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1.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(11):990-993
2,6‐Diaminopyridine (26‐DAP, C5H7N3) is a common intermediate in the synthesis of aromatic azo chromophores, which are widespread in the dyes and pigments industry. Sublimation of commercial 26‐DAP powder yielded a new polymorph, denoted Form II, which grew as colorless orthorhombic needles. Recrystallization from acetone or toluene also yielded Form II as the major phase. Thermal analysis shows that Form II is a less stable polymorph and it converts upon heating at 335 K to the previously reported Form I. 相似文献
2.
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(10):760-766
A new monoclinic polymorph of ferrocenecarboxylic anhydride, [Fe2(C5H5)2(C12H8O3)], was obtained. Three molecules are present in the asymmetric unit, two of them being nearly identical (r.m.s. deviation = 0.11 Å), with the Fe atoms on the same side of the anhydride functional group. In the third molecule, the two Fe atoms are located at opposite sides of the functional group (ferrocene–ferrocene pseudo‐torsion angle = 146.2°), a very unsual feature in metallocene anhydrides. A network of weak intermolecular hydrogen bonds was also disclosed. 相似文献
3.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(5):529-533
A novel polymorph of RbCuCl3 (rubidium copper trichloride), denoted ϵ‐RbCuCl3, has been prepared by chemical vapour transport (CVT) from a mixture of CuO, CuCl2, SeO2 and RbCl. The new polymorph crystallizes in the orthorhombic space group C2221. The crystal structure is based on an octahedral framework of the 4H perovskite type. The Rb+ and Cl− ions form a four‐layer closest‐packing array with an ABCB sequence. The Cu2+ cations reside in octahedral cavities with a typical [4 + 2]‐Jahn–Teller‐distorted coordination, forming four short and two long Cu—Cl bonds. ϵ‐RbCuCl3 is the most structurally complex and most dense among all currently known RbCuCl3 polymorphs, which allows us to suggest that it is a high‐pressure phase, which is unstable under ambient conditions. 相似文献
4.
《Acta Crystallographica. Section C, Structural Chemistry》2018,74(6):690-695
Cisapride monohydrate (systematic name: 4‐amino‐5‐chloro‐N‐{(3RS,4SR)‐1‐[3‐(4‐fluorophenoxy)propyl]‐3‐methoxypiperidin‐4‐yl}‐2‐methoxybenzamide monohydrate), C23H29ClFN3O4·H2O, is a nondopamine‐blocking gastrokinetic drug. A new polymorph of cisapride monohydrate has been reported nearly three decades after the report of its first known crystal structure [Collin et al. (1989). J. Mol. Struct. 214 , 159–175]. The second polymorph is also monoclinic, but with different unit‐cell parameters. A comparison of both polymorphic forms shows that the difference is thus not in the molecular conformation but in the arrangements of molecules in the crystal packing. The crystal morphology of two forms was predicted with the BFDH model in Materials Studio and inferred that the powder of the new polymorph has better flowability than the original polymorph. The results of DSC (differential scanning calorimetry) analysis and slurry experiments show that both polymorphs are stable at room temperature. 相似文献
5.
Chlorido(2,3,7,8,12,13,17,18‐octaethylporphyrinato)iron(III): a new triclinic polymorph of Fe(OEP)Cl
Saifon A. Kohnhorst Kenneth J. Haller 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(4):368-374
The previous structure determination of the title compound, [Fe(C36H44N4)Cl], was of a monoclinic polymorph [Senge (2005). Acta Cryst. E 61 , m399–m400]. The crystal structure of a new triclinic polymorph has been determined based on single‐crystal X‐ray diffraction data collected at 100 K. The asymmetric unit contains one molecule of the high‐spin square‐pyramidal iron(III) porphyrinate. The structure exhibits distinct nonstatistical alternative positions for most atoms and was consequently modeled as a whole‐molecule disorder. The compound is characterized by an average Fe—N bond length of 2.065 (2) Å, an Fe—Cl bond length of 2.225 (4) Å, and the iron(III) cation displaced by 0.494 (4) Å from the plane of the 24‐atom porphyrinate core, essentially the same as in the previously determined polymorph. Common features of the porphyrin plane–plane stacking involve two types of synthons, each of which can be further stabilized with additional H...Cl interactions to the axial chloride ligand, exhibiting concerted interactions of H atoms from the ethyl groups with the π‐cloud electron density of adjacent molecules; the shortest methylene H‐atom contacts are in the range 2.75–2.91 Å, resulting in plane–plane separations of 3.407 (4) and 3.416 (4) Å, and the shortest methyl H‐atom contacts are 2.56–2.95 Å, resulting in plane–plane separations of 4.900 (5) and 4.909 (5) Å in the monoclinic polymorph. The plane‐to‐plane stacking synthons in the triclinic polymorph are similar, but at greater distances; the shortest methylene H‐atom contacts are 2.86–2.94 Å, resulting in plane–plane separations of 3.45 (2) and 3.45 (3) Å, and the shortest methyl H‐atom contacts are 2.89–3.20 Å, resulting in plane–plane separations of 5.081 (13) and 5.134 (13) Å, consistent with the density of the triclinic polymorph being 1.5% lower, suggesting lesser packing efficiency and lower stability in the triclinic polymorph. The major molecular differences found in the polymorphs is in three different orientations of the ethyl‐group side chains on the periphery of the porphyrin core. 相似文献
6.
Structural and computational analysis of intermolecular interactions in a new 2‐thiouracil polymorph
《Acta Crystallographica. Section C, Structural Chemistry》2017,73(12):1078-1086
The crystallization and characterization of a new polymorph of 2‐thiouracil by single‐crystal X‐ray diffraction, Hirshfeld surface analysis and periodic density functional theory (DFT) calculations are described. The previously published polymorph (A ) crystallizes in the triclinic space group P , while that described herein (B ) crystallizes in the monoclinic space group P 21/c . Periodic DFT calculations showed that the energies of polymorphs A and B , compared to the gas‐phase geometry, were −108.8 and −29.4 kJ mol−1, respectively. The two polymorphs have different intermolecular contacts that were analyzed and are discussed in detail. Significant differences in the molecular structure were found only in the bond lengths and angles involving heteroatoms that are involved in hydrogen bonds. Decomposition of the Hirshfeld fingerprint plots revealed that O…H and S…H contacts cover over 50% of the noncovalent contacts in both of the polymorphs; however, they are quite different in strength. Hydrogen bonds of the N—H…O and N—H…S types were found in polymorph A , whereas in polymorph B , only those of the N—H…O type are present, resulting in a different packing in the unit cell. QTAIM (quantum theory of atoms in molecules) computational analysis showed that the interaction energies for these weak‐to‐medium strength hydrogen bonds with a noncovalent or mixed interaction character were estimated to fall within the ranges 5.4–10.2 and 4.9–9.2 kJ mol−1 for polymorphs A and B , respectively. Also, the NCI (noncovalent interaction) plots revealed weak stacking interactions. The interaction energies for these interactions were in the ranges 3.5–4.1 and 3.1–5.5 kJ mol−1 for polymorphs A and B , respectively, as shown by QTAIM analysis. 相似文献
7.
One‐pot synthesis of various unsymmetrical 2‐bromo‐5‐pyridylselenium compounds has been carried out under non‐cryogenic conditions by selective single bromine–magnesium exchange of 2,5‐dibromopyridine using isopropylmagnesium chloride. This exchange gives 2‐bromo‐5‐pyridylmagnesium chloride, which upon the insertion of elemental selenium followed by the treatment with alkyl halide gives the title compounds in good yield. This exchange has also been extended towards bromine–magnesium exchange of 2‐bromopyridine for the improved synthesis of 2‐pyridylselenium compounds. The molecular structure of 2‐bromo‐5‐selenopyridyltribromomethane has been examined by single crystal X‐ray diffraction. This compound crystallizes in the monoclinic space group P21/n. From the molecular structure it was found that intermolecular BrBr, NSe and SeBr interactions control its crystal packing. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
8.
Willian Hermoso Naziah B. Jaufeerally Ponnadurai Ramasami Fernando R. Ornellas 《International journal of quantum chemistry》2013,113(2):112-118
This investigation is concerned with the characterization of seleno‐sulfide‐halogen model systems, the isomerization processes, and the dissociation into diatomic fragment channels on the [H, S, Se, Cl] potential energy surface. Structural, energetic, and vibrational data were obtained at the CCSD(T) and MP2 levels of theory with the series of correlation consistent basis sets and extrapolated to the complete basis set (CBS) limit. For the frequencies, additional computations were performed to include the contribution of anharmonic effects, and for the determination of the heats of formation, important corrections incorporating core‐valence correlation effects and relativistic effects (scalar and spin‐orbit) were taken into account. CCSD(T)/CBS relative stability (kcal mol?1) follows the order: HSSeCl (0.0), HSeSCl (8.80), SSeHCl (23.52), and SeSHCl (25.87). The cis‐rotational barrier for the two lowest isomers is practically identical (10.14 and 10.09 kcal mol?1), whereas for the trans barrier, we obtained 9.25 (HSSeCl) and 8.45 (HSeSCl) kcal mol?1. Dissociation of HSSeCl (HSeSCl) into HS (HSe) + SeCl (SCl) requires 59.70 (56.30) kcal mol?1. For the most stable isomer, we predict a value of the heat of formation at 298.15 K of 2.53 kcal mol?1. One of the outcomes of this research is that the MP2 results are consistent with those of CCSD(T). The MP2 method turns out to be a reliable alternative for a first exploration of larger catenated species, although it accounts for a lesser fraction of correlation effects. © 2012 Wiley Periodicals, Inc. 相似文献
9.
Rim Benali‐Cherif Radhwane Takouachet El‐Eulmi Bendeif Nourredine Benali‐Cherif 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(3):323-325
The crystal structure of a polymorph of 4‐aminobenzoic acid (PABA), C7H7NO2, at 100 K is noncentrosymmetric, as opposed to centrosymmetric in the structures of the other known polymorphs. The two crystallographically independent PABA molecules form pseudocentrosymmetric O—H...O hydrogen‐bonded dimers that are further linked by N—H...O hydrogen bonds into a three‐dimensional network. The benzene rings stack in the b direction. The CO2 moieties are bent out slightly from the benzene ring plane. 相似文献
10.
M. Perrin C. Bavoux F. Vocanson R. Lamartine C. Desroches P. Miele S. Parola 《Journal of inclusion phenomena and macrocyclic chemistry》2003,46(1-2):15-17
p-Tetrakis(phenylazo)-tetra-hydroxythiacalix[4]arene shows complexing properties with neutral molecules. A complex with pyridine was crystallized and the crystal structure determined. The crystals are monoclinic, space group C2/c, a = 49.953(10), b = 21.566(4), c = 23.448(5) Å, = 105.12(3)°, V = 24386(8) Å 3, Z = 16. Two macrocycles are positioned in such a way that they form a cavity where two pyridine molecules are encapsulated giving a 2:2 endocomplex. 5.5 other pyridine molecules are trapped between the macrocycles, two of them giving H-bonds with the calixarenes. 相似文献
11.
Eynav Kats Joel Bernstein Andreas Lemmerer 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(2):208-212
Succinic acid has been known since 1546 and was first chemically identified in the mid‐19th century. In an attempt to prepare a molecular salt of succinic acid with (S)‐(?)‐α‐methylbenzylamine, we have obtained the second polymorph of the monoammonium salt of succinic acid, NH4+·C4H5O4?. The crystal structure determination proves the structure of the ionic compound and the intimate role of the ammonium ion in the structure, which is compared to the earlier described polymorph. 相似文献
12.
Damian Rosiak Andrzej Okuniewski Jarosaw Chojnacki 《Acta Crystallographica. Section C, Structural Chemistry》2021,77(1):11-19
By the reaction of benzoyl chloride, potassium isothiocyanate and the appropriate halogenoaniline, i.e. 2/3/4‐(bromo/iodo)aniline, we have obtained five new 1‐benzoyl‐3‐(halogenophenyl)thioureas, namely, 1‐benzoyl‐3‐(2‐bromophenyl)thiourea and 1‐benzoyl‐3‐(3‐bromophenyl)thiourea, C14H11BrN2OS, and 1‐benzoyl‐3‐(2‐iodophenyl)thiourea, 1‐benzoyl‐3‐(3‐iodophenyl)thiourea and 1‐benzoyl‐3‐(4‐iodophenyl)thiourea, C14H11IN2OS. Structural and conformational features of the compounds have been analyzed using X‐ray diffraction and theoretical calculations. The novel compounds were characterized by solid‐state IR and 1H/13C NMR spectroscopy. The conformations and intermolecular interactions, such as hydrogen bonds, π–π and S(6)…π stacking, and X…O (X = I or Br), I…S and I…π, have been examined and rationalized, together with four analogous compounds described previously in the literature. The set of nine compounds was chosen to examine how a change of the halogen atom and its position on the phenyl ring affects the molecular and crystal structures. 相似文献
13.
The crystal structure of 5‐fluorosalicylic acid is known from the literature [Choudhury & Guru Row (2004). Acta Cryst. E 60 , o1595–o1597] as crystallizing in the monoclinic crystal system with space‐group setting P21/n and with one molecule in the asymmetric unit (polymorph I). We describe here a new polymorph which is again monoclinic but with different unit‐cell parameters (polymorph II). Polymorph II has two molecules in the asymmetric unit. Its structure was modelled as a twin, with a pseudo‐orthorhombic C‐centred twin cell. 相似文献
14.
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. 相似文献
15.
Svitlana V. Shishkina Irina S. Konovalova Svitlana S. Kovalenko Lyudmila L. Nikolaeva Natalya D. Bunyatyan Sergiy M. Kovalenko 《Acta Crystallographica. Section C, Structural Chemistry》2021,77(1):20-28
The dipharmacophore compound 3‐cyclopropyl‐5‐(3‐methyl‐[1,2,4]triazolo[4,3‐a]pyridin‐7‐yl)‐1,2,4‐oxadiazole, C12H11N5O, was studied on the assumption of its potential biological activity. Two polymorphic forms differ in both their molecular and crystal structures. The monoclinic polymorphic form was crystallized from more volatile solvents and contains a conformer with a higher relative energy. The basic molecule forms an abundance of interactions with relatively close energies. The orthorhombic polymorph was crystallized very slowly from isoamyl alcohol and contains a conformer with a much lower energy. The basic molecule forms two strong interactions and a large number of weak interactions. Stacking interactions of the `head‐to‐head' type in the monoclinic structure and of the `head‐to‐tail' type in the orthorhombic structure proved to be the strongest and form stacked columns in the two polymorphs. The main structural motif of the monoclinic structure is a double column where two stacked columns interact through weak C—H…N hydrogen bonds and dispersive interactions. In the orthorhombic structure, a single stacked column is the main structural motif. Periodic calculations confirmed that the orthorhombic structure obtained by slow evaporation has a lower lattice energy (0.97 kcal mol?1) compared to the monoclinic structure. 相似文献
16.
Volodymyr Pavlyuk Grygoriy Dmytriv Malgorzata Szyrej Sergii Levkovets Oleh Parasyuk 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(6):550-554
A novel quaternary mixed halogenide, Tl5Hg2Br5I4, was synthesized by fusion of thallium bromide and mercury iodide in a 5:2 molar ratio. The crystal structure of Tl5Hg2Br5I4 represents a new series of composite structures described by the general formula nTlBr*mTl2[HgBr2I2]; in this case, n = 4 and m = 8. Electronic structure calculations indicate that the title compound is a semiconductor. 相似文献
17.
N,N‐Diethyldithiocarbamate complexes of 2‐alkoxycarbonylethyltin trichloride, ROCOCH2CH2 SnCl3?x[S2CNEt2]x (R = CH3 ( a ); CH3CH2 ( b ); CH2?CHCH2 ( c ); CH3CH2CH2 ( d ); CH3CH2CH2CH2 ( e ); x = 1 ( 1 ), 2 ( 2 )) were synthesized and characterized by means of elemental analysis, IR, and NMR (1H, 13C and 119Sn) spectra. The crystal structure of 1b (i.e. R = CH3CH2, x = 1) was determined and shows that the tin atom adopts a distorted octahedral geometry with both a five‐membered chelate ring, formed via carbonyl coordination to tin, and a four‐membered chelate ring, formed by the bidentate dithiocarbamate. The spectral data and ab initio calculations indicate that intramolecular carbonyl‐oxygen to tin coordination in 1a–1e persists, but not in 2a–2e , owing to the preference of the dithiocarbamate ligands to chelate the tin centre. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
18.
Daniel Nicholls Carole Elleman Norman Shankland Kenneth Shankland 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(7):904-909
A new crystalline form of αβ‐d ‐lactose (C12H22O11) has been prepared by the rapid drying of an approximately 40% w/v syrup of d ‐lactose. Initially identified from its novel powder X‐ray diffraction pattern, the monoclinic crystal structure was solved from a microcrystal recovered from the generally polycrystalline mixed‐phase residue obtained at the end of the drying step. This is the second crystalline form of αβ‐d ‐lactose to be identified and it has a high degree of structural three‐dimensional similarity to the previously identified triclinic form. 相似文献
19.
The title compound is a polymorph of [Na11(OSiMe3)10(OH)] and was crystallized from a toluene solution containing NaOSiMe3 and water. The molecular structure is best described as being composed of two subunits, a square antiprism built from eight sodium atoms and an Na4O4 heterocubane, both sharing a sodium atom. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
20.
The enhancing effects of molecule X (X = PH2Cl,SHCl, ClCl) on chalcogen–chalcogen interactions in cyclic trimers Y···Y···X (Y = SHCl,SeHCl)
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Lixin Mo Yanli Zeng Xiaoyan Li Lingpeng Meng 《International journal of quantum chemistry》2017,117(8)
The enhancing effects of molecule X (X = PH2Cl, SHCl, ClCl) on S···S and Se···Se chalcogen–chalcogen bonds in the cyclic trimers SHCl···SHCl···X and SeHCl···SeHCl···X were investigated by calculations at the MP2/aug‐cc‐pVTZ level. When molecule X is added to the dimer SHCl···SHCl (SeHCl···SeHCl), cyclic trimers are formed. Compared with the dimer, all the cyclic trimers have shorter S···S (Se···Se) lengths, greater electron densities, negative three‐body interaction energies, and larger second‐order perturbation energies. These results indicate that the addition of molecule X strengthens the original S···S (Se···Se) bond. For the SHCl···SHCl···X cyclic trimers, the S···S bond is strongest in SHCl···SHCl···PH2Cl, weaker in SHCl···SHCl···SHCl, and weakest in SHCl···SHCl···ClCl. This same trend is observed for the Se···Se bond in SeHCl···SeHCl···X. This means that PH2Cl provides the greatest enhancement to the S···S (Se···Se) interaction. 相似文献