Coordination geometry of chromium(VI) species. The first example of cis-bridging chromate ions in helically structured catena(μ-CrO4-O,O′)[Ni(HIm)3H2O]

Nickel(II) chromate complex with imidazole (HIm) was isolated from the [Ni²⁺–HIm–CrO₄²⁻] system in various experimental conditions, i.e. reagent molar ratios and nickel(II) salts. The catena(μ-CrO₄-O,O′)[Ni(HIm)₃H₂O] (1) crystallizes in monoclinic crystal system—space group P2₁/n with cell parameters: a=11.784(2), b=8.899(2), c=13.934(3) (Å), β=95.19(3) (°). The unit cell contains two independent helixes, left- and right-handed, stabilized by intrahelical and interhelical hydrogen bonds (HB) and π–π interactions. The cis coordination of the CrO₄²⁻ anions and the HB systems appeared to be the main determinants of the helical architecture. To the best of our knowledge the cis-chromate coordination was observed for the first time. The cis coordination causes the distortion of the nickel octahedron, which was analysed by 4 K single crystal electronic spectra with D_4h symmetry approximation (gaussian resolution and crystal field parameters). This symmetry was also confirmed with the polarised electronic spectra. The magnetic properties of the complex suggest the occurrence of weak intrachain antiferromagnetic interactions between the magnetic Ni^II center. The computational DFT studies of complex 1 assuming three possible isomers mer[(HIm)₃]–cis[(CrO₄²⁻)₂], mer–trans and fac–cis suggested that the main contribution to the stability of 1 might have interhelical and intrahelical hydrogen bonds.     

N‐Meth­yl‐N‐(2‐nitro­phen­yl)nitramine and N‐meth­yl‐N‐(3‐nitro­phen­yl)­nitramine

The structures of the two title isomeric compounds (systematic names: N‐meth­yl‐N,2‐dinitro­aniline and N‐meth­yl‐N,3‐di­nitro­aniline, both C₇H₇N₃O₄) are slightly different because they exhibit different steric hindrances and hydrogen‐bonding environments. The aromatic rings are planar. The –N(Me)NO₂ and –NO₂ groups are not coplanar with the rings. Comparison of the geometric parameters of the ortho, meta and para isomers together with those of N‐meth­yl‐N‐phenyl­nitramine suggests that the position of the nitro group has a strong influence on the aromatic ring distortion. The crystal packing is stabilized by weak C—H⋯O hydrogen bonds to the nitramine group.     

Crystallographic, vibrational and theoretical studies of 2,3-diaminopyridinium selenate

The new organic–inorganic salt, 2,3-diaminopyridinium selenate, has been synthesized and characterized by means of single-crystal X-ray crystallography, FT-IR and FT-Raman spectroscopy. A diprotonated organic ligand, H₂^1,3L²⁺, existing in the crystal structure was theoretically shown to be the most stable cationic species of 2,3-diaminopyridine. The weak non-covalent forces of N–H?O type between the hydrogen atoms of the amino and ammonio groups of 2,3-diaminopyridinium cation and oxygen atoms of tetrahedral selenate anions determine three-dimensional arrangement with complex network of intermolecular interactions of hydrogen bond type (donor–acceptor distances from 2.697(3) Å to 3.088(3) Å). Vibrational spectra have been discussed in comparison with X-ray results. Juxtaposition of spectra of the complex with the pure organic ligand and deuterated analogue of the title compound allowed to give reliable assignments of most observed vibrational bands. Presented data can be useful in elucidation of molecular mechanism of uptake of tetrahedral SeO₄²⁻ anion by the living organisms.     

2,4,6‐Trimethyl‐N‐nitro­aniline

In 2,4,6‐trimethyl‐N‐nitro­aniline (alternatively called mesitylnitramine), C₉H₁₂N₂O₂, the primary nitramino group is planar with a short N—N bond and is nearly perpendicular to the aromatic ring. The methyl group located in the para position is disordered, each H atom having half‐occupancy. The mol­ecules are linked together along the [100] axis by inter­molecular N—H⋯O hydrogen bonds.     

DFT and experimental studies on structure and spectroscopic parameters of 3,6-diiodo-9-ethyl-9H-carbazole

Structural Chemistry - The first report on crystal and molecular structure of 3,6-diiodo-9-ethyl-9H-carbazole is presented. Experimental room-temperature X-ray and 13C chemical shift studies were...     

Structural and Vibrational Studies of Sr2[W(CN)8]·10H2O

The crystal structure of distrontium octacyanotungstate decahydrate, Sr₂[W(CN)₈] · 10H₂O, was solved using X‐ray single crystal diffraction. The tungsten atom lies on a two fold axis. Eight cyanide anions create tetragonal antiprismatic coordination sphere of tungsten atom. The two edge‐sharing tetragonal antiprisms of [Sr(NC)₃(OH₂)₅], create a dimer, [Sr₂(CN)₆(H₂O)₆(μ‐H₂O)₂], which lies on the inversion center. One symmetry independent water molecule is located in a void of 40 Å³. Vibrational (FT‐IR and FT‐Raman spectroscopic) behavior of main structural units is discussed. It was spectroscopically confirmed that the geometry of [W(CN)₈]^4– anion is slightly distorted from that corresponding to “free” anion. The number of observed bands is significantly lower than that expected for C₂ point group.     

Crystal Structure of the RE2PbS4 (RE = Y,Dy, Ho,Er, and Tm) Compounds and a Comparison with the Crystal Structures of other Rare Earth Lead Chalcogenides

The crystal structure of the RE₂PbS₄ (RE = Y, Dy, Ho, Er and Tm) compounds (space group Cmc2₁, Pearson symbol oC112, a = 0.79301(3) nm, b = 2.86966(9) nm, c = 1.20511(5) nm, R_Bragg = 0.0979 for Y₂PbS₄; a = 0.79484(8) nm, b = 2.8721(3) nm, c = 1.2039(1) nm, for Dy₂PbS₄; a = 0.79081(2) nm, b = 2.86222(7) nm, c = 1.20220(4) nm, R_Bragg = 0.0859 for Ho₂PbS₄; a = 0.7863(2) nm, b = 2.8525(5) nm, c = 1.1995(2) nm, R1 = 0.0482 for Er₂PbS₄ and a = 0.78419(3) nm, b = 2.84184(9) nm, c = 1.19655(4) nm, R_Bragg = 0.0893 for Tm₂PbS₄) was investigated by means of X‐ray single crystal and powder diffraction. Each RE atoms is octahedrally coordinated by six S atoms. Each Pb atoms is surrounded by seven S atoms to form a mono‐capped trigonal prism.     

Monodentate coordinated chromate(VI) ion in [Cu(phen)<Subscript>2</Subscript>OCrO<Subscript>3</Subscript>](phen)<Subscript>0.5</Subscript>·4H<Subscript>2</Subscript>O completing the square pyramidal geometry of the copper(II) in the solid state

Novel copper(II) complex of the formula [Cu(phen)₂OCrO₃](phen)_0.5 ·4H₂O (1) (phen = 1,10-phenantroline) was prepared in the crystalline form and characterized by X-ray diffraction and spectroscopic methods (IR-FIR, NIR-Vis–UV, EPR). In the solid state, the CuN₄O chromophore adopts a slightly distorted square-pyramidal geometry around the Cu²⁺ ion with a magnitude of a distortion parameter τ = 0.14. The chromate unit in (1) was found to be a monodentate.