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New Polymorph (new + polymorph)

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Chemistry100%

Selected Abstracts

ChemInform Abstract: A New Polymorph of Layered LiCoO2.

CHEMINFORM, Issue 4 2010
Shinichi Komaba
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

ChemInform Abstract: A New Polymorph with a Layered Structure ,-CaTe2O5.

CHEMINFORM, Issue 19 2009
N. Barrier
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

,-CaB4O7: A New Polymorph Synthesized under High-Pressure/High-Temperature Conditions.

CHEMINFORM, Issue 29 2003
Hubert Huppertz
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

A conformational polymorphic transition in the high-temperature ,-form of chlorpropamide on cooling: a new ,,-form

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 6 2009
Tatiana N. Drebushchak
Structural changes in the high-temperature ,-polymorph of chlorpropamide, 4-chloro- N -(propylaminocarbonyl)benzenesulfonamide, C10H13ClN2O3S, on cooling down to 100,K and on reverse heating were followed by single-crystal X-ray diffraction. At temperatures below 200,K the phase transition into a new polymorph (termed the ,,-form) has been observed for the first time. The polymorphic transition preserves the space group Pna21, is reversible and is accompanied by discontinuous changes in the cell volume and parameters, resulting from changes in molecular conformation. As shown by IR spectroscopy and X-ray powder diffraction, the phase transition in a powder sample is inhomogeneous throughout the bulk, and the two phases co-exist in a wide temperature range. The cell parameters and the molecular conformation in the new polymorph are close to those in the previously known ,-polymorph, but the packing of the z-shaped molecular ribbons linked by hydrogen bonds inherits that of the ,-form and is different from the packing in the ,-polymorph. A structural study of the ,-polymorph in the same temperature range has revealed no phase transitions. [source]

The incommensurately modulated crystal structure of ,-Pb2BiVO6: interpretation of the phase transition ,,,,, and conduction properties of related materials

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2009
Pascal Roussel
A new polymorph of Pb2BiVO6 was prepared under ambient conditions and its crystal structure was determined by single-crystal X-ray diffraction. The phase transitions ,,, and ,,, were identified in the mother phase; the high-temperature form ,-Pb2BiVO6 eventually decomposes at 753,K to a mixture of Pb4BiVO8 and the high-temperature form of PbBiVO5 before showing recombination at 923,K. ,-Pb2BiVO6 has an incommensurate monoclinic modulated structure. This crystal structure is twinned and complementary structural investigations of a powder sample of ,-Pb2BiVO6 by TEM diffraction studies confirmed the lattice and incommensurate modulation character. Log , = f(T,1) dependences for Pb2BiVO6 -related materials (6% M -for-V-substituted compositions; M = Cr, Mn, P) are reported, which allow the characterization (Ea and isothermal , values) of the ,- as well as the ,- and ,-Pb2BiVO6 varieties. [source]

Structure and hydrogen bonding in 2,4-dihydroxybenzoic acid at 90, 100, 110 and 150,K; a theoretical and single-crystal X-ray diffraction study

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2007
Andrew Parkin
A new polymorph of 2,4-dihydroxybenzoic acid is reported. The structure was characterized by multiple-temperature X-ray diffraction and solid-state DFT computations. The material shows a geometric pattern of hydrogen bonding consistent with cooperativity between the intermolecular carboxylic acid dimer and intramolecular hydrogen bonds. The presence of proton disorder within this hydrogen-bond system, which would support such a cooperative model, was not fully ruled out by the initial X-ray studies. However, solid-state calculations on the three possible end-point tautomers indicate that the dominant crystallographically observed configuration is substantially lower in energy than the other tautomers (by at least 9,kJ,mol,1), indicating that no disorder should be expected. It is therefore concluded that no disorder is observed either in the intra- or intermolecular hydrogen bonds of the title compound and that the cooperativity between the hydrogen bonds is not present within the temperature range studied. [source]

Two new structures in the glycine,oxalic acid system

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010
Nikolay A. Tumanov
Glycinium semi-oxalate-II, C2H6NO2+·C2HO4,, (A), and diglycinium oxalate methanol disolvate, 2C2H6NO2+·C2O42,·2CH3OH, (B), are new examples in the glycine,oxalic acid family. (A) is a new polymorph of the known glycinium semi-oxalate salt, (C). Compounds (A) and (C) have a similar packing of the semi-oxalate monoanions with respect to the glycinium cations, but in (A) the two glycinium cations and the two semi-oxalate anions in the asymmetric unit are non-equivalent, and the binding of the glycinium cations to each other is radically different. Based on this difference, one can expect that, although the two forms grow concomitantly from the same batch, a transformation between (A) and (C) in the solid state should be difficult. In (B), two glycinium cations and an oxalate anion, which sits across a centre of inversion, are linked via strong short O,H...O hydrogen bonds to form the main structural fragment, similar to that in diglycinium oxalate, (D). Methanol solvent molecules are embedded between the glycinium cations of neighbouring fragments. These fragments form a three-dimensional network via N,H...O hydrogen bonds. Salts (B) and (D) can be obtained from the same solution by, respectively, slow or rapid antisolvent crystallization. [source]

A new polymorph of dichloridotriphenylantimony

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
Daniel J. MacDonald
In a new polymorphic form of dichloridotriphenylantimony, [Sb(C6H5)3Cl2], there are two crystallographically unique molecules in the asymmetric unit and it has been determined that this polymorph is one of two kinetically favoured phases of pure dichloridotriphenylantimony, both of which have Z, > 1. A third polymorph, corresponding to (C6H5)3SbCl1.8F0.2, is also known and has Z, = 2. By contrast, the thermodynamically preferred polymorph of pure (C6H5)3SbCl2 has Z, = 1. A brief comparison of the known polymorphic forms of dichloridotriphenylantimony is presented. [source]

A third polymorph of 4-(2,6-difluorophenyl)-1,2,3,5-dithiadiazolyl

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2010
Elisabeth M. Fatila
The crystal structure of a third polymorphic form of the known 4-(2,6-difluorophenyl)-1,2,3,5-dithiadiazolyl radical, C7H3F2N2S2, is reported. This new polymorph represents a unique crystal-packing motif never before observed for 1,2,3,5-dithiadiazolyl (DTDA) radicals. In the two known polymorphic forms of the title compound, all of the molecules form cis -cofacial dimers, such that two molecules are ,-stacked with like atoms one on top of the other, a common arrangement for DTDA species. By contrast, the third polymorph, reported herein, contains two crystallographically unique molecules organized such that only 50% are dimerized, while the other 50% remain monomeric radicals. The dimerized molecules are arranged in the trans -antarafacial mode. This less common dimer motif for DTDA species is characterized by ,,, interactions between the S atoms [S...S = 3.208,(1),Å at 110,K], such that the two molecules of the dimer are related by a centre of inversion. The most remarkable aspect of this third polymorph is that the DTDA dimers are co-packed with monomers. The monomeric radicals are arranged in one-dimensional chains directed by close lateral intermolecular contacts between the two S atoms of one DTDA heterocycle and an N atom of a neighbouring coplanar DTDA heterocycle [S...N = 2.857,(2) and 3.147,(2),Å at 110,K]. [source]

A new polymorph of benzene-1,2-diamine: isomorphism with 2-aminophenol and two-dimensional isostructurality of polymorphs

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010
Agnieszka Czapik
A new crystalline form of benzene-1,2-diamine, C6H8N2, crystallizing in the space group Pbca, has been identified during screening for cocrystals. The crystals are constructed from molecular bilayers parallel to (001) that have the polar amino groups directed to the inside and the aromatic groups, showing a herringbone arrangement, directed to the outside. The known monoclinic form and the new orthorhombic polymorph exhibit two-dimensional isostructurality as the crystals consist of nearly identical bilayers. In the monoclinic form, neighbouring bilayers are generated by a unit translation along the a axis, whereas in the orthorhombic form they are generated by a c -glide. Moreover, the new form of benzene-1,2-diamine is essentially isomorphous with the only known form of 2-aminophenol. [source]

A new polymorph of Cu3B2O6

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2009
Natalia V. Kuratieva
A new polymorph of nonacopper(II) bis(orthoborate) bis(hexaoxodiborate), Cu9(BO3)2(B2O6)2, or Cu3B2O6 with Z, = 3, has a pseudo-layered monoclinic structure containing BO3 triangles and B2O6 units consisting of corner-sharing BO3 triangles and BO4 tetrahedra. The compound was obtained during an investigation of the Li,Cu,B,O system. In contrast to the triclinic form of Cu3B2O6, the layers are linked to one another by BO4 tetrahedra. [source]

A new polymorph of 2-methyl-6-nitroaniline

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2009
Samantha K. Callear
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. [source]

A new polymorph of triphenylmethylamine: the effect of hydrogen bonding

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2009
Victor N. Khrustalev
Crystallization of the hexane reaction mixture after treatment of LiGe(OCH2CH2NMe2)3 with Ph3CN3 gives rise to a new triclinic (space group P) polymorph of triphenylmethylamine, C19H17N, (I), containing dimers formed by N,H...N hydrogen bonds, whereas the structure of the known orthorhombic (space group P212121) polymorph of this compound, (II), consists of isolated molecules. While the dimers in (I) lie across crystallographic inversion centres, the molecules are not truly related by them. The centrosymmetric structure is due to the statistical disordering of the amino H atoms participating in the N,H...N hydrogen-bonding interactions, and thus the inversion centre is superpositional. The conformations and geometric parameters of the molecules in (I) and (II) are very similar. It was found that the polarity of the solvent does not affect the capability of triphenylmethylamine to crystallize in the different polymorphic modifications. The orthorhombic polymorph, (II), is more thermodynamically stable under normal conditions than the triclinic polymorph, (I). The experimental data indicate the absence of a phase transition in the temperature interval 120,293,K. The densities of (I) (1.235,Mg,m,3) and (II) (1.231,Mg,m,3) at 120,K are practically equal. It would seem that either the kinetic factors or the effects of the other products of the reaction facilitating the hydrogen-bonded dimerization of triphenylmethylamine molecules are the determining factor for the isolation of the triclinic polymorph (I) of triphenylmethylamine. [source]

A new polymorph of poly[bis(,2 -perchlorato-,2O:O,)(2,2,:6,,2,,-terpyridine-,3N,N,,N,,)lead(II)] with a greatly extended chain repeat distance

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009
Alexander J. Blake
In the title compound, [Pb(ClO4)2(C15H11N3)]n, two molecules occupy general positions while the third lies on a crystallographic twofold axis, giving a total of two and a half molecules per asymmetric unit. Each metal centre is coordinated equatorially by three 2,2,:6,,2,,-terpyridine (terpy) N-donor atoms and axially by two perchlorate O-donor atoms. The distorted pentagonal bipyramidal geometry is completed by two equatorial O-donor atoms from two perchlorate anions which bridge to two different adjacent metal centres. The coordination about each metal centre is very similar to that seen at the unique PbII centre in the previously published polymorph [Engelhardt, Harrowfield, Miyamae, Patrick, Skelton, Soudi & White (1996). Aust. J. Chem.49, 1135,1146], but the new polymorph differs from it by the insertion on each side of an existing [bis(perchlorato)(terpy)lead(II)] molecule of two additional such units. Pairs of asymmetrically bridging perchlorate anions link irregularly spaced PbII centres into undulating chains parallel to [201] which exhibit a repeat distance of 26.280,(4),Å. The significance of this new polymorph lies in the fact that, while it is chemically identical to the known polymorph, it is structurally distinct from it. [source]

A new polymorph of tetraphenyldiboroxane

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 10 2007
Linda Kaufmann
A new polymorph of tetraphenyldiboroxane [or oxybis(diphenylborane)], C24H20B2O, (Ia), has been found. It is monoclinic, like the already known form, (Ib), and can be refined in the same space group, namely P21/c, or in the equivalent setting P21/n. The molecular conformations of the two polymorphs differ in the rotations of two of the phenyl rings about the B,C bonds, leading to markedly different packing patterns and cell dimensions. [source]

Crystallographic report: A new polymorph for bis[bis(N,N -dibenzyldithiocarbamato)cadmium(II)]

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 2 2004
M. Saravanan
Abstract The title compound is a centrosymmetric dimer with each cadmium in a distorted CdS5 square pyramidal geometry. The Cd,S bond distances range from 2.5626(11) to 2.8459(11) Å. Copyright © 2004 John Wiley & Sons, Ltd. [source]

A new polymorph of cis,transoid,cis -dicyclohexano-18-crown-6.

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2003
Erratum
In the Comment of the paper by Kravtsov et al. [Acta Cryst. (2002), C58, o683o684], there in an error in a cited Cambridge Structural Database (Allen, 2002) refcode. The correct text is `Only recently, the atomic coordinates for the known monoclinic polymorph of the cis,transoid,cis isomer became available from a private communication (Nazarenko, 2002; CCDC refcode DCHXCS01).' The updated reference is given below. [source]

Hetero-Seeding and Solid Mixture to Obtain New Crystalline Forms

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2009
Dario Braga Prof.
Abstract Para -methyl benzyl alcohol (p -MeBA,II) and para -chloro benzyl alcohol (p -ClBA) are quasi-isostructural and share the same hydrogen-bond patterns, but their crystals are not isomorphous. No new polymorphs could be obtained by conventional polymorph screening based on different solvents and different crystallization conditions. Formation of a new polymorph of p -MeBA named p -MeBA,I, isomorphous with the crystal of p -ClBA, was induced by hetero-seeding with a small quantity of powdered p -ClBA added to a supersaturated solution of p -MeBA in hexane, while seeding of p -ClBA with p -MeBA,II failed to give a new phase of p -ClBA isomorphous with known crystalline p -MeBA,II. Mixed crystals of p -MeBA and p -ClBA were also prepared with different p -MeBA/p -ClBA ratios to understand the role of the different functional groups in the crystal structure. Crystal phases were characterized by combined use of single-crystal and powder X-ray diffraction, differential scanning calorimetry, and solid-state NMR spectroscopy. [source]

Experimental and predicted crystal structures of Pigment Red 168 and other dihalogenated anthanthrones

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2010
Martin U. Schmidt
The crystal structures of 4,10-dibromo-anthanthrone (Pigment Red 168; 4,10-dibromo-dibenzo[def,mno]chrysene-6,12-dione), 4,10-dichloro- and 4,10-diiodo-anthanthrone have been determined by single-crystal X-ray analyses. The dibromo and diiodo derivatives crystallize in P21/c, Z = 2, the dichloro derivative in , Z = 1. The molecular structures are almost identical and the unit-cell parameters show some similarities for all three compounds, but the crystal structures are neither isotypic to another nor to the unsubstituted anthanthrone, which crystallizes in P21/c, Z = 8. In order to explain why the four anthanthrone derivatives have four different crystal structures, lattice-energy minimizations were performed using anisotropic atom,atom model potentials as well as using the semi-classical density sums (SCDS-Pixel) approach. The calculations showed the crystal structures of the dichloro and the diiodo derivatives to be the most stable ones for the corresponding compound; whereas for dibromo-anthanthrone the calculations suggest that the dichloro and diiodo structure types should be more stable than the experimentally observed structure. An experimental search for new polymorphs of dibromo-anthanthrone was carried out, but the experiments were hampered by the remarkable insolubility of the compound. A metastable nanocrystalline second polymorph of the dibromo derivative does exist, but it is not isostructural to the dichloro or diiodo compound. In order to determine the crystal structure of this phase, crystal structure predictions were performed in various space groups, using anisotropic atom,atom potentials. For all low-energy structures, X-ray powder patterns were calculated and compared with the experimental diagram, which consisted of a few broad lines only. It turned out that the crystallinity of this phase was not sufficient to determine which of the calculated structures corresponds to the actual structure of this nanocrystalline polymorph. [source]

Conformational polymorphism in a Schiff-base macrocyclic organic ligand: an experimental and theoretical study

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2010
Leonardo Lo Presti
Polymorphism in the highly flexible organic Schiff-base macrocycle ligand 3,6,9,17,20,23-hexa-azapentacyclo(23.3.1.111,15.02,6.016,20)triaconta-1(29),9,11,13,15(30),23,25,27-octaene (DIEN, C24H30N6) has been studied by single-crystal X-ray diffraction and both solid-state and gas-phase density functional theory (DFT) calculations. In the literature, only solvated structures of the title compound are known. Two new polymorphs and a new solvated form of DIEN, all obtained from the same solvent with different crystallization conditions, are presented for the first time. They all have symmetry, with the macrocycle positioned on inversion centres. The two unsolvated polymorphic forms differ in the number of molecules in the asymmetric unit Z,, density and cohesive energy. Theoretical results confirm that the most stable form is (II°), with Z, = 1.5. Two distinct molecular conformations have been found, named `endo' or `exo' according to the orientation of the imine N atoms, which can be directed towards the interior or the exterior of the macrocycle. The endo arrangement is ubiquitous in the solid state and is shared by two independent molecules which constitute an invariant supramolecular synthon in all the known crystal forms of DIEN. It is also the most stable arrangement in the gas phase. The exo form, on the other hand, appears only in phase (II°), which contains both the conformers. Similarities and differences among the occurring packing motifs, as well as solvent effects, are discussed with the aid of Hirshfeld surface fingerprint plots and correlated to the results of the energy analysis. A possible interconversion path in the gas phase between the endo and the exo conformers has been found by DFT calculations; it consists of a two-step mechanism with activation energies of the order of 30,40,kJ,mol,1. These findings have been related to the empirical evidence that the most stable phase (II°) is also the last appearing one, in accordance with Ostwald's rule. [source]

Two new polymorphs of di­phenyl(4-pyridyl)­methyl methacryl­ate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 11 2004
Gerrit Gobius du Sart
The title compound (D4PyMA), C22H19NO2, exhibits polymorphism after crystallization by slow evaporation from a binary mixture of chloro­form and hexane. Long needle-like crystals have an orthorhombic structure (space group Fdd2), with one mol­ecule in the asymmetric unit, while small tablet-like crystals exhibit a monoclinic crystal structure (space group P21/n), in which two independent but chemically identical mol­ecules comprise the asymmetric unit. The bond lengths and angles are normal, while the torsion angles around the ,C,O, bond linking the di­phenyl(4-pyridyl)methyl and methacryl­ate groups show the flexibility of the mol­ecule by way of packing effects. The two polymorphs both contain weak C,H,, and C,H,O/N contacts but have different conformations. [source]

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

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2004
Georgia M. Arvanitis
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 , interactions (not observed in earlier reports on this substance) are described. The mol­ecules have crystallographically imposed inversion symmetry, with stacking and copper,olefin , distances ranging from 3.226,(2) to 3.336,(1),Å. [source]

Hetero-Seeding and Solid Mixture to Obtain New Crystalline Forms

CHEMISTRY - A EUROPEAN JOURNAL, Issue 6 2009
Dario Braga Prof.
Abstract Para -methyl benzyl alcohol (p -MeBA,II) and para -chloro benzyl alcohol (p -ClBA) are quasi-isostructural and share the same hydrogen-bond patterns, but their crystals are not isomorphous. No new polymorphs could be obtained by conventional polymorph screening based on different solvents and different crystallization conditions. Formation of a new polymorph of p -MeBA named p -MeBA,I, isomorphous with the crystal of p -ClBA, was induced by hetero-seeding with a small quantity of powdered p -ClBA added to a supersaturated solution of p -MeBA in hexane, while seeding of p -ClBA with p -MeBA,II failed to give a new phase of p -ClBA isomorphous with known crystalline p -MeBA,II. Mixed crystals of p -MeBA and p -ClBA were also prepared with different p -MeBA/p -ClBA ratios to understand the role of the different functional groups in the crystal structure. Crystal phases were characterized by combined use of single-crystal and powder X-ray diffraction, differential scanning calorimetry, and solid-state NMR spectroscopy. [source]