Cocrystallization

Aqueous solutions of zirconium oxide dinitrate [13826-66-9] (zirconium oxynitrate) and zirconium oxychloride behave very similarly these two compounds have been cocrystallized in soHd solution (202) where ZrO(N03 -5H2 O was the stable hydrate. 

Two cocrystallization processes employ dibasic crystals as intermediates. The PPG process (199—202) is discussed under commercial processes. The PPC process (203) forms dibasic crystals from lime and recovered filtrates. The dibasic crystals are separated from thek mother liquor by decantation, slurried in caustic solution and chlorinated to produce a cocrystalline slurry of Ca(OCl)2 and NaCl. The slurry is sent to a flotation cell where the larger salt crystals settle out and the smaller hypochlorite crystals float to the top with the aid of ak and flotation agent. The hypochlorite slurry is centrifuged the cake going to a dryer and the centrate to the flotation cell. The salt-rich bottoms from the flotation cell are centrifuged and washed with dibasic mother Hquor. The centrates are recycled to the precipitation step. 

A similar effect is produced by cocrystallization with protic solvents capable of forming a hydrogen bond-stabilized environment. Thus, dihydropyrimidine 47 (R = R = aryl,R = R = COOR, R = H) cocrystallizes with water (1 1) exclusively as the 1,6 tautomer (98T9837). 2,4,6,6-Tetraphenyldihydropyrimidine 47 (R = R = R = R = Ph, R = H) exists as the 1,6 tautomer in its solvate with... 

First of all it is worth to remind that there are not well documented cases of cocrystallizations between different components of a polymer blend. Hence, also... 

For instance, also the homopolymers PVF and PVDF have been described to crystallize in separate crystals in their blends [99] (Though constituted by isomorphous monomeric units which can cocrystallize in the copolymers in the whole range of composition, as seen in Sect. 4.1). Moreover, at least for the studied conditions, the polymorphic behavior of PVDF is not altered by the presence of PVF [99]. 

Starkweather H.W., Cocrystallization and polymer miscibility, J. Appl. Polym. Sci., 25, 139, 1980. Seguela R. and Pmd homme J., Affinity of grain deformation in mesomorphic block polymers submitted to simple elongation. Macromolecules, 21, 635, 1988. 

Fig. 11. A view parallel to the columns of hydrogen-bonded But2SiOH2(SnCl3OH)2 molecules, showing the linking of the columns by the cocrystallized (Bul2H0Si)20 molecules. All hydrogen atoms and Bul groups have been omitted for clarity. Drawn using coordinates taken from the Cambridge Crystallographic Database.

The reaction between Bul2Si(OH)2 and Cl4Sn affords, after workup and crystallization from CH2C12, the tin complex 51 containing a bridging But2Si(OH)2 molecule, which is cocrystallized with (H0Bu 2Si)20, the structure of which is described in Section IV,D,1 (272). 

For a note on the reported differenes in the structure of Bul2Si(OH)2, see Ref. 292. c Compound cocrystallizes with (Bul2H0Si)20. 

Finally, the tris(pyrazolyl)hydroborato ligand system has also provided an interesting example in which a crystallographic site is disordered between a vacancy and a chain of three atoms. Thus, the x-ray structure of the cobalt complex [TpAnt]CoNCS (Ant = 9-anthryl) revealed the presence of the cocrystallized thallium derivative... 

TpAnt]Tl, and that the composition of the crystal studied was approximately [TpAnt](CoNCS)0.94TI0.06. As a consequence of the cocrystallization, the crystallographic site occupied by the CoNCS moiety was disordered with a thallium atom (Fig. 57). The ability of [TpAnt]CoNCS and [TpAnt]Tl, which differ substantially in the number of atoms at the disordered site, to cocrystallize is presumably due to the fact that the disordered site is enclosed within the pocket that is provided by the tris(pyrazolyl)hydroborato ligand. 

Fig. 57. Cocrystallized [TpAnt]CoNCS and [TpAnt]Tl. Reprinted from Polyhedron, 14, Han, R., Parkin, G., and Trofimenko, S The tris[3-(9-anthryl)pyrazol-l-yl]hydroborato ligand, [TpAnt] Compositional disorder between a vacancy and a chain of three atoms, p. 387, copyright 1995, with kind permission from Elsevier Science Ltd, The Boulevard, Langford Lane, Kidlington 0X5 1GB, UK.

Compound 15 has an ill-defined structure 70) due to poor crystal quality. It is, however, interesting to note that 15 became resolved (space group 7 2,2, Z = 8) in an attempted cocrystallization experiment in the presence of optically pure 1. The two molecules of 15 in the asymmetric unit may be seen as a sort of a self inclusion , where molecules are again linked into infinite H-bond chains analogous to 13. 

Diphenylurea Crystallization. 1,3-hfsphenylurea (13) is the parent compound of a large family of derivatives, most of which do not cocrystallize with guest molecules (Etter et al. 1990). Even when put into solution with strong hydrogen bond acceptors, e.g., dimethyl sulfoxide (DMSO), triphenylphosphineoxide (TPPO) and tetrahydrofuran (THF), most diphenyl ureas crystallize with other molecules of the same kind in a connectivity pattern viewed as is shown below (14), instead of forming cocrystals (e.g., 15). 

Etter, M. C., Z. Urbanczyk-Lipowska, M. Zia-Ebrahimi, and T. W. Pananto. 1990. Hydrogen Bond Directed Cocrystallization and Molecular Recognition Properties of Diaryl Ureas. J. Am Chem. Soc. 112, 8415. 

Copolyesters of poly(3HB-co-3HV) have approximately the same degree of crystallinity as the homopolymer PHB and all copolymers show similar conformation characteristics as those observed for PHB [24,26,65]. They show a minimum in their melting point versus composition curve at a 3HV content of approximately 40 mol%. The apparent ability of the two different monomeric units to cocrystallize might result from the fact that the copolymers are prone to show isodimorphic behavior [21, 26, 66-70]. However, the considerable reduction of the heat of fusion upon 3HV inclusion, as reported by Bluhm et al. 

Only molecular S7 and Se7 are firmly known, yet only the former has been characterized by X-ray analysis. However, Re complexes of Se7 are known55,56 and the neutral Se7 homocycle cocrystallized with salts of polyselenides.57,58 S7+ is thought to be present in S02 solutions of sulfur cations however, this is an unproven but likely hypothesis. Other than that, only the structures of Sig2+ and Se172+ contain E7 homocycles (see there). 

The MALDI-TOF technique was first developed for the analysis of large biomolecules (Karas and others 1987). This technique presents some interesting characteristics. Of these, the high speed of analysis and the sensitivity of the technique have been pointed out as important advantages compared with other methods. In MALDI the samples are cocrystallized with a matrix that is usually composed of organic compounds, such as 3,5-dimethoxy-4-hydroxycinnamic acid (sinapic acid), 2, 4, 6 -trihydroxyacetophenone, a-cyano-4-hydroxycinnamic acid (alpha-cyano or alpha-matrix), and 2,5-dihydroxybenzoic acid (DHB). After the cocrystallization, the laser is fired and the matrix absorbs energy and allows a soft ionization of the samples. Afterward the ions are analyzed by a TOF mass spectrometer. 

Fe(Cp-C0NHCH2S03)2] anion have been identified (TTF)2[Fe(Cp-CONHCH2 S03)2] and the solvated (TTF)2[Fe(Cp-C0NHCH2S03)2]-2CH30H. Both crystal structures contain face-to-face dimers, with the main structural differences probably attributed to hydrogen bonding to the cocrystallized methanol. No physical properties of these salts have yet been published. 

Certain pairs of enantiomers, such as 25°C solutions of camphor in aqueous ethanol (Fig. 26a), 2,2,5,5-tetramethyl-l-pyrrolidinoxy-3-carboxylic acid in chloroform (Fig. 26b), or carvoxime in hexane (Fig. 26c), cocrystallize throughout the entire range of mole fractions. The crystals that are in equilibrium with the saturated liquid solution are solid solutions (mixed crystals), since they constitute a single phase. The racemic solid solution is termed a pseudoracemate [141]. 

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