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.     

Two polymorphs of bis(2‐bromophenyl) di­sulfide

Colourless crystals of the title compound, bis(2‐bromo­phenyl) di­sulfide, C₁₂H₈Br₂S₂, are obtained from the reaction of 2‐bromo­phenyl­mercaptan with metallic sodium and either zinc chloride or cadmium chloride in methanol. In the presence of Zn^II ions, the crystals are orthorhombic (space group Pbca, with Z′ = 1); with Cd^II ions present, the product is triclinic (space group , with Z′ = 4). Both polymorphs exhibit significant intramolecular C—H⋯S hydrogen bonds. In the ortho­rhombic form, mol­ecules are linked by intermolecular C—H⋯Br hydrogen bonds, while in the triclinic form, mol­ecules exhibit Br⋯Br contacts.     

Two polymorphs of bis(2‐carbamoylguanidinium) fluorophosphonate dihydrate

Two polymorphs of bis(2‐carbamoylguanidinium) fluorophosphonate dihydrate, 2C₂H₇N₄O⁺·FO₃P²⁻·2H₂O, are presented. Polymorph (I), crystallizing in the space group Pnma, is slightly less densely packed than polymorph (II), which crystallizes in Pbca. In (I), the fluorophosphonate anion is situated on a crystallographic mirror plane and the O atom of the water molecule is disordered over two positions, in contrast with its H atoms. The hydrogen‐bond patterns in both polymorphs share similar features. There are O—H...O and N—H...O hydrogen bonds in both structures. The water molecules donate their H atoms to the O atoms of the fluorophosphonates exclusively. The water molecules and the fluorophosphonates participate in the formation of R⁴₄(10) graph‐set motifs. These motifs extend along the a axis in each structure. The water molecules are also acceptors of either one [in (I) and (II)] or two [in (II)] N—H...O hydrogen bonds. The water molecules are significant building elements in the formation of a three‐dimensional hydrogen‐bond network in both structures. Despite these similarities, there are substantial differences between the hydrogen‐bond networks of (I) and (II). The N—H...O and O—H...O hydrogen bonds in (I) are stronger and weaker, respectively, than those in (II). Moreover, in (I), the shortest N—H...O hydrogen bonds are shorter than the shortest O—H...O hydrogen bonds, which is an unusual feature. The properties of the hydrogen‐bond network in (II) can be related to an unusually long P—O bond length for an unhydrogenated fluorophosphonate anion that is present in this structure. In both structures, the N—H...F interactions are far weaker than the N—H...O hydrogen bonds. It follows from the structure analysis that (II) seems to be thermodynamically more stable than (I).     

Dichlorobis(2‐methylquinoline N‐oxide‐κO)zinc(II) from powder data

The crystal structure of the title compound, [ZnCl₂(C₁₀H₉NO)₂], has been determined from laboratory powder diffraction data. Although the powder pattern was initially indexed with tetragonal unit‐cell dimensions, the correct solution was found in an orthorhombic space group using a combination of grid‐search and simulated‐annealing techniques. The subsequent bond‐restrained Rietveld refinement gave bond lengths and angles within expected ranges. The molecule has crystallographically imposed twofold symmetry.     

Two polymorphs of (2‐carboxyethyl)(phenyl)phosphinic acid

Two polymorphs of (2‐carboxyethyl)(phenyl)phosphinic acid, C₉H₁₁O₄P, crystallize in the chiral P2₁2₁2₁ space group with similar unit‐cell parameters. They feature an essentially similar hydrogen‐bonding motif but differ slightly in their detailed geometric parameters. For both polymorphs, the unequivocal location of the hydroxy H atoms together with the expected differences in the P—O bond lengths establish unequivocally that both forms contain the S isomer; the protonated phosphinic acid and carboxy O atoms serve as hydrogen‐bond donors, while the second phosphinic acid O atom acts as a double hydrogen‐bond acceptor and the remaining carboxy O atom is not involved in hydrogen bonding. Thus, an undulating two‐dimensional supramolecular layer aggregate is formed based on an R₄³(20) ring unit. Such polymorphism derives from the rotation of the C—C single bonds between the two hydrogen‐bond‐involved carboxy and phosphinic acid moieties.     

Two polymorphs of 2‐(4‐chlorophenyl)‐4‐methylchromenium perchlorate

Crystallization (from ethyl acetate solution) of 2‐(4‐chlorophenyl)‐4‐methylchromenium perchlorate, C₁₆H₁₂ClO⁺·;ClO₄⁻, (I), yields two monoclinic polymorphs with the space groups P2₁/n [polymorph (Ia)] and P2₁/c [polymorph (Ib)]; in both cases, Z = 4. Cations and anions, disordered in polymorph (Ib), form ion pairs in both polymorphs as a result of Cl—O...π interactions. Related by a centre of symmetry, neighbouring ion pairs in polymorph (Ia) are linked viaπ–π interactions between cationic fragments, and the resulting dimers are linked through a network of C—H...O(perchlorate) interactions between adjacent cations and anions. The ion pairs in polymorph (Ib), arranged in pairs of columns along the a axis, are linked through a network of C—H...O(perchlorate), C—Cl...π, π–π and C—Cl...O(perchlorate) interactions. The aromatic skeletons in polymorph (Ia) are parallel in the cationic fragments involved in dimers, but nonparallel in adjacent ion pairs not constituting dimers. In polymorph (Ib), these skeletons are parallel in pairs of columns, but nonparallel in adjacent pairs of columns; this is visible as a herring‐bone pattern. Differences in the crystal structures of the polymorphs are most probably the cause of their different colours.     

8‐Hydroxyquinaldinic acid and its nickel(II) complex

The molecules of 8‐hydroxy­quinolinium‐2‐carboxyl­ate, C₁₀H₇NO₃, have a planar structure, in which the carboxyl group is ionized and the ring N atom is protonated. The derived nickel(II) complex, bis(8‐hydroxy­quinoline‐2‐carboxyl­ato‐κ³O²,N,O⁸)­nickel(II) trihydrate, [Ni(C₁₀H₆NO₃)₂]·3H₂O, contains an octahedral central Ni^II ion coordinated by the hydroxyl O atom, the ring N atom and the carboxyl­ate O atom of each of the two tridentate ligands, with a perpendicular orientation of the quinoline rings.     

Synthesis,spectral and antibacterial activity of Co(II), Ni(II) and Zn(II) complexes with 2‐hydroxy‐benzoic acid(3,4‐dihydro‐2H‐naphthalen‐1‐ylidene)‐hydrazide

A bioactive Schiff base HL i.e. 2‐hydroxy‐benzoic acid(3,4‐dihydro‐2H ‐naphthalen‐1‐ylidene)‐hydrazide was synthesized by reacting equimolar amount of salicylic acid hydrazide and 1‐tetralone. Co(II), Ni(II) and Zn(II) complexes of ligand HL was synthesized in 1:1 and 1:2 molar ratio of metal to ligand. The structure of the synthesized ligand and metal complexes was established by elemental analysis, molar conductance, magnetic susceptibility measurements, electronic, IR and EPR spectral techniques. For determining the thermal stability the TGA has been done. In DFT studies the geometries of Schiff bases and metal complexes were fully optimized with respect to the energy using the 6–31 + g(d,p) basis set. Spectral data reveal that ligand behave uninegative tridentate in ML complexes and uninegative bidentate in ML₂ complexes. On the basis of characterization octahedral geometry has been assigned for Co(II) and Ni(II) complexes, while tetrahedral for Zn(II) complexes. Antibacterial activity of the synthesized compounds were evaluated against Staphylococcus aureus , Bacillus subtilis, Escherichia coli , Xanthomonas campestris and Pseudomonas aeruginosa and the results revealed that metal complexes show enhanced activity in comparison to free ligand.     

Two new polymorphs of trans‐bis(hinokitiolato)copper(II)

The title complex [systematic name: trans‐bis(3‐iso­propyl‐7‐oxo­cyclo­hepta‐1,3,5‐trienolato)copper(II)], [Cu(C₁₀H₁₁O₂)₂],is a substance possessing antimicrobial activity. The compound crystallizes in a number of polymorphic forms, the structures for two of which are reported here. Stacks of square‐planar mol­ecules exhibiting weak intermolecular copper–olefin π interactions (not observed in earlier reports on this substance) are described. The mol­ecules have crystallographically imposed inversion symmetry, with stacking and copper–olefin π distances ranging from 3.226 (2) to 3.336 (1) Å.     

Two polymorphs of 20‐desmethyl‐β‐carotene

Two polymorphs of 20‐desmethyl‐β‐carotene (systematic name: 20‐nor‐β,β‐carotene), C₃₉H₅₄, in monoclinic and triclinic space groups, were formed in the same vial by recrystallization from pyridine and water. Each polymorph crystallizes with the complete molecule as the asymmetric unit, and the two polymorphs show differing patterns of disorder. The β end rings of both polymorphs have the 6‐s‐cis conformation, and are twisted out of the plane of the polyene chain by angles of −53.2 (8) and 47.3 (8)° for the monoclinic polymorph, and −43.6 (3) and 56.1 (3)° for the triclinic polymorph. The cyclohexene end groups are in the half‐chair conformation, but the triclinic polymorph shows disorder of one ring. Overlay of the molecules shows that they differ in the degree of nonplanarity of the polyene chains and the angles of twist of the end rings. The packing arrangements of the two polymorphs are quite different, with the monoclinic polymorph showing short intermolecular contacts of the disordered methyl groups with adjacent polyene chain atoms, and the triclinic polymorph showing π–π stacking interactions of the almost parallel polyene chains. The determination of the crystal structures of the two title polymorphs of 20‐desmethyl‐β‐carotene allows information to be gained regarding the structural effects on the polyene chain, as well as on the end groups, versus that of the parent compound β‐carotene. The absence of the methyl group is known to have an impact on various functions of the title compound.     

A ruthenium(II) complex with p‐cymene and (S)‐2‐(anilinomethyl)pyrrolidine

The title compound, [(S)‐2‐(anilino­methyl)­pyrrolidine‐N,N′]‐chloro(η⁶‐para‐cymene)­ruthenium(II) chloride, [RuCl‐(C₁₀H₁₄)(C₁₁H₁₆N₂)]Cl, has been synthesized by the reaction of [RuCl₂(p‐cymene)]₂ (p‐cymene is para‐iso­propyl­toluene) with (S)‐2‐(anilinomethyl)­pyrrolidine in triethyl­amine/2‐propanol. The Ru atom is in a pseudo‐tetrahedral environment coordinated by a chloride ligand, the aromatic hydro­carbon is linked in a η⁶ manner and the amine is linked via its two N atoms. The chloride anion is involved in hydrogen bonding with the di­amine moieties through N—H?Cl interactions, with N?Cl distances of 3.273 (4) and 3.352 (4) Å.     

Two polymorphs of 1,8‐dichloroanthracene

A second, monoclinic, polymorph of the title compound, C₁₄H₈Cl₂, has been found. In addition to the structure of this monoclinic form, the structure of the previously described orthorhombic form [Desvergne, Chekpo & Bouas‐Laurent (1978). J. Chem. Soc. Perkin Trans. 2, pp. 84–87; Benites, Maverick & Fronczek (1996). Acta Cryst. C 52 , 647–648] has been redetermined at low temperature and using modern methods. The low‐temperature structure of the orthorhombic form is of significantly higher quality than the previously published structure and additional details can be derived. A comparison of the crystal packing of the two forms with a focus on weak intermolecular C—H...Cl interactions shows the monoclinic structure to have one such interaction linking the molecules into infinite ribbons, while two crystallographically independent C—H...Cl interactions give rise to an interesting infinite three‐dimensional network in the orthorhombic crystal form.     

A facile synthesis of cytogenin (8‐hydroxy‐3‐hydroxymethyl‐6‐methoxyisocoumarin)

A facile and straightforward synthesis of cytogenin 1 (8‐hydroxy‐3‐hydroxymethyl‐6‐methoxyisocoumarin) metabolite of Streptoverticillium eurocidicum and Certocystis fimbriata has been achieved. Condensation of chloroacetyl chloride with 3,5‐dimethoxyhomophthalic acid 2 directly furnished 3‐chloromethyl‐6,8‐dimethoxyisocoumarin 3 which was hydrolyzed to 6,8‐dimethoxy‐3‐hydroxymethylisocoumarin 4 using 0.05% aqueous sodium hydroxide in THF. Regioselective demethylation of 4 yielded cytogenin 1 . In model experiments, 3‐chloromethylisocoumarin was prepared and converted into 3‐hydroxymethyl isocoumarin.     

Poly[(μ5‐3‐carboxybenzene‐1,2‐dicarboxylato)lead(II)]: a helical lead(II) coordination polymer

In the title polymer, [Pb(C₉H₄O₆)]_n, the asymmetric unit contains a monomer of a Pb^II cation with a doubly deprotonated 3‐carboxybenzene‐1,2‐dicarboxylate dianion (1,2,3‐Hbtc²⁻). Each Pb^II centre is seven‐coordinated by seven O atoms of bridging carboxy/carboxylate groups from five 1,2,3‐Hbtc²⁻ ligands, forming a distorted pentagonal bipyramid. The Pb^II cations are bridged by 1,2,3‐Hbtc²⁻ anions, yielding two‐dimensional chiral layers. The layers are stacked above each other to generate a three‐dimensional supramolecular architecture via a combination of C—H...O interactions. The thermogravimetric and optical properties are also reported.     

Two new polymorphs of 2,6‐diaminopyrimidin‐4(3H)‐one monohydrate

The title compound, C₄H₆N₄O·H₂O, crystallized simultaneously as a triclinic and a monoclinic polymorph from an aqueous solution of 2,4‐diaminopyrimidin‐6‐ol. Previously, an orthorhombic polymorph was isolated under the same experimental conditions. The molecular geometric parameters in the two present polymorphs and the previously reported orthorhombic polymorph are similar, but the structures differ in the details of their crystal packing. In the triclinic system, the diaminopyrimidinone molecules are connected to one another via N—H...O and N—H...N hydrogen bonding to form infinite chains in the [011] direction. The chains are further hydrogen bonded to the water molecules, resulting in a three‐dimensional network. In the monoclinic system, the diaminopyrimidinone molecules are hydrogen bonded together into two‐dimensional networks parallel to the bc plane. The water molecules link the planes to form a three‐dimensional polymeric structure.     

7‐Carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate at 100 K

Both 7‐carboxyl­ato‐8‐hydroxy‐2‐methyl­quinolinium monohydrate, C₁₁H₉NO₃·H₂O, (I), and 7‐carboxy‐8‐hydroxy‐2‐methyl­quinolinium chloride monohydrate, C₁₁H₁₀NO₃⁺·Cl⁻·H₂O, (II), crystallize in the centrosymmetric P space group. Both compounds display an intramolecular O—H⋯O hydrogen bond involving the hydroxy group; this hydrogen bond is stronger in (I) due to its zwitterionic character [O⋯O = 2.4449 (11) Å in (I) and 2.5881 (12) Å in (II)]. In both crystal structures, the HN⁺ group participates in the stabilization of the structure via intermolecular hydrogen bonds with water mol­ecules [N⋯O = 2.7450 (12) Å in (I) and 2.8025 (14) Å in (II)]. In compound (II), a hydrogen‐bond network connects the Cl⁻ anion to the carboxylic acid group [Cl⋯O = 2.9641 (11) Å] and to two water mol­ecules [Cl⋯O = 3.1485 (10) and 3.2744 (10) Å].     

Synthesis of 3‐(2‐hydroxy‐1‐phenylethyl)‐ and 3‐(2‐hydroxy‐2‐phenylethyl)adenine,DNA adducts derived from styrene

3‐(2‐Hydroxy‐2‐phenylethyl)‐ and 3‐(2‐hydroxy‐1‐phenylethyl)adenine, DNA adducts derived from styrene, along with their 9‐substituted analogues were prepared by alkylation of 8‐bromoadenine with corresponding allyl‐protected bromohydrins followed by a new deallylation procedure using tetrakis(triphenylphosphine)palladium catalyzed reductive cleavage by poly(methylhydrosiloxane) in the presence of p‐toluenesulphonic acid. This novel procedure proved to be useful for purine derivatives, which were resistant to other deallylation protocols. Structure of positional isomers was assigned using 2D NMR experiments HMBC and HMQC.     

A tetranuclear cadmium(II) complex based on the 2‐(quinolin‐8‐yloxy)acetonitrile ligand

The hydrothermal reaction of 2‐(quinolin‐8‐yloxy)acetonitrile and Cd(ClO₄)₂ yielded the noncentrosymmetric coordination complex tetrakis[μ‐2‐(quinolin‐8‐yloxy)acetato]tetrakis[μ‐2‐(quinolin‐8‐yloxy)acetonitrile]tetracadmium tetrakis(perchlorate) dihydrate, [Cd₄(C₁₁H₈NO₃)₄(C₁₁H₈N₂O)₄](ClO₄)₄·2H₂O. The local coordination environment around the Cd^II cation can be best described as a capped octahedron defined by two N atoms and five O atoms from three ligands. The Cd^II cations are linked by the ligands with Cd—O—Cd and Cd—O—C—C—O—Cd bridges, forming tetranuclear units, there being two independent tertranuclear units in the structure. The fourfold rotoinversion centre sits at the centre of each Cd₄ core. The two perchlorate anions in the asymmetric unit are linked by the water molecule through O—H...O hydrogen bonds.     

Syntheses,characterization and biological studies of zinc(II), copper(II) and cobalt(II) complexes with Schiff base ligand derived from 2‐hydroxy‐1‐naphthaldehyde and selenomethionine

Novel zinc(II), copper(II), and cobalt(II) complexes of the Schiff base derived from 2‐hydroxy‐1‐naphthaldehyde and D, L ‐selenomethionine were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and powder XRD. The analytical data showed the composition of the metal complex to be ML(H₂O), where L is the Schiff base ligand and M = Co(II), Cu(II) and Zn(II). IR results confirmed the tridentate binding of the Schiff base ligand involving azomethine nitrogen, naphthol oxygen and carboxylato oxygen atoms. ¹H NMR spectral data of lithium salt of the Schiff base ligand [Li(HL)] and ZnL(H₂O) agreed with the proposed structures. The conductivity values of complexes between 12.50 and 15.45 S cm² mol^?1 in DMF suggested the presence of non‐electrolyte species. The powder XRD studies indicated that Co(II) complex is amorphous, whereas Cu(II) and Zn(II) complexes are crystalline. The results of antibacterial and antifungal screening studies indicated that Li(HL) and its metal complexes are active, but CuL(H₂O) is most active among them. Copyright © 2010 John Wiley & Sons, Ltd.     

Two polymorphs of 2,5‐dichloro‐3,6‐bis(dibenzylamino)‐p‐hydroquinone with flexible dibenzylamino groups

We obtained two conformational polymorphs of 2,5‐dichloro‐3,6‐bis(dibenzylamino)‐p‐hydroquinone, C₃₄H₃₀Cl₂N₂O₂. Both polymorphs have an inversion centre at the centre of the hydroquinone ring (Z′ = ), and there are no significant differences between their bond lengths and angles. The most significant structural difference in the molecular conformations was found in the rotation of the phenyl rings of the two crystallographically independent benzyl groups. The crystal structures of the polymorphs were distinguishable with respect to the arrangement of the hydroquinone rings and the packing motif of the phenyl rings that form part of the benzyl groups. The phenyl groups of one polymorph are arranged in a face‐to‐edge motif between adjacent molecules, with intermolecular C—H…π interactions, whereas the phenyl rings in the other polymorph form a lamellar stacking pattern with no significant intermolecular interactions. We suggest that this partial conformational difference in the molecular structures leads to the significant structural differences observed in their molecular arrangements.