Polymorphs

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Polymorphs

  • crystalline polymorph
  • different polymorph
  • monoclinic polymorph
  • new polymorph
  • second polymorph
  • stable polymorph
  • third polymorph
  • triclinic polymorph


  • Selected Abstracts


    Polymorphism and piezochromicity in the three-dimensional network-based phosphate RbCuPO4

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 4 2010
    Paul F. Henry
    Rubidium copper phosphate, RbCuPO4, forms two room-temperature polymorphs that have been investigated with neutron powder diffraction. Polymorph (II) can be converted quantitatively into (I) by grinding the material or by pelletization, and the phase transition is accompanied by a significant colour change from very pale green to sky blue. Polymorph (II) can be obtained essentially free of (I) by quenching from 723,K. Each polymorph shows two unique Cu atoms: in (I) both sites are four-coordinate in a 2:1 ratio, whereas in (II) the atoms are four- and five-coordinate in a 1:1 ratio. In each case these sites are linked by phosphate tetrahedra to form three-dimensional frameworks based on the 42638- a four-connected net. The Rb atoms are hosted in the six- and eight-ring channels that are similar to those observed in zeolite ABW. The (II) , (I) phase transition is also accompanied by a volume reduction of 2.1% even though the average coordination of the Cu atoms also falls. The structures of the polymorphs are critically examined and compared with those of KNiPO4 and KCuPO4 in terms of hexagonal close packing containing ordered phosphate arrays. As a result of buckling of the six-ring layers, one-dimensional chains of dimerized copper polyhedra are identified in (II), chains that become trimers with mirror symmetry in (I). [source]


    Concomitant polymorphic behavior of di-,-thiocyanato-,2N:S;,2S:N -bis[bis(tri- p -fluorophenylphosphine-,P)silver(I)]

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 1 2010
    Bernard Omondi
    The structures of two polymorphs, both monoclinic P21/n [polymorph (I)] and P21/c [polymorph (II)], of di-,-thiocyanato-,2N:S;,2S:N -bis[bis(tri- p -fluorophenylphosphine-,P)silver(I)] complexes have been determined at 100,K. In both polymorphs the complex has a dinuclear structure where the silver(I) coordinates to two phosphine ligands and two bridging thiocyanate anions to form complexes with distorted tetrahedral geometry. Polymorph (I) has just one half of the [Ag2(SCN)2{P(4-FC6H4)3}4] molecule at (0, , 0) from the origin in the asymmetric unit. Polymorph (II) has one and a half molecules of [Ag2(SCN)2{P(4-FC6H4)3}4] in the asymmetric unit; the half molecule is situated at (0, 1, ), while the full molecule is located at (1/3, , 1/3) from the origin. The Ag,P bond distances range from 2.4437,(4) to 2.4956,(7), in both polymorphs. The Ag,S distances are 2.5773,(7), in (I) and 2.5457,(5), 2.5576,(5) and 2.5576,(5), in (II). The full molecule in polymorph (II) has slightly shorter Ag,N bond distances [2.375,(1) and 2.367,(2),] compared with the half molecules in both polymorphs [2.409,(2), in (II) and 2.395,(2), in (I)]. The two polymorphs are compared using r.m.s. overlay calculations as well as half-normal probability plot analysis. [source]


    Unmasking a Third Polymorph of a Benchmark Crystal-Structure-Prediction Compound,

    ANGEWANDTE CHEMIE, Issue 45 2009
    Saikat Roy Dr.
    Auf der Jagd nach Polymorphen: Eine Form,III (N blau, S gelb, O rot) von 6-Amino-2-phenylsulfonylimino-1,2-dihydropyridin, einem fr Blindtests in der Kristallstrukturvorhersage genutzten Molekl, wurde durch polymerinduzierte Heteronukleation erhalten. Die experimentellen Stabilitten zeigen, dass die als thermodynamisch stabil berechnete Form,II in Wirklichkeit die am wenigsten stabile unter den drei Polymorphen ist. [source]


    Two concomitant polymorphs of N,N,-bis[4-(diethylamino)phenyl]terephthaldiamide

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010
    Piotr Ku
    The title compound, C28H34N4O2, crystallizes simultaneously as a monoclinic, (Im), and a (twinned) triclinic polymorph, (It), from d6 -dimethyl sulfoxide. Polymorph (It) (P, Z = 1) displays the standard `ladder' packing for this group of compounds, with neighbouring inversion-symmetric molecules related by translation and connected by hydrogen bonds of the form N,H...O=C. Polymorph (Im) (Cc, Z = 4) has no imposed symmetry; there are three independent hydrogen bonds, one classical N,H...O=C and a bifurcated system with N,H...O=C augmented by a short C,H...O=C interaction. Each molecule is thereby linked to four neighbouring molecules, two lower and two higher, so that a crosslinked three-dimensional pattern is formed rather than the standard ladder. [source]


    Polymorph of {2-[(2-hydroxyethyl)iminiomethyl]phenolato-,O}dioxido{2-[(2-oxidoethyl)iminomethyl]phenolato-,3O,N,O,}molybdenum(VI)

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2008
    Dominique Agustin
    A second polymorphic form (form I) of the previously reported compound {2-[(2-hydroxyethyl)iminiomethyl]phenolato-,O}dioxido{2-[(2-oxidoethyl)iminomethyl]phenolato-,3O,N,O,}molybdenum(VI) (form II), [Mo(C9H9NO2)O2(C9H11NO2)], is presented. The title structure differs from the previously reported polymorph [G,owiak, Jerzykiewicz, Sobczak & Zi,kowski (2003). Inorg. Chim. Acta, 356, 387,392] by the fact that the asymmetric unit contains three molecules linked by O,H...O hydrogen bonds. These trimeric units are further linked through O,H...O hydrogen bonds to form a chain parallel to the [11] direction. As in the previous polymorph, each molecule is built up from an MoO22+ cation surrounded by an O,N,O,-tridentate ligand (O,C6H4CH=NCH2CH2O,) and weakly coordinated by a second zwitterionic ligand (O,C6H4CH=N+HC2H4OH). All complexes are chiral with the absolute configuration at Mo being C or A. The main difference between the two polymorphs results from the alternation of the chirality at Mo within the chain. [source]


    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: Unique LaTaO4 Polymorph for Multiple Energy Applications.

    CHEMINFORM, Issue 2 2010
    May Nyman
    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]


    ChemInform Abstract: A Non-Twinned Polymorph of CaTe2O5 from a Hydrothermally Grown Crystal.

    CHEMINFORM, Issue 50 2008
    Matthias Weil
    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]


    ChemInform Abstract: Structural Studies on a High-Pressure Polymorph of NaYSi2O6.

    CHEMINFORM, Issue 6 2008
    Volker Kahlenberg
    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]


    A Second Polymorph of [H3N(CH2)3NH3] [V4O10].

    CHEMINFORM, Issue 7 2007
    Nicholas F. Stephens
    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, please click on HTML or PDF. [source]


    High-Pressure Synthesis and Crystal Structure of the New Orthorhombic Polymorph ,-HgB4O7.

    CHEMINFORM, Issue 46 2005
    Holger Emme
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Synthesis and Structure of a Second Polymorph of Strontium Germanium Nitride: ,-Sr2GeN2.

    CHEMINFORM, Issue 34 2005
    Dong Gon Park
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Synthesis and Characterization of a New High Pressure Polymorph of Cu2WS4.

    CHEMINFORM, Issue 49 2003
    Clare J. Crossland
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    Synthesis, Structure and Thermal Contraction of a New Low-Temperature Polymorph of ZrMo2O8.

    CHEMINFORM, Issue 48 2003
    Simon Allen
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    A Monoclinic Polymorph of Uranyl Dinitrate Trihydrate, [UO2(NO3)2(H2O)2] H2O.

    CHEMINFORM, Issue 46 2003
    Robert R. Shuvalov
    Abstract For Abstract see ChemInform Abstract in Full Text. [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]


    The Synthesis, Photophysical Characterization, and X-Ray Structure Analysis of Two Polymorphs of 4,4,-Diacetylstilbene

    HELVETICA CHIMICA ACTA, Issue 6 2010
    Cameron Pye
    Abstract A palladium(II) acetate-catalyzed synthesis of 1 that utilizes the novel triazene 1-{4-[(E)-morpholin-4-yldiazenyl]phenyl}ethanone as a synthon is described. The room temperature absorption spectra of 1 in various solvents exhibited a ,,,* transition in the range of 330,350,nm. Compound 1 was observed to be luminescent, with room-temperature solution and solid-state emission spectra that exhibited maxima in the range 400,500,nm. All room-temperature absorption and emission spectra exhibited some degree of vibrational structure. The emission spectrum of 1 at 77,K in propanenitrile glass was broad and featureless with a maximum at 447,nm. Compound 1 crystallized as a yellow and colorless polymorph. X-Ray structure analyses of both of these polymorphs and 1-{4-[(E)-morpholin-4-yldiazenyl]phenyl}ethanone are presented. [source]


    High-Performance Single Crystal Organic Field-Effect Transistors Based on Two Dithiophene-Tetrathiafulvalene (DT-TTF) Polymorphs

    ADVANCED MATERIALS, Issue 37 2010
    Raphael Pfattner
    Solution prepared single crystal organic field-effect transistors (OFETs) combine low-cost with high performance due to structural ordering of molecules. However, in organic crystals polymorphism is a known phenomenon, which can have a crucial influence on charge transport. Here, the performance of solution-prepared single crystal OFETs based on two different polymorphs of dithiophene-tetrathiafulvalene, which were investigated by confocal Raman spectroscopy and X-ray diffraction, are reported. OFET devices prepared using different configurations show that both polymorphs exhibited excellent device performance, although the ,-phase revealed charge carrier mobility between two and ten times higher in accordance to the closer stacking of the molecules. [source]


    Differences in Wetting Characteristics of Bi2O3 Polymorphs in ZnO Varistor Materials

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2000
    Mattias Elfwing
    Detailed analysis of the microstructure of grain boundaries, especially triple-grain and multiple-grain junctions, in ZnO varistor materials has been performed using transmission electron microscopy. Different polymorphs of Bi2O3 are shown to exhibit different wetting properties on ZnO interfaces. Recent investigations suggest that the equilibrium configuration consists of crystalline Bi2O3 in the triple-grain and multiple-grain junctions and an amorphous bismuth-rich film in the ZnO/ZnO grain boundaries. The present investigation supports this suggestion for ,-Bi2O3 and also adds to the microstructural image and wetting properties of ,-Bi2O3. [source]


    Polymorphs and pseudopolymorphs of N,N,-dithiobisphthalimide

    ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2002
    Dorcas M. M. Farrell
    N,N,-Dithiobisphthalimide, C16H8N2O4S2 (I), forms a wide range of polymorphs and solvates (pseudopolymorphs). When (I) is crystallized from methanol it yields a solvent-free polymorph (4), in Pna21 with Z, = 1, in which the molecules are linked into chains by a single C,H,O hydrogen bond: crystallization from either acetonitrile or dimethylformamide produces a monoclinic polymorph (5), in P21/c with Z, = 2, also solvent-free, in which the molecules are linked into molecular ladders. Nitromethane forms a monosolvate, C16H8N2O4S2CH3NO2 (6), in P21/c with Z, = 1, in which the solvent molecules are linked to the molecules of (I) not only via a conventional C,H,O hydrogen bond but also via a polarized multicentre interaction involving all three C,H bonds of the solvent molecule. Chlorobenzene forms a precise hemisolvate, C16H8N2O4S20.5C6H5Cl (7), in P with Z, = 1, while ethylbenzene forms an approximate hemisolvate 2C16H8N2O4S20.913C6H5C2H50.087H2O (8), in P21/c with eight molecules of (I) per unit cell. In both solvates the molecules of (I) are linked, in (7) by ,,, stacking interactions augmented by weak C,H,O hydrogen bonds and in (8) by stronger C,H,O hydrogen bonds: the solvent molecules lie in isolated cavities, disordered across inversion centres in (7) and fully ordered in general positions in (8). Crystallization of (I) either from tetrahydrofuran or from wet tert -butanol yields isomorphous solvates (9) and (10), respectively, in C2/c with Z, = 0.5, in which molecules of (I) lie across twofold rotation axes and are linked by ,,, stacking interactions and very weak C,H,O hydrogen bonds, forming a framework enclosing continuous channels: highly disordered solvent molecules lie within these channels. p -Xylene and toluene form isomorphous hemisolvates (11) and (12) with unit cells metrically very similar to those of (9) and (10), but in P21/n with Z, = 1: in these two solvates the molecules of (I) are linked into a framework by very short C,H,O hydrogen bonds; the solvent molecules lie within continuous channels, but they are localized across inversion centres so that the toluene is disordered across an inversion centre. [source]


    Polymorphs of DABCO monohydrate as structural analogues of NaCl

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010
    Barbara Wicher
    A new crystalline form of 1,4-diazabicyclo[2.2.2]octane (DABCO) monohydrate, C6H12N2H2O, crystallizing in the space group P31, has been identified during screening for cocrystals. There are three DABCO and three water molecules in the asymmetric unit, with two DABCO molecules exhibiting disorder over two positions related by rotation around the N...N axis. As in the monoclinic C2/c (Z, = 2) polymorph, the molecular components are connected via O,H...N hydrogen bonds into a polymeric structure that consists of linear O,H...N(CH2CH2)3N...H,O segments, which are approximately mutually perpendicular. The two polymorphic forms of DABCO monohydrate can be considered as structural analogues of NaCl, with the nearly globular DABCO molecules showing distorted cubic closest packing and all octahedral interstices occupied by water molecules. [source]


    High Pressure Response of Rutile Polymorphs and Its Significance for Indicating the Subduction Depth of Continental Crust

    ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2008
    MENG Dawei
    Abstract: ,-PbO2 -type TiO2 (TiO2 -II) is an important index mineral for ultrahigh-pressure metamorphism. After the discovery of a natural high-pressure phase of titanium oxide with ,-PbO2 -structure in omphacite from coesite-bearing eclogite at Shima in the Dabie Mountains, China, a nano-scale (<2 nm) ,-PbO2 -type TiO2 has been identified through electron diffraction and high-resolution transmission electron microscopy in coesite-bearing jadeite quartzite at Shuanghe in the Dabie Mountains. The crystal structure is orthorhombic with lattice parameters a = 4.58times10,1 nm, b = 5.42times10,1 nm, c = 4.96times10,1 nm and space group Pbcn. The analysis results reveal that rutile {011}R twin interface is a basic structural unit of ,-PbO2 -type TiO2. Nucleation of ,-PbO2 -type TiO2 lamellae is caused by the displacement of one half of the titanium cations within the {011}R twin slab. This displacement reduces the Ti-O-Ti distance and is favored by high pressure. The identification of ,-PbO2 -type TiO2 in coesite-bearing jadeite quartzite from Shuanghe, Dabie Mountains, provides a new and powerful evidence of ultrahigh-pressure metamorphism at 4,7 GPa, 850C-900C, and implies a burial of continental crustal rocks to 130,200 kilometers depth or deeper. The ,-PbO2 -type TiO2 may be a useful indicator of the pressure and temperature in the diamond stability field. [source]


    ChemInform Abstract: Comparative Studies on the Phase Stability, Electronic Structure, and Topology of the Charge Density in the Li3XO4 (X: P, As, V) Lithium Orthosalt Polymorphs

    CHEMINFORM, Issue 31 2009
    Christine Frayret
    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]


    ChemInform Abstract: A Comparative Study of GaAsO4 Polymorphs: Ab initio Calculations on High-Pressure Forms.

    CHEMINFORM, Issue 33 2008
    Elena Arroyo y de Dompablo
    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]


    ChemInform Abstract: Two Cuprous Cyanide Polymorphs: Diamond Net versus 3,4-Connected Net.

    CHEMINFORM, Issue 28 2008
    Xian-Ming Zhang
    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]


    ChemInform Abstract: Stability of Alkali Metal Halide Polymorphs as a Function of Pressure

    CHEMINFORM, Issue 20 2008
    Zeljko P. Cancarevic
    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]


    ChemInform Abstract: Two Ce(SO4)24H2O Polymorphs: Crystal Structure and Thermal Behavior.

    CHEMINFORM, Issue 5 2008
    Barbara M. Casari
    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]


    Crystal Structures and Photocatalysis of the Triclinic Polymorphs of BiNbO4 and BiTaO4.

    CHEMINFORM, Issue 13 2007
    B. Muktha
    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, please click on HTML or PDF. [source]


    Density Functional Theory Calculations of Dense TiO2 Polymorphs: Implication for Visible-Light-Responsive Photocatalysts.

    CHEMINFORM, Issue 31 2005
    Ming-Yu Kuo
    No abstract is available for this article. [source]