The reactions of a series of transition-metal sulfates, in the form of their respective hydrates, with β-picoline (3-methylpyridine) and water yield crystals of compounds in the form catena -poly[[diaquabis(3-methylpyridine-κ N ) M II ]-μ-sulfato-κ 2 O : O ′], [ M (SO 4 )(C 6 H 7 N) 2 (H 2 O) 2 ] n , where M = Mn ( 1 ), Co ( 2 ), Ni ( 3 ), Cu ( 4 ), Zn ( 5 ), and Cd ( 6 ). The six compounds are isostructural, displaying polymeric structures with infinite chains of M 2+ ions adopting an octahedral N 2 O 4 coordination environment involving two β-picoline ligands, two water ligands, and two bridging sulfate anions. The infinite chains are along [001] and are joined together through O—H...O hydrogen bonds between water ligands and sulfate anions to form double chains. The other notable feature of the series is a significant Jahn–Teller-like distortion for d 9 Cu 2+ compound ( 4 ).
A series of hybrid organic–inorganic chloride salts containing 1-butyl-3-methylimidazolium, [BMIm] + , cations was synthesized using [BMIm]Cl as an ionic liquid (IL) reaction medium and the corresponding M Cl n salts ( M = Cd, Se, Sn, Bi; n = 2, 3, 4). The resulting compounds, bis(1-butyl-3-methylimidazolium) tetrachloridocadmate(II), (C 8 H 15 N 2 ) 2 [CdCl 4 ] or [BMIm] 2 [CdCl 4 ], ( I ), bis(1-butyl-3-methylimidazolium) hexachloridoselenate(IV), (C 8 H 15 N 2 ) 2 [SeCl 6 ] or [BMIm] 2 [SeCl 6 ], ( II ), bis(1-butyl-3-methylimidazolium) hexachloridostannate(IV), (C 8 H 15 N 2 ) 2 [SnCl 6 ] or [BMIm] 2 [SnCl 6 ], ( III ), and tris(1-butyl-3-methylimidazolium) hexachloridobismuthate(III), (C 8 H 15 N 2 ) 3 [BiCl 6 ] or [BMIm] 3 [BiCl 6 ], ( IV ), were characterized with the aid of the single-crystal X-ray diffraction method at 100 K. Compound ( I ) crystallizes in the monoclinic space group Cc , compounds ( II ) and ( III ) are isostructural and crystallize in the orthorhombic space group P 2 1 2 1 2 1 , and compound ( IV ) crystallizes in the monoclinic space group P 2 1 / c . All four structures contain discrete [CdCl 4 ] 2− , [ M Cl 6 ] 2− ( M = Se or Sn), or [BiCl 6 ] 3− anions charge-balanced by [BMIm] + cations. Ionic interactions and C—H...Cl hydrogen bonds, as well as cation–cation C—H...π and ring–ring contacts, are discussed. The novel compounds are discussed in the context of a literature survey, thereby providing suggestions for future discoveries. Electronic structure calculations yield band gaps of 4.44, 2.91, 2.92, and 3.84 eV for ( I )–( IV ), respectively.
Five new solvate forms of the complex bis(thiocyanato-κ N )[tris(pyridin-2-ylmethyl)amine-κ 4 N , N ′, N ′′, N ′′′]iron(II), [Fe(NCS) 2 (C 18 H 18 N 4 )] or [Fe(NCS) 2 (tpa)], a known spin-crossover compound, are reported. Among the incorporated solvents are all four phenyl monohalides (fluoro-, chloro-, bromo- and iodobenzene) and pyridine. Through variable-temperature single-crystal X-ray diffraction, we characterized the transition by means of lattice parameters, Fe—N bond lengths and distortion of the coordination sphere. The structures remain isostructural across the compound series, but exhibit distinct transition temperatures indicating a solvate-dependent behaviour. Hirshfeld surface, noncovalent interaction analyses and energy frameworks provide a more detailed view of how the structural response affects the intermolecular interaction network. In particular, the temperature dependence of the dominant pairwise interaction along the crystallographic b direction closely mirrors the evolution of the b -axis lattice parameter, suggesting that this interaction plays a key role in directing the structural response to spin crossover. Our comparison demonstrates that different transition behaviour is not caused by one fundamental change in the packing architecture but rather by subtle solvate-dependent changes.
Single-crystal X-ray diffraction analysis of two isoreticular MOFs, poly[[(μ-4,4′-diazenediyldibenzoato)[μ-1,3-bis(pyridin-4-yl)propane]cadmium(II)] dimethylformamide tetrasolvate], {[Cd(C 14 H 8 N 2 O 4 )(C 13 H 14 N 2 )]·4C 3 H 7 NO} n or {[Cd(adc)(bpp)]·4DMF} n ( 1 ), and poly[aqua(μ-4,4′-diazenediyldibenzoato)[μ-1,3-bis(pyridin-4-yl)propane]cobalt(II)], [Co(C 14 H 8 N 2 O 4 )(C 13 H 14 N 2 )(H 2 O)] n or [Co(adc)(bpp)(H 2 O)] n ( 2 ), obtained via one-pot solvothermal synthesis, reveals a counterintuitive relationship in interpenetration behaviour [adc = azobenzene-4,4′-dicarboxylate or 4,4′-diazenediyldibenzoate, bpp = 1,3-bis(pyridin-4-yl)propane and DMF = N , N -dimethylformamide]. MOF 1 crystallizes in the orthorhombic system ( Pccn , Z = 8) and adopts a non-interpenetrating 3D architecture with a calculated solvent-accessible void volume of 40.4%. The [Cd(adc)] n sublayers in 1 exhibit twofold interpenetration, resulting in closely packed layers that prevent further 3D interpenetration upon bridging by flexible bpp ligands. In contrast, MOF 2 crystallizes in the space group P 2 1 / c ( Z = 4) and adopts a twofold interpenetrated 3D framework with a reduced solvent-accessible void volume of 4.4%. This architecture originates from non-interpenetrated yet loosely packed [Co(adc)] n layers. Photoluminescence studies corroborate this structural dichotomy. Dense intralayer packing in 1 induces concentration quenching, whereas rigid non-interpenetrated layers in 2 preserve linker-based emission. This comparative crystallographic study demonstrates that the packing density of 2D layers dictates the propensity for higher-order catenation, highlighting interpenetration as a geometric constraint rather than a synthetic flaw.
In this study, the hydrogen-bonding network in the crystal structure of ammonium molybdate tetrahydrate, (NH 4 ) 6 [Mo 7 O 24 ]·4H 2 O, was investigated using single-crystal time-of-flight neutron diffraction. The H-atom positions were determined and refined using anisotropic displacement parameters. Three of the six ammonium ions exhibit hydrogen-site disorder, which is attributable to the availability of multiple hydrogen-bonding configurations around each disordered ion. Ammonium ions are connected to a heptamolybdate polyanion and water molecules through N—H...O hydrogen bonds. Water molecules form O—H...O hydrogen bonds with the heptamolybdate polyanion. The extensive N—H...O and O—H...O hydrogen bonds form a three-dimensional supramolecular structure.
