Crystal structures of <i>trans</i>-di­chlorido­tetra­kis­[1-(2,6-diiso­propyl­phen­yl)-1<i>H</i>-imidazole-Κ<i>N</i>³]iron(II), <i>trans</i>-di­bromido­tetra­kis­[1-(2,6-diiso­propyl­phen­yl)-1<i>H</i>-imidazole-Κ<i>N</i>³]iron(II) and <i>trans</i>-di­bromido­tetra­kis­[1-(2,6-diiso­propyl­phen­yl)-1<i>H</i>-imidazole-Κ<i>N</i>³]iron(II) diethyl ether disolvate

The title compounds, [FeCl₂(C₁₅H₂₀N₂)₄], (I), [FeBr₂(C₁₅H₂₀N₂)₄], (II), and [FeBr₂(C₁₅H₂₀N₂)₄]·2C₄H₁₀O, (IIb), respectively, all have triclinic symmetry, with (I) and (II) being isotypic. The FeII atoms in each of the structures are located on an inversion center. They have octa­hedral FeX₂N₄ (X = Cl and Br, respectively) coordination spheres with the FeII atom coordinated by two halide ions in a trans arrangement and by the tertiary N atom of four aryl­imidazole ligands [1-(2,6-diiso­propyl­phen­yl)-1H-imidazole] in the equatorial plane. In the two independent ligands, the benzene and imidazole rings are almost normal to one another, with dihedral angles of 88.19 (15) and 79.26 (14)° in (I), 87.0 (3) and 79.2 (3)° in (II), and 84.71 (11) and 80.58 (13)° in (IIb). The imidazole rings of the two independent ligand mol­ecules are inclined to one another by 70.04 (15), 69.3 (3) and 61.55 (12)° in (I), (II) and (IIb), respectively, while the benzene rings are inclined to one another by 82.83 (13), 83.0 (2) and 88.16 (12)°, respectively. The various dihedral angles involving (IIb) differ slightly from those in (I) and (II), probably due to the close proximity of the diethyl ether solvent mol­ecule. There are a number of C-H***Missing image substitution***halide hydrogen bonds in each mol­ecule involving the CH groups of the imidazole units. In the structures of compounds (I) and (II), mol­ecules are linked via pairs of C-H...halogen hydrogen bonds, forming chains along the a axis that enclose R₂²(12) ring motifs. The chains are linked by C-H...π inter­actions, forming sheets parallel to (001). In the structure of compound (IIb), mol­ecules are linked via pairs of C-H...halogen hydrogen bonds, forming chains along the b axis, and the diethyl ether solvent mol­ecules are attached to the chains via C-H...O hydrogen bonds. The chains are linked by C-H...π inter­actions, forming sheets parallel to (001). In (I) and (II), the methyl groups of an isopropyl group are disordered over two positions [occupancy ratio = 0.727 (13):0.273 (13) and 0.5:0.5, respectively]. In (IIb), one of the ethyl groups of the diethyl ether solvent mol­ecule is disordered over two positions (occupancy ratio = 0.5:0.5)

Pyroelectric and piezoelectric scanning microscopy applied to reveal the bipolar state of 4-iodo-4 '-nitrobiphenyl (INBP)

Two recent scanning probe techniques were applied to investigate the bipolar twin state of 4-iodo-4′-nitrobiphenyl (INBP) crystals. Solution grown crystals of INBP show typically a morphology which does not express that of a mono-domain polar structure (Fdd2, mm2). From previous X-ray diffraction a twinning volume ratio of [similar]70 : 30 is now explained by two unipolar domains (Flack parameter: 0.075(29)) of opposite orientation of the molecular dipoles, joined by a transition zone showing a width of [similar]140 μm. Scanning pyroelectric microscopy (SPEM) demonstrates a continuous transition of the polarization P from +P into −P across the zone. Application of piezoelectric force microscopy (PFM) confirms unipolar alignment of INBP molecules down to a resolution of [similar]20 nm. A previously proposed real structure for INBP crystals built from lamellae with antiparallel alignment is thus rejected. Anomalous X-ray scattering was used to determine the absolute molecular orientation in the two domains. End faces of the polar axis 2 are thus made up by NO2 groups. Using a previously determined negative pyroelectric coefficient pc leads to a confirmation also by a SPEM analysis. Calculated values for functional group interactions (DA), (AA), (DD) and the stochastic theory of polarity formation allow us to predict that NO2 groups should terminate corresponding faces. Following the present analysis, INBP may represent a first example undergoing dipole reversal upon growth to end up in a bipolar state

Crystal structures of trans-dichloridotetrakis[1-(2,6-diisopropylphenyl)-1H-imidazole-κN3]iron(II), trans-dibromidotetrakis[1-(2,6-diisopropylphenyl)-1H-imidazole-κN3]iron(II) and trans-dibromidotetrakis[1-(2,6-diisopropylphenyl)-1H-imidazole-κN3]iron(II) diethyl ether disolvate

The title compounds, [FeCl2(C15H20N2)4], (I), [FeBr2(C15H20N2)4], (II), and [FeBr2(C15H20N2)4]·2C4H10O, (IIb), respectively, all have triclinic symmetry, with (I) and (II) being isotypic. The FeII atoms in each of the structures are located on an inversion center. They have octahedral FeX2N4 (X = Cl and Br, respectively) coordination spheres with the FeII atom coordinated by two halide ions in a trans arrangement and by the tertiary N atom of four arylimidazole ligands [1-(2,6-diisopropylphenyl)-1H-imidazole] in the equatorial plane. In the two independent ligands, the benzene and imidazole rings are almost normal to one another, with dihedral angles of 88.19 (15) and 79.26 (14)° in (I), 87.0 (3) and 79.2 (3)° in (II), and 84.71 (11) and 80.58 (13)° in (IIb). The imidazole rings of the two independent ligand molecules are inclined to one another by 70.04 (15), 69.3 (3) and 61.55 (12)° in (I), (II) and (IIb), respectively, while the benzene rings are inclined to one another by 82.83 (13), 83.0 (2) and 88.16 (12)°, respectively. The various dihedral angles involving (IIb) differ slightly from those in (I) and (II), probably due to the close proximity of the diethyl ether solvent molecule. There are a number of C—H...halide hydrogen bonds in each molecule involving the CH groups of the imidazole units. In the structures of compounds (I) and (II), molecules are linked via pairs of C—H...halogen hydrogen bonds, forming chains along the a axis that enclose R22(12) ring motifs. The chains are linked by C—H...π interactions, forming sheets parallel to (001). In the structure of compound (IIb), molecules are linked via pairs of C—H...halogen hydrogen bonds, forming chains along the b axis, and the diethyl ether solvent molecules are attached to the chains via C—H...O hydrogen bonds. The chains are linked by C—H...π interactions, forming sheets parallel to (001). In (I) and (II), the methyl groups of an isopropyl group are disordered over two positions [occupancy ratio = 0.727 (13):0.273 (13) and 0.5:0.5, respectively]. In (IIb), one of the ethyl groups of the diethyl ether solvent molecule is disordered over two positions (occupancy ratio = 0.5:0.5)

Helical zinc complexes of pyrazine-pyridine hybrids

The zinc(II) complexes 1aZnCl(2) and 1bZnCl(2) (1a: 2-(6,2"-bipyrid-2'-yl)-3-(2-pyridyl)pyrazine; 1b: 2-(6',2'-bipyrid-2'-yl)-5,6-dinitrilo-3-(2-pyridyl)pyrazine) were prepared by treatment of the ligands with ZnCl2. The structures of both were investigated by Xray crystallography and H-1 NMR spectroscopy. Both complexes display proton deshielding phenomena that are attributed to a twisted solution-state molecular conformation. In the solid state, 1aZnCl(2) exhibits a high degree of torsion about the axis through the uncomplexed pyridine ring and the pendant chlorine atoms. The solid-state structure and solution-state self-associative behavior of 1bZnCl(2) are indicative of a partial self-assembly motif