Crystal structures of two polymorphic forms of DOTAM‐mono‐acid dihydrate

The structural chemistry of 2‐[4,7,10‐tris(carbamoylmethyl)‐1,4,7,10‐tetraazacyclododecan‐1‐yl]acetic acid dihydrate, C₁₆H₃₁N₇O₅·2H₂O, is described. The macrocyclic compound, also known by the abbreviation DOTAM‐mono‐acid, crystallized at room temperature and was isolated concomitantly as two polymorphic forms. The structures of both polymorphs were determined at 90 K. The first polymorph crystallized as a zwitterionic dihydrate [systematic name: 4,7,10‐tris(carbamoylmethyl)‐1‐(carboxylatomethyl)‐1,4,7,10‐tetraazacyclododecan‐1‐ium dihydrate] in the space group P2₁/n, with Z′ = 1. The second polymorph crystallized as a zwitterionic dihydrate in the space group P2₁ at 90 K, with Z′ = 2. The two independent molecules are related by a local center. In each polymorph, the zwitterion is formed between the negatively‐charged carboxylate group and the ring N atom that bears the acetate pendant arm. Extensive inter‐ and intramolecular hydrogen bonding exists in both polymorphic structures. In polymorph 1, an intermolecular hydrogen‐bonding network propagating parallel to the a direction creates an infinite chain. A second hydrogen‐bonding network is observed through a water molecule of hydration in the b direction. Polymorph 2 also has two intermolecular hydrogen‐bonding networks. One propagates parallel to the a direction, while the other propagates in the [10] direction. Increasing the temperature of polymorph 2 yields the same structure at T = 180 K, but the pseudocenter becomes exact at 299 K. The higher‐temperature structure has Z′ = 1 in the space group P2₁/c.     

2,2,2‐Trinitroethanol

2,2,2‐Trinitroethanol, C₂H₃N₃O₇, at 100 (2) K has Z′ = 2 in the space group P2₁/c. The structure displays intramolecular O—H...O hydrogen bonds, as well as intermolecular O—H...O and C—H...O hydrogen bonding; the O—H...O hydrogen bonds, forming R₄⁴(8) rings, and dipolar nitro–nitro interactions account for the high density of 1.839 Mg m⁻³.     

A comparative study of two polymorphs of bis(1‐hydroxy‐2‐methylpropan‐2‐aminium) carbonate

Alkanolamines have been known for their high CO₂ absorption for over 60 years and are used widely in the natural gas industry for reversible CO₂ capture. In an attempt to crystallize a salt of (RS)‐2‐(3‐benzoylphenyl)propionic acid with 2‐amino‐2‐methylpropan‐1‐ol, we obtained instead a polymorph (denoted polymorph II) of bis(1‐hydroxy‐2‐methylpropan‐2‐aminium) carbonate, 2C₄H₁₂NO⁺·CO₃²⁻, (I), suggesting that the amine group of the former compound captured CO₂ from the atmosphere forming the aminium carbonate salt. This new polymorph was characterized by single‐crystal X‐ray diffraction analysis at low temperature (100 K). The salt crystallizes in the monoclinic system (space group C2/c, Z = 4), while a previously reported form of the same salt (denoted polymorph I) crystallizes in the triclinic system (space group P, Z = 2) [Barzagli et al. (2012). ChemSusChem, 5 , 1724–1731]. The asymmetric unit of polymorph II contains one 1‐hydroxy‐2‐methylpropan‐2‐aminium cation and half a carbonate anion, located on a twofold axis, while the asymmetric unit of polymorph I contains two cations and one anion. These polymorphs exhibit similar structural features in their three‐dimensional packing. Indeed, similar layers of an alternating cation–anion–cation neutral structure are observed in their molecular arrangements. Within each layer, carbonate anions and 1‐hydroxy‐2‐methylpropan‐2‐aminium cations form planes bound to each other through N—H…O and O—H…O hydrogen bonds. In both polymorphs, the layers are linked to each other via van der Waals interactions and C—H…O contacts. In polymorph II, a highly directional C—H…O contact (C—H…O = 156°) shows as a hydrogen‐bonding interaction. Periodic theoretical density functional theory (DFT) calculations indicate that both polymorphs present very similar stabilities.     

The low‐temperature phase transition of 9‐methylfluoren‐9‐ol: comparison of the crystal structures at 100 and 200 K

Crystals of 9‐methyl­fluoren‐9‐ol, C₁₄H₁₂O, undergo a reversible phase transition at 176 (2) K. The structure of the high‐temperature α form at 200 K is compared with that of the low‐temperature β form at 100 K. Both polymorphs crystallize in space group P with Z = 4 and contain discrete hydrogen‐bonded R(8) ring tetramers arranged around crystallographic inversion centres. The most obvious changes observed on cooling the crystals to below 176 K are an abrupt increase of ca 0.5 Å in the shortest lattice translation, and a thermal transition with ΔH = 1 kJ mol^?1.     

Methyl (±)‐1‐ethyl‐2‐hydroxy‐4‐(4‐methoxybenzoyl)‐5‐(4‐methoxyphenyl)‐3‐oxo‐2,3‐di­hydro‐1H‐pyrrole‐2‐acetate

The title compound, C₂₄H₂₅NO₇, is a racemic mixture of 2,3‐di­hydro‐1H‐pyrrol‐3‐ones. It crystallizes in the triclinic system, space group P1, with Z = 2. The asymmetric unit contains two enantiomorphic mol­ecules and the structure is stabilized by hydrogen‐bond contacts.     

A new polymorph of 2‐methyl‐6‐nitroaniline

A new crystal form of 2‐methyl‐6‐nitroaniline, C₇H₈N₂O₂, crystallizing with Z′ = 2 in the space group P2₁/c, has been identified during screening for salts and cocrystals. The different N—H...O hydrogen‐bonding synthons result in linear V‐shaped chains in the new polymorph, rather than the helical chain arrangement seen in the known form where Z′ = 1. The presence of a second component during crystallization appears to have determined the resultant crystal form of 2‐methyl‐6‐nitroaniline.     

Pentane‐1,5‐diaminium dibromide

The crystal structure of the title salt, C₅H₁₆N₂²⁺·2Br⁻, with Z = 12 and more unusually Z′ = 3, forms part of a small group of crystal structures in the Cambridge Structural Database that are ammonium bromide salts. One of the diaminium cation chains in the asymmetric unit exhibits positional disorder, which was modelled using a suitable disorder model. This compound also exhibits organic–inorganic layering in its packing arrangement that is typical of this class of compound. An extensive complex three‐dimensional hydrogen‐bonding network is also identified. The hydrogen bonds evident in this crystal structure were identified as being most likely strong charge‐assisted hydrogen bonds.     

Three new quinuclidine‐based structures: second harmonic generation response for 1,2‐bis(1‐azoniabicyclo[2.2.2]octan‐3‐ylidene)hydrazine dichloride

The crystal structures of three quinuclidine‐based compounds, namely (1‐azabicyclo[2.2.2]octan‐3‐ylidene)hydrazine monohydrate, C₇H₁₃N₃·H₂O ( 1 ), 1,2‐bis(1‐azabicyclo[2.2.2]octan‐3‐ylidene)hydrazine, C₁₄H₂₂N₄ ( 2 ), and 1,2‐bis(1‐azoniabicyclo[2.2.2]octan‐3‐ylidene)hydrazine dichloride, C₁₄H₂₄N₄²⁺·2Cl^? ( 3 ), are reported. In the crystal structure of 1 , the quinuclidine‐substituted hydrazine and water molecules are linked through N—H…O and O—H…N hydrogen bonds, forming a two‐dimensional array. The compound crystallizes in the centrosymmetric space group P2₁/c. Compound 2 was refined in the space group Pccn and exhibits no hydrogen bonding. However, its hydrochloride form 3 crystallizes in the noncentrosymmetric space group Pc. It shows a three‐dimensional network structure via intermolecular hydrogen bonding (N—H…C and N/C—H…Cl). Compound 3 , with its acentric structure, shows strong second harmonic activity.     

Reversible phase transition of 2‐carboxypyridinium perchlorate–pyridinium‐2‐carboxylate (1/1)

The title salt, C₆H₆NO₂⁺·ClO₄⁻·C₆H₅NO₂, was crystallized from an aqueous solution of equimolar quantities of perchloric acid and pyridine‐2‐carboxylic acid. Differential scanning calorimetry (DSC) measurements show that the compound undergoes a reversible phase transition at about 261.7 K, with a wide heat hysteresis of 21.9 K. The lower‐temperature polymorph (denoted LT; T = 223 K) crystallizes in the space group C2/c, while the higher‐temperature polymorph (denoted RT; T = 296 K) crystallizes in the space group P2/c. The relationship between these two phases can be described as: 2a_RT = a_LT; 2b_RT = b_LT; c_RT = c_LT. The crystal structure contains an infinite zigzag hydrogen‐bonded chain network of 2‐carboxypyridinium cations. The most distinct difference between the higher (RT) and lower (LT) temperature phases is the change in dihedral angle between the planes of the carboxylic acid group and the pyridinium ring, which leads to the formation of different ten‐membered hydrogen‐bonded rings. In the RT phase, both the perchlorate anions and the hydrogen‐bonded H atom within the carboxylic acid group are disordered. The disordered H atom is located on a twofold rotation axis. In the LT phase, the asymmetric unit is composed of two 2‐carboxypyridinium cations, half an ordered perchlorate anion with ideal tetrahedral geometry and a disordered perchlorate anion. The phase transition is attributable to the order–disorder transition of half of the perchlorate anions.     

2,5‐O‐Methyl­ene‐d‐mannitol: two polymorphs and the NaI complex

Two polymorphs of the title compound, (4R,5R,6R,7R)‐4,7‐bis­(hydroxy­methyl)‐1,3‐dioxepane‐5,6‐diol, C₇H₁₄O₆, both have Z′ = 2 at 100 K, and differ in their hydrogen‐bonding patterns. The sodium iodide complex, NaI·C₇H₁₄O₆, is isomorphous with the NaCl complex, and has the mannitol, cation and anion all lying on twofold axes. The dioxepane rings of all three mol­ecules are in the twist‐chair conformation.     

A dimeric layered structure of a 4‐oxo‐4,5‐di­hydro‐1H‐pyrazolo­[3,4‐d]­pyrimidine compound

The title compound, 6‐methyl­sulfanyl‐1‐(3‐phenyl­propyl)‐4,5‐di­hydro‐1H‐pyrazolo­[3,4‐d]­pyrimidin‐4‐one, C₁₅H₁₆N₄OS, crystallizes in space group Pbca, with two mol­ecules of similar structure in the asymmetric unit. The molecular structure shows the absence of intramolecular stacking in the crystalline state, as indicated by earlier ¹H NMR analysis in solution. In addition, the crystal packing reveals the formation of a layered structure, due mainly to intermolecular N—H?O=C hydrogen bonding and arene–arene interactions.     

(S,S)‐4′′‐Cyano‐7,7′′‐dimethoxy‐3′,6′‐dioxodispiro[indane‐2,2′‐piperazine‐5′,2′′‐indane]‐4‐carboxamide methanol solvate: interrupting the amide‐to‐amide hydrogen‐bonded tape

The title methanol solvate, C₂₄H₂₂N₄O₅·CH₃OH, forms an extended three‐dimensional hydrogen‐bonded structure, assisted by the presence of several good donor and acceptor sites. It shows none of the crystal packing features typically expected of piperazinediones, such as amide‐to‐amide R₂²(8) hydrogen bonding. In this structure the methanol solvent appears to play only a space‐filling role; it is not involved in any hydrogen bonding and instead is disordered over several sites. This study reports, to the best of our knowledge, the first crystal structure of an indane‐containing piperazinedione compound which exhibits a three‐dimensional hydrogen‐bonded structure formed by classical (N—H...O and N—H...N) hydrogen‐bonding interactions.     

Crystal structure,thermal behaviour and detonation characterization of bis(4,5‐diamino‐1,2,4‐triazol‐3‐yl)methane monohydrate

Bis(4,5‐diamino‐1,2,4‐triazol‐3‐yl)methane monohydrate (BDATZM·H₂O or C₅H₁₀N₁₀·H₂O) was synthesized and its crystal structure characterized by single‐crystal X‐ray diffraction; it belongs to the space group P (triclinic) with Z = 2. The structure of BDATZM·H₂O can be described as a two‐dimensional ladder plane with extensive hydrogen bonding and no disorder. The thermal behaviour was studied under non‐isothermal conditions by differential scanning calorimetry (DSC) and thermogravimetric/differential thermogravimetric (TG/DTG) methods. The detonation velocity (D) and detonation pressure (P) of BDATZM were estimated using the nitrogen equivalent equation according to the experimental density. A comparison between BDATZM·H₂O and bis(5‐amino‐1,2,4‐triazol‐3‐yl)methane (BATZM) was made to determine the effect of the amino group; the results suggest that the amino group increases the hydrophilicity, space utilization and energy, and decreases the thermal stability and symmetry of the resulting compound.     

Barium chlorite hydrate,Ba(ClO2)2·3.5H2O

The structure of barium chlorite hydrate, Ba(ClO₂)₂·3.5H₂O, has been determined by single‐crystal X‐ray analysis at 150 K. The structure is monoclinic, space group C2/c, with Z = 8. It contains layers of Ba²⁺ cations coordinated by ClO₂⁻ anions and water mol­ecules. There are also solvate water mol­ecules involved only in hydrogen bonding of the layers. Three solvate water O atoms are on sites of twofold symmetry, while all other atoms are in general positions. The full coordination environment of the Ba²⁺ cation consists of ten O atoms belonging to six chlorites and three water mol­ecules, forming a bicapped square antiprism.     

A re‐examination of supra­molecular aggregation in two polymorphs of acetone 2,4‐dinitro­phenyl­hydrazone

The structure of the triclinic polymorph of acetone 2,4‐dinitrophenylhydrazone, C₉H₁₀N₄O₄, has been redetermined from diffraction data collected at 120 (2) K; the mol­ecules are linked by C—H⋯O hydrogen bonds into centrosymmetric R₂²(10) dimers which are themselves linked into a chain by an aromatic π–π stacking inter­action. In the monoclinic polymorph, which crystallizes with Z′ = 2 in the space group P2₁/n, one type of mol­ecule forms dimers exactly as in the triclinic polymorph, while the other forms C(6) chains.     

Wave‐like structure in 3‐(4,6‐diamino‐1,3,5‐triazin‐2‐yl)‐2‐naphthonitrile

In the title compound, C₁₄H₁₀N₆, which crystallizes with Z′ = 2 in the C2/c space group, the molecules are linked by N—H...N hydrogen bonds into chains, which are arranged in a wave‐like form stabilized by aromatic π–π stacking interactions. This work demonstrates the usefulness of aromatic triazine derivatives in crystal engineering.     

(±)‐(2,3,4,4a,5,6,7,8‐Octa­hydro‐2‐oxo­naphthalen‐1‐yl)acetic acid: hydrogen‐bonding pattern of the mono­hydrate of an unsaturated bicyclic γ‐keto acid

In the title compound, C₁₂H₁₆O₃·H₂O, the water of hydration accepts a hydrogen bond from the carboxyl group and donates hydrogen bonds to the carboxyl carbonyl and the ketone groups of two different neighbors, yielding a complex three‐dimensional hydrogen‐bonding array. There are two independent hydrated mol­ecules in the asymmetric unit (Z′ = 2) related by a pseudo‐translation.     

Hydro­gen‐bonded adducts of ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol): monomeric and dimeric 1:1 adducts with 1,2‐bis(4‐pyridyl)­ethane and 1,2‐­diamino­ethane

In ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–4,4′‐ethyl­enedi­pyridine (1/1), [Fe(C₁₈H₁₅O)₂]·C₁₂H₁₂N₂, there is an intra­molecular O—H?O hydrogen bond in the ferrocenediol component and a single O—H?N hydrogen bond linking the two components into a finite monomeric adduct. Ferrocene‐1,1′‐diyl­bis­(di­phenyl­methanol)–ethyl­enedi­amine (1/1), [Fe(C₁₈H₁₅O)₂]·C₂H₈N₂, crystallizes with Z′ = 2 in space group P, and there are two independent four‐component aggregates in the structure, both of which are centrosymmetric. In the first type of aggregate, the molecular components are linked by O—H?N and N—H?O hydrogen bonds, in which both di­amine N atoms participate; in the second type of aggregate, the di­amine component is disordered over two sets of sites, but only one N atom is involved in the hydrogen bonding.     

7‐Methoxy‐1H‐indazole,a new inhibitor of neuronal nitric oxide synthase

The crystal structure of 7‐methoxy‐1H‐indazole, C₈H₈N₂O, an inhibitor of nitric oxide synthase, shows that the methoxy group lies in the plane of the indazole system with its methyl group located trans to the indazole N—H group. The crystal packing consists principally of hydrogen‐bonded trimers. Intermolecular hydrogen‐bonding interactions are formed between the indazole N atoms, with the N—H group as a hydrogen‐bond donor and the remaining N atom as an acceptor.     

4‐Ethynyl‐4‐hydroxycyclohexan‐1‐one and 4‐ethynyl‐4‐hydroxy‐2,3,5,6‐tetramethylcyclohexa‐2,5‐dien‐1‐one

The title compounds, C₈H₁₀O₂, (I), and C₁₂H₁₄O₂, (II), occurred as by‐products in the controlled synthesis of a series of bis­(gem‐alkynols), prepared as part of an extensive study of synthon formation in simple gem‐alkynol derivatives. The two 4‐(gem‐alkynol)‐1‐ones crystallize in space group P2₁/c, (I) with Z′ = 1 and (II) with Z′ = 2. Both structures are dominated by O—H?O=C hydrogen bonds, which form simple chains in the cyclo­hexane derivative, (I), and centrosymmetric dimers, of both symmetry‐independent mol­ecules, in the cyclo­hexa‐2,5‐diene, (II). These strong synthons are further stabilized by C[triple‐bond]C—H?O=C, C_methylene—H?O(H) and C_methyl—H?O(H) interactions. The direct intermolecular interactions between donors and acceptors in the gem‐alkynol group, which characterize the bis­(gem‐alkynol) analogues of (I) and (II), are not present in the ketone derivatives studied here.