Acta Crystallographica Section B-structural Science最新文献

{"title":"Unique thermodynamic relationships for ΔfHo and ΔfGo for crystalline inorganic salts. I. Predicting the possible existence and synthesis of Na2SO2 and Na2SeO2.","authors":"Angel Vegas,&nbsp;Joel F Liebman,&nbsp;H Donald Brooke Jenkins","doi":"10.1107/S0108768112030686","DOIUrl":"https://doi.org/10.1107/S0108768112030686","url":null,"abstract":"<p><p>The concept that equates oxidation and pressure has been successfully utilized in explaining the structural changes observed in the M(2)S subnets of M(2)SO(x) (x = 3, 4) compounds (M = Na, K) when compared with the structures (room- and high-pressure phases) of their parent M(2)S `alloy' [Martínez-Cruz et al. (1994), J. Solid State Chem. 110, 397-398; Vegas (2000), Crystallogr. Rev. 7, 189-286; Vegas et al. (2002), Solid State Sci. 4, 1077-1081]. These structural changes suggest that if M(2)SO(2) would exist, its cation array might well have an anti-CaF(2) structure. On the other hand, in an analysis of the existing thermodynamic data for M(2)S, M(2)SO(3) and M(2)SO(4) we have identified, and report, a series of unique linear relationships between the known Δ(f)H(o) and Δ(f)G(o) values of the alkali metal (M) sulfide (x = 0) and their oxyanion salts M(2)SO(x) (x = 3 and 4), and the similarly between M(2)S(2) disulfide (x = 0) and disulfur oxyanion salts M(2)S(2)O(x) (x = 3, 4, 5, 6 and 7) and the number of O atoms in their anions x. These linear relationships appear to be unique to sulfur compounds and their inherent simplicity permits us to interpolate thermochemical data (Δ(f)H(o)) for as yet unprepared compounds, M(2)SO (x = 1) and M(2)SO(2) (x = 2). The excellent linearity indicates the reliability of the interpolated data. Making use of the volume-based thermodynamics, VBT [Jenkins et al. (1999), Inorg. Chem. 38, 3609-3620], the values of the absolute entropies were estimated and from them, the standard Δ(f)S(o) values, and then the Δ(f)G(o) values of the salts. A tentative proposal is made for the synthesis of Na(2)SO(2) which involves bubbling SO(2) through a solution of sodium in liquid ammonia. For this attractive thermodynamic route, we estimate ΔG(o) to be approximately -500 kJ mol(-1). However, examination of the stability of Na(2)SO(2) raises doubts and Na(2)SeO(2) emerges as a more attractive target material. Its synthesis is likely to be easier and it is stable to disproportionation into Na(2)S and Na(2)SeO(4). Like Na(2)SO(2), this compound is predicted to have an anti-CaF(2) Na(2)Se subnet.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 5","pages":"511-27"},"PeriodicalIF":1.9,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112030686","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30916926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cl-OH ion-exchanging process in chlorapatite (Ca5(PO4)3Cl(x)(OH)(1-x))--a deep insight.","authors":"Esther García-Tuñón,&nbsp;Bruno Dacuña,&nbsp;Guillermo Zaragoza,&nbsp;Jaime Franco,&nbsp;Francisco Guitián","doi":"10.1107/S0108768112019520","DOIUrl":"https://doi.org/10.1107/S0108768112019520","url":null,"abstract":"<p><p>We have synthesized large chlorapatite [ClAp, Ca(5)(PO(4))(3)Cl(x)(OH)(1-x), where x = 1] single crystals using the molten salt method. We have corroborated that the hexagonal symmetry P6(3)/m describes the crystal structure best, even though the crystals are synthetic and stoichiometric. Moreover, we have performed several thermal treatments on these ClAp crystals, generating new single crystals in the apatite system [Ca(5)(PO(4))(3)Cl(x)(OH)(1-x), where x ≤ 1], where the chloride anions (Cl(-)) were systematically substituted by hydroxyl anions (OH(-)). These new single crystals were methodically characterized by powder and single-crystal X-ray diffraction (SXRD), scanning electron microscopy (SEM), Fourier transform-IR spectroscopy (FT-IR), and energy-dispersive X-ray spectroscopy (EDS). We have discovered a previously unreported OH(-) inclusion site substituting the Cl(-) anion during the ion-exchanging process. Finally, we evaluated the atomic rearrangements of the other species involved in the structure. These movements are associated with ionic exchange, which can be justified from an energetic point of view. We also found a novel phase transformation at high temperature. When the crystals are heated over 1753 K the apatite system evolves to a less ordered monoclinic structure, in which the complete loss of the species in the anionic channel (Cl(-), OH(-)) has been confirmed.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 5","pages":"467-79"},"PeriodicalIF":1.9,"publicationDate":"2012-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112019520","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30916922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cocrystals of 5-fluorocytosine. I. Coformers with fixed hydrogen-bonding sites.","authors":"Maya Tutughamiarso,&nbsp;Guido Wagner,&nbsp;Ernst Egert","doi":"10.1107/S010876811202561X","DOIUrl":"https://doi.org/10.1107/S010876811202561X","url":null,"abstract":"<p><p>The antifungal drug 5-fluorocytosine (4-amino-5-fluoro-1,2-dihydropyrimidin-2-one) was cocrystallized with five complementary compounds in order to better understand its drug-receptor interaction. The first two compounds, 2-aminopyrimidine (2-amino-1,3-diazine) and N-acetylcreatinine (N-acetyl-2-amino-1-methyl-5H-imidazol-4-one), exhibit donor-acceptor sites for R(2)(2)(8) heterodimer formation with 5-fluorocytosine. Such a heterodimer is observed in the cocrystal with 2-aminopyrimidine (I); in contrast, 5-fluorocytosine and N-acetylcreatinine [which forms homodimers in its crystal structure (II)] are connected only by a single hydrogen bond in (III). The other three compounds 6-aminouracil (6-amino-2,4-pyrimidinediol), 6-aminoisocytosine (2,6-diamino-3H-pyrimidin-4-one) and acyclovir [acycloguanosine or 2-amino-9-[(2-hydroxyethoxy)methyl]-1,9-dihydro-6H-purin-6-one] possess donor-donor-acceptor sites; therefore, they can interact with 5-fluorocytosine to form a heterodimer linked by three hydrogen bonds. In the cocrystals with 6-aminoisocytosine (Va)-(Vd), as well as in the cocrystal with the antiviral drug acyclovir (VII), the desired heterodimers are observed. However, they are not formed in the cocrystal with 6-aminouracil (IV), where the components are connected by two hydrogen bonds. In addition, a solvent-free structure of acyclovir (VI) was obtained. A comparison of the calculated energies released during dimer formation helped to rationalize the preference for hydrogen-bonding interactions in the various cocrystal structures.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"431-43"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S010876811202561X","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pressure‐induced phase transitions in l‐alanine, revisited. Corrigendum","authors":"N. Tumanov, E. Boldyreva, B. Kolesov, A. Kurnosov, R. Cabrera","doi":"10.1107/S010876811203193X","DOIUrl":"https://doi.org/10.1107/S010876811203193X","url":null,"abstract":"Tables 2 and 3 in the paper by Tumanov et al. [(2010), Acta Cryst. B66, 458–471] are corrected.","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 1","pages":"465-465"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87603205","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Crystallographic input data for (001)-, (110)- and (111)-oriented superlattices.","authors":"Z Touaa,&nbsp;Nadir Sekkal","doi":"10.1107/S0108768112030091","DOIUrl":"https://doi.org/10.1107/S0108768112030091","url":null,"abstract":"<p><p>General aspects concerned with (001)-, (110)- and (111)-oriented superlattices (SLs) have been investigated. In particular, the symmetry of these systems have been derived and given in detail. As a test, the obtained data have been utilized to calculate electronic structures and gaps of a standard GaAs/AlAs system using an accurate version of the first principle full potential linear muffin-tin orbital (FPLMTO) method based on a local-density functional approximation (LDA).</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"378-88"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112030091","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure determination of L-arabinitol by powder X-ray diffraction.","authors":"Patrick Derollez,&nbsp;Yannick Guinet,&nbsp;Frédéric Affouard,&nbsp;Florence Danède,&nbsp;Laurent Carpentier,&nbsp;Alain Hédoux","doi":"10.1107/S0108768112019994","DOIUrl":"https://doi.org/10.1107/S0108768112019994","url":null,"abstract":"<p><p>Powder X-ray diffraction patterns of the commercial phase of L-arabinitol were recorded with a laboratory diffractometer. The starting structural model was found by a Monte-Carlo simulated annealing method. The final structure was obtained through Rietveld refinements with soft restraints on the interatomic bond lengths and bond angles. H atoms of hydroxyl groups were localized by minimization of the crystalline energy. The cell is triclinic with the space group P1 and contains two molecules. The crystalline cohesion is achieved by an important network of O-H···O hydrogen bonds.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"407-11"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112019994","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"[Ni(MeCN)(H2O)2(NO3)2]·(15-crown-5)·MeCN: detailed study of a four-phase sequence that includes an intermediate modulated phase.","authors":"Maxime A Siegler,&nbsp;Sean Parkin,&nbsp;Carolyn Pratt Brock","doi":"10.1107/S0108768112018319","DOIUrl":"https://doi.org/10.1107/S0108768112018319","url":null,"abstract":"<p><p>A sequence of four phases has been found for an acetonitrile-solvated co-crystal with 15-crown-5 of the nickel complex [acetonitrilediaqua-κ(1)O-nitrato-κ(2)O-nitratonickel(II)]. The structure could be determined at intervals of ca 10 K in the range 90-273 K because crystals remain single through the three transitions. In phase (I) (T ≥ ca 240 K; P2(1)/m, Z' = ½), there is extensive disorder, which is mostly resolved in phase (III) (ca 230-145 K; P2(1)/c, Z' = 1). Phase (IV) (ca 145-90 K, and probably below; P ̅1, Z' = 2) is ordered. Phase (II) (ca 238-232 K) is modulated, but the satellite reflections are too weak to allow the structure to be determined within its stability range by standard methods. Most crystals that were flash-cooled from room temperature to 90 K have a metastable P2(1), Z' = 5 superstructure that (at least in a commensurate approximation) was identified as similar to the structure of phase (II) by comparison of reconstructed reciprocal-lattice slices and by analogy with the phase behavior of the very similar compound [Ni(H(2)O)(6)](NO(3))(2)·(15-crown-5)·2H(2)O [Siegler et al. (2011). Acta Cryst. B67, 486-498]. In the phase (II) structure slab-like regions that are like the disordered phase (I) structure alternate with regions of similar shape and size that are like the more ordered phase (III) structure.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"389-400"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112018319","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"X-ray diffraction and Raman study of DL-alanine at high pressure: revision of phase transitions.","authors":"Nikolay A Tumanov,&nbsp;Elena V Boldyreva","doi":"10.1107/S0108768112028972","DOIUrl":"https://doi.org/10.1107/S0108768112028972","url":null,"abstract":"<p><p>The effect of pressure on DL-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ~6 GPa). No structural phase transitions have been observed. At ~1.5-2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107-111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"412-23"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112028972","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cocrystals of 5-fluorocytosine. II. Coformers with variable hydrogen-bonding sites.","authors":"Maya Tutughamiarso,&nbsp;Ernst Egert","doi":"10.1107/S0108768112029977","DOIUrl":"https://doi.org/10.1107/S0108768112029977","url":null,"abstract":"Two flexible molecules, biuret and 6-acetamidouracil, were cocrystallized with 5-fluorocytosine to study their conformational preferences. In the cocrystal with 5-fluorocytosine (I), biuret exhibits the same conformation as in its hydrate. In contrast, 6-acetamidouracil can adopt two main conformations depending on its crystal environment: in crystal (II) the trans form characterized by an intramolecular hydrogen bond is observed, while in the cocrystal with 5-fluorocytosine (III), the complementary binding induces the cis form. Three cocrystals of 6-methylisocytosine demonstrate that complementary binding enables the crystallization of a specific tautomer. In the cocrystals with 5-fluorocytosine, (IVa) and (IVb), only the 3H tautomer of 6-methylisocytosine is present, whereas in the cocrystal with 6-aminoisocytosine, (V), the 1H tautomeric form is adopted. The complexes observed in the cocrystals are stabilized by three hydrogen bonds similar to those constituting the Watson-Crick C·G base pair.","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"444-52"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112029977","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773897","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A time-resolved powder diffraction study of in-situ photodimerization kinetics of 9-methylanthracene using a CCD area detector and parametric Rietveld refinement.","authors":"Ahmed F Mabied,&nbsp;Melanie Müller,&nbsp;Robert E Dinnebier,&nbsp;Shunsuke Nozawa,&nbsp;Manabu Hoshino,&nbsp;Ayana Tomita,&nbsp;Tokushi Sato,&nbsp;Shin-ichi Adachi","doi":"10.1107/S0108768112027450","DOIUrl":"https://doi.org/10.1107/S0108768112027450","url":null,"abstract":"<p><p>The [4π + 4π] photodimerization process of the 9-substituted anthracene derivative crystalline 9-methylanthracene (9-MA) was investigated using time-resolved X-ray powder diffraction. The study was carried out in-situ using a CCD area detector. Sequential and parametric Rietveld refinement was applied for quantitative phase analysis. The results of traditional sequential Rietveld refinement showed that the evolution of the dimerization process can be described using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model. The parameters of the JMAK equation were obtained successfully by parametric Rietveld refinement and suggest that the reaction follows heterogeneous nucleation and one-dimensional growth with a decreasing nucleation rate.</p>","PeriodicalId":7107,"journal":{"name":"Acta Crystallographica Section B-structural Science","volume":"68 Pt 4","pages":"424-30"},"PeriodicalIF":1.9,"publicationDate":"2012-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1107/S0108768112027450","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"30773344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}