Orthorhombic Space Group Pbcn Research Articles

First Full Structural Characterization of Chloro Formamidinium Salts

While the synthesis of chloro formamidinium chloride has been known for over one century, no solid‐state structure of a chlorine‐substituted formamidinium compound has been reported up to now. Herein, we describe syntheses, solid‐state structures, and vibrational properties of four chloro formamidinium compounds, namely [ClC(NH2)2]Cl (1), [ClC(NH2)2](AuCl4) (2), [ClC(NH2)2]2(PdCl4) (3), and [ClC(NH2)2]2(PtCl6) (4), as determined by single‐crystal X‐ray diffraction (SCXRD). 1 and 3 crystallize in the monoclinic space group P21/c, 2 in the orthorhombic space group Pbcn, whereas 4 adopts the triclinic space group P1. By using a combination of high‐resolution time‐of‐flight neutron powder diffraction, state‐of‐the‐art DFT calculations as well as IR spectroscopy, the prior SCXRD result was fully confirmed and augmented by determining the hydrogen‐bonded molecular networks. First‐principles electronic‐structure calculations corroborate the ionic nature of these salts by showing very flat, molecular‐like bands next to the Fermi level, in addition to indirect bandgaps. This study underlines the upmost importance of complementing diffraction data by ab initio calculations, as theory‐derived anisotropic displacement parameters served as fixed numerical entries.

The Smaller the Better: Hosting Trivalent Rare-Earth Guests in Cu–P Clathrate Cages

Summary The most striking difference between the trivalent rare-earth cations and their alkali and alkaline-earth peers is the presence of localized 4 f electrons. Placing trivalent rare-earth cations inside fullerene molecules or in between blocks of intermetallics has given rise to a plethora of fascinating properties and materials. A long-sought-after yet undiscovered material is a semiconducting compound with rare-earth cations situated inside the oversized polyhedral cages of a three-dimensional framework. In this work, we present a synthesis of unconventional clathrates, Ba 8−x R x Cu 16 P 30 , with the smallest pentagonal dodecahedral cages encapsulating La 3+ and Ce 3+ . Their composition and crystal structure were unambiguously determined by a combination of synchrotron powder diffraction, time-of-flight neutron powder diffraction, scanning transmission electron microscopy, and electron energy-loss spectroscopy. Our quantum-mechanical calculations and experimental characterizations show that the incorporation of the rare-earth cations significantly enhances hole mobility and reduces hole concentration, resulting in a drastic (700%) increase in the thermoelectric performance.

A new calcium 2,5-dihydroxybenzoate: Synthesis, characterization and antioxidant studies and stress mediated cytotoxity in MCF-7 cells

The structure and composition of the calcium 2,5-dihydroxybenzoate (calcium gentisate) were studied by single-crystal and powder X-ray diffraction. Single-crystal X-ray analysis revealed that the compound crystallizes in the orthorhombic space group Pbcn. The Ca(II) cation is coordinated in a monodentate fashion by two symmetry-related gentisate anions and five water molecules. The metal ion and one of the water molecules are located on a 2-fold rotation axis. The adjacent monomeric units are assembled into a 3-D supramolecular framework via O–H…O hydrogen bonds. Comparison of the experimental powder pattern with that simulated from single-crystal X-ray data confirmed the purity and homogeneity of the sample. The FT-IR, UV/VIS, 1H and 13C NMR spectra of the calcium 2,5-dihydroxybenzoic acid were registered and analysed. Moreover the effect of calcium complex and 2,5-dihydroxybenzoic acid on basic oxidative stress parameters, such as thiol group content and lipid peroxidation in the human breast cancer cells MCF-7 was studied. The antiradical and ferric reducing power of these compounds was measured by DPPH, CUPRAC and FRAP methods. The chemical reactivity parameters (e.g. HOMO and LUMO orbitals, ionization potential, electron affinity) for Ca 2,5-dHB and 2,5-dHB were calculated at B3LYP/6-311++G∗∗ level of theory and discussed in relation to their antioxidant properties.

Synthesis, structure and electronic calculation of alkali metals borate Li2Na[B5O8(OH)2

A new alkali metals borate complex, Li2Na[B5O8(OH)2], has been successfully synthesized by a facile hydrothermal method. Single-crystal X-ray diffraction analysis reveals that it crystallizes in orthorhombic space group Pbcn with a=8.919(3)Å, b=9.181(3)Å, c=8.416(2)Å, Z=4. The crystal structure is constructed of two dimensional (2D) [(B5O8)(OH)2]∞ layers, while stacking along b axis and then connected by Li+ and Na+ cations to extend to 3D framework Li2Na[B5O8(OH)2]. UV-vis-NIR spectrum shows that Li2Na[B5O8(OH)2] possesses a wide range of transparency and a UV cut-off edge below 190 nm which indicates that it may be applied in the deep ultraviolet region. The calculated band structures and the density of states indicate that Li2Na[B5O8(OH)2] is a direct band gap compound with a band gap of 5.68 eV. In addition, IR spectroscopy, thermal stability and theoretical calculations of Li2Na[B5O8(OH)2] are also reported in this work.

Iridium(III) and Rhodium(III) compounds of dipyridyl-N-alkylimine and dipyridyl-NH-ketimine: Spectral characterization and crystal structure

Pentamethylcyclopentadienyl iridium(III) and rhodium(III) complexes of formulation [(η 5-C 5Me 5)M{(C 5 H 4N) 2 C=NR)}Cl]PF 6 were prepared by the reaction of [MCl 2(η 5-C 5Me 5)] 2(M = Ir or Rh) with dipyridyl-N-alkylimine ligands, (C 5 H 4N) 2 C=NR (R = Me or Et) in the presence of NH 4 PF 6 at room temperature. The reaction also produced an unexpected dipyridyl-NH-ketimine organometallic compound [(η 5-C 5Me 5)M {(C 5 H 4N) 2 C=NH}Cl]PF 6 as minor product when the reaction was performed under refluxing acetonitrile. The NH-ketimine compounds were formed via N-C single bond cleavage of imine ligand resulting in coordination of the transformed ligand, (C 5 H 4N) 2 C=NH to the metal centre. Complexes were obtained as their hexafluorophosphate salts and characterized based on IR, NMR and ESI-MS spectroscopic data. Authenticity of NH-ketimine organometallic compound was established by single crystal X-ray analysis of a representative compound, which crystallized in orthorhombic space group Pbcn and has a pseudo-octahedral geometry around the metal ion. Pentamethylcyclopentadienyl iridium(III) and rhodium(III) complexes containing dipyridyl-N-alkylimine and dipyridyl-NH-ketimine ligands of formulation [(η 5-C5Me5)M{(C5H4N)2C=NR}Cl]PF6 and [(η 5-C5Me5)M{(C5H4N)2C=NH}Cl]PF6 were synthesized and characterized on the basis of spectroscopic data. Solid state structure of one representative NH-ketimine compound [6]PF 6 has been determined by X-ray crystallography

Crystal structure and spin-trimer magnetism of Rb2.3(H2O)0.8Mn3[B4P6O24(O,OH)2

The novel borophosphate Rb2.3(H2O)0.8Mn3[B4P6O24(O,OH)2] was prepared under hydrothermal conditions at 553 K. Its crystal structure was determined using single-crystal X-ray diffraction data obtained from a non-merohedral twin and refined against F2 to R = 0.057. The compound crystallizes in the orthorhombic space group Pbcn, with unit-cell parameters a = 20.076(2) Å, b = 9.151(1) Å, c = 12.257(1) Å, V = 2251.8(2) Å3, and Z = 4. The title compound is the first example of a borophosphate with manganese ions adopting both octahedral and tetrahedral coordinations. Its unique crystal structure is formed by borophosphate slabs and chains of Mn2+-centered polyhedra sharing edges and vertices. These 2D and 1D fragments interconnect into a framework with open channels that accommodate Rb+ cations and water molecules. Topological relationships between borophosphates built from three-membered rings of two borate and one phosphate tetrahedra sharing oxygen vertices, amended by additional PO4 and HPO4 tetrahedra, are discussed. The temperature dependence of the magnetic susceptibility of Rb2.3(H2O)0.8Mn3[B4P6O24(O,OH)2] reveals predominant antiferromagnetic exchange interactions and the high-temperature effective magnetic moment corresponding to the high-spin S = 5/2 state of Mn2+ ions. At 12.5 K, a magnetic transition is evidenced by ac-susceptibility and specific heat measurements. A spin-trimer model with the leading exchange interaction J ∼ 3.2 K is derived from density-functional band-structure calculations and accounts for all experimental observations.

Acetic anhydride at 100 K: the first crystal structure determination.

Acetic anhydride (ethanoic anhydride), (CH3CO)2O, is a widely used acetylation reagent in organic synthesis. The crystal and molecular structure, as determined by single-crystal X-ray analysis at 100 K, is reported for the first time. A crystal of the title compound (m.p. 200 K) suitable for X-ray diffraction was grown from the melt at low temperature. The title compound crystallizes in the orthorhombic space group Pbcn, with Z = 4. In the crystal, the molecule adopts an exact C2-symmetric conformation about a crystallographic twofold axis. The molecules are densely packed. Two of the methyl H atoms form short intermolecular contacts to a neighbouring carbonyl O atom, which can be viewed as weak hydrogen bonds.

Tetrakis(dimethoxyboryl)methane

The title compound, tetrakis(dimethoxyboryl)methane (systematic name: octamethyl methanetetrayltetraboronate), C9H24B4O8or C[B(OMe)2]4, is a useful synthetic intermediate. Crystals of this compound at 102 K conform to the orthorhombic space groupPbcn. The molecules, which reside on sites of crystallographic twofold symmetry, have idealized -4 point symmetry like most other CX4molecules in which eachXgroup bears two non-H substituents at the 1-position. The central C atom has a slightly distorted tetrahedral coordination geometry, with C—B bond lengths of 1.5876 (16) and 1.5905 (16) Å. One of the methoxy groups is disordered over two sets of sites; the major component has an occupancy factor of 0.676 (8).

Synthesis, characterization, crystal structures, and antimicrobial activity of cobalt(II) and iron(III) complexes derived from N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide

A new cobalt(II,III) complex, [CoIIIL2]2[Co2II(HL)2(OH2)2(CH3OH)2] • 2H2O (I) and a new iron(III) complex, [FeIII(HL)2](NO3) (II), where L2– and HL– are the dianionic and monoanionic form of N'-(2-hydroxybenzylidene)-3-methylbenzohydrazide, respectively, have been prepared and characterized by elemental analyses, infrared and UV-Vis spectroscopy and single-cyrstal X-ray diffraction (CIF files CCDC nos. 1417971 (I), 1417979 (II)). Complex I crystallizes in the monoclinic space group P21/n with unit cell dimensions a = 16.1665(9), b = 14.5692(8), c = 19.086(1) A, β = 96.347(1)°, V = 4467.9(4) A3, Z = 2, R1 = 0.0521, and wR2 = 0.1411. Complex II crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a = 12.475(1), b = 12.202(1), c = 18.859(2) A, V = 2870.8(4) A3, Z = 4, R1 = 0.0796, and wR2 = 0.1981. The metal atoms in the complexes are in octahedral coordination. Crystals of the complexes are stabilized by hydrogen bonds. The efficiency of the aroylhydrazone and the two complexes was evaluated against B. subtilis, S. aureus, E. coli, P. fluorescence, C. albicans and A. niger, with the complexes demonstrating enhanced activity relatively to the free ligand.

Conformational and Molecular Structures of α,β-Unsaturated Acrylonitrile Derivatives: Photophysical Properties and Their Frontier Orbitals.

We report single crystal X-ray diffraction (hereafter, SCXRD) analyses of derivatives featuring the electron-donor N-ethylcarbazole or the (4-diphenylamino)phenyl moieties associated with a -CN group attached to a double bond. The compounds are (2Z)-3-(4-(diphenylamino)-phenyl)-2-(pyridin-3-yl)prop-2-enenitrile (I), (2Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-4-yl)-prop-2-enenitrile (II) and (2Z)-3-(9-ethyl-9H-carbazol-3-yl)-2-(pyridin-2-yl)enenitrile (III). SCXRD analyses reveal that I and III crystallize in the monoclinic space groups P2/c with Z’ = 2 and C2/c with Z’ = 1, respectively. Compound II crystallized in the orthorhombic space group Pbcn with Z’ = 1. The molecular packing analysis was conducted to examine the pyridine core effect, depending on the ortho, meta- and para-positions of the nitrogen atom, with respect to the optical properties and number of independent molecules (Z’). It is found that the double bond bearing a diphenylamino moiety introduced properties to exhibit a strong π-π-interaction in the solid state. The compounds were examined to evaluate the effects of solvent polarity, the role of the molecular structure, and the molecular interactions on their self-assembly behaviors. Compound I crystallized with a cell with two conformers, anti and syn, due to interaction with solvent. DFT calculations indicated the anti and syn structures of I are energetically stable (less than 1 eV). Also electrochemical and photophysical properties of the compounds were investigated, as well as the determination of optimization calculations in gas and different solvent (chloroform, cyclohexane, methanol, ethanol, tetrahydrofuran, dichloromethane and dimethyl sulfoxide) in the Gaussian09 program. The effect of solvent by PCM method was also investigated. The frontier HOMO and LUMO energies and gap energies are reported.

Naphthoquinone based Chemosensor 2-(2′-aminoethylpyridine)-3-chloro-1,4-naphthoquinone: Detection of metal ions, X-ray -crystal structures and DFT studies

Naphthoquinone based Chemosensor 2; 2-(2′-aminoethylpyridine)-3-chloro-1,4-napthoquinone have been synthesized and characterized. Chemosensor 2 crystallizes in the orthorhombic space group Pbcn and shows extensive intramolecular as well as intermolecular hydrogen bonding interactions. Each molecule of Chemosensor 2 showed interaction with five neighboring molecules via C–H⋯N, N–H⋯N, C–H⋯Cl and C–H⋯O interactions. Slipped π–π stacking interaction was observed in adjacent quinonoid and benzenoid rings. Chemosensor abilities of Chemosensor 2 ligand have been evaluated with metal ions viz. Cu2+, Ni2+, Zn2+, Co2+, Fe3+, Mn2+, Cr3+, Hg2+, La3+ and Cd2+ in methanol, methanol-water mixture and in presence of mild base triethylamine. Stoichiometry of Chemosensor 2 with metal ions such as Cu2+, Ni2+, Zn2+and Co2+ ions was determined by Jobs method in methanol and were found as 1:1 for Cu2+and 2:1 for Ni2+, Zn2+ Co2+. The variation in the metal ligand ratio is observed in aqueous media for Cu2+. Chemosensor 2 can be used selectively for naked eye detection of Cu2+ ions. The association constant obtained in methanol shows the trend Cu2+>Ni2+>Co2+. Cu2+ and two (Ni-1 and Ni-2) Ni2+ complexes were synthesized. Ni-2 complex showed coordination of Chemosensor 2 ligands was through pyridine nitrogen's only. The Chemosensor 2 and its deprotonated forms in methanol, water and triethylamine were also studied by TD-DFT studies.

The synthesis, structure and properties of a new lithium-rich manganese(ii) phosphate Li5CsMn(P2O7)2: a congruently melting compound with a 'lithium hamburger' structure.

The crystals of the title compound have been grown in molten salt media. Single-crystal X-ray diffraction experiment revealed that the compound crystallizes in an orthorhombic space group Pbcn (no. 60) with cell parameters: a = 5.1023(10) Å, b = 19.717(4) Å, c = 12.557(3) Å, and Z = 4. The structure of Li5CsMn(P2O7)2 consists of one-dimensional manganese pyrophosphate chains [MnP4O14]∞ interleaved with Cs(+) and Li(+) cations. A pseudo-two-dimensional layer [CsMnP4O14]∞ parallel to the ab plane is made up of [MnP4O14]∞ chains and Cs-O polyhedra through sharing the oxygen atoms. The three crystallographically distinct Li atoms are all located in the interlayered space to form a 'lithium hamburger' structure. Magnetic studies demonstrated that the compound shows paramagnetic behavior. DSC and XRD investigations revealed that the compound melts congruently. AC impedance studies show that the conductivity is 1.3 × 10(-5) S cm(-1) at 573 K and the activation energy is 0.42 eV. In addition, Li ion diffusional pathways were obtained using the bond valence map.

Synthesis, Crystal Structure and Characterization of a 2D-Hybrid Cobalt Hypophosphite

A new two-dimensional inorganic–organic hybrid ortho-phenylenediamine cobalt hypophosphite chloride, [Co(H2PO2)(C12N4H16)]Cl2, has been prepared by slow evaporation from an aqueous solution. It was investigated by means of single-crystal X-ray diffraction, infrared spectroscopy and thermal analysis. The title compound crystallise in orthorhombic space group Pbcn, with unit cell parameters at 298(1) K of a = 9.5538(19) A, b = 9.1466(18) A, c = 21.9222(4) A, V = 1915.7(7) A3, Z = 2. Its structure is characterised by inorganic layers parallel to (001) of alternating CoO4N2 octahedra and H2PO2 tetrahedra establishing eight-membered ring cavities. This mixed-polyhedral motive is decorated with the ortho-phenylenediamine ligands towards the inter-layer region thus forming a cationic organic–inorganic hybrid layer charge compensated by the chlorine anions. Infrared spectroscopy revealed absorption bands corresponding to the ortho-phenylenediamine molecule and the hypophosphite anion. The compound was proven to be stable up to 474 K under N2 atmosphere. A new two-dimensional inorganic–organic hybrid ortho-phenylenediamine cobalt hypophosphite chloride, [Co(H2PO2)(C12N4H16)]Cl2, has been prepared by slow evaporation from an aqueous solution and characterized by means of single-crystal X-ray diffraction, infrared spectroscopy and thermal analysis.

A three-dimensional coordination polymer based on 3,5-pyrazoledicarboxylic acid (H3Pdc): [Cd2(HPdc)1.5Cl(H2O)2] n

The title coordination polymer, [Cd2(HPdc)1.5Cl(H2O)2]n (I) (H3Pdc = 3,5-pyrazoledicarboxylic acid), has been hydrothermally synthesized and structurally characterized by single-crystal X-ray diffraction (CIF file CCDC no. 1037505). Complex I crystallizes in orthorhombic space group Pbcn with a = 10.2631(11), b = 17.1997(18), c = 14.3044(15) A, V = 2525.0(5) A3, C15H14Cd4Cl2N6O16, M = 1054.82, ρc = 2.775 g/cm3, μ(MoKα) = 3.627 mm−1, F(000) = 2000, GOOF = 1.067, Z = 4, the final R1 = 0.0562 and wR2 = 0.1301 for I > 2σ(I). The Cd(1) ions and HPdc2- ligands connect to form a serial of the 2D corrugated 63 sheets packing parallel along the z axis. Each 63 sheet is connected with the two neighboring sheets by the Cl− and Cd(2) ions to construct the 3D framework of I. The 3D structure can also be rationalized as a 4-connected trinodal (4.5.72.8.9)(4.52.62.7)(4.5.6.73) topological network (the long Schlafli symbol is (4.5.7.7.102)(4.124.5.6.5.7)(4.5.6.7.7.7)) by considering the Cd(1), Cd(2) ions and HPdc2− ligands as 4-connected nodes, the Cl− ions as linkers, respectively.

Vanadium(V) complex with Schiff-base ligand containing a flexible amino side chain: Synthesis, structure and reactivity

The Schiff-base ligand (H2salhyhNH3)Cl (1) derived from salicylaldehyde and 6-aminohexanoic acid hydrazide hydrochloride reacts with ammonium metavanadate in methanol solution to yield the dioxidovanadium(V) complex [VO2(salhyhNH3)] (2). The utilized hydrazone ligand contains a flexible and protonated amino side chain. Crystallization from methanol affords complex 2 in the monoclinic space group P21/n, whereas crystallization from a methanol/water mixture 1:1 yields crystals, containing a water molecule of crystallization per two formula units (2⋅1/2H2O), in the orthorhombic space group Pbcn. In both cases the protonated amino group compensates the negative charge on the dioxidovanadium moiety and is involved in an extensive hydrogen bonding network particularly including the oxido groups from neighboring vanadium complexes. The reactivity of complex 2 toward protonation in aqueous solution has been investigated by spectrophotometric titrations and is characterized by two subsequent protonation steps at the hydrazide nitrogen atom of the ligand system and an oxido group leading to the formation of an oxidohydroxidovanadium(V) species with corresponding pKa values of 3.2 and 2.9, respectively. With larger excess of acid the oxidohydroxidovanadium(V) species starts to form the corresponding anhydride. The formation of the anhydride is strongly favored in the presence of methanol. The reaction of complex 2 with hydrogen peroxide in methanol solution leads to the formation of an oxidoperoxidovanadium(V) species, whereas in aqueous solution the addition of one equivalent of acid is required. Complex 2 catalyzes the oxidation of methylphenylsulfane to the corresponding sulfoxide in methanol/dichloromethane mixture using hydrogen peroxide as oxidant at room temperature.

Neue aromatische Bisguanidin-Kupfer-Komplexe und ihre Anwendung in der ATRP / New Aromatic Bisguanidine Copper Complexes and Their Application in ATRP

We synthesized and structurally characterized two new copper(II) monochelate complexes with the ligand 2,2'-(1,2-phenylenebis(1,1,3,3-tetramethyl)guanidine) (TMG2b), [Cu(TMG2b)Cl2] and [Cu(TMG2b)Br2]. Single-crystal structure determination has shown that the complexes [Cu(TMG2b)Cl2] and [Cu(TMG2b)Br2] both crystallize in the orthorhombic space group Pbcn. The copper atoms in all complex cations reside in a coordination environment between tetrahedral and square-planar geometry. Furthermore, the application of the copper complexes with TMG2b as ligand in atom transfer radical polymerization (ATRP) was investigated with styrene as monomer. This study has shown a controlled polymerization process with moderate conversions, but excellent molecular weight distributions that are evidence of a well-controlled ATRP. However, small changes in the ligand structure can have a high impact, and therefore process optimizations and ligand tuning are necessary to develop highly active catalysts for ATRP.

Hydroflux Crystal Growth of Platinum Group Metal Hydroxides: Sr6NaPd2(OH)17, Li2Pt(OH)6, Na2Pt(OH)6, Sr2Pt(OH)8, and Ba2Pt(OH)8

Crystals of five complex metal hydroxides containing platinum group metals were grown by a novel low-temperature hydroflux technique, a hybrid approach between the aqueous hydrothermal and the molten hydroxide flux techniques. Sr6NaPd2(OH)17 (1) crystallizes in orthorhombic space group Pbcn with lattice parameters a = 19.577(4) Å, b = 13.521(3) Å, and c = 6.885(1) Å. This compound has a three-dimensional framework structure with Sr(OH)n polyhedra, Na(OH)6 octahedra, and Pd(OH)4 square planes. Isostructural phases Li2Pt(OH)6 (2) and Na2Pt(OH)6 (3) crystallize in trigonal space group P-3 with lattice parameters of a = 5.3406(8) Å and c = 4.5684(9) Å and a = 5.7984(8) Å and c = 4.6755(9) Å, respectively. Structures of these materials consist of layers of A(OH)6 (A = Li (2), Na (3)) and Pt(OH)6 octahedra. Sr2Pt(OH)8 (4) crystallizes in monoclinic space group P2(1)/c with lattice parameters a = 5.9717(6) Å, b = 10.997(1) Å, c = 6.0158(6) Å, and β = 113.155(2)°, while Ba2Pt(OH)8 (5) crystallizes in orthorhombic space group Pbca with lattice parameters a = 8.574(2) Å, b = 8.673(2) Å, and c = 10.276(2) Å. Both of these compounds have three-dimensional structures composed of Pt(OH)6 octahedra surrounded by either Sr(OH)8 or Ba(OH)9 polyhedra. Decomposition of these materials into condensed metal oxides, which is of importance to possible catalytic applications, was monitored via thermogravimetric analysis. For example, Na2Pt(OH)6 (3) converts cleanly via dehydration into α-Na2PtO3.

Copper(II) halide coordination complexes and salts of 3-halo-2-methylpyridines: Synthesis, structure and magnetism

Two families of compounds have been prepared from the reaction of 3-X′-2-methylpyridine with CuX2 (X, X′=Cl, Br) in the presence or absence of HX. Four salts, (3-X′-2-methylpyridinium)2CuX4 were prepared, three of which crystallize in the orthorhombic space group Pbcn while the fourth (X=Br and X′=Cl) crystallizes in the monoclinic space group C2/c. All four neutral compounds of formula (3-X′-2-methylpyridine)2CuX2 crystallize in the space group P1¯. Of these, three form weakly bridged chains via long Cu⋯X contacts, while the fourth (X=X′=Cl) forms centrosymmetric dimers. Most of the complexes exhibit only very weak antiferromagnetic interactions and can be modeled as weak uniform chains. Compound 4, (3-Cl-2-methylpyridinium)2CuBr4, shows behavior that models an isolated 2D-Heisenberg antiferromagnetic layer with J=−5.09(2)K, while compound 7, (3-Cl-2-methylpyridine)2CuCl2, crystallizes as a bichloride bridged centrosymmetric dimer with J=−29.31(6)K.

Polymorphism in 3,4-bis(2-benzimidazolyl)pyridine: Controlled synthesis, crystal structures and photophysical properties

Abstract Two polymorphs of 3,4-bis(2-benzimidazolyl)pyridine (1) were prepared and characterized by infrared, nuclear magnetic resonance spectroscopy and single-crystal X-ray crystallography. The metastable greenish polymorph 1a (hexagonal space group P6522) was solvothermally formed first, which can be irreversibly transformed into the stable yellow polymorph 1b (orthorhombic space group Pbcn) on heating or recrystallization. The structure of 1a shows a dihedral angle of 45.3° between the benzimidazolyl/pyridyl rings and a dihedral angle of 52.2° between the benzimidazolyl/benzimidazolyl rings, while the corresponding dihedral angles in the structure of 1b are 48.0° and 67.9°, respectively. The two polymorphs exhibit different combination of intermolecular interactions (N–H⋯N hydrogen bonds, π–π stacking or C–H⋯π interaction), leading to significantly different supramolecular assemblies. The photophysical properties of 1a and 1b have also been studied.

ChemInform Abstract: A New Mixed‐Valent High Nuclearity Polyoxovanadate Cluster Based on the {V18O42} Archetype.

AbstractThe new VIV/VV mixed‐valent compound (II) crystallizes in the orthorhombic space group Pbcn with Z = 4 (single crystal XRD).