e,e-trans-Cyclo­hexane-1,4-carb­oxy­lic acid–hexa­methyl­ene­tetra­mine (1/2)

The asymmetric unit of the title compound, 2C6H12N4·C8H12O4, contains one half-mol­ecule of e,e-trans-cyclo­hexane-1,4-dicarb­oxy­lic acid (the complete molecule being generated by inversion symmetry) and one mol­ecule of hexa­methyl­ene­tetra­mine (HMTA), which are connected by O—H⋯N hydrogen bonds. This forms isolated trimers that pack in a herringbone fashion

The hydrogen-bonding patterns of 3-phenylpropylammonium benzoate and 3-phenylpropylammonium 3-iodobenzoate: generation of chiral crystals from achiral molecules

The crystal structures and hydrogen-bonding patterns of 3-phenyl­propyl­ammonium benzoate, C9H14N+·C7H5O2-, (I), and 3-phenyl­propyl­ammonium 3-iodo­benzoate, C9H14N+·C7H4IO2-, (II), are reported and compared. The addition of the I atom on the anion in (II) produces a different hydrogen-bonding pattern to that of (I). In addition, the supra­molecular heterosynthon of (II) produces a chiral crystal packing not observed in (I). Compound (I) packs in a centrosymmetric fashion and forms achiral one-dimensional hydrogen-bonded columns through charge-assisted N-H...O hydrogen bonds. Compound (II) packs in a chiral space group and forms helical one-dimensional hydrogen-bonded columns with 21 symmetry, consisting of repeating R43(10) hydrogen-bonded rings that are commonly observed in ammonium carboxyl­ate salts con­tain­ing chiral mol­ecules. This hydrogen-bond pattern, which has been observed repeatedly in ammonium carboxyl­ate salts, thus provides a means of producing chiral crystal structures from achiral mol­ecules

rac-(rel-1R,2R,4S)-Spiro­[bicyclo­[2.2.1]heptane-2,3′-indol]-2′-amine

In the racemic title compound, C14H16N2, the aromatic ring component of the amino­indoline system occupies the endo cavity of the norbornane component. The aromatic ring lies at an angle of 74.12 (5)° to the plane defined by the four C atoms that comprises the rigid part of the boat-shaped six-membered ring of the norbornane unit. Pairs of mol­ecules assemble in the crystal structure, forming centrosymmetric hydrogen-bonded dimers via pairs of N—H⋯N hydrogen bonds through the syn H atom of the amine group

Phase transitions and structural motifs of inorganic-organic lead halide hybrids

Abstract Layered inorganic-organic hybrid compounds have been widely studied as new potential sources of semiconductors and other optical devices. They simulate natural quantum well materials, where the inorganic part acts as semiconductors, separated by an organic part. This class of hybrid materials has no covalent bonds between the inorganic and organic parts; instead, weak hydrogen bonds and van der Waals forces bind and stabilise the overall structure. The inorganic part is made up of layers of corner-sharing metal halide octahedra, MX6, where the metal must be in a divalent state and the halides are Cl, Br or I. The 2-D layers extend infinitely in two directions and are separated themselves by layers of primary ammonium cations, with only one ammonium group at one end of the chain, [(R-NH3)2MX4], or two ammonium groups at either of the chain, [(H3N-R-NH3)MX4]. Due to its similarity to the cubic perovskite structure, this inorganic motif is referred to as "layered perovskite-type". Depending on the choice of the organic ammonium cation, the materials can display phase transitions and / or have optical and electronic properties. Various investigations of inorganic-organic hybrids have concentrated on the phase transitions of the hybrids of general formula [(CnH2n+1NH3)2MX4] and [(NH3CnH2nNH3)MX4] (n = 1-18; X = Cl, Br, I; M = Cu2+, Mn2+, Cd2+) to elucidate their mechanism. There are two types of displasive transitions, a minor one were small conformational changes within the alkylammonium chain occurs, and a major one, when the entire alkylammonium chain becomes disordered along its long axis. The interlayer spacing between the inorganic layers increases with temperature and during the major phase transition. The methods used to identify the temperatures and the enthalpies of the phase transitions are Differential Scanning Calorimetry (DSC); and Single Crystal X-ray Diffraction (SC-XRD) as well as Powder X-Ray Diffraction (P-XRD) to follow the structural changes. In contrast, only a few reports on investigations of the lead iodide hybrids, [(CnH2n+1NH3)2PbI4] were found in the literature, with only two single crystal structures previously reported. Due to the difficulty in growing good quality crystals, the previous studies on the lead iodide hybrids have been only researched using DSC and P-XRD. The phase transition behaviour has been found to show the same trends as the previous hybrids. The primary aim of this study was to follow the same phase transitions via SC-XRD, ideally single-crystal to single-crystal, and to determine the detailed structural changes with the hopes of elucidating their detailed phase transition mechanism. A secondary aim was to synthesize as many inorganic-organic hybrids as possible using a variety of primary ammonium cations to find different inorganic motifs apart from the layered perovskite-type. Other inorganic motifs can have purely corner-, edge or face-sharing octahedra or combinations thereof to give 2-D net-type networks or 1-D extended chains. The effect that the identity of the ammonium cation has on the type of inorganic motif and the effect on the detailed structural geometry within the inorganic motif are investigated. Examples of structural geometries within the layered perovskite-type inorganic motif that can differ from compound to compound are the relative positions of the inorganic and organic moieties; the N---H….X hydrogen bonding geometry between the halides and the ammonium group; and the relative positions of successive inorganic layers

N′-Cyclo­dodecyl­idene­pyridine-4-carbohydrazide

The title compound, C18H27N3O, is a derivative of the anti­tuberculosis drug isoniazid (systematic name: pyridine-4-carbohydrazidei). The crystal structure consists of repeating C(4) chains along the b axis, formed by N—H⋯O hydrogen bonds with adjacent amide functional groups that are related by a b-glide plane. The cyclo­dodecyl ring has the same approximately ‘square’ conformation, as seen in the parent hydro­carbon cyclo­dodecane

Redetermination of the salt hexa­methyl­ene­tetra­minium fumarate

The crystal structure of the title compound [systematic name: 3,5,7-triaza-1-azoniatricyclo­[3.3.1.13,7]decane (E)-3-carb­oxy­prop-2-enoate], C6H13N4 +·C4H3O4 −, had been determined previously by Bowes et al. [Acta Cryst. (2003), B59, 100–117]. Their structure contained an approximately 3:1 ratio of fumarate and succinate monoanions disordered over the same position. The succinate anion component forms a similar structural role to the fumarate anion and came about due to an impurity in the starting material, fumaric acid. In this work, the crystal structure of the pure salt is presented, which is identical, apart from the lack of disorder of the anions, to the previous structure. In the crystal, the ions assemble in the solid state, forming chains via N+—H⋯O− and O—H⋯O− hydrogen bonds, which are linked into a three-dimensional network by C—H⋯O inter­actions

Form II of adipic acid–nicotinohydrazide (1/2)

The crystal structure of the title co-crystal, 2C6H7N3O·C6H10O4, is a second polymorph, designated form II, of the co-crystal formed between the two mol­ecules [Lemmerer et al. (2011 ▶). CrystEngComm, 13, 55–59]. The asymmetric unit comprises one mol­ecule of nicotinic acid hydrazide, and one half-mol­ecule of adipic acid (the entire mol­ecule is completed by the application of a centre of inversion). In the crystal, mol­ecules assemble into a three-dimensional network of hydrogen bonds, formed by three N—H⋯O hydrogen bonds and one O—H⋯N hydrogen bond. The O—H⋯N hydrogen bond formed between the carboxyl group and the pyridine ring is supported by a C—H⋯O hydrogen bond

Bis(2-methyl-4-nitro­anilinium) tetra­chloridomercurate(II)

The title compound, (C7H9N2O2)2[HgCl4], self-assembles into cationic organic bilayers containing the 2-methyl-4-nitro­anilinium cations, sandwiched between anionic inorganic layers built up by the distorted tetra­hedral [HgCl4]2− groups. The organic sheets are inter­linked through weak C—H⋯O hydrogen bonds, while they inter­act with the anionic part via strong charge-assisted N+—H⋯Cl—Hg hydrogen bonds. The [HgCl4]2− anions are bis­ected by a mirror plane passing through the metal and two of the chloride ions

Benzoic acid–3,4-bis­[(pyridin-3-ylmeth­yl)amino]­cyclo­but-3-ene-1,2-dione (1/2)

In the title co-crystal, C16H14N4O2·2C7H6O2, the 3,4-bis­[(pyridin-3-ylmeth­yl)amino]­cyclo­but-3-ene-1,2-dione squareamide mol­ecules assemble into chains along the b axis via N—H⋯O hydrogen bonds. The benzoic acid mol­ecules then hydrogen bond to the pyridine rings via O—H⋯N hydrogen bonds, supported by weaker C—H⋯O hydrogen bonds, forming extended ribbons. The asymmetric unit consists of a half squareamide mol­ecule, sitting on a special position around a twofold axis, and one benzoic acid mol­ecule on a general position

3-Bromo­pyridin-2-amine

In the crystal structure of the title compound, C5H5BrN2, mol­ecules assemble via pairs of N—H⋯N hydrogen bonds into inversion dimers using only the syn H atom on the amine group. These dimers then assemble further into two-dimensional layers via type I C—Br⋯Br [Br⋯Br = 3.693 (s6) Å] halogen bonding along the (102) plane