μ2-cyanido-dicyanidobis{2,2′-[ethane-1,2-diylbis(nitrilo­methyl­idyne)]diphenolato}(1,4,8,11-tetra­azacyclo­tetra­deca­ne)dichromium(III)nickel(II) methanol disolvate

In the title compound, [Cr2Ni(C16H14N2O2)2(CN)4(C10H24N4)]·2CH3OH, each [Cr(salen)(CN)2] unit {salen is 2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolate} acts as a monodentate ligand through one of its two cyanide groups N bound to a central [Ni(cyclam)]2+ core (cyclam is 1,4,8,11-tetraazacyclotetradecane). Each CrIII ion is coordinated by two N and two O atoms from a salen ligand situated in the equatorial plane with two trans cyanide C atoms, yielding a distorted octahedral coordination geometry. The NiII atom lies on an inversion center and is octahedrally coordinated by a cyclam ligand lying in the equatorial plane and by two cyanide N atoms. The asymmetric unit contains one half of the complex molecule and a methanol solvent molecule. In the crystal structure, the complex molecule is linked to the methanol solvent molecules via O—H⋯O and N—H⋯O hydrogen bonds. Individual complex molecules are linked by C—H⋯N hydrogen bonds, forming chains along b.

Supramolecular assemblies through host–guest interactions of 18-crown-6 with ammonium salts: geometric effects of amine groups on the hydrogen-bonding architectures

A series of ammonium salts were introduced into the self-assembly with the same host 18-crown-6, yielding five supramolecular salts, that is [(C4H6N3)·(18-crown-6)2]+·() (1), [(C6H14N)·(18-crown-6)]+·() (2), [(C6H14N)·(18-crown-6)]+·() (3), [(C6H10N2)·(18-crown-6)]2+·()2 (4) and [(C6H8NO2)·(18-crown-6)]+·[(C7H3N2O6)− ]2 (5). Structural analysis indicates that different kinds of guest amines, ranging from chain-like aliphatic amine, annular aliphatic amine to aromatic amine, have a great impact on host–guest interactions and supramolecular architectures. The major driving force in host–guest systems is found to be the strong N–H…O or/and weak C–H…O hydrogen-bonding interactions, with various ring motifs and interesting substructures such as the butterfly-like trimer in 1 and the rotator–stator assembly in 2–5. By analysing and summing up, we can come to the conclusion that the group in 4 exhibits an optimum value of around 0.755 Å from the O-plane and the 18-crown-6 macrocycle displays the minimum distortion. On the whole, ammonium cations show control over supramolecular assemblies, but counter anions that easily form hydrogen bonds will affect crystal structures, for instance, anion in 4 facilitates the formation of the 3D hydrogen-bonding network and helical hydrogen-bonding sheets while deprotonated 3,5-dinitrobenzoic acid assists the formation of discrete subunits.

3-Amino-benzonitrile-3,5-dinitro-benzoic acid (1/1).

The asymmetric unit of the title co-crystal, C7H6N2·C7H4N2O6, contains two formula units of both components. The crystal structure is stabilized by intermolecular O—H⋯O, N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds, generating a two-dimensional wave-like network. π–π stacking interactions [centroid–centroid distances = 3.702 (2), 3.660 (2)and 3.671 (2) Å] stabilize the crystal packing.

cis-Diaqua­bis(2,2′,2′′-tripyridylamine)zinc(II) bis­(perchlorate)

In the title compound, [Zn(2,2′,2′′-tpa)2(H2O)2](ClO4)2 (2,2′,2′′-tpa is 2,2′,2′′-tripyridylamine, C15H12N4), the Zn center lies on a twofold axis and is coordinated octahedrally by two water molecules and two bidentate 2,2′,2′′-tpa ligands. The perchlorate anions are linked to the coordinated water molecules in the complex cations via O—H⋯O hydrogen bonds.