Flattened Tetrahedron Research Articles

Rotation about a Covalent Bond and Pyramidalization of an Adjacent sp2 Center are a Synchronized Molecular Motion.

The correlation of the rotation about the Cα-C' bond and the pyramidalization of the sp2-hybridized carbon atom C' and its three bonding partners to a flattened tetrahedron in the substructure Cβ-CαH-C'(═O)-OMe of substituted methyl acetates revealed that the two processes are not independent of each other but parts of a common molecular motion, as outlined in the preceding back-to-back paper. In the present study, we generalized the substructure to Xβ-CαH-C'(═Y)-Z with X, Y, and Z = O, N, C, and S, extending the analysis to several hundred thousand structures of the type carboxylates, carboxamides, ketones, imines, olefins, peptides, lactates, carbothioates, and phenyl derivatives, retrieved from the Cambridge Structural Database. ψ/θ Scatter plots of the individual structure points and their averaging in ψ/θav curves result in wavelike patterns with three maxima and minima and inversion symmetry at ψ = 0° and ±180 for a 360° rotation of Cβ about the Cα-C' bond. The pyramidalization of the sp2-hybridized group CαCiCoCo', which is part of the aromatic system, even disturbs the planarity of phenyl rings. Density functional theory calculations confirm the results of the CSD search.

Chirality of the Conformation Attacks the Planarity of the sp2 Carbon Atom in a Covalent Bond.

The correlation of the rotation about the bond C'-Cα and the pyramidalization of the sp2 hybridized carbon atom C' and its three bonding partners to a flattened tetrahedron was investigated for the substructure Cβ-CαH-C'(═O)-OMe. A search in the Cambridge Structural Database (CSD) gave 15,295 structures with a substituted methyl acetate group at the end of the molecules. The scatter plot of the rotation angle ψ = O═C'-Cα-Cβ versus the pyramidalization angle θ = O(MeO)C'Cα and the ψ/θav curve show an unusual undulating pattern with three maxima and minima for a 360° rotation about the bond C'-Cα. There is no net chiral induction from the (Mψ)/(Pψ) conformations of the bond C'-Cα to the (Rθ)/(Sθ) configurations of the flattened tetrahedron because the contributions of the three maxima and minima cancel each other. The wavelike ψ/θav curve demonstrates that the rotation about the bond C'-Cα and the pyramidalization of the group C'(═O)(OMe)Cα are not independent processes. They are coupled with each other in one common molecular motion. The ψ/θav curve appears as the third harmonic of a sinusoidal fundamental frequency. DFT calculations of the propanoate anion, methyl propanoate, and methyl 2-methylpropanoate confirm the results of the CSD search.

Spectroscopic, structural and DFT studies of luminescent Pt(II) and Ag(I) complexes with an asymmetric 2,2′-bipyridine chelating ligand

A new unsymmetrically substituted 2,2′-bipyridine ligand, 5-methyl-5′-carbomethoxy-2,2′-bipyridine (L) was isolated from the dry distillation of the copper(II) complex, mono-aqua-bis(trans-5-methyl-pyridine-2-carboxylato-N,O)copper(II). The ligand was fully characterized. The spectroscopic and single-crystal X-ray diffraction (SCXRD) studies of the coordination compounds of the ligand with platinum(II) and silver(I); cis-Pt(L)Cl2 (1) and [Ag(L)2]PF6 (2), respectively are reported. In 1, the Pt centre coordinates to tertiary N atoms of the ligand and two chloride ions to form a neutral square-planar coordination sphere, while in 2, the Ag(I) centre is coordinated by two ligands through N atoms to generate a cationic flattened tetrahedron geometry in which two mean planes intersect each other at 50.93°. The pyridine rings are nearly coplanar as revealed by the torsion angle of N2-C7-C6-N1 1.32(5)°. In both complexes, L acts as a chelating ligand through pyridyl N atoms. In 1, the molecular units are stacked in a head-to-tail fashion with a Pt···Pt separation of 3.5 Å. Supramolecular self-assembly of the molecular units by extensive intermolecular contacts through C‒H···Cl and C‒H···O between the adjacent units results in an infinite two-dimensional flattened-out herringbone structure in the crystalline state. In 2, the molecular units are interconnected with each other by C‒H···O contacts between the adjacent units running parallel to each other. Both complexes are fluorescent in solution and have emission maxima in the UV-Vis regions, which is a very important property for optoelectronic applications. DFT (density functional theory) and TD-DFT (time-dependent-DFT) calculations were performed at B3LYP/6-311+G(d,p)/LANL2DZ level to explore structural, electronic, and spectroscopic properties to compare with the experimental results. The molecular orbitals (MOs) were carried out with DFT at the same level.

Terminal Regions Confer Plasticity to the Tetrameric Assembly of Human HspB2 and HspB3

Heterogeneity in small heat shock proteins (sHsps) spans multiple spatiotemporal regimes—from fast fluctuations of part of the protein, to conformational variability of tertiary structure, plasticity of the interfaces, and polydispersity of the inter-converting, and co-assembling oligomers. This heterogeneity and dynamic nature of sHsps has significantly hindered their structural characterization. Atomic coordinates are particularly lacking for vertebrate sHsps, where most available structures are of extensively truncated homomers. sHsps play important roles in maintaining protein levels in the cell and therefore in organismal health and disease. HspB2 and HspB3 are vertebrate sHsps that are found co-assembled in neuromuscular cells, and variants thereof are associated with disease. Here, we present the structure of human HspB2/B3, which crystallized as a hetero-tetramer in a 3:1 ratio. In the HspB2/B3 tetramer, the four α-crystallin domains (ACDs) assemble into a flattened tetrahedron which is pierced by two non-intersecting approximate dyads. Assembly is mediated by flexible “nuts and bolts” involving IXI/V motifs from terminal regions filling ACD pockets. Parts of the N-terminal region bind in an unfolded conformation into the anti-parallel shared ACD dimer grooves. Tracts of the terminal regions are not resolved, most likely due to their disorder in the crystal lattice. This first structure of a full-length human sHsp heteromer reveals the heterogeneous interactions of the terminal regions and suggests a plasticity that is important for the cytoprotective functions of sHsps.

Flexibility of the coordination geometry at the N-site of Cu(II)2 human serum-transferrin induced by the different orientations of Arg124.

The ESR spectra of dicupric human serum-transferrin (serum-Tf) were measured from -20 to 37°C in the liquid state (56% glycerol at pH 7.6). Two coordination geometries (types B-1 and B-2) with different ESR parameters were present at the N-site. The contents of the coordination geometry of type B-1 at the N-site increased as the temperature increased. The equilibrium constant between the coordination geometries of types B-1 and B-2 was determined by ESR spectra. The enthalpy value from type B-2 to B-1 was +5.3 kcal/mol, as obtained from a van't Hoff plot. The two conformational energies of the cluster models of the copper-binding site at the N-site of dicupric human serum-Tf, where the Arg124 residue was oriented in two different directions (conformations I and II), were calculated by Density Functional Theory, and the enthalpy value from conformation II to I was +2.1 kcal/mol. The enthalpy value was similar to that (+5.3 kcal/mol) obtained by the coordination geometrical change from type B-2 to B-1 in Cu(II)2 serum-Tf. In conformations I and II, the residue of Arg124 at the N-site is located either far from or near the copper-binding site, respectively, and in both cases the coordination geometry of the cupric ions at the N-site has changed from a flattened tetrahedron to a trigonal bipyramid. This result implies that the ESR spectral change from type B-2 to B-1 is caused by the presence of two different orientations of Arg124 in the change from conformation II to I.

Synthesis, structure, and photocatalytic properties of new dinuclear helical complex of silver(I) ions

The 6′,6″-(2-phenylpyrimidine-4,6-diyl)bis(6-methyl-2,2′-bipyridine) ligand L reacts with trifluoromethanesulfonate silver(I) to give dinuclear helical complex [Ag2L2](CF3SO3)2·H2O in which metal ions are in approximately heavily flattened tetrahedron coordination geometry. The complex has been characterized by spectroscopic techniques, elemental analysis, transmission and scanning electron microscopies, and thermogravimetry. The solid state structure of complex has been determined by X-ray diffractometry. The methylene blue (MB) degradation was studied with UV–Vis spectrophotometry. A maximum degradation efficiency of 90% of the dye has been achieved. Photodegradation of the dye follows second-order kinetics. [Ag2L2](CF3SO3)2·H2O is active photocatalyst of MB degradation under UV–Vis and sunlight irradiation.

Copper(I) complex with α-(3,3-dimethyl-3,4-dihydroisoquinolyl-1)hydroxyiminoacetonitrile [Cu(LH)L]2 · CH3CN: Synthesis, crystal structure, and spectroscopic characteristics

The complex of univalent copper with α-(3,3-dimethyl-3,4-dihydroisoquinolyl-1)hydroxyiminoacetonitrile (LH) is synthesized and studied by X-ray diffraction and IR spectroscopy. As shown by X-ray diffraction analysis, structural crystal units are a binuclear complex consisting of two independent [Cu(LH)L] molecules joined by very strong hydrogen bonds O-H⋯O and an acetonitrile solvate molecule: [Cu(LH)L]2 · CH3CN (I). The ligands coordinate the copper(I) atom at the vertices of a flattened tetrahedron in the bidentate-chelating mode through their nitrogen atoms. The two independent ligands are linked to each copper atom, and one of the ligands exists in the molecular form LH, whereas the other exists in the form of the L− anion. The Cu-N bond lengths range from 1.995 to 2.051 A, and the NCuN angles are 80.7°–132.8°. All ligands exist in the same E-s-cis isomeric form. The IR spectroscopic characteristics of the complex are presented.

Synthesis and crystal structure of bis(2,2,2-cryptand potassium) tetrakis(isocyanato)cuprate(II)

A new complex compound, bis(2,2,2-cryptand potassium) tetrakis(isocyanato)cuprate(II), 2[K(Crypt-222)]+ [Cu(NCS)4]2− was prepared and its crystal structure was studied by X-ray structural analysis. The structure includes one symmetrically independent complex cation [K(Crypt-222)]+ of a guest-host type and independent one half of [Cu(NCS)4]2− anion. Through the center of the anion passes crystallographic symmetry axis 2, the approximate point symmetry of the anion is D2, while the approximate point symmetry of the complex cation is D3. The coordination polyhedron of the [Cu(NCS)4]2− anion (four N atoms) conjugated with Cu2+ cation is a nonplanar square considerably screwed into a flattened tetrahedron. The K+ cation (coordination number 8) of the complex cation [K(Crypt-222)]+ is coordinated by all eight heteroatoms (6O + 2N) of the 2,2,2-cryptand ligand, and its coordination polyhedron can be described as bis-basecentered trigonal prism slightly screwed into an anti-prism.

Two modifications of bis(μ2-chloro)tetrachlorodicuprate(II) bis[(18-crown-6)potassium]: Synthesis and crystal structure

Two crystal modifications of a novel complex bis(μ2-chloro)tetrachlorodicuprate(II) bis[(18-crown-6)potassium, [K{(18-crown-6)}2Cu2Cl6] were synthesized and studied by X-ray diffraction. The structures of two monoclinic modifications—Iα (space group P21/n, a = 9.053, b = 33.815, c = 13.469 A, β = 101.29°, Z = 4) and Iβ (space group P21/c, a = 10.991, b = 8.187, c = 22.542 A, β = 98.15°, Z = 2) were solved by the direct method and refined by the full-matrix least-squares method in anisotropic approximation to R = 0.073 (Iα) and 0.068 (Iβ) for 4883 (Iα) and 3525 (Iβ) independent reflections (CAD-4 automated diffractometer, λMoKα). The molecules of Iα and Iβ consist of the central binuclear complex anion [Cu2Cl6]2− and two peripheral host-guest cationic fragments [K(18-crown-6)]+, each linked with the [Cu2Cl6]2− anions through the K-Cl bonds. The molecule of Iα and centrosymmetric Iβ molecule have different structures, since they have different orientation of the [K(18-crown-6)]+ fragments relative to the central [Cu2Cl6]2− anion. The coordination polyhedron of the Cu2+ cation in the latter anion in Iα and Iβ is intermediate between flattened tetrahedron and square. In the [K(18-crown-6)]+ ions of Iα and Iβ, the K+ cation has the distorted hexagonal pyramidal coordination polyhedron with six O atoms of the 18-crown-6 ligand in a base and bifurcate vertex at two Cl atoms of the [Cu2Cl6]2− anion. The 18-crown-6 ligands of Iα and Iβ have standard crown conformation.

4,7,13,16,21,24-hexaoxa-1,10-diazaniabicyclo[8.8.8]hexacosane tetra(nitrato-O)copper(II): Synthesis and crystal structure

A new crystalline complex salt, 4,7,13,16,21,24-hexaoxa-1,10-diazaniabicyclo[8.8.8]hexacosane tetra(nitrato-O)copper(II) [H2(Crypt-222)]2+ · [Cu(NO3)4]2−(I), is synthesized and studied using X-ray diffraction analysis (space group P21/c, a = 10.264 A, b = 14.798 A, c = 19.516 A, β = 100.20°, Z = 4). The structure is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.032 for 4050 independent reflections (CAD-4 automated diffractometer, λMoK α radiation). Salt I exist in crystals as individual ions: the [Cu(NO3)4]2− complex anion and the slightly disordered dication of 2.2.2-cryptand with two protonated nitrogen atoms. The Cu2+ cation has a square coordination somewhat distorted toward a flattened tetrahedron with four coordination bonds with the O atoms of the four NO 3 − ligands. Trifurcate hydrogen bonds of the [H2(Crypt-222)]2+ type are observed in the N-H(⋯ O)3 dication.

The crystal structure of tetrakis(dimethylamino)titanium(IV)

Ti(NMe 2) 4 is a monomeric species in the gas phase and in solution, and this remains true on crystallisation. The crystal structure is triclinic, with space group P 1 ¯ , and unit cell dimensions a = 8.277(6), b = 8.407(6), c = 11.167(7) Å, α = 105.36(4)°, β = 97.03(3)° and γ = 116.01(2)° at 105 K. Electron-diffraction measurements show that in the gas-phase Ti(NMe 2) 4 takes the form of a slightly flattened tetrahedron with overall S 4 symmetry. In the solid state the symmetry changes to C 1; the reduction of point-symmetry results from the twisting of one of the amino groups away from its gas-phase configuration. DFT calculations indicate that the energy of the C 1 structure lies only 0.2 kJ mol −1 above that of the S 4 conformer. The change in structure on crystallisation can be ascribed to the avoidance of prohibitively short intermolecular methyl–methyl interactions which would have been formed had the S 4 structure been retained.

Crystal structure of tetrakis(phenylamino)silane, Si(C6H5NH)4

C24H24N4Si, monoclinic, C12/cl (no. 15), a = 16.217(3) k,b= 16.409(4) A, c = 17.302(4) A, β = 110.14(2)°, V= 4322.7 A, Z= 8, Rp(F) = 0.077, wR^F) = 0.186, T= 293 K. Source of material The compound was synthesized according to the method of Reynolds [1] by reacting silicon tetrachloride with aniline in diethyl ether as a solvent. Crystals were obtained by recrystallizing the crude product from carbon disulfide. A single crystal was sealed in a glass capillary under argon atmosphere for the crystal structure determination. Discussion Tetrakis-(phenylamino)silane crystallizes monoclinically with one molecule per asymmetric unit. The Si—Ν bond lengths correspond to those found in tetrakis(methylamino)silane [2] and tetrakis(pentafluorophenylamino)silane [3]. The N-Si-N bond angles partly show considerable deviations from the tetrahedral Table 3. Atomic coordinates and displacement parameters (in A). angle, resulting in a flattened tetrahedron, which has been similarly found in other silazanes and reflects the center undercoordination of silicon. Table 1. Data collection and handling. Crystal: Wavelength: μ· Diffractometer, scan mode: 20m«: NWhn^Nihklhniq,*: Criterion for / 2<r(W, 1445 263 SHELXS-86 [4], SHELXL-93 [5] Table 2. Atomic coordinates and displacement parameters (in A).

Four bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)oligosulfanes.

The four oligosulfanes, bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)disulfane, C(16)H(24)Cl(2)O(2)S(2), (III), 1,3-bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)trisulfane, C(16)H(24)Cl(2)O(2)S(3), (V), 1,4-bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)tetrasulfane, C(16)H(24)Cl(2)O(2)S(4), (VII), and 1,6-bis(1-chloro-2,2,4,4-tetramethyl-3-oxocyclobutan-1-yl)hexasulfane, C(16)H(24)Cl(2)O(2)S(6), (VIII), all have similar geometric parameters, with the C-C bond lengths involving the chloro-substituted cyclobutanyl C atom being elongated to about 1.59 A. There are two molecules in the asymmetric units of the tri- and tetrasulfanes, and the molecules in the latter compound have local C(2) symmetry. The molecule of the hexasulfane has crystallographic C(2) symmetry. Most of the cyclobutanyl rings are not perfectly planar and have slight but varying degrees of distortion towards a flattened tetrahedron. The polysulfane chain in each structure has a helical conformation, with each additional S atom in the chain adding approximately one quarter of a turn to the helix.

Cr(bpym)(C 2O 4) 2] − in designing heterometallic complexes. Crystal structures and magnetic properties of PPh 4[Cr(bpym)(C 2O 4) 2]·H 2O and [Ag(bpym)][Cr(C 2O 4) 2](H 2O) 2]·2H 2O (bpym=2,2′-bipyrimidine)

The preparation, crystal structure and magnetic properties of PPh 4[Cr(bpym)(C 2O 4) 2]·H 2O ( 1) and [Ag(bpym)][Cr(C 2O 4) 2(H 2O) 2]·2H 2O ( 2) (C 2O 4 2− =oxalate dianion, bpym=2,2′-bipyrimidine and PPh 4 + =tetraphenylphosphonium cation) are described. The structure of 1 is made up of discrete (2,2′-bipyrimidine)bis(oxalato)chromate(III) anions, teraphenylphosphonium cations and uncoordinated water molecules. The structure of 2 consists chains of univalent silver cations bridged by bis-chelating 2,2′-bypyrimidine, cis-diaquabis(oxalato)chromate(III) anions and crystallisation water molecules. The chromium atom in 1 and 2 has a slightly distorted octahedral geometry with two bidentate oxalate groups ( 1 and 2), and one bidentate bpym ligand ( 1) or two cis-coordinated water molecules ( 2). The CrO(ox) bonds are in the ranges 1.951(3)–1.981(3) Å ( 1) and 1.9575(12)–1.9585(14) Å ( 2), values which are shorter than the CrO(w) bonds in 2 [1.9999(16) Å]. The CrN(bpym) bond lengths are 2.064(4) and 2.090(4) Å for 1. The silver atom in 2 is disordered with two different four-coordinated environments from two bpym groups. One of these environments can be defined as a flattened tetrahedron with AgN(bpym) distances of 2.331(2) Å (x2) and 2.360(2) Å (x2) and the second one is distorted with values of the AgN(bpym) bonds in the range 2.132(18) and 2.59(2) Å. The silver–silver separation across bridging bpym is 6.1854(8) Å. Magnetic susceptibility measurements of 1 and 2 in the temperature range 1.9–290 K reveal the occurrence of weak antiferromagnetic interactions together with zero-field splitting effects. The use of the [Cr(bpym)(C 2O 4) 2] − unit of 1 as a ligand towards different univalent and divalent metal ions is discussed in the light of the available structural information.

Reactivity of Ammonium Chloride/Mercuric Chloride Mixtures with Monel Containers. The New Compounds (NH4)2(NH3)x[Ni(NH3)2Cl4] and (NH4)5Cl2[CuCl2][CuCl4

Ammonium chloride/mercuric chloride mixtures (molar ratio 2:1) react at 350°C with Monel (Cu68Ni32) to yield (NH4)NiCl3 and mercury and copper amalgam, respectively. With larger amounts of (NH4)Cl in the reaction mixture, dark green (NH4)2(NH3)x[Ni(NH3)2Cl4] (x≈0.77) (1) is also formed as a main product. Light blue crystals of the mixed-valent copper(I,II) chloride (NH4)5Cl2[CuCl2][CuCl4] (2) were obtained as a minor byproduct from a 4:1 reaction mixture. The crystal structures were determined from single crystal X-ray data; (1): tetragonal, I4/mmm, a=770.9(1), c=794.2(2) pm, 190 reflections, R1=0.0263; (2): tetragonal, I4/mcm, a=874.8(1), c=2329.2(3) pm, 451 reflections, R1=0.0736. In (1) Ni2+ resides in trans-[Ni(NH3)2Cl4]2− octahedra, and in (2) copper(I) is linearly two-coordinated in [CuCl2]− and copper(II) resides in a flattened tetrahedron [CuCl4]2− with a tetrahedricity of 89%.

3-Dimensional organization of the N-terminal vinculin head fragment

The cytoskeleton-associated protein vinculin is composed of a globular head and an elongated tail domain. The protein can be cleaved by V8 protease treatment into two fragments with apparent molecular masses of 90 and 29/27 kDa, respectively. So far, no high-resolution data on the tertiary structure of the N-terminal 90-kDa fragment are available. We analyzed the 90-kDa fragment in detail, using electron spectroscopic imaging in conjunction with modelling experiments. The front view projection of this fragment appears roughly rhomboidal, with 4 intensity maxima arranged at the vertices and a stain-filled region in the center. Based on a detailed examination of different particle projections, a 3-dimensional model was constructed which appears as a flattened tetrahedron. A comparison of the 90-kDa fragment with the intact protein allows for a correlation between the subdomain organization of the vinculin head and the biochemically defined V8 protease cleavage sites (aa 851 and 857).

Electron Spin Resonance of High-Spin Cobalt in Microporous Crystalline Cobalt-Containing Aluminophosphates

Four highly crystalline, cobalt-containing microporous aluminophosphates (CoAPO-5, CoAPO-11, CoAPO-44, and CoAPO-46) have been investigated by using liquid He X- and/or Q-band electron spin resonance (ESR) spectroscopy in order to investigate the coordination of high-spin cobalt before and after calcination. The ESR spectra of the four zeolite structures are characterized by an axial signal with an effective g⊥ ≈ 5.80−5.44 and g|| ≈ 2.00. Quantitative temperature dependence measurements of this axial signal in the temperature range 4−30 K reveal a Curie−Weiss behavior for both as-synthesized and calcined samples confirming (a) the ms = ± 1/2 ground state of magnetically isolated high-spin cobalt and (b) a zero field splitting Δ > 0 cm-1. Quantitation of the ESR signals indicated that most of the Co2+ is ESR active and that only about 30% of this Co2+ can be oxidized to the ESR-inactive Co3+ after calcination. The spin Hamiltonian parameters of as-synthesized and calcined CoAPO-5 material, as determined by spectrum simulation and the microwave power saturation technique, support the presence of framework Co2+ in a flattened or elongated tetrahedron (D2d).

Crystal and molecular structures of eight-coordinate (CuN 4O 4) and six-coordinate (CuN 4O 2) Cu(II) complexes with 4-methyl-5-imidazole-carboxaldehyde or 1-benzyl-2-hydroxymethylimidazole, respectively : Spectroscopic and potentiometric studies

The synthesis and characterisation of two novel Cu(II) eight and six coordinate compounds with the bidentate ligands 4-methyl-5-imidazolecarboxaldehyde (4-Me-5-CHOIm) and 1-benzyl-2-hydroxymethylimidazole (1-Bz-2-CH 2OHIm) are described. Single crystals of [Cu(4-Me-5-CHOIm) 4](H 2O) 2(NO 3) 2 ( 1) and [Cu(1-Bz-2-CH 2OHIm) 4](NO 3) 2 ( 2) were used in structure determinations. The two compounds both crystallise in the monoclinic space group P1̄ with Z=2 for ( 1) and Z=1 for ( 2). The structural data for ( 1) indicated that Cu(II) ion is involved in a flattened tetrahedron of N(1), N(2), N(3) and N(4) atoms of imidazoles ring as well as in a more distant elongated tetrahedron of four of the z-axis oxygen atoms O(1), O(2), O(3), O(4) of aldehyde groups. The coordination scheme of the six-coordinate Cu(II) complex ( 2) is a slightly distorted tetragonal bipyramid and the ligands act as a monodentate and bidentate. Additionally, the coordination processes with Cu(II) were detected and characterised in solution using spectroscopic (EPR and UV–VIS) as wall as potentiometric methods.

Synthesis, crystal structures and electrochemical properties of Cu II and Ni II complexes with hexadentate ligands containing thioether-amido-pyridyl donor set

Novel two acyclic hexadentate ligands, 1,4-bis[ o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane (H 2bpctb) and 1,4-bis[ o-(pyridine-2-carboxamidophenyl)]-1,5-dithiopentane (H 2bpctp), containing thioether functions were synthesized and their copper(II) and nickel(II) complexes [(Cu(bpctb)], 1 ; [Cu(bpctp)], 2; [Ni(bpctb)], 3 and [Ni(bpctp)], 4) were prepared. The structures of 1–4 were determined by X-ray crystallography. The coordination geometries of 3 and 4 are octahedral with two amido and two pyridyl nitrogen atoms and two thioether sulfur atoms of hexadentate ligand. However, the coordination geometry of 2 is a flattened tetrahedron combining two amido nitrogen atoms and two pyridyl nitrogen atoms of hexadentate ligand without thioether coordination. X-ray crystallography and ESR spectroscopic studies revealed that the coordination geometry of 1 is an uncommon equatorially elongated octahedron in solid state. However, this coordination geometry changes to an axially elongated one in solution. The copper(II/I) redox processes for 1 and 2 are around −1.2 V and the nickel(II/III) processes for 3 and 4 at around 0.3 V vs ferrocene/ferrocenium couple were observed in DMSO.

Tetrakis[1-(1-phenylcyclohexyl)piperidinium] Tetrachloromanganate(II) Dichloride

The crystal structure of the title compound, (C17H26N)4[MnCl4]Cl2, has been determined. The cation is 1-(1-phenylcyclohexyl)piperidinium. The metal atom is located on a \overline{4} rotation axis with four Cl atoms coordinated to form a flattened tetrahedron.