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Journal articles on the topic 'Polymorphous crystallization'

Author: Grafiati

Published: 4 June 2021

Last updated: 1 February 2022

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1

Rath, Chandana, J. Farjas, P. Roura, F. Kail, P. Roca i Cabarrocas, and E. Bertran. "Thermally Induced Structural Transformations on Polymorphous Silicon." Journal of Materials Research 20, no. 9 (2005): 2562–67. http://dx.doi.org/10.1557/jmr.2005.0322.

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Polymorphous Si is a nanostructured form of hydrogenated amorphous Si that contains a small fraction of Si nanocrystals or clusters. Its thermally induced transformations such as relaxation, dehydrogenation, and crystallization have been studied by calorimetry and evolved gas analysis as a complementary technique. The observed behavior has been compared to that of conventional hydrogenated amorphous Si and amorphous Si nanoparticles. In the temperature range of our experiments (650–700 °C), crystallization takes place at almost the same temperature in polymorphous and in amorphous Si. In contrast, dehydrogenation processes reflect the presence of different hydrogen states. The calorimetry and evolved gas analysis thermograms clearly show that polymorphous Si shares hydrogen states of both amorphous Si and Si nanoparticles. Finally, the total energy of the main Si–H group present in polymorphous Si has been quantified.

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2

Morin, B., K. R. Elder, M. Sutton, and Martin Grant. "Model of the Kinetics of Polymorphous Crystallization." Physical Review Letters 75, no. 11 (1995): 2156–59. http://dx.doi.org/10.1103/physrevlett.75.2156.

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3

Parthasarathy, G., S. Asokan, E. S. R. Gopal, and A. K. Bandyopadhyay. "Pressure induced polymorphous crystallization in bulk Ge20Te80 glass." Physica B+C 139-140 (May 1986): 266–68. http://dx.doi.org/10.1016/0378-4363(86)90574-7.

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4

Asokan, S., E. S. R. Gopal, and G. Parthasarathy. "Pressure-induced polymorphous crystallization in bulk Si20Te80 glass." Journal of Materials Science 21, no. 2 (1986): 625–29. http://dx.doi.org/10.1007/bf01145533.

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5

Ye, F., and K. Lu. "Pressure effect on polymorphous crystallization kinetics in amorphous selenium." Acta Materialia 46, no. 16 (1998): 5965–71. http://dx.doi.org/10.1016/s1359-6454(98)00240-7.

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6

Fellah, Noalle, Carolyn Jin Zhang, Catherine Chen, et al. "Highly Polymorphous Nicotinamide and Isonicotinamide: Solution versus Melt Crystallization." Crystal Growth & Design 21, no. 8 (2021): 4713–24. http://dx.doi.org/10.1021/acs.cgd.1c00547.

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7

Farjas, J., J. Serra-Miralles, P. Roura, E. Bertran, and P. Roca i. Cabarrocas. "Anomalous crystallization of hydrogenated amorphous silicon during fast heating ramps." Journal of Materials Research 20, no. 2 (2005): 277–81. http://dx.doi.org/10.1557/jmr.2005.0037.

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Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700 °C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At 100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials.

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8

Gallagher, D. Travis, Edward Eisenstein, Kathryn E. Fisher, et al. "Polymorphous crystallization and diffraction of threonine deaminase from Escherichia coli." Acta Crystallographica Section D Biological Crystallography 54, no. 3 (1998): 467–69. http://dx.doi.org/10.1107/s0907444997011360.

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The biosynthetic threonine deaminase from Escherichia coli, an allosteric tetramer with key regulatory functions, has been crystallized in several crystal forms. Two distinct forms, both belonging to either space group P3121 or P3221, with different sized asymmetric units that both contain a tetramer, grow under identical conditions. Diffraction data sets to 2.8 Å resolution (native) and 2.9 Å resolution (isomorphous uranyl derivative) have been collected from a third crystal form in space group I222.

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9

Pan, Pengju, Weihua Kai, Bo Zhu, Tungalag Dong, and Yoshio Inoue. "Polymorphous Crystallization and Multiple Melting Behavior of Poly(l-lactide): Molecular Weight Dependence." Macromolecules 40, no. 19 (2007): 6898–905. http://dx.doi.org/10.1021/ma071258d.

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10

Kitamura, M., and T. Tanaka. "Crystallization behavior of polymorphous Ni-complex clathrate in the presence of 2-methylnaphthalene." Journal of Crystal Growth 142, no. 1-2 (1994): 165–70. http://dx.doi.org/10.1016/0022-0248(94)90284-4.

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11

Volpe, Valentina, Fabiana Foglia, and Roberto Pantani. "Flow-induced crystallization of a Poly(Lactic acid): Effect of the application of low shear rates on the polymorphous crystallization." Polymer 229 (August 2021): 123997. http://dx.doi.org/10.1016/j.polymer.2021.123997.

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12

Girin, Oleg. "Phase Transformations in the Metallic Materials Being Electrodeposited and their Application for the Development of Advanced Technologies for Anticorrosive Protection of Canned-Food Steel Sheet." Materials Science Forum 561-565 (October 2007): 2369–72. http://dx.doi.org/10.4028/www.scientific.net/msf.561-565.2369.

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It has been found that during the electrodeposition of metallic material a supercooled metallic liquid is being formed that is solidified at the deposition temperature in the form of a crystalline or amorphous phase. These phase transformations are proved by the existence in the electrodeposited metals of metastable structures that correspond to: the amorphous structure of the solidified metallic liquid, the highly defective crystalline structure of the metal quenched from the liquid state, and the intermediate modifications that had appeared during the fast crystallization of the liquid phase of the polymorphous metal. On the basis of this phenomenon there have been developed the technologies for producing of protective texturally-composite tin electrocoat, nanostructurally-texturally-composite chromium electrocoat, and amorphous composite chromium electrocoat on canned-food steel sheet.

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13

Kamyshinsky, Roman, Yury Chesnokov, Liubov Dadinova, et al. "Polymorphic Protective Dps–DNA Co-Crystals by Cryo Electron Tomography and Small Angle X-Ray Scattering." Biomolecules 10, no. 1 (2019): 39. http://dx.doi.org/10.3390/biom10010039.

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Rapid increase of intracellular synthesis of specific histone-like Dps protein that binds DNA to protect the genome against deleterious factors leads to in cellulo crystallization—one of the most curious processes in the area of life science at the moment. However, the actual structure of the Dps–DNA co-crystals remained uncertain in the details for more than two decades. Cryo-electron tomography and small-angle X-ray scattering revealed polymorphous modifications of the co-crystals depending on the buffer parameters. Two different types of the Dps–DNA co-crystals are formed in vitro: triclinic and cubic. Three-dimensional reconstruction revealed DNA and Dps molecules in cubic co-crystals, and the unit cell parameters of cubic lattice were determined consistently by both methods.

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14

Inoue, A., T. Zhang, M. W. Chen, T. Sakurai, J. Saida, and M. Matsushita. "RETRACTED – Formation and properties of Zr-based bulk quasicrystalline alloys with high strength and good ductility." Journal of Materials Research 15, no. 10 (2000): 2195–208. http://dx.doi.org/10.1557/jmr.2000.0316.

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The crystallization mode of the Zr–Al–Ni–Cu amorphous alloys changed from a single stage to become two stages by the addition of Ag or Pd, and the first-stage exothermic reaction was found to result from the precipitation of nanoscale icosahedral particles with a size of 20 to 50 nm. The precipitation took place by high nucleation and low growth rates in a polymorphous mode for the Ag-containing alloys, and a diffusioncontrolled mode for the Pd-containing alloys. The nanoscale mixed structure alloys exhibited improved strength and ductility as compared with the corresponding amorphous single-phase alloys. The findings of the dispersion strengthening as well as the dispersion ductilization gave a future opportunity to fabricate a new bulk nonequilibrium phase alloy by use of the new phenomenon.

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15

Krüger, Martin, A. Ken Inge, Helge Reinsch, et al. "Polymorphous Al-MOFs Based on V-Shaped Linker Molecules: Synthesis, Properties, and in Situ Investigation of Their Crystallization." Inorganic Chemistry 56, no. 10 (2017): 5851–62. http://dx.doi.org/10.1021/acs.inorgchem.7b00202.

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16

Tol, R. T., V. B. F. Mathot, H. Reynaers, B. Goderis, and G. Groeninckx. "Confined crystallization phenomena in immiscible polymer blends with dispersed micro-and nanometer sized PA6 droplets part 4: polymorphous structure and (meta)-stability of PA6 crystals formed in different temperature regions." Polymer 46, no. 9 (2005): 2966–77. http://dx.doi.org/10.1016/j.polymer.2005.02.021.

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17

Kien, P. H., N. T. Thao, and P. K. Hung. "The local structure and crystallization of FeB nanoparticle." Modern Physics Letters B 28, no. 31 (2014): 1450246. http://dx.doi.org/10.1142/s0217984914502467.

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Using molecular dynamics simulation, we have studied the structural evolution of FeB nanoparticle under annealing and the physical properties of its polymorphs such as crystalline, amorphous and mixed samples. The main focus of present work is the crystallization mechanism and the local structure of polymorphs of FeB nanoparticle. The simulation result shows that the amorphous sample undergoes the crystallization via the nucleation mechanism. During the crystallization, B atoms move out the places where the Fe crystal locates, and diffuse to the boundary region of Fe crystal. The crystal growth proceeds when this boundary region attains specific properties which are defined by the fraction of B atoms and the energies of AB -atoms and CB -atoms. Further our study indicates that unlike amorphous sample, the crystalline and mixed samples consist of three distinct parts including Fe crystalline and two FeB amorphous parts ( B -poor and B -rich amorphous part). The different polymorphs of FeB nanoparticle differ in the local structure, size of Fe crystal and energies of different type atoms.

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18

Beckmann, W. "Crystallization of Pharmaceutical Compounds Polymorphs, Pseudo-Polymorphs and Particle Formation." Engineering in Life Sciences 3, no. 3 (2003): 113–20. http://dx.doi.org/10.1002/elsc.200390013.

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19

Xue, Chen, Heng Xu, Rong-Yi Huang, and Xiao-Ming Ren. "Mutual transformation between crystalline phases and dielectric properties of coordination polymers with the formula [Cd(N-methylimidazole)2(H2O)x(glutarate)]·nH2O (x = 0 or 1; n = 0 or 4)." CrystEngComm 16, no. 42 (2014): 9857–65. http://dx.doi.org/10.1039/c4ce00997e.

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20

Bruno, M. "A two-step nucleation model based on diffuse interface theory (DIT) to explain the non-classical view of calcium carbonate polymorph formation." CrystEngComm 21, no. 33 (2019): 4918–24. http://dx.doi.org/10.1039/c9ce00610a.

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21

Zhang, Shuai, Thomas W. Y. Lee, and Albert H. L. Chow. "Crystallization of Itraconazole Polymorphs from Melt." Crystal Growth & Design 16, no. 7 (2016): 3791–801. http://dx.doi.org/10.1021/acs.cgd.6b00342.

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22

Zhang, Geoff G. Z., Chonghui Gu, Mark T. Zell, R. Todd Burkhardt, Eric J. Munson, and David J. W. Grant. "Crystallization and Transitions of Sulfamerazine Polymorphs." Journal of Pharmaceutical Sciences 91, no. 4 (2002): 1089–100. http://dx.doi.org/10.1002/jps.10100.

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23

Cesur, S., and S. Gokbel. "Crystallization of mefenamic acid and polymorphs." Crystal Research and Technology 43, no. 7 (2008): 720–28. http://dx.doi.org/10.1002/crat.200711119.

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24

Diao, Ying, Kristen E. Whaley, Matthew E. Helgeson, et al. "Gel-Induced Selective Crystallization of Polymorphs." Journal of the American Chemical Society 134, no. 1 (2011): 673–84. http://dx.doi.org/10.1021/ja210006t.

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25

Jia, Lina, Shijie Xu, Shiyuan Liu, Shichao Du, Songgu Wu, and Junbo Gong. "Polymorphs of daidzein and intermolecular interaction effect on solution crystallization." CrystEngComm 19, no. 47 (2017): 7146–53. http://dx.doi.org/10.1039/c7ce01716b.

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26

Ševčík, Radek, Petra Mácová, and Marta Pérez-Estébanez. "Crystallization of Aragonite from Vaterite Precursor during Various Refluxing Times." Advanced Materials Research 1119 (July 2015): 466–70. http://dx.doi.org/10.4028/www.scientific.net/amr.1119.466.

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CaCO3 polymorphs are intensively studied due to their importance in the nature and the widespread use in the industry as well. This work is dealing with the crystallization of aragonite from vaterite dispersion during the refluxation at 100°C. The characterization of CaCO3 polymorphs during vaterite transformation was performed with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). The influence of the different refluxing times on the aragonite crystallization was discussed. The purest aragonite, 70.7(2) wt.%, was synthetized in the sample refluxed for 60 minutes. Prolonged refluxation strongly affected aragonite crystals with gradual transformation into calcite.

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27

Abe, Hiroshi, Takahiro Takekiyo, Yukihiro Yoshimura, Nozomu Hamaya, and Shinichiro Ozawa. "Crystal Polymorphs and Multiple Crystallization Pathways of Highly Pressurized 1-Ethyl-3-Methylimidazolium Nitrate." Australian Journal of Chemistry 72, no. 2 (2019): 87. http://dx.doi.org/10.1071/ch18368.

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Crystal polymorphs and multiple crystallization pathways of a room-temperature ionic liquid (RTIL) were observed only under high pressure (HP). The RTIL was 1-ethyl-3-methylimidazolium nitrate, [C2mim][NO3]. The HP-crystal polymorphs were related to conformations of the C2mim+ cation, and the HP-crystal pathways determined by the presence or absence of the planar′ (P′) conformation of the C2mim+ cation were switched at the bifurcation pressure (PB). Above PB, modulated crystal structures derived from the HP-inherent P′ conformer. Simultaneous X-ray diffraction and differential scanning calorimetry measurements, accompanied by optical microscope observations, confirmed the normal low-temperature crystallization of [C2mim][NO3] under ambient pressure.

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28

Zhang, Keke, Noalle Fellah, Alexander G. Shtukenberg, Xiaoyan Fu, Chunhua Hu, and Michael D. Ward. "Discovery of new polymorphs of the tuberculosis drug isoniazid." CrystEngComm 22, no. 16 (2020): 2705–8. http://dx.doi.org/10.1039/d0ce00440e.

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29

Mallia, Ajith R., Ramarani Sethy, Vinayak Bhat, and Mahesh Hariharan. "Crystallization induced enhanced emission in conformational polymorphs of a rotationally flexible molecule." Journal of Materials Chemistry C 4, no. 14 (2016): 2931–35. http://dx.doi.org/10.1039/c5tc03188e.

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30

De la Mora, Eugenio, Edith Flores-Hernández, Jean Jakoncic, et al. "SdsA polymorph isolation and improvement of their crystal quality using nonconventional crystallization techniques." Journal of Applied Crystallography 48, no. 5 (2015): 1551–59. http://dx.doi.org/10.1107/s1600576715016556.

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SdsA, a sodium dodecyl sulfate hydrolase, fromPseudomonas aeruginosawas crystallized in three different crystal polymorphs and their three-dimensional structure was determined. The different polymorphs present different crystal packing habits. One of the polymorphs suggests the existence of a tetramer, an oligomeric state not observed previously, while the crystal packing of the remaining two polymorphs obstructs the active site entrance but stabilizes flexible regions of the protein. Nonconventional crystallization methods that minimize convection, such as counterdiffusion in polyvinyl alcohol gel coupled with the influence of a 500 MHz (10.2 T) magnetic field, were necessary to isolate the poorest diffracting polymorph and increase its internal order to determine its structure by X-ray diffraction. The results obtained show the effectiveness of nonconventional crystallographic methods to isolate different crystal polymorphs.

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31

Kränzlin, N., M. Staniuk, F. J. Heiligtag, et al. "Rationale for the crystallization of titania polymorphs in solution." Nanoscale 6, no. 24 (2014): 14716–23. http://dx.doi.org/10.1039/c4nr04346d.

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32

García-Peñas, Alberto, José M. Gómez-Elvira, María L. Cerrada, and Ernesto Pérez. "Dependence of phase transitions on composition in isotactic poly(propylene-co-1-pentene-co-1-hexene) terpolymers." RSC Advances 6, no. 86 (2016): 82907–15. http://dx.doi.org/10.1039/c6ra16575c.

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Several polymorphs (monoclinic, orthorhombic, trigonal and mesomorphic) are observed in metallocenic isotactic poly(propylene-co-1-pentene-co-1-hexene) terpolymers, depending on composition and crystallization conditions.

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33

Capes, Jacqueline S., and Ruth E. Cameron. "Contact Line Crystallization To Obtain Metastable Polymorphs." Crystal Growth & Design 7, no. 1 (2007): 108–12. http://dx.doi.org/10.1021/cg0605988.

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34

Safari, Fatemeh, Anna Olejniczak, and Andrzej Katrusiak. "Pressure-Dependent Crystallization Preference of Resorcinol Polymorphs." Crystal Growth & Design 19, no. 10 (2019): 5629–35. http://dx.doi.org/10.1021/acs.cgd.9b00610.

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35

Khoshkhoo, S., and J. Anwar. "Crystallization of polymorphs: the effect of solvent." Journal of Physics D: Applied Physics 26, no. 8B (1993): B90—B93. http://dx.doi.org/10.1088/0022-3727/26/8b/013.

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36

Lu, Jie, Xiu‐Juan Wang, Xia Yang, and Chi‐Bun Ching. "Characterization and Selective Crystallization of Famotidine Polymorphs." Journal of Pharmaceutical Sciences 96, no. 9 (2007): 2457–68. http://dx.doi.org/10.1002/jps.20868.

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37

Kitamura, Mitsutaka. "Strategy for control of crystallization of polymorphs." CrystEngComm 11, no. 6 (2009): 949. http://dx.doi.org/10.1039/b809332f.

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38

Punmalee, Neeranuch, Lek Wantha, and Adrian E. Flood. "Antisolvent Crystallization of Polymorphs of L -Histidine." Chemical Engineering & Technology 41, no. 6 (2018): 1132–38. http://dx.doi.org/10.1002/ceat.201700676.

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39

Piaggi, Pablo M., and Michele Parrinello. "Predicting polymorphism in molecular crystals using orientational entropy." Proceedings of the National Academy of Sciences 115, no. 41 (2018): 10251–56. http://dx.doi.org/10.1073/pnas.1811056115.

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We introduce a computational method to discover polymorphs in molecular crystals at finite temperature. The method is based on reproducing the crystallization process starting from the liquid and letting the system discover the relevant polymorphs. This idea, however, conflicts with the fact that crystallization has a timescale much longer than that of molecular simulations. To bring the process within affordable simulation time, we enhance the fluctuations of a collective variable by constructing a bias potential with well-tempered metadynamics. We use as a collective variable an entropy surrogate based on an extended pair correlation function that includes the correlation between the orientations of pairs of molecules. We also propose a similarity metric between configurations based on the extended pair correlation function and a generalized Kullback–Leibler divergence. In this way, we automatically classify the configurations as belonging to a given polymorph, using our metric and a hierarchical clustering algorithm. We apply our method to urea and naphthalene. We find different polymorphs for both substances, and one of them is stabilized at finite temperature by entropic effects.

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40

Losev, E. A., and E. V. Boldyreva. "A salt or a co-crystal – when crystallization protocol matters." CrystEngComm 20, no. 16 (2018): 2299–305. http://dx.doi.org/10.1039/c7ce02204b.

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By controlling nucleation and growth through choice of crystallization conditions, the stable co-crystal or metastable salt can be reproducibly obtained in accordance with Ostwald's rule of stages and the concept of ‘disappearing polymorphs’.

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41

Croitor, Lilia, Mihaela F. Petric, Elisabeta I. Szerb, et al. "The role of 4-nitrobenzoic acid polymorphs in the crystallization process of organic acid–base multicomponent systems." CrystEngComm 21, no. 40 (2019): 6038–47. http://dx.doi.org/10.1039/c9ce01239g.

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An investigation of the role of 4-nitrobenzoic acid polymorphs in the crystallization process of dimethylethanolammonium 4-nitrobenzoate from solution and comprehensive characterization of time-dependent changes associated with solid-state transformations are presented.

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42

Jing, Yanwei, Xueying Nai, Li Dang, et al. "Reinforcing polypropylene with calcium carbonate of different morphologies and polymorphs." Science and Engineering of Composite Materials 25, no. 4 (2018): 745–51. http://dx.doi.org/10.1515/secm-2015-0307.

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Abstract The influence of calcium carbonate (CaCO3) with different polymorphs (calcite and aragonite) and morphologies (granular and rod-like) on mechanical and crystallization properties of polypropylene (PP) was investigated. Meanwhile, these CaCO3 fillers coated with oleic acid were added in different contents to PP. The results indicate that the tensile strength, flexural strength, modulus, and crystallization property of the filler-treated samples are improved, but the impact strength decreased. The crystallinity of the composites is higher than that of neat PP. Moreover, in the rod shape filler-treated sample, in both whisker species, the mechanical properties of composites are superior to the particles filled. Differential scanning calorimetry, X-ray diffraction, and mechanical tests display that calcite whisker-reinforced composite has higher crystallization enthalpy, melting enthalpy, degree of crystallinity, and mechanical properties than aragonite whiskers and calcite particles filled composites.

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43

Chewle, Surahit, Franziska Emmerling, and Marcus Weber. "Effect of Choice of Solvent on Crystallization Pathway of Paracetamol: An Experimental and Theoretical Case Study." Crystals 10, no. 12 (2020): 1107. http://dx.doi.org/10.3390/cryst10121107.

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The choice of solvents influences crystalline solid formed during the crystallization of active pharmaceutical ingredients (API). The underlying effects are not always well understood because of the complexity of the systems. Theoretical models are often insufficient to describe this phenomenon. In this study, the crystallization behavior of the model drug paracetamol in different solvents was studied based on experimental and molecular dynamics data. The crystallization process was followed in situ using time-resolved Raman spectroscopy. Molecular dynamics with simulated annealing algorithm was used for an atomistic understanding of the underlying processes. The experimental and theoretical data indicate that paracetamol molecules adopt a particular geometry in a given solvent predefining the crystallization of certain polymorphs.

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44

Ziemecka, Gokalp, Stroobants, Brau, Maes, and Wit. "Polymorph Selection of ROY by Flow-Driven Crystallization." Crystals 9, no. 7 (2019): 351. http://dx.doi.org/10.3390/cryst9070351.

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The selection of polymorphs of the organic compound 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile, ROY, is studied experimentally in the confined space between two horizontal glass plates when an acetone solution of ROY of variable concentration is injected at a variable flow rate into water. Depending on the local concentration within the radial flow, a polymorph selection is observed such that red prisms are favored close to the injection center while yellow needles are the preferred polymorph close to the edge of the injected ROY domain. At larger flow rates, a buoyancy-driven instability induces stripes at the outer edge of the displacement pattern, in which specific polymorphs are seen to crystallize. Our results evidence the possibility of a selection of ROY polymorph structures in out-of-equilibrium flow conditions.

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45

Falk, Jacqueline, Detlef Hofmann, and Klaus Merz. "Controlled usage of H/D exchange to circumvent concomitant polymorphs of ROY." IUCrJ 5, no. 5 (2018): 569–73. http://dx.doi.org/10.1107/s2052252518009995.

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The hypothesis that H/D exchange affects the structural formation of organic compounds in the solid state is supported by a deeper understanding of the altering polymorphism of ROY (a substance striking for its high number of polymorphic forms) through deuteration. Therefore, ROY was deuterated at its amine function, which leads to a seemingly small yet effective modification of the hydrogen-bond strength. In contrast to the crystallization of the non-deuterated ROY in methanol or ethanol, which leads to the simultaneous formation of two forms (OP and Y polymorphs), so-called concomitant polymorphs, the crystallization of d 1-ROY leads to the selective formation of the Y polymorph exclusively. The preferred aggregation behavior of the Y form of d 1-ROY is assigned to the weakening of an intramolecular hydrogen bond and a consequently strengthened intermolecular hydrogen bond after deuteration.

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46

Takeguchi, Seiya, Arisa Sato, Hironori Hondoh, Mio Aoki, Hidetaka Uehara та Satoru Ueno. "Multiple β Forms of Saturated Monoacid Triacylglycerol Crystals". Molecules 25, № 21 (2020): 5086. http://dx.doi.org/10.3390/molecules25215086.

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We have investigated the polymorphism of triacylglycerol (TAG) crystals as they affect the qualities such as shelf life, mouth feel, and texture of chocolate and other products. Saturated monoacid TAGs, like trilaurin, are considered as models for TAG crystallization; however, there is still debate about the number of their polymorphs that exist. In this study, we characterized a set of novel polymorphs, β forms of saturated monoacid TAGs, which were obtained via different pathways depending on the crystallization history, by polarized light microscopy, X-ray diffraction, and differential scanning calorimetry. Saturated monoacid TAGs were crystallized as the unstable polymorphs, the α or β’ forms first, and then they were transformed into β forms by solid–solid transformations. The β form that had transformed from β’ changed its morphology by a polymorphic transformation, while the β form made from the α form kept its spherulite morphology. The β forms obtained showed different melting points. Additional heat treatment promoted further polymorphic transformation. Four novel β forms were found for each of the saturated monoacid TAGs, trilaurin, trimyristin, tripalmitin, and tristearin. They showed similar polymorphism with the same subcell packing.

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47

Kitamura, Mitsutaka. "Thermodynamic stability and transformation of pharmaceutical polymorphs." Pure and Applied Chemistry 77, no. 3 (2005): 581–91. http://dx.doi.org/10.1351/pac200577030581.

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The thermodynamic stability and transformation of pharmaceutical polymorphs was investigated, especially those of the thiazole derivative pharmaceutical, 2-(3-cyano-4-isobutyloxyphenyl)-4-methyl-5-thiazolecarboxylic acid (BPT). The influence of methanol compositions in solvents and temperature on the solubility and the transformation behavior of BPT was clarified. The transformation behavior was explained by the chemical potential difference between the stable and metastable forms. It was shown that a specific solute–solvent interaction contributes to the preferential nucleation and growth of the stable or metastable forms and influences the transformation behaviors. The solubility of BPT of the solvated crystals is much more influenced by the solvent compositions than the true polymorphs. The solubility ratio of the solvated crystals depends on the solvent composition, whereas the solubility ratio of the true polymorphs is considered to be independent of the solvents. The crystallization behavior was also investigated. The transformation rate after crystallization appeared to depend on the initial concentration of BPT and the addition rate of the antisolvent. The cause of this phenomenon was presumed to be a slight inclusion of the stable form in the metastable form.

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48

Peresypkina, Eugenia V., Mark B. Bushuev, Alexander V. Virovets, Victor P. Krivopalov, Ludmila G. Lavrenova, and Stanislav V. Larionov. "Three differently coloured concomitant polymorphs: synthesis, structure and packing analysis of (4-(3′,5′-dimethyl-1H-pyrazol-1′-yl)-6-methyl-2-phenylpyrimidine)dichlorocopper(II)." Acta Crystallographica Section B Structural Science 61, no. 2 (2005): 164–73. http://dx.doi.org/10.1107/s010876810403294x.

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A novel pyrazolylpyrimidine ligand (L) and its complex CuLCl2 were prepared and structurally characterized. The simultaneous crystallization of three polymorphs of CuLCl2, green (G), emerald green (EG) and orange (O), was discovered. The molecular structures vary only slightly between the three forms. The Cu atom forms four coordinate bonds with the two N and two Cl atoms, and a shortened Cu...H contact with an H atom of the phenyl ring in L. The structural difference between polymorphs was analyzed with the boundary surfaces of molecular Voronoi–Dirichlet polyhedra. The difference in colour of the polymorphs is likely to be due to the different π–π stackings. There is no stacking in the G modification, but EG and O polymorphs demonstrate face-to-face and slipped stacking, resulting in dimers and infinite chains, respectively. The EG and O polymorphs are packed according to the hexagonal close-packing motif, while in G no special topology is found.

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49

Biju, A. R., and M. V. Rajasekharan. "Polymorphism in the nitrate salt of the [Mn(acetylacetonate)2(H2O)2]+ ion." Acta Crystallographica Section B Structural Science 66, no. 3 (2010): 373–79. http://dx.doi.org/10.1107/s0108768110009961.

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The crystallization of [Mn(acac)2(H2O)2]+ from solutions containing excess nitrate leads to the formation of four polymorphs. All polymorphs contain two different types of complex ions, one containing essentially coplanar acac ligands and the other in which the two acac ligands together assume a chair conformation. Molecular modelling using DFT (density-functional theory) calculations shows that the coplanar conformation is the electronically stable one. The hydrogen bonding between the trans-water molecules and the nitrate ion produces a one-dimensional chain of 12-membered rings, which are further organized into a two-dimensional network via a lattice water molecule. Lattice-energy calculations have been carried out to compare the stabilities of the four polymorphs.

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50

Gnutzmann, Tanja, Yen Nguyen Thi, Klaus Rademann, and Franziska Emmerling. "Solvent-Triggered Crystallization of Polymorphs Studied in Situ." Crystal Growth & Design 14, no. 12 (2014): 6445–50. http://dx.doi.org/10.1021/cg501287v.

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