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Kansas City, MO — OSHA has launched a Regional Emphasis Program addressing hazards stemming from exposure to fertilizer-grade ammonium nitrate and agricultural anhydrous ammonia.

Children's Geographies; 08/01/2022
(AN 158427715); ISSN: 14733285
Academic Search Premier

[Science] :
Two U.S. experts who inspected North Korea’s uranium enrichment facility at the Yongbyon nuclear complex in 2010 have analyzed recent images of a similar facility in the North and pointed out differences.  Stanford University professor emeritus Siegfried Hecker and Robert Carlin, a scholar at the ...

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Crystal structure and topology of two new thiosulfates formed with mono- and diprotonated species of 1-methylpiperazine is reported.

A unique phase transition, twinning and ferroelastic domain structure in [NH3(CH2)2NH3]2[ZnBr4]Br2 is found. The new additional domain structure is observed at the phase transition on heating, which is preserved after cooling to room temperature.

The structures of nine hexa­methyl-[1,1'-bi­phenyl]-4,4'-di­ammonium (HMB) salts are described

Single-crystal growth, differential thermal analysis (DTA), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X-ray structural studies and polarized microscopy observations of bis(ethylenediammonium) tetrabromozincate(II) bromide [NH3(CH2)2NH3]2[ZnBr4]Br2 are presented. A reversible phase transition is described. At room temperature, the complex crystallizes in the monoclinic system. In some cases, the single crystals are twinned into two or more large domains of ferroelastic type with domain walls in the (100) crystallographic plane. DTA and DTG measurements show chemical stability of the crystal up to ∼538 K. In the DSC studies, a reversible isostructural phase transition was revealed at ∼526/522 K on heating/cooling run, respectively. Optical observation on the heating run reveals that at the phase transition the plane of twinning (domain wall) does not disappear and additionally the appearance of a new domain structure of ferroelastic type with domain walls in the planes (101), (101), (100) and (001) is observed. The domain structure pattern is preserved after cooling to the room-temperature phase and the symmetry of this phase is unchanged.

In the complex, the ligand binds to the metal through an oxygen atom. The geometry of the seven-coordinate U atom is penta­gonal bipyramidal, with the uranyl O atoms in apical positions.

In the title compound, the tellurium(VI) and vanadium(V) atoms are statistically disordered over two of the ten metal-atom sites in the unprotonated [TeV9O28]5– heteropolyanion.

The crystal structure of the co-crystal salt solvate 1,10-phenanthrolinium violurate violuric acid penta­hydrate features a tri-periodic hydrogen-bonded network with the violurate and violuric acid residues each assembled into tapes and the phenanthrolinium cations residing in channels.

Crystallization of the title compound from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and ortho­rhom­bic (Pna21; β form) space groups. The ReI complex mol­ecules in either polymorph adopt a six-coordinate octa­hedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitro­gen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds.

Crystallization of the title compound, fac-[ReBr(ppt-OMe)(CO)3] (ppt-OMe = C15H12N2OS), from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and orthorhombic (Pna21; β form) space groups. The ReI complex molecules in either polymorph adopt a six-coordinate octahedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitrogen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds. In polymorph α, two types of hydrogen bonds (C—H...O) are found while, in polymorph β, four types of hydrogen bonds (C—H...O and C—H...Br) exist.

The title compound, [RuCl2(C25H22P2)2] or [RuCl2(dppm)2] (dppm = bis­(di­phenyl­phosphan­yl)methane, C25H22P2) crystallizes as two half-mol­ecules (completed by inversion symmetry) in space group Poverline{1} (Z = 2), with the RuII atoms occupying inversion centers at 0,0,0 and 1/2, 1/2, 1/2, respectively. The bidentate phosphane ligands occupy equatorial positions while the chlorido ligands complete the distorted octa­hedral coordination spheres at axial positions. The bite angles of the phosphane chelates are similar for the two mol­ecules [(P—Ru—P)avg. = 71.1°], while there are significant differences in the twisting of the methyl­ene backbone, with a distance of the methyl­ene C atom from the RuP4 plane of 0.659 (2) and 0.299 (3) Å, respectively, and also for the phenyl substituents for both mol­ecules due to variations in weak C—H⋯Cl inter­actions.

A new square-planar palladium complex salt hydrate, (C9H12NO)2[PdCl4]·0.5H2O, has been characterized. The asymmetric unit of the complex salt comprises two [PdCl4]2− dianions, four 2-hy­droxy-2,3-di­hydro-1H-inden-1-aminium cations, each derived from (1R,2S)-(+)-1-amino­indan-2-ol, and one water mol­ecule of crystallization. In the crystal, a two-dimensional layer parallel to (001) features a number of O—H⋯O, N—H⋯O, O—H⋯Cl and N—H⋯Cl hydrogen bonds.

In the title complex, [Ru(C10H8N2)2(C6H6N2O)(H2O)](CF3SO3)2, the central RuII atom is sixfold coordinated by two bidentate 2,2'-bi­pyridine, an isonic­otinamide ligand, and a water mol­ecule in a distorted octa­hedral environment with tri­fluoro­methane­sulfonate ions completing the outer coordination sphere of the complex. Hydrogen bonding involving the water mol­ecule and weak π–π stacking inter­actions between the pyridyl rings in adjacent mol­ecules contribute to the alignment of the complexes in columns parallel to the c axis.

The structure of the title compound, [RuCl2(C7H10N2)2(C2H6OS)2], has monoclinic (P21/n) symmetry. The Ru—N distances of the coordination compound are influenced by the trans chloride or di­methyl­sulfoxide-κS ligands. The mol­ecular structure exhibits disorder for two of the terminal methyl groups of a dimethyl sulfoxide ligand.

The title compound, [Ru(C19H13N5)2](PF6)2·3C4H10O, was obtained from the reaction of Ru(bimpy)Cl3 [bimpy is 2,6-bis­(1H-benzimidazol-2-yl)pyridine] and bimpy in refluxing ethanol followed by recrystallization from diethyl ether/aceto­nitrile. At 125 K the complex has ortho­rhom­bic (Pca21) symmetry. It is remarkable that the structure is almost centrosymmetric. However, refinement in space group Pbcn leads to disorder and definitely worse results. It is of inter­est with respect to potential catalytic reduction of CO2. The structure displays N—H⋯O, N—H⋯F hydrogen bonding and significant π–π stacking and C—H⋯π stacking inter­actions.

In the title compound, {(C6H8N)[Zn2(HPO3)2(H2PO3)]}n, the constituent ZnO4, HPO3 and H2PO3 polyhedra of the inorganic component are linked into (010) sheets by Zn—O—P bonds (mean angle = 134.4°) and the layers are reinforced by O—H⋯O hydrogen bonds. The protonated templates are anchored to the inorganic sheets via bifurcated N—H⋯(O,O) hydrogen bonds.

In the title salt, (C8H20N)8[Mo10O34], the [Mo10O34]8− polyanion is located about an inversion centre and can be considered as a β-type octa­molybdate anion to which two additional MoO4 tetra­hedra are linked via common corners. The [Mo10O34]8− polyanions are packed in rows extending parallel to [001] and are connected to the di­butyl­ammonium counter-cations through N—H⋯O hydrogen-bonding inter­actions.

The inter­action between 8-hy­droxy­quinoline (8HQ, C9H7NO) and naphthalene-1,5-di­sulfonic acid (H2NDS, C10H8O6S2) in aqueous media results in the formation of the salt hydrate bis­(8-hy­droxy­quinolinium) naphthalene-1,5-di­sulfonate tetra­hydrate, 2C9H8NO+·C10H6O6S22−·4H2O. The asymmetric unit comprises one protonated 8HQ+ cation, half of an NDS2– dianion symmetrically disposed around a center of inversion, and two water mol­ecules. Within the crystal structure, these components are organized into chains along the [010] and [10overline{1}] directions through O—H⋯O and N—H⋯O hydrogen-bonding inter­actions, forming a di-periodic network parallel to (101). Additional stabilizing inter­actions such as C—H⋯O, C—H⋯π, and π–π inter­actions extend this arrangement into a tri-periodic network structure

The title compound, [RuGa2Cl6(C7H8)(CO)2] or [(CO)2(GaCl2)(η6-toluene)Ru]+[GaCl4]−, was isolated from the reaction of Ga2Cl4 with di­phenyl­silanediol in toluene, followed by the addition of Ru3(CO)12. The compound contains a ruthenium–gallium metal–metal bond with a length of 2.4575 (2) Å.

The title compound, (C2H10N2)2[(C10H12N2O8)(MoO3)2]·4H2O, which crystallizes in the monoclinic C2/c space group, was obtained by mixing molybdenum oxide, ethyl­enedi­amine and ethyl­enedi­amine­tetra­acetic acid (H4edta) in a 2:4:1 ratio. The complex anion contains two MoO3 units bridged by an edta4− anion. The midpoint of the central C—C bond of the edta4− anion is located on a crystallographic inversion centre. The independent Mo atom is tridentately coordin­ated by a nitro­gen atom and two carboxyl­ate groups of the edta4− ligand, together with the three oxo ligands, producing a distorted octa­hedral coordination environment. In the three-dimensional supra­molecular crystal structure, the dinuclear anions, the organo­ammonium counter-ions and the solvent water mol­ecules are linked by N—H⋯Ow, N—H⋯Oedta and O—H⋯O hydrogen bonds.

The title compound, [Ru(C12H14NO2)Cl(η6-C6H6)], exhibits a half-sandwich tripod stand structure and crystallizes in the ortho­rhom­bic space group P212121. The arene group is η6 π-coordinated to the Ru atom with a centroid-to-metal distance of 1.6590 (5) Å, with the (S)-2-(4-isopropyl-4,5-di­hydro­oxazol-2-yl)phenolate chelate ligand forming a bite angle of 86.88 (19)° through its N and phenolate O atoms. The pseudo-octa­hedral geometry assumed by the complex is completed by a chloride ligand. The coordination of the optically pure bidentate ligand induces metal centered chirality onto the complex with a Flack parameter of −0.056.

Crystals of the title salt, (C8H20N)[Sn(C6H5)3(C2H2O2S)], comprise diisobutyl­ammonium cations and mercapto­acetato­tri­phenyl­stannate(IV) anions. The bidentate binding mode of the mercapto­acetate ligand gives rise to a five-coordinated, ionic tri­phenyl­tin complex with a distorted cis-trigonal–bipyramidal geometry around the tin atom. In the crystal, charge-assisted ammonium-N—H⋯O(carboxyl­ate) hydrogen-bonding connects two cations and two anions into a four-ion aggregate. Two positions were resolved for one of the phenyl rings with the major component having a site occupancy factor of 0.60 (3).

In the title salt [systematic name: 4-(3-carb­oxy-1-ethyl-6-fluoro-4-oxo-1,4-di­hydro­quin­olin-7-yl)piperazin-1-ium nitrate], C16H19FN3O3+·NO3−, proton transfer from nitric acid to the N atom of the piperazine ring of norfloxacin has occurred to form a mol­ecular salt. In the extended structure, N—H⋯O hydrogen bonds link alternating cations and anions into [100] chains, which are reinforced by aromatic π–π stacking inter­actions between the quinoline moieties of the norfloxacinium cations.

In the hydrated title salt, (C10H8NO2)2[SnCl6]·2H2O, the tin(IV) atom is located about a center of inversion. In the crystal structure, the organic cation, the octa­hedral inorganic anion and the water mol­ecule of crystallization inter­act through O—H⋯O, N—H⋯O and O—H⋯Cl hydrogen bonds, supplemented by weak π–π stacking between neighboring cations, and C—Cl⋯π inter­actions.

The title compound (systematic name: pyridinium 4-methyl­benzene­sulfonate), C5H6N+·C7H7O3S−, is the pyridinium salt of para-toluene­sulfonic acid. In the crystal, classical N—H⋯O hydrogen bonds as well as C—H⋯O contacts connect the cationic and anionic entities into sheets lying parallel to the ab plane.

The title compound, [Ru(C12H14NO2)2(C12H8N2)]PF6 crystallizes in the tetra­gonal Sohnke space group P41212. The two bidentate chiral salicyloxazoline ligands and the phenanthroline co-ligand coordinate to the central RuIII atom through N,O and N,N atom pairs to form bite angles of 89.76 (15) and 79.0 (2)°, respectively. The octa­hedral coordination of the bidentate ligands leads to a propeller-like shape, which induces metal-centered chirality onto the complex, with a right-handed (Δ) absolute configuration [the Flack parameter value is −0.003 (14)]. Both the complex cation and the disordered PF6− counter-anion are located on twofold rotation axes. Apart from Coulombic forces, the crystal cohesion is ensured by non-classical C—H⋯O and C—H⋯F inter­actions.

The title compound, C14H20NO5+·Cl−, was prepared as a racemate of R,R- and S,S-enanti­omers by reduction of the corresponding hy­droxy­imino­ketone. In the crystal, layers are formed via hydrogen bridges of four ammonium groups to chloride ions; these lamellae are connected via inter­digitated benzoic ester groups.

The structures of five ammonium salt forms of mono­sulfonated azo dyes, derivatives of 4-(2-phenyldiazen-1-yl)benzenesulfonate, with the general formula [NH4][O3S(C6H4)NN(C6H3)RR']·XH2O [R = OH, NH2 or N(C2H4OH)2; R' = H or OH] are presented. All form simple layered structures with alternating hydro­phobic (organic) and hydro­philic (cation, solvent and polar groups) layers. To assess for isostructural behaviour of the ammonium cation with M+ ions, the packing of these structures is compared with literature examples. To aid this comparison, the corresponding structures of four potassium salt forms of the mono­sulfonated azo dyes are also presented herein. Of the five ammonium salts it is found that three have isostructural equivalents. In two cases this equivalent is a potassium salt form and in one case it is a rubidium salt form. The isostructurality of ion packing and of unit-cell symmetry and dimensions tolerates cases where the ammonium ions form somewhat different inter­action types with coformer species than do the potassium or rubidium ions. No sodium salt forms are found to be isostructural with any ammonium equivalent. However, similarities in the anion packing within a single hydro­phobic layer are found for a group that consists of the ammonium and rubidium salt forms of one azo anion species and the sodium and silver salt forms of a different azo species.

The salt ammonium 2-am­ino­mal­on­ate (systematic name: ammonium 2-aza­niumyl­propane­dioate), NH4+·C3H4NO4−, was synthesized in diethyl ether from the starting materials malonic acid, ammonia and bromine. The salt was recrystallized from water as colourless blocks. In the solid state, intra­molecular medium–strong N—H⋯O, weak C—H⋯O and weak C—H⋯N hydrogen bonds build a three-dimensional network.

The reaction of titanium(IV) chloride with sodium hexa­fluoro­iso­pro­pox­ide, carried out in hexa­fluoro­iso­propanol, produces titanium(IV) hexa­fluoro­iso­pro­pox­ide, which is a liquid at room temperature. Recrystallization from coordinating solvents, such as aceto­nitrile or tetra­hydro­furan, results in the formation of bis-solvate com­plexes. These com­pounds are of inter­est as possible Ziegler–Natta polymerization catalysts. The aceto­nitrile com­plex had been structurally characterized previously and adopts a distorted octahedral structure in which the nitrile ligands adopt a cis configuration, with nitro­gen lone pairs coordinated to the metal. The low-melting tetra­hydro­furan com­plex has not provided crystals suitable for single-crystal X-ray analysis. However, the structure of chlorido­tris­(hexa­fluoro­isopropoxido-κO)bis­(tetra­hydro­furan-κO)titanium(IV), [Ti(C3HF6O)3Cl(C4H8O)2], has been obtained and adopts a distorted octa­hedral coordination geometry, with a facial arrangement of the alkoxide ligands and adjacent tetra­hydro­furan ligands, coordinated by way of metal–oxygen polar coordinate inter­actions.

Lanthanide ions have ideal chemical properties for catalysis, such as hard Lewis acidity, fast ligand-exchange kinetics, high coordination-number preferences and low geometric requirements for coordination. As a result, many small-molecule lanthanide catalysts have been described in the literature. Yet, despite the ability of enzymes to catalyse highly stereoselective reactions under gentle conditions, very few lanthanoenzymes have been investigated. In this work, the mononuclear binding of europium(III) and gadolinium(III) to the active site of a mutant of the model enzyme phosphotriesterase are described using X-ray crystallography at 1.78 and 1.61 Å resolution, respectively. It is also shown that despite coordinating a single non-natural metal cation, the PTE-R18 mutant is still able to maintain esterase activity.

Metal-based complexes with their unique chemical properties, including multiple oxidation states, radio-nuclear capabilities and various coordination geometries yield value as potential pharmaceuticals. Understanding the interactions between metals and biological systems will prove key for site-specific coordination of new metal-based lead compounds. This study merges the concepts of target coordination with fragment-based drug methodologies, supported by varying the anomalous scattering of rhenium along with infrared spectroscopy, and has identified rhenium metal sites bound covalently with two amino acid types within the model protein. A time-based series of lysozyme-rhenium-imidazole (HEWL-Re-Imi) crystals was analysed systematically over a span of 38 weeks. The main rhenium covalent coordination is observed at His15, Asp101 and Asp119. Weak (i.e. noncovalent) interactions are observed at other aspartic, asparagine, proline, tyrosine and tryptophan side chains. Detailed bond distance comparisons, including precision estimates, are reported, utilizing the diffraction precision index supplemented with small-molecule data from the Cambridge Structural Database. Key findings include changes in the protein structure induced at the rhenium metal binding site, not observed in similar metal-free structures. The binding sites are typically found along the solvent-channel-accessible protein surface. The three primary covalent metal binding sites are consistent throughout the time series, whereas binding to neighbouring amino acid residues changes through the time series. Co-crystallization was used, consistently yielding crystals four days after setup. After crystal formation, soaking of the compound into the crystal over 38 weeks is continued and explains these structural adjustments. It is the covalent bond stability at the three sites, their proximity to the solvent channel and the movement of residues to accommodate the metal that are important, and may prove useful for future radiopharmaceutical development including target modification.

At room temperature, the title salt, C7H10NO+·Cl−, is ortho­rhom­bic, space group Pbca with Z' = 1, as previously reported [Zhao (2009). Acta Cryst. E65, o2378]. Between 250 and 200 K, there is a solid-state phase transition to a twinned monoclinic P21/c structure with Z' = 2. We report the high temperature structure at 250 K and the low-temperature structure at 100 K. In the low-temperature structure, the –NH3 hydrogen atoms are ordered and this group has a different orientation in each independent mol­ecule, in keeping with optimizing N—H⋯Cl hydrogen bonding, some of which are bifurcated: these hydrogen bonds have N⋯Cl distances in the range 3.1201 (8)–3.4047 (8) Å. In the single cation of the high-temperature structure, the NH hydrogen atoms are disordered into the average of the two low-temperature positions and the N⋯Cl hydrogen bond distances are in the range 3.1570 (15)–3.3323 (18) Å. At both temperatures, the meth­oxy group is nearly coplanar with the rest of the mol­ecule, with the C—C—O—C torsion angles being −7.0 (2)° at 250 K and −6.94 (12) and −9.35 (12)° at 100 K. In the extended ortho­rhom­bic structure, (001) hydrogen-bonded sheets occur; in the monoclinic structure, the sheets propagate in the (010) plane.

Syntheses of the acyclic amidinium salts, morpholino­formamidinium hexa­fluorido­phosphate [OC4H8N—CH=NH2]PF6 or C5H11N2O+·PF6−, 1, and pyrrolidinoformamidinium hexa­fluorido­phosphate [C4H8N—CH= NH2]PF6 or C5H11N2+·PF6−, 2, were carried out by heating either morpholine or pyrrolidine with triethyl orthoformate and ammonium hexa­fluorido­phosphate. Crystals of 1 obtained directly from the reaction mixture contain one cation and one anion in the asymmetric unit. The structure involves cations linked in chains parallel to the b axis by N—H⋯O hydrogen bonds in space group Pbca, with glide-related chains pointing in opposite directions. Crystals of 1 obtained by recrystallization from ethanol, however, showed a similar unit cell and the same basic structure, but unexpectedly, there was positional disorder [occupancy ratio 0.639 (4):0.361 (4)] in one of the cation chains, which lowered the crystal symmetry to the non-centrosymmetric space group Pca21, with two cations and anions in the asymmetric unit. In the pyrrolidino compound, 2, cations and anions are ordered and are stacked separately, with zigzag N—H⋯F hydrogen-bonding between stacks, forming ribbons parallel to (101), extended along the b-axis direction. Slight differences in the delocalized C=N distances between the two cations may reflect the inductive effect of the oxygen atom in the morpholino compound.

The title compound, (C4H12N)[V(C12H8N4O2)O2]·H2O, was synthesized via aerial oxidation on refluxing picolinohydrazide with ethyl picolinate followed by addition of VIVO(acac)2 and di­ethyl­amine in methanol. It crystallizes in the triclinic crystal system in space group Poverline{1}. In the complex anion, the dioxidovanadium(V) moiety exhibits a distorted square-pyramidal geometry. In the crystal, extensive hydrogen bonding links the water mol­ecule to two complex anions and one di­ethyl­ammonium ion. One of the CH2 groups in the di­ethyl­amine is disordered over two sets of sites in a 0.7:0.3 ratio.

The crystal structure of the tetra­ethyl­ammonium salt of the non-steroidal anti-inflammatory drug nimesulide (polymorph II) (systematic name: tetra­ethyl­ammonium N-methane­sulfonyl-4-nitro-2-phen­oxy­anilinide), C8H20N+·C13H11N2O5S−, was determined using single-crystal X-ray diffraction. The title compound crystallizes in the monoclinic space group P21/c with one tetra­ethyl­ammonium cation and one nimesulide anion in the asymmetric unit. In the crystal, the ions are linked by C—H⋯N and C—H⋯O hydrogen bonds and C—H⋯π inter­actions. There are differences in the geometry of both the nimesulide anion and the tetra­ethyl­ammonium cation in polymorphs I [Rybczyńska & Sikorski (2023). Sci. Rep. 13, 17268] and II of the title compound.

The structures of fourteen halochalcogenyl­phospho­nium tetra­halogen­ido­aurates(III), phosphane chalcogenide derivatives with general formula [R13–nR2nPEX][AuX4] (R1 = t-butyl; R2 = isopropyl; n = 0 to 3; E = S or Se; X = Cl or Br) are presented. The eight possible chlorido derivatives are: 17a, n = 3, E = S; 18a, n = 2, E = S; 19a, n = 1, E = S; 20a, n = 0, E = S; 21a, n = 3, E = Se; 22a, n = 2, E = Se; 23a, n = 1, E = Se; and 24a, n = 0, E = Se, and the corresponding bromido derivatives are 17b–24b in the same order. Structures were obtained for all compounds except for the tri-t-butyl derivatives 24a and 24b. Isotypy is observed for 18a/18b/22a/22b, 19a/23a, 17b/21b and 19b/23b. In eleven of the compounds, X⋯X contacts (mostly very short) are observed between the cation and anion, whereby the E—X⋯X groups are approximately linear and the X⋯X—Au angles approximately 90°. The exceptions are 17a, 19a and 23a, which instead display short E⋯X contacts. Bond lengths in the cations correspond to single bonds P—E and E—X. For each group with constant E and X, the P—E—X bond-angle values increase monotonically with the steric bulk of the alkyl groups. The packing is analysed in terms of E⋯X, X⋯X (some between anions alone), H⋯X and H⋯Au contacts. Even for isotypic compounds, some significant differences can be discerned.

Two 2,4,6-tri­methyl­aniline-based trifuloro­methane­sulfonate (tri­fluoro­methane­sulfonate) salts were synthesized and characterized by single-crystal X-ray diffraction. N,2,4,6-Tetra­methyl­anilinium tri­fluoro­methane­sulfonate, [C10H14NH2+][CF3O3S−] (1), was synthesized via methyl­ation of 2,4,6-tri­methyl­aniline. N-Iso­propyl­idene-N,2,4,6-tetra­methyl­anilinium tri­fluoro­meth­ane­sulfonate, [C13H20N+][CF3O3S−] (2), was synthesized in a two-step reaction where the imine, N-iso­propyl­idene-2,4,6-tri­methyl­aniline, was first prepared via a dehydration reaction to form the Schiff base, followed by methyl­ation using methyl tri­fluoro­methane­sulfonate to form the iminium ion. In compound 1, both hydrogen bonding and π–π inter­actions form the main inter­molecular inter­actions. The primary inter­action is a strong N—H⋯O hydrogen bond with the oxygen atoms of the tri­fluoro­methane­sulfonate anions bonded to the hydrogen atoms of the ammonium nitro­gen atom to generate a one-dimensional chain. The [C10H14NH2+] cations form dimers where the benzene rings form a π–π inter­action with a parallel-displaced geometry. The separation distance between the calculated centroids of the benzene rings is 3.9129 (8) Å, and the inter­planar spacing and ring slippage between the dimers are 3.5156 (5) and 1.718 Å, respectively. For 2, the [C13H20N+] cations also form dimers as in 1, but with the benzene rings highly slipped. The distance between the calculated centroids of the benzene rings is 4.8937 (8) Å, and inter­planar spacing and ring slippage are 3.3646 (5) and 3.553 Å, respectively. The major inter­molecular inter­actions in 2 are instead a series of weaker C—H⋯O hydrogen bonds [C⋯O distances of 3.1723 (17), 3.3789 (18), and 3.3789 (18) Å], an inter­action virtually absent in the structure of 1. Fluorine atoms are not involved in strong directional inter­actions in either structure.

The few examples of structures containing the 2-chloro-N,N-di­methyl­ethan-1-aminium or 3-chloro-N,N-di­methyl­propan-1-aminium cations show a compet­ition between gauche and anti conformations for the chloro­alkyl chain. To explore further the conformational landscape of these cations, and their possible use as mol­ecular switches, the title salts, (C4H11ClN)2[CoCl4] and (C4H11ClN)2[ZnCl4], were prepared and structurally characterized. Details of both structures are in close agreement. The inorganic complex exhibits a slightly flattened tetra­hedral geometry that likely arises from bifurcated N—H hydrogen bonds from the organic cations. The alkyl chain of the cation is disordered between gauche and anti conformations with the gauche conformation occupancy refined to 0.707 (2) for the cobaltate. The gauche conformation places the terminal Cl atom at a tetra­hedral face of the inorganic complex with a contact distance of 3.7576 (9) Å to the Co2+ center. The anti conformation places the terminal Cl atom at a contact distance to a neighboring anti conformation terminal Cl atom that is ∼1 Å less than the sum of the van der Waals radii. Thus, if the anti conformation is present at a site, then the nearest neighbor must be gauche. DFT geometry optimizations indicate the gauche conformation is more stable in vacuo by 0.226 eV, which reduces to 0.0584 eV when calculated in a uniform dielectric. DFT geometry optimizations for the unprotonated mol­ecule indicate the anti conformation is stabilized by 0.0428 eV in vacuo, with no strongly preferred conformation in uniform dielectric, to provide support to the notion that this cation could function as a mol­ecular switch via deprotonation.

4,4'-(Disulfanedi­yl)dipyridinium chloride triiodide, C10H10N2S22+·Cl−·I3−, (1) was synthesized by reaction of 4,4'-di­pyridyl­disulfide with ICl in a 1:1 molar ratio in di­chloro­methane solution. The structural characterization of 1 by SC-XRD analysis was supported by elemental analysis, FT–IR, and FT–Raman spectroscopic measurements.

The crystal structures of 2-[1'-(carb­oxy­meth­yl)-4,4'-bi­pyridine-1,1'-diium-1-yl]acetate tetra­fluoro­borate, C14H13N2O4+·BF4− or (Hbcbpy)(BF4), and neutral 1,1'-bis­(carboxyl­atometh­yl)-4,4'-bi­pyridine-1,1'-diium (bcbpy), C14H20N2O8, are reported. The asymmetric unit of the (Hbcbpy)(BF4) consists of a Hbcbpy+ monocation, a BF4− anion, and one-half of a water mol­ecule. The BF4− anion is disordered. Two pyridinium rings of the Hbcbpy+ monocation are twisted at a torsion angle of 30.3 (2)° with respect to each other. The Hbcbpy monocation contains a carb­oxy­lic acid group and a deprotonated carboxyl­ate group. Both groups exhibit both a long and a short C—O bond. The cations are linked by inter­molecular hydrogen-bonding inter­actions between the carb­oxy­lic acid and the deprotonated carboxyl­ate group to give one-dimensional zigzag chains. The asymmetric unit of the neutral bcbpy consists of one-half of the bcbpy and two water mol­ecules. In contrast to the Hbcbpy+ monocation, the neutral bcbpy mol­ecule contains two pyridinium rings that are coplanar with each other and a carboxyl­ate group with similar C—O bond lengths. The mol­ecules are connected by inter­molecular hydrogen-bonding inter­actions between water mol­ecules and carboxyl­ate groups, forming a three-dimensional hydrogen-bonding network.