Structural and computational analysis of intermolecular interactions in a new 2‐thiouracil polymorph

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.     

颜色可区分的氰桥五边形带经亲铜作用聚集的异金属多形体

水热条件下,环境友好的K₂[Ni(CN)₄]能缓慢水解形成cis-[Ni(CN)₂(H₂O)₄]单元和氰基配体,并进一步与金属铜(Ⅰ)原子组装形成异金属的五边形带。这些五边形带通过亲铜聚集作用形成二维有色的超分子多形体[(CuCN)₂Ni(CN)₂(H₂O)₄](1和2)。研究发现,低温条件下形成了密集态的深蓝色的化合物1,然而高温反应条件形成疏松态的紫色化合物2,这一现象与高温高压的反应条件形成密集态的物质这一规律相违背。结构的进一步分析发现五边形环尺寸的微小改变和二维超分子层间距离的差异是引起这一反常的原因。除此之外,这两个新的化合物也是少见的由亲铜性聚集作用诱导的着色异常的多形体的例子,显示了从深蓝色到紫色的颜色改变。磁性研究证实了平面正方形的[Ni(CN)₄]^2-中的金属镍(Ⅱ)转换成了有着基态自旋S=1的八面体配位几何中心。     

ECNU-36: A Quasi-Pure Polymorph CH Beta Silicate Composed of Hierarchical Nanosheet Crystals for Effective VOCs Adsorption

A quasi-pure C_H polymorph of microporous zeolite beta, named ECNU-36, was obtained as a highly crystalline silicate using 1,5-bis(tetramethylimidazolium) hydroxide as organic structure-directing agent (OSDA) in fluoride media. An appropriate concentration of free fluoride in the synthetic mother liquor was crucial to purify the C_H-phase. The framework structure of ECNU-36 consists of polymorph C_H (>95 %) and polymorph B, elucidated by a combination of PXRD data, DIFFaX simulation, EDT, and HRTEM techniques. For the first time, the framework structure of beta C_H polymorph was directly confirmed and solved using electron diffraction data. The pure-silica ECNU-36 showed an unusual crystal morphology, composed of stacked nanosheets, with typical 17 nm thickness and exposed {100} facets, which exhibited attractive adsorption performance for hydrocarbons and aromatics.     

Two Polymorphs of the Inclusion Compound [（n-C4H9）4N] ＋（C13H9O3）-H2O

Two polymorphs of the inclusion compound [(n-C4H9)4N]+·(C13H9O3)-·H2O havebeen prepared and characterized by X-ray crystallography. Polymorph 1: triclinic P 1 , a =13.4982(2), b = 13.5743(2), c = 17.1996(2) , α = 67.045(1), β = 77.845(1), γ = 88.762(1)°, V =2830.43(7)3, Z = 4, R = 0.0491, wR = 0.1276; Polymorph 2: tetragonal P43, a = b = 13.53690(1) , c = 30.8491(8) , V = 5653.02(16)3, Z = 8, R = 0.0448, wR = 0.0984. In these two crystalstructures, the hydrogen-bonded ribbons built of 4,4 -dihydroxybenzophenone (DHBP, C13H10O3)anions and water molecules are orderly arranged to generate two-dimensional host layers, withtetrabutylammonium cations contained between the layers to form the sandwich-like inclusioncompounds. The structures of 1 and 2, which exist as two polymorphs, both display the similarpacking pattern and hydrogen-bond linking model.     

Electronic structure and thermodynamics of V2O3 polymorphs

A metastable bixbyite‐type polymorph of vanadium sesquioxide, V₂O₃, has recently been synthesized, and it transforms to the corundum‐type phase at temperatures around 550 °C. The possibility of a paramagnetic to canted antiferromagnetic or even spin‐glass‐like transition has been discussed. Quantum‐chemical calculations on the density‐functional theory level including explicit electronic correlation confirm the metastability as well as the semiconducting behavior of the material and predict that the bixbyite‐type structure is about 0.1 eV less stable than the well‐known corundum‐type phase. Nonetheless, quasiharmonic phonon calculations manifest that bixbyite‐type vanadium sesquioxide is a dynamically stable compound. Other possible V₂O₃ polymorphs are shown to be even less suitable candidates for the composition V₂O₃. © 2012 Wiley Periodicals, Inc.     

In situ monitoring of the solution‐mediated polymorphic transformation of glycine: characterization of the polymorphs and observation of the transformation rate using Raman spectroscopy and microscopy

The aim of this work was to investigate the mechanism and progression of the solution‐mediated polymorphic transformation and crystallization of glycine. The identification of the α‐ and γ‐forms of glycine crystals was performed using powder X‐ray diffraction (PXRD), Raman microscopy and in situ probe Raman spectroscopy. The influence of the addition of NaCl and of the process parameters such as saturation temperature, seed size and stirring speed on the transformation behavior from the metastable α‐ form to the stable γ‐ form was examined. In situ probe Raman spectroscopy was used to monitor the solid‐phase properties—polymorphic composition. Fourier transform infrared spectroscopy (FTIR) with a ZnSe window was used to track the liquid‐phase concentration at different times. Besides, the polymorphic transformation of glycine in the solvent was also examined in situ using a microscope with a heating/cooling stage. The integration of the different offline and in situ analytical measurement techniques greatly assisted in accurately and quantitatively perceiving the fundamental phenomena that govern the transformation process. Copyright © 2008 John Wiley & Sons, Ltd.     

Crystal and Molecular Structure of Sulfadimethoxine,Polymorph III

Crystal structure of sulfadimethoxine, C₁₂H₁₄N₄O₄S, has been determined and refined to an R‐value of 0.043 using direct methods. It crystallizes in the triclinic space group P with a = 7.946(1), b = 9.330(1), c = 10.407(1)Å, α = 93.46(1), β = 95.43(1), γ = 114.62(1)° and Z = 2. The dihedral angle between the two six ‐ membered rings of the molecule is 77.6(8)°. Molecule adopts a gauche conformation about S8‐N11 bond with torsional angle of 60.0(2)°. The structure is mainly stable due to strong hydrogen bonds, amino nitrogen plays the role of donor in two different intermolecular hydrogen bonds where sulfonyl oxygen and pyrimidine nitrogen act as acceptor.     

铜酞菁同质多晶现象的研究及其超细粒子的制备

采用路易斯酸配位法溶解了铜酞菁,并对路易斯酸溶解铜酞菁的机理进行了简单讨论,同时研究了溶解过程中不同溶剂对铜酞菁晶型的影响.最后,用路易斯酸溶解配位法和微射流纳米分散技术相结合的方法成功制备了铜酞菁超细粒子,并用激光粒度仪、原子力显微镜、紫外可见分光光度计对超细粒子的粒径和吸收光谱进行了表征.     

The [4 + 4] thermocyclization of 9‐anthraldehyde: synthesis,crystal structure,experimental and theoretical UV spectra,natural bonding orbital analysis and prediction of third‐order nonlinear optical properties

The dimer of 9‐anthraldehyde, namely heptacyclo[8.6.6.6^2,9.0^3,8.0^11,16.0^17,22.0^23,28]octacosa‐3,5,7,11,13,15,17(22),18,20,23(28),24,26‐dodecaene‐1,9‐carbaldehyde, C₃₀H₂₀O₂, has been synthesized by refluxing an ethanol solution in the presence of M(ClO₄)₂ and 1,3‐diaminopropan‐2‐ol (M = Co²⁺ or Cu²⁺). Its structure has been determined by single‐crystal X‐ray diffraction, showing it to be a new polymorph, referred to as polymorph II, in the monoclinic space group P2₁/n. It is compared with the previously reported triclinic modification [Ehrenberg (1968). Acta Cryst. B 24 , 1123–1125], which is referred to as polymorph I. The asymmetric unit of polymorph II contains two half molecules located on crystallographic centres, while the asymmetric unit of polymorph I includes one half molecule, also located on a crystallographic centre. Time‐dependent density functional theory (TD‐DFT) at the RB3LYP level using the 6‐31G(d,p) basis set was applied. The predicted electronic absorption spectrum is in good agreement with the experimental one. The analysis of the calculated electronic absorption spectrum of polymorph II was carried out in order to assign the observed electronic transitions and to determine their character. A natural bonding orbital (NBO) analysis was executed at the same level to evaluate charge‐transfer, intramolecular hydrogen‐bonding interactions and hyperconjugative interactions. The third‐order nonlinear optical (NLO) properties of the compound were appraised by the ZINDO/sum‐over‐states method in both static and dynamic states. The orientationally averaged (isotropic) value of γ for the compound is greater than the corresponding value of 4‐nitroaniline (pNA).     

Polymorphic Phase Transformation in In2La and CeIn2

Nuclear quadrupole interactions of ¹¹¹Cd probes in In₂La and CeIn₂ were measured using perturbed angular correlation of gamma rays (PAC). Near room temperature, a single non-axially symmetric quadrupole interaction was observed in each compound, with ω ₀ = eQV _zz /ℏ = 78.8(2) Mrad/s and η = 0.312(1) for In₂La at 11°C and ω ₀ = 80(1) Mrad/s and η = 0.29(2) for CeIn₂ at 34°C. The observed non-axial symmetry is consistent with the reported CeCu₂ structure of the phases. The non-axially symmetric interactions were replaced completely by axially symmetric interactions (η = 0) at 524°C, with ω ₀ = 101.0(1) Mrad/s in In₂La and ω ₀ = 96.9(4) Mrad/s in CeIn₂. The change in symmetry is attributed to a polymorphic phase transformation. Based on symmetry information from the quadrupole interaction and on chemical arguments, it is proposed that high-temperature phases of In₂La and CeIn₂ both have the AlB₂ (C32) structure.