Full-matrix Least-squares Refinement Research Articles

Synthesis, Crystal Structure, and Electrical and Magnetic Characterizations of the Monoclinic Compounds Ln3Mo4+xSi1–xO14 (Ln = La, Ce, Pr, and Nd; x = 0 and 0.35) Containing Mo3 Clusters and Mo2 Dimers

Powder samples of the new monoclinic compounds Ln3Mo4SiO14 (Ln = La, Ce, Pr, and Nd) and single crystals of Pr3Mo4.35Si0.65O14 were obtained by the solid-state reaction. The crystal structure of Pr3Mo4.35Si0.65O14 was determined by single-crystal X-ray diffraction. Pr3Mo4.35Si0.65O14 crystallizes in the monoclinic space group P21/n with unit-cell parameters a = 5.6361 (2) Å, b = 17.5814 (8) Å, c = 10.9883 (4) Å, and Z = 4. Full-matrix least-squares refinement on F2 using 7544 independent reflections for 203 refinable parameters results in R1 = 0.0359 and wR2 = 0.0831. The structure contains chains of Mo3O13 clusters and chains of edge-sharing MoO6 octahedra with alternately short (2.508 Å) and long (3.161 Å) Mo-Mo distances running parallel to the a axis that are separated by 8- or 10-coordinate Pr-O polyhedra. Magnetic susceptibility measurements on the Ln3Mo4SiO14 (Ln = La, Ce, Pr, and Nd) are in agreement with a trivalent state of the rare earths for the Ce, Pr, and Nd compounds, while that on the lanthanum compound confirms the presence of one unpaired electron per Mo3 as expected. Resistivity measurements on a single crystal show that Pr3Mo4.35Si0.65O14 is a small band gap semi-conductor.

Refinement of anomalous dispersion correction parameters in single-crystal structure determinations.

Correcting for anomalous dispersion is part of any refinement of an X-ray dif-fraction crystal structure determination. The procedure takes the inelastic scattering in the diffraction experiment into account. This X-ray absorption effect is specific to each chemical compound and is particularly sensitive to radiation energies in the region of the absorption edges of the elements in the compound. Therefore, the widely used tabulated values for these corrections can only be approximations as they are based on calculations for isolated atoms. Features of the unique spatial and electronic environment that are directly related to the anomalous dispersion are ignored, although these can be observed spectroscopically. This significantly affects the fit between the crystallographic model and the measured intensities when the excitation wavelength in an X-ray diffraction experiment is close to an element's absorption edge. Herein, we report on synchrotron multi-wavelength single-crystal X-ray diffraction, as well as X-ray absorption spectroscopy experiments which we performed on the mol-ecular compound Mo(CO)6 at energies around the molybdenum K edge. The dispersive (f') and absorptive (f'') terms of the anomalous dispersion can be refined as independent parameters in the full-matrix least-squares refinement. This procedure has been implemented as a new feature in the well-established OLEX2 software suite. These refined parameters are in good agreement with the independently recorded X-ray absorption spectrum. The resulting crystallographic models show significant improvement compared to those employing tabulated values.

Site splitting at M3 in allanite-(Ce)

AbstractWe report the crystal structure of allanite-(Ce), with composition (Ca1.0REE0.9□0.1)Σ2.0(Al1.46Fe3+0.52Fe2+0.76Mg0.12Ti0.15)Σ3.01Si3O12(OH) from the Xinfeng rare earth element (REE)-bearing granite in Guangdong Province, China. It has the unit cell a = 8.9550(4) Å, b = 5.77875(16) Å, c = 10.2053(4) Å, β = 114.929(5)° and Z = 2 in space group P21/m and is characterised by site splitting at M3 into M3a and M3b, at a distance of 0.38(3) Å, which are occupied partially by Fe0.764Mg0.12 and Ti0.15, respectively. The structure was determined by single-crystal X-ray diffraction and refined with anisotropic full-matrix least-squares refinement on F2 to R1 = 2.82%, wR2 = 7.77% for 1856 independent reflections (8772 collected reflections). However, M3 splitting is not present in either ferriallanite-(Ce) or epidote, in which M3 is almost fully occupied either by Fe2+ or by Fe3+. Comparisons of bond lengths and volumes in cation polyhedra among allanite-(Ce), ferriallanite-(Ce) and epidote tend to indicate that the essential factor that facilitates site splitting of M3 in allanite-(Ce) is heterovalent substitution and occupation of a crystallographic site between Fe2+(Mg2+/Mn2+)–Al3+(Ti4+), a common phenomenon in minerals, such as the plagioclase series. Fine structure analysis of the M3 split model revealed that deformation of A2 is related closely to distorted M3, which is consistent with Fe2+ incorporation following REE substitution.

Crystal structure of the compound ScCo2Si2: single crystal investigation

For the first time, the complete single crystal structure study of the compound ScCo 2 Si 2 was performed. It belongs to the CeGa 2 Al 2 structure type, Pearson’s symbol tI 10,139, space group I 4/ mmm , lattice parameters a =3.7775(3) c =9.6208(11) Å. The compound was prepared by arc-melting of the initial elements with the purity of not less than 99.9 % under argon followed by annealing in silica tubes at 800 °C for 350 h. Single crystals for structural examination were selected under a microscope from the broken alloys obtained. X-ray diffraction data of one of the irregularly faceted single crystals obtained at a temperature of 300(2) K by means of single crystal X-ray diffractometer Bruker D8 Venture with monochromatized Mo K α-radiation. The structure is refined using the program SHELXL, version 2018/3 (full-matrix least-squares refinement with anisotropic atomic parameters), R 1 = 0,0247, wR 2 = 0,0614 for 57 unique reflections with I o > 2 σ(I o ) and 8 refined parameters. Coordinates of atoms are the following: 2Sc at 2 а 0 0 0; 4Co at 4 d 0 1/2 1/4; 4Si at 4 e 0 0 z , z =0.3776(2). Coordination numbers of Sc, Co and Si atoms are 20, 12 and 9, respectively. The interatomic distances, with the exception of Co–Si, are longer than the sum of the metal radii of the corresponding atoms. Co–Si distances (2.2525(9) Å) are smaller than the sum of the radii of these atoms (2.42 Å) and indicate a significant interaction between Co and Si in the structure. Currently known three scandium ternary compounds ScM 2 Si 2 (M=Co, Ni, Cu) are members of complete series of compounds RM 2 Si 2 (R=rare earths) isotypic with CeGa 2 Al 2 . Crystal chemical analysis of scandium intermetallic compounds of stoichiometric composition ScM 2 X 2 (M= d -element; X= p -element) was performed. Scandium occupies a special place among rare earths and shows crystal chemical affinity both with rare earths and Zr and Hf. Keywords : ternary silicides, rare earth elements, single crystal, crystal structure.

Growth, single crystal investigation, hirshfeld surface analysis, DFT studies, molecular docking, physico-chemical characterization and, in vitro, antioxidant activity of a novel hybrid complex

Interaction of the diphosphoric acid (H4P2O7) and organic ligand (3.4-dimethylaniline) with transition metal ions, cobalt (II) chloride leads to the formation of novel stable Co(II)-diphosphate cluster with empirical formula (C8H12N)2[Co(H2P2O7)2(H2O)2].2H2O. The structure of the synthesized material was confirmed by single crystal XRD at 120 ​K. The crystal was plate and crystallized in the triclinic P 1¯ space group with a ​= ​7.5340(4) Å, b ​= ​7.5445(4) Å, c ​= ​13.6896(8) Å, α ​= ​84.215(5)°, β ​= ​76.038(5)°, γ ​= ​74.284(5)°, V ​= ​726.38(7) Å3 and Z ​= ​1. Full-matrix least-squares refinement converged at R ​= ​0.035 and Rw ​= ​0.088 for 3636 independent observed reflections. Indeed, the purity phase was confirmed by the powder X-ray diffraction. A detailed analysis of the intermolecular close interactions and their percentage contribution has been performed based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. In this context, spectroscopic studies were performed to distinguish the different chemical functional groups and their environments in this molecule. To determine the optical properties, the UV–Visible and luminescence behavior were investigated. The magnetic properties have been investigated in the temperature range 2–300 k. The geometry of the hybrid complex was optimized in the gas phase, using density functional theory (B3LYP) with the 6-31+G (d,p) basis sets, it is found that the calculated and the experimental results were in good consistency. Furthermore, the synthesized product was screened for its antioxidant activities. Molecular docking study was additionally carried.

Synthesis, FT-IR, UV-VIS, DFT studies and SCXRD structure of 1-(tert-butyl) 3-ethyl-3-(hydroxy(thiophen-2-yl)methyl)piperidine-1,3-dicarboxylate

The crystal structure of 1-(tert-butyl) 3-ethyl 3-(hydroxy(thiophen-2-yl)methyl)piperidine-1,3-dicarboxylate (C 18 H 25 NO 5 S) I has been determined by Single Crystal X-ray Diffraction (SCXRD) techniques. It crystallizes in the orthorhombic space group Pca2 1 with unit cell parameters a = 19.4502(13)Å, b= 6.3571(4)Å, c= 15.2577(10) Å and number of molecules per unit cell, z = 4. The intensity data have been collected at room température (293 K) and the structure has been solved by direct methods. The full matrix least-squares refinement has converged the final R-value to 0.035 for 2251 observed reflections. The piperidine ring adopts a chair conformation. The structure is stabilized by two C–H…O (intermolecular interactions) and five C–H…O (intramolecular interactions). The structural and spectral studies of 1-(tert-butyl) 3-ethyl 3-(hydroxy(thiophen-2-yl)methyl)piperidine-1,3-dicarboxylate have been carried out by using both experimental and quantum chemical techniques.

Electrocatalytic activity and chemical sensor application of Mn-MOF: synthesis, crystal structure and photo luminescent properties

A solvothermal method was used to synthesize a Manganese metal-organic framework (Mn-MOF), [Mn(Tpa)(Mi)(DMF)] (Tpa = Terephthalic acid, Mi = Methylimidazole, DMF = Dimethylformamide). The Mn-MOF molecule has a three dimensional network in which the θ ranges from 5.942–50 with monoclinic I2/a space group. The final full matrix least-squares refinement over F2 is converged on R1 = 0.0558, wR2 = 0.1696 through GOF = 1.095. Mn-MOF shows a strong luminescence along with red-shift, which indicates that these are the potential candidates for various luminescent applications. Electro catalytic activities of Mn-MOF electrode have also been tested for in 5 mM K4FeCN6 and K3FeCN6 in 0.5 M KCl solution. The electrochemical sensor detection of ascorbic acid (AA) in Mn-MOF was used as a buffer solution (pH-7.0). The ascorbic acid peak potential is a great deal nearer to the Mn-MOF electrode peak potential is ΔEp = 0.062 V. These results indicate that Mn-MOF electrode exhibits a very good electro catalytic activity and good chemical sensor by a quick reply in favor of ascorbic acid detection.

Single crystal investigation of the YbAl2 compound

A sample of nominal composition Yb33,3Al66,7 was synthesized from high-purity elements (Yb ≥ 98.9 wt.% and Al ≥ 99.999 wt.%) by arc-melting under a purified argon atmosphere, using Ti as a getter and a tungsten electrode. To achieve high efficiency of the interaction between the components, the sample was melted twice. The ingot was annealed at 500°C in an evacuated quartz ampoule for 720 h and subsequently quenched in cold water. The weight loss during the preparation of the sample was less than 1 % of the total mass, which was 2 g. The chemical composition of the selected crystals was checked with a field-emission scanning electron microscope (FEINovaNanoSEM 230) equipped with an EDS analyzer.
 Laue and rotation diffraction patterns of selected single crystals showed cubic symmetry. Integrated intensities measured with graphite-monochromatized Мо Kα radiation (l = 0.71073 Å) on an Xcalibur Atlas CCD diffractometer confirmed the cubic lattice. The structure type MgCu2 was assigned and the structure was refined using the program SHELXL (full-matrix least-squares refinement on F2)] with anisotropic displacement parameters for all of the atoms: Pearson symbol cF24, space group Fd-3m, a = 7.7011(4) Å, V = 456.73(7) Å3, Z = 8, R = 0.0261, Rw = 0.0726 for 42 reflections.
 It is well-known that the trivalent state is usual one for the rare earth metals. The dependence of the mean atomic volume of the RAl2 binary showed of the so-called “valence” fluctuation state for Eu and Yb.

Crystal and Molecular Structure and DFT Calculations of the Steroidal Oxime 6E-Hydroximino-androst-4-ene-3,17-dione (C19H25NO3) a Molecule with Antiproliferative Activity

The single crystal X-ray structure of the novel steroid derivative, 6E-hydroximino-androst-4-ene-3,17-dione (C19H25NO3) (code name RB-499), possessing antiproliferative activity against various cell lines is presented. The analysis produced the following results: chemical formula C19H25NO3; Mr = 315.40; crystals are orthorhombic space group P212121 with Z = 4 molecules per unit cell with a = 6.2609(2), b = 12.5711(4), c = 20.0517(4) Å,Vc = 1578.18(7) Å3, crystal density Dc = 1.327 g/cm³. Structure determination was performed by direct methods, Fourier and full-matrix least-squares refinement. Hydrogens were located in the electron density and refined in position with isotropic thermal parameters. The final R-index was 0.0324 for 3140 reflections with I > 2σ and 308 parameters. The Absolute Structure Parameter − 0.07(5) confirms the correct allocation of the absolute configuration. The presence of the double bond C=O at position 3 in Ring A has caused a distortion from the usual chair conformation and created an unusual distorted sofa conformation folded across an approximate m-plane through C(1)–C(4). Ring B is a distorted chair, its conformation being influenced by the presence of the C(6)=N(6)–O(6)H group in position 6. Ring C is a symmetrical chair. Ring D exhibits both a distorted mirror symmetry conformation [influenced by the C(17)=O(17) group] and a distorted twofold conformation. DFT calculations indicated some degree of flexibility in rings A, C and D with ring A showing the greatest variation in torsion angles. The crystal packing is governed by H-bonds involving O(3), O(6) and O(17). DFT calculations of bond distances and angles, optimized at the B3LYP/6–31++G(d,p) level, were in good agreement with the X-ray structure.Graphical Ring A conformations: (a) Experimental and (b) Calculated. The differences in torsion angle values indicate a degree of flexibility in the ring. The ring conformations are shown in Figures (ii) and (iv) respectively (drawn with BIOVIA [12]. Regions A1 and A2 are approximately planar in both, being planar within 0.048 Å and 0.105 Å respectively.

Crystal structure, quantum mechanical investigation, IR and NMR spectroscopy of two new organic salts: (C8H12NO)·[NO3] (I) and (C8H14N4)·[ClO4]2 (II)

Two new organic-inorganic hybrid materials, 4-methoxybenzylammonium nitrate, (C8H12NO)·[NO3] (I), and 2-(1-piperazinyl)pyrimidinium bis(perchlorate), (C8H14N4)·[ClO4]2(II), have been synthesized by an acid/base reaction at room temperature, their structures were determined by single crystal X-ray diffraction. Compound (I) crystallizes in the orthorhombic system and Pnma space group with a = 15.7908 (7), b = 6.8032 (3), c = 8.7091 (4) Å, V = 935.60 (7) Å3 with Z = 4. Full-matrix least-squares refinement converged at R = 0.038 and wR(F2) = 0.115. Compound (II) belongs to the monoclinic system, space group P21/c with the following parameters: a = 10.798(2), b = 7.330(1), c = 21.186(2) Å, β = 120.641 (4)°, V = 1442.7 (3) Å3and Z = 4. The structure was refined to R = 0.044, wR(F2) = 0.132.In the structures of (I) and (II), the anionic and cationic entities are interconnected by hydrogen bonding contacts forming three-dimensional networks. Intermolecular interactions were investigated by Hirshfeld surfaces and the contacts of the four different chloride atoms in (II) were compared. The Molecular Electrostatic Potential (MEP) maps and the HOMO and LUMO energy gaps of both compounds were computed. The vibrational absorption bands were identified by infrared spectroscopy. These compounds were also investigated by solid-state 13C, 35Cl and 15N NMR spectroscopy. DFT calculations allowed the attribution of the IR and NMR bands.

Crystal structure, quantum mechanical study and spectroscopic studies of nitrate and perchlorate salts of 3-chloroaniline, [C6H7ClN]NO3 (I) and [C6H7ClN]ClO4 (II)

Two new organic-inorganic hybrid compounds, 3-chloroanilinium nitrate (I) and 3-chloanilinium perchlorate (II), have been synthesized by an acid/base reaction at room temperature in the presence of 3-chloroaniline as an organic-structure directing agent and their structures were determined by single crystal X-ray diffraction. Compound I, [C6H7ClN]NO3, crystallizes in the orthorhombic space group Pbca with a = 10.4137(16), b = 9.6232(11), c = 16.059(2) Å, V = 1609.3(4) and z = 8. Full-matrix least-squares refinement converged at R = 0.041 and Rw = 0.121. Compound II, [C6H7ClN]ClO4, belongs to the monoclinic system, space group P21/n with the following parameters: a = 10.684(2), b = 7.2667(12), c = 12.229(2) Å, β = 104.27(2)°, V = 920.1(3) and z = 4. The structure was refined to R = 0.054 and Rw = 0.102.Both salts form anionic parallel layers alternating with thick slabs of [C6H7NCl]+ organic molecules. Charge balance is achieved by the protonated amine which interacts with the inorganic framework through hydrogen bonding. Solid-state 13C CP-MAS NMR spectroscopy is in agreement with the X-ray structures. Ab initio calculations allow the partial attribution of carbon signals to the various atoms of the organic groups. Electronic properties such as HOMO and LUMO energies were studied by Quantum mechanical evaluation by using the B3LYP/6-31+G* method.

Synthesis and Crystal Structure of a Tetranuclear Mn(III)-Ni(II) Heterometal Complex of <i>N</i>-(2-oxymethylphenyl)salicylideneimine

Hetero-metal complexes assembled by bridging polydentate ligands have been of great interest in magnetochemistry.1–4 We have reported on the structure and magnetic properties of a hetero-metal tetranuclear complex, [MnNi(L1-H)2Cl(H2O)]2 (A) [H2L1-H = N-(2-oxymethylphenyl)salicylideneimine], which has a rather strong ferromagnetic interaction.5 The magnetic behaviors of A might depend on the Mn–O–Ni angles and axial ligands. While attempting to prepare a new complex with simple coordinating anions instead of chloride anions in A, we obtained single crystals of a new hetero-metal complex, [MnNi(L1-H)2(OAc)]2·2CH3OH (1). Here, we report on the synthesis and the crystal structure of 1. The Schiff-base ligand H2L1-H was obtained by a literature method.6 A mixture of H2L1-H (0.114 g, 0.5 mmol), manganese acetate tetrahydrate (0.122 g, 0.5 mmol), and triethylamine (0.102 g, 1.0 mmol) in dry methanol (4 ml) was stirred for 30 min. To the resulting dark-brown solution was added a dry methanol solution (2 ml) of nickel acetate tetrahydrate (0.127 g, 0.5 mmol). The mixture was stirred for 5 min. The obtained dark-brown solution was filtered, and the filtrate was allowed to stand overnight to give brown single crystals suitable for X-ray crystallography. [MnNi(L1-H)2(OAc)]2·2CH3OH (Yield, 0.050 g, 30.5%). C31H29MnN2NiO7 (655.22): calcd. C 55.27, H 4.44, N 4.19%; found C 55.30, H 4.64, N 4.16%. X-ray diffraction measurements were made on a Rigaku Saturn CCD diffractometer with graphite monochromated Mo Ka radiation at 113 K. The structure was solved by direct methods (SHELX2013) and expanded using Fourier techniques.7 The non-hydrogen atoms were refined anisotropically. All hydrogen atoms were located on the calculated positions, and refined using the riding model. The final cycle of a full-matrix least-squares refinement on F2 using SHELXL2013 was based on observed reflections and variable parameters, and converged with unweighted and weighted agreement factors of R and Rw. Details of the X-ray structure determination are listed in Table 1. Synthesis and Crystal Structure of a Tetranuclear Mn(III)-Ni(II) Heterometal Complex of N-(2-oxymethylphenyl)salicylideneimine

The cluster compound In4Ti1.5Mo0.5Mo14O26 containing Mo14 clusters and the new mono- and bi-capped trioctahedral Mo15 and Mo16 clusters: Synthesis, crystal structure, and electrical and magnetic properties

Single crystals of the new quaternary compound In4Ti1.5Mo0.5Mo14O26 were obtained by solid state reaction. The crystal structure was determined by single-crystal X-ray diffraction. In4Ti1.5Mo0.5Mo14O26 crystallizes in the orthorhombic space group Pbca with unit-cell parameters a=9.4432(14)Å, b=11.4828(12)Å, c=20.299(4)Å and Z=4. Full-matrix least-squares refinement on F2 using 3807 independent reflections for 219 refinable parameters resulted in R1=0.0259 and wR2=0.0591. The crystal structure contains in addition to Mo14 clusters the first examples of mono- and bi-capped trioctahedral Mo14 i.e. Mo15 and Mo16 clusters. The oxygen framework derives from a stacking along the a direction of close-packed layers with sequence (…ABAC…). The Mo–Mo distances range between 2.6938(5) and 2.8420(6)Å and the Mo–O distances between 1.879(5) and 2.250(3)Å, as usually observed in molybdenum oxide clusters. The indium atoms form In46+ bent chains with In–In distances of 2.6682(5) and 2.6622(8)Å and the Ti atoms are in highly distorted octahedral sites of oxygen atoms with Ti–O distances ranging between 1.865(4) and 2.161(4)Å. Magnetic susceptibility measurements confirm the presence of Ti4+ cations and the absence of localized moments on the Mo network. Electrical resistivity measurements on a single crystal of In4Ti1.5Mo0.5Mo14O26 show a semimetallic behavior.

Structural Feature of an Hexakis-<i>N</i>-methylformamide Cobalt(II) Complex: <i>Pseudo</i>-<i>S</i><sub>6</sub> and <i>Pseudo</i>-<i>C</i><sub>2</sub> Complex Cations

The magnetic properties of octahedral high-spin cobalt(II) complexes are of interest because of the significant magnetic anisotropy caused by the spin-orbit coupling. Previously, the crystal structure of the hexakis-DMF cobalt(II) complex [Co(DMF)6](BPh4)2 (DMF = N,N-dimethylformamide) was determined;1 magnetic studies are in progress. Since the effect of spin-orbit coupling is strongly dependent on the environment around the cobalt(II) center,2 it is of important to study various types of cobalt(II) complexes. In this study, we prepared a cobalt(II) complex, [Co(NMF)6](BPh4)2 [hexakis(Nmethylformamide-kO)cobalt(II) bis(tetraphenylborate)] [NMF = N-methylformamide], and elucidated the crystal structure. The cobalt(II) complex [Co(NMF)6](BPh4)2 was prepared by the addition of a 2-propanol solution (2.0 mL) of sodium tetraphenylborate (~1.1 mmol, 0.37 g) to an NMF solution (1.0 mL) of cobalt(II) nitrate hexahydrate (~0.5 mmol, 0.14 g). After removing the firstly obtained purple crystalline compound, slow diffusion of 2-propanol to the resulting purple solution gave purple single crystals suitable for X-ray analysis. The crystal data are included in Table 1. The structure was solved by direct methods and expanded using Fourier techniques. The non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using the riding model. The final cycle of a full-matrix least-squares refinement on F2 was allowed to satisfactory converge with R1 = 0.0381 [I > 2s(I)]. The crystal consists of complex cations [Co(NMF)6] and Structural Feature of an Hexakis-N-methylformamide Cobalt(II) Complex: Pseudo-S6 and Pseudo-C2 Complex Cations

<i>Pseudo</i>-<i>S</i><sub>6</sub> Complex Cations of a Hexakis-<i>N</i>-methylformamide Nickel(II) Complex

Nickel(II) complexes are typical good examples for studying any magnetostructural relationship. A slight distortion around the nickel(II) center influences the sign of the zero-field splitting, which will determine the magnetic behavior.1 We previously determined the crystal structures of nickel(II) complexes [Ni(DMF)6](BPh4)2 [hexakis(N,Ndimethylformamide-kO)nickel(II) bis(tetraphenylborate)]2 and [Ni(DMSO)6](BPh4)2 [hexakis(dimethylsulfoxide-kO)nickel(II) bis(tetraphenylborate)],3 where DMF and DMSO represent N,Ndimethylformamide and dimethylsulfoxide, respectively. The [Ni(DMF)6] complex cations were found to take a trigonally compressed pseudo-S6 structure, while the [Ni(DMSO)6] complex cations were found to take both a trigonally compressed pseudo-S6 structure and a pseudo-S4 structure. For the purpose of gaining further examples, in this study, we prepared a niclel(II) complex, [Ni(NMF)6](BPh4)2 [hexakis(Nmethylformamide-kO)cobalt(II) bis(tetraphenylborate)] [NMF = N-methylformamide], and elucidated the crystal structure. The nickel(II) complex [Ni(NMF)6](BPh4)2 was prepared by the addition of a 2-propanol solution (2.0 mL) of sodium tetraphenylborate (~1.1 mmol, 0.37 g) to an NMF solution (1.0 mL) of nickel(II) nitrate hexahydrate (~0.5 mmol, 0.15 g). Slow evaporation of the resulting green solution gave a green single crystal suitable for X-ray analysis. Crystal data are included in Table 1. The structure was solved by direct methods and expanded using Fourier techniques. The non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using the riding model. The final cycle of a full-matrix least-squares refinement on F2 was allowed to satisfactory converge with R1 = 0.0460 [I > 2s(I)]. The crystal consists of complex cations, [Ni(NMF)6], and Pseudo-S6 Complex Cations of a Hexakis-N-methylformamide Nickel(II) Complex

Synthesis, crystal structure, and electrical and magnetic properties of BaMo6Te6: A novel reduced molybdenum telluride containing infinite chains of trans-face shared Mo6 octahedra

Powder samples and single crystals of the new ternary compound BaMo6Te6 were obtained by solid state reaction. The structure was determined by single-crystal X-ray diffraction. BaMo6Te6 crystallizes in the hexagonal space group P63/m (No. 176) with unit-cell parameters a=9.3941(2)Å, c=4.5848(1)Å and Z=1. Full-matrix least-squares refinement on F2 using 452 independent reflections for 17 refinable parameters resulted in R1=0.0208 and wR2=0.0539. The structure consists of one-dimensional infinite chains of trans-face shared Mo6 octahedra capped by Se atoms. These chains that are running along the c axis are separated from each other by nine-coordinate Ba atoms. Resistivity measurements on a single crystal indicated that the BaMo6Te6 compound is metallic down to 160K and semiconductor below. Magnetic susceptibility measurements showed that BaMo6Te6 is weakly diamagnetic with no anomaly at the metal–semiconductor transition.

Synthesis, crystal and electronic structures and magnetic properties of Li2SnMo3O8: A novel reduced molybdenum oxide containing Mo3O13 cluster units

Abstract Powder samples and single crystals of the quaternary oxide Li 2 SnMo 3 O 8 were obtained by solid state reaction. The structure was determined by single-crystal X-ray diffraction. Li 2 SnMo 3 O 8 crystallizes in the hexagonal space group P 6 3 mc with unit-cell parameters a =5.7720 (2) A, c =10.3941 (3) A and Z =2. Full-matrix least-squares refinement on F 2 using 930 independent reflections for 31 refinable parameters results in R 1 =0.0354 and w R 2 =0.0643. The crystal structure consists of distorted hexagonal-close-packed oxygen layers with stacking sequence abac along [0 0 1] and that are held together by alternating lithium-tin and molybdenum layers. The Li + and Sn 4+ ions occupy, respectively, tetrahedral and octahedral sites in the ratio 2:1. The Mo atoms occupy octahedral sites and form strongly bonded triangular clusters involving three MoO 6 octahedra that are each shared along two edges, constituting a Mo 3 O 13 unit. Magnetic susceptibility measurements are in agreement with a spin-pairing of the eight d electrons per Mo 3 cluster. The electronic structure of Li 2 SnMo 3 O 8 is analyzed using periodic density functional calculations.

Structural diversity of the lanthanide oxalates: Condensation of neodymium oxygen polyhedra under hydrothermal conditions

Abstract New neodymium hydroxo-oxalate and oxalate [Nd6(H2O)6(C2O4)7(OH)4]·4H2O (1) and [Nd2(H2O)4(C2O4)3]·2H2O (2) were synthesized by hydrothermal reaction at 150 °C between neodymium nitrate and oxalic acid solutions at pH = 10–11 obtained by adding various monoamines. The structures were determined from single-crystal X-ray diffraction data. The two compounds crystallize in the monoclinic system with space group P21/c and a = 17.4384 (11), b = 8.1717 (5), c = 12.9929 (7), β = 94.66 (1)°, V = 1845.38 (19) A3, Z = 2 for 1 and a = 9.8249 (2) A, b = 8.2487 (2) A, c = 10.1911 (3) A, β = 99.09 (1), V = 815.53 (4) A3, Z = 2 for 2. Full matrix least-squares refinement yielded R1 = 0.0365 and 0.0267 for 6033 and 3382 independent reflections for 1 and 2 respectively. In 2, the three-dimensional neodymium–oxalate arrangement results from dimeric units of edge shared NdO9 polyhedra connected through oxalate ions acting as bis-bidentate. In 1, the neodymium atoms are connected through μ2-OH and μ3-OH ions to form a hexanuclear inorganic core [Nd6(OH)4(H2O)6] with an unprecedently reported geometry leading to a hexanuclear polyhedra block. The blocks are connected through an O–O bridge involving two oxygen atoms of two oxalate ions to build a centipede-like ribbon. The ribbons are further connected through oxalate ions to form a three dimensional neodymium oxalate arrangement. In 1, oxalates adopt four distinct bridging modes of coordination, μ2, μ3, μ4 and μ5.

Molten salt flux synthesis and crystal structure of a new open-framework uranyl phosphate Cs3(UO2)2(PO4)O2: Spectroscopic characterization and cationic mobility studies

The reaction of triuranyl diphosphate tetrahydrate precursor (UO2)3(PO4)2(H2O)4 with a CsI flux at 750°C yields a yellow single crystals of new compound Cs3(UO2)2(PO4)O2. The crystal structure (monoclinic, space group C2/c, a=13.6261 (13)Å, b=8.1081(8)Å, c=12.3983(12)Å, β=114.61(12)°, V=1245.41(20)Å3 with Z=4) has been solved using direct methods and Fourier difference techniques. A full-matrix least-squares refinement on the basis of F2 yielded R1=0.028 and wR2=0.071 for 79 parameters and 1352 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with MoKα radiation and a charge-coupled device detector. The crystal structure is built by two independent uranium atoms in square bipyramidal coordination, connected by two opposite corners to form infinite chains [UO5]∞1 and by one phosphorus atom in a tetrahedral environment PO4. The two last entities [UO5]∞1 and PO4 are linked by sharing corners to form a three-dimensional structure presenting different types of channels occupied by Cs+ alkaline cations. Their mobility within the tunnels were studied between 280 and 800°C and compared with other tunneled uranyl minerals. The infrared spectrum shows a good agreement with the values inferred from the single crystal structure analysis of uranyl phosphate compound.

Properties of a Model Aryl Boronic Acid and Its Boroxine

Many boronic acid-containing molecules are currently under investigation as possible therapeutics. An increase in the knowledge of the physical and chemical properties of these compounds will lead to their improved formulation into usable dosage forms. The current study describes the formation and characterization of a boronic acid anhydride, called a boroxine. The model boronic acid, 4-methoxybenzeneboronic acid is used. The current study demonstrates the utility of thermal (differential scanning calorimetry and thermogravimetric analysis) and spectral (solid-state nuclear magnetic resonance and ultraviolet spectroscopy) methods to quantitate and characterize the boronic acid and its boroxine, validated against definitive structures solved by single-crystal X-ray diffraction. The present work also demonstrates that the hydrolysis of the boroxine in the presence of water is very rapid in a time scale relative to drug substance manufacture and product formulation.