Structural and Electronic Properties of the Iron(II) and Nickel(II) Bis(ligand) Complexes of 6-(5-Methyl-1,2,4-oxadiazol-3-yl)-2,2′-bipyridine— a Terpyridine-Based Tridentate

1999 ◽  
Vol 52 (7) ◽  
pp. 673 ◽  
Author(s):  
Bradley J. Childs ◽  
Marcia L. Scudder ◽  
Donald C. Craig ◽  
Harold A. Goodwin
Keyword(s):  
Electronic Properties ◽  
Spectroscopic Data ◽  
Room Temperature ◽  
Spin Transition ◽  
Iron Complex ◽  
Ligand Field ◽  
Monoclinic Space Group ◽  
Space Group ◽  
C 23 ◽  
Structural And Electronic Properties

Iron(II) and nickel(II) bis(ligand) complexes of 6-(5-methyl-1,2,4-oxadiazol-3-yl)-2,2′-bipyridine (L) are described. The ligand field in the iron complex is close to that at the singlet ( 1 A1) ? quintet ( 5 T2) crossover and magnetic and Mössbauer spectral evidence indicates that a spin transition occurs in salts of the iron complex but is centred above room temperature. The structures of [FeL2] [CF3SO3]2.CH3CN and [NiL2] [BF4]2.CH3CN were determined and both are very similar to the structures of the corresponding terpyridine complexes. Spectroscopic data indicate that for the iron complex π-interaction between the metal and the ligand is less than that in the terpyridine system. [FeL2] [CF3SO3]2.CH3CN is monoclinic, space group P 21/c; a 8 . 232(5), b 25 . 273(10), c 17 . 306(10) Å, β 92 . 37(3)°, Z 4; [NiL2] [BF4]2.CH3CN is monoclinic, space group P 21/c; a 8 . 136(2), b 17 . 558(2), c 23 . 783(7) Å, β 109 . 32(1)°, Z 4.

Structural and Electronic Properties of Bis[2-(pyrazin-2-ylamino)-4-(pyridin-2-yl)thiazolato]iron(II) and Its Solvated Derivatives

1994 ◽  
Vol 47 (5) ◽  
pp. 891 ◽  
Author(s):  
BJ Childs ◽  
DC Craig ◽  
KA Ross ◽  
ML Scudder ◽  
HA Goodwin
Keyword(s):  
Electronic Properties ◽  
Room Temperature ◽  
Singlet State ◽  
Methanol Solution ◽  
Monoclinic Space Group ◽  
Deprotonated Form ◽  
Complex Molecules ◽  
Quintet State ◽  
Structural And Electronic Properties ◽  
Continuous Temperature

The uncharged complex [Fe( pzapt )2] [ pzapt is the deprotonated form of 2-(pyrazin-2-ylamino)-4-(pyridin-2-yl) thiazole ] crystallizes with varying degrees of solvation , depending on the solvent. The electronic properties of the solvates differ. For all of them temperature dependence of the magnetic moment is observed, associated with a continuous temperature-induced singlet (1A1) ↔ quintet (5T2) transition. The transition is centred below room temperature for the benzene solvates but the unsolvated and chloroform solvate complexes exist predominantly in a singlet low-spin state. Overall the stabilization of the singlet state is greater in this system than in the previously studied [Fe( papt )2] [ paptH = 2-(pyridin-2-ylamino)-4-(pyridin-2-yl) thiazole ]. A spin equilibrium has been characterized for both [Fe( pzapt )2] and [Fe( papt )2] in methanol solution. The crystal structure of [Fe( pzapt )2].3/2C6H6 reveals Fe-N bond lengths consistent with both singlet and quintet state iron(II) being present. The benzene molecules are incorporated into the lattice as groups of three by occupying channels created by the packing of the complex molecules. Bis [2-(pyrazin-2-ylamino)-4-(pyridin-2-yl) thiazole ]iron(II) sesquibenzene solvate: monoclinic, space group P 21/c, a 14.894(7), b 12.601(2), c 16.777(8) Ǻ, β 94.57(2)°, Z 4.

STRUCTURAL AND ELECTRONIC PROPERTIES OF THE Li/Si(001) SURFACE

1996 ◽  
Vol 03 (03) ◽  
pp. 1487-1494
Author(s):  
J.W. CHUNG
Keyword(s):  
Electronic Properties ◽  
Binding Sites ◽  
Room Temperature ◽  
Structural Models ◽  
Metallic Phase ◽  
Surface Band ◽  
Ordered Structures ◽  
Initial Stage ◽  
Structural And Electronic Properties ◽  
Characteristic Features

Atomic arrangements and electronic properties of the Li-adsorbed Si(001) surface are briefly reviewed. Characteristic features of a series of ordered structures with increasing Li coverage at room temperature are described. Structural models invoking a dimer flipping mechanism are discussed for the first two ordered structures, (2×2)-Li and (2×1)-Li, which are proposed as reconstructions of the silicon substrate. It is shown that the metallic phase found at an initial stage of adsorption is a result of substrate metallization, which explains the presence of an intraband surface plasmon. The features of the surface band structures for the first two ordered structures are discussed in terms of variation of the binding sites with coverage. All the unique features of the Li/Si(001) surface essentially exhibit the size effects of Li.

Tuning the Steric and Electronic Properties of Chiral Rhenium Thiolate Complexes

1998 ◽  
Vol 53 (8) ◽  
pp. 893-899 ◽  
Author(s):  
Nicolai Burzlaff ◽  
Michael Hagel ◽  
Wolfdieter A. Schenk
Keyword(s):  
Electronic Properties ◽  
Monoclinic Space Group ◽  
Substitution Product ◽  
Triclinic Space Group ◽  
Space Group ◽  
Co Substitution ◽  
Thiolate Complexes ◽  
Co Removal ◽  
Complex Fragment

Abstract Reaction of the complex [CpRe(NO)(CO)2]BF4 with triisopropylphosphine gives the chiral CO substitution product [CpRe(NO){P(i-Pr)3}(CO)]BF4. The corresponding triphenylphosphite complex [CpRe(NO){P(OPh)3}(CO)]BF4 may be obtained by oxidative CO removal. Reduction of the remaining CO ligand with NaBH4 furnishes the corresponding methyl com­plexes [CpRe(NO)(L)(CH3)]. The structure of [CpRe(NO){P(i-Pr)3}(CH3)] was determined: triclinic space group P1̄ (No. 2), a = 8.442(4), b = 9.582(5), c -11.820(8) Å, α= 81.81 (4), β = 87.18(4), γ = 63.87(5)°, Z = 2. Reaction of the methyl complexes with HBF4 in the presence of thiols gives, after chromatographic workup, the thiolate derivatives [CpRe(NO)(L)(SR)] (L = CO, P(OPh)3, P(i-Pr)3, R = CH2Ph, CH2(4-C6H4Cl), CH2(4-C6H4OMe), CH3, C2H5). The structure of [CpRe(NO){P(i-Pr)3}(SCH3)] was determined: monoclinic space group P21 (No. 3), a = 7.0515(7), b = 17.3469(10), c = 7.9727(7) Å, β = 114.021(7)°, Z = 2. In both structures, a significant opening of the angle N-Re-X (X = C, S) suggests that antibonding interactions between orbitals of the ligand X and the second-highest MO of the [CpRe(NO)(L)] complex fragment are avoided.

Magnetic, Spectral and Structural Aspects of Spin Transitions in Iron(II) Complexes of 2-(Pyrazol-3-yl)pyridine and 3-(Thiazol-2-yl)pyrazole

1999 ◽  
Vol 52 (2) ◽  
pp. 109 ◽  
Author(s):  
Lucia S. Harimanow ◽  
Kristian H. Sugiyarto ◽  
Donald C. Craig ◽  
Marcia L. Scudder ◽  
Harold A. Goodwin
Keyword(s):  
Hydrogen Bonding ◽  
Hysteresis Loop ◽  
Room Temperature ◽  
Thermal Hysteresis ◽  
Structural Data ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Thermal Hysteresis Loop ◽  
Lower Temperature ◽  
Structural Aspects

Tris(ligand)iron(II) complexes of 2-(pyrazol-3-yl)pyridine (3ppH) and 3-(thiazol-2-yl)pyrazole (3tpH) undergo temperature-induced singlet (1A1) ⇔ quintet (5T2) transitions. The transition in [Fe(3ppH)3] [CF3SO3]2.2H2O is continuous and centred above room temperature while that in the anhydrous triflate salt is discontinuous and is centred below room temperature. The latter transition occurs via a thermal hysteresis loop of width 12 K, Tc↓ and Tc↑ being 229 and 241 K, respectively. The displacement of the transition to lower temperature in the anhydrous salt is believed to be associated with the loss of hydrogen bonding involving the uncoordinated pyrazole >NH group and solvate water. In [Fe(3tpH)2(3tp)] [ClO4].2H2O and [Fe(3tpH)2(3tp)] [BF4].2H2O (3tp is the deprotonated ligand) continuous transitions are observed, centred below room temperature. In these instances the displacement is consistent with the intrinsically weaker field of the bidentate system containing two five-membered heterocycles. Structural data were obtained for [Fe(3ppH)3][CF3SO3]2.2H2O, [Fe(3tpH)3] [BF4]2.1·5H2O and [Ni(3tpH)3] [BF4]2.2(3tpH). The average metal–nitrogen distances in the complexes are 1·97, 2·18 and 2·09 Å, severally. The large difference in the distances for the two iron complexes arises from the different ground states: a singlet for the 3ppH complex and a quintet for the 3tpH complex. In all three salts there is extensive hydrogen bonding involving the pyrazole >NH groups, the anions and the solvate molecules. [Fe(3ppH)3] [CF3SO3]2.2H2O: monoclinic, space group P21/c, a 12·33(1), b 24·44(1), c 12·55(1) Å, β 115·27(4)°, Z 4. [Fe(3tpH)3] [BF4]2.1·5H2O: monoclinic, space group C 2/c, a 41·56(2), b 16·418(3), c 18·154(7) Å, β 106·94(2)°, Z 8. [Ni(3tpH)3] [BF4]2.2(3tpH):P bcn, a 14·928(2), b 15·310 (3), c 17·882 (3) Å, Z 4.

Structural, Magnetic and Mössbauer Studies of Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) Triflate and its Hydrates

1997 ◽  
Vol 50 (9) ◽  
pp. 869 ◽  
Author(s):  
Kristian H. Sugiyarto ◽  
Karyn Weitzner ◽  
Donald C. Craig ◽  
Harold A. Goodwin
Keyword(s):  
Electronic Properties ◽  
Low Temperatures ◽  
Room Temperature ◽  
Spin Transition ◽  
Water Molecules ◽  
Triclinic Space Group ◽  
Discontinuous Transition ◽  
A Minor ◽  
Spin Species ◽  
Anhydrous Complex

The electronic properties of bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) triflate depend markedly on the extent of hydration. The trihydrate is low spin while the monohydrate is high spin at room temperature but undergoes a discontinuous transition to low spin at low temperatures. In the anhydrous complex magnetic and Mössbauer spectral data indicate that there is a minor fraction of low-spin species at room temperature and this fraction increases at low temperatures. The spin transition in the anhydrous salt is continuous and incomplete at 80 K. The structure of the trihydrate reveals an extensive hydrogen-bonding network which involves the uncoordinated >NH groups of the pyrazolyl groups in the ligands, the water molecules and the anions. The disruption of this network on loss of water is believed to be responsible for the change in electronic properties. Bis(2,6-bis(pyrazol-3-yl)pyridine)iron(II) triflate trihydrate: triclinic, space group P-1, a 11·490(5), b 12·218(6), c 13·666(6) Å, α 104 ·67(2), β 104·58(2), γ 104·35(2)°, Z 2.

Preparation and crystal structure of SbV1.50InIII0.50(PO4)3 and (SbV0.50InIII0.50)P2O7

2008 ◽  
Vol 23 (3) ◽  
pp. 232-240
Author(s):  
Abderrahim Aatiq ◽  
Rachid Bakri ◽  
Aaron Richard Sakulich
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Room Temperature ◽  
Rietveld Method ◽  
Monoclinic Space Group ◽  
Unit Cell Parameters ◽  
Orthorhombic System ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

Synthesis and structure of two phosphates belonging to the ternary Sb2O5–In2O3–P2O5 system are realized. Structures of SbV1.50InIII0.50(PO4)3 and (SbV0.50InIII0.50)P2O7 phases, obtained by solid state reaction in air at 950 °C, were determined at room temperature from X-ray powder diffraction using the Rietveld method. SbV1.50InIII0.50(PO4)3 have a monoclinic (space group P21/n) distortion of the Sc2(W O4)3-type framework. Its structure is constituted by corner-shared SbO6 or InO6 octahedra and PO4 tetrahedra. Monoclinic unit cell parameters are a=11.801(2) Å, b=8.623(1) Å, c=8.372(1) Å, and β=90.93(1)°. (Sb0.50In0.50)P2O7 is isotypic with (Sb0.50Fe0.50)P2O7 and crystallizes in orthorhombic system (space group Pna21) with a=7.9389(1) Å, b=16.0664(2) Å, and c=7.9777(1) Å. Its structure is built up from corner-shared SbO6 or InO6 octahedra and P2O7 groups (two group-types). Each P2O7 group shares its six vertices with three SbO6 and three InO6 octahedra, and each octahedron is connected to six P2O7 groups.

scholarly journals Phase transition and structures of the twinned low-temperature phases of (Et4N)[ReS4]

2020 ◽  
Vol 76 (3) ◽  
pp. 231-235
Author(s):  
Eduard Bernhardt ◽  
Regine Herbst-Irmer
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Title Compound ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Rapid Cooling ◽  
Space Group ◽  
Disordered Structure ◽  
Β Phase ◽  
Α Phase

The title compound, tetraethylammonium tetrathiorhenate, [(C2H5)4N][ReS4], has, at room temperature, a disordered structure in the space group P63 mc (Z = 2, α-phase). A phase transition to the monoclinic space group P21 (Z = 2, γ-phase) at 285 K leads to a pseudo-merohedral twin. The high deviation from the hexagonal metric causes split reflections. However, the different orientations could not be separated, but were integrated using a large integration box. Rapid cooling to 110–170 K produces a metastable β-phase (P63, Z = 18) in addition to the γ-phase. All crystals of the β-phase are contaminated with the γ-phase. Additionally, the crystals of the β-phase are merohedrally twinned. In contrast to the α-phase, the β- and γ-phases do not show disorder.

Synthese und Kristallstrukturen von N-[ω-(Dimethylammonio)alkyl]- N´,N´,N´´,N´´-tetramethylguanidinium-chlorid-tetraphenylboraten / Synthesis and Crystal Structures of N-[ω-(Dimethylammonio)alkyl]-N´,N´,N´´,N´´- tetramethylguanidinium Chloride Tetraphenylborates

2010 ◽  
Vol 65 (7) ◽  
pp. 907-916 ◽  
Author(s):  
Ioannis Tiritiris ◽  
Falk Lissner ◽  
Thomas Schleid ◽  
Willi Kantlehner
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Hydrogen Bonds ◽  
Crystal Structures ◽  
Room Temperature ◽  
Chloride Ions ◽  
Monoclinic Space Group ◽  
Temperature Structure ◽  
Space Group ◽  
Temperature Modification

Dicationic N,N´,N´,N´´,N´´-pentasubstituted guanidinium dichlorides 4a, b are obtained from the chloroformamidinium salt 2 and diamines 3a, b. N-[2-(Dimethylammonio)ethyl]-N´,N´,N´´,N´´-tetramethylguanidinium chloride tetraphenylborate (5a) and N-[3-(dimethylammonio)propyl]-N´,N´,N´´,N´´-tetramethylguanidinium chloride tetraphenylborate (5b) were synthesized from 4a, b by anion metathesis with one equivalent of sodium tetraphenylborate. The thermal properties of the salts 5a, b were studied by means of DSC methods, and their crystal structures were determined by single-crystal X-ray diffraction analysis. For 5a a solid-solid phase transition is observed at −156 ◦C to a low-temperature structure. The room-temperature modification (α-5a) crystallizes in the centrosymmetric orthorhombic space group Pbca (a = 13.1844(4), b = 13.8007(4), c = 34.7537(11) A° ).The guanidinium ions are interconnected via chloride ions through bridging N-H· · ·Cl hydrogen bonds, providing isolated units. The tetraphenylborate ions show some dynamic disordering in the crystal structure. The low-temperature modification (β -5a) also crystallizes orthorhombically, but in the non-centrosymmetric space group Pna21 (a = 13.1099(4), b = 69.1810(11), c = 13.5847(5) A° ) and consists of four crystallographically independent cations and anions in the unit cell. Compared with the room-temperature structure, a similar N-H· · ·Cl hydrogen bond pattern is observed in the β -phase, but the tetraphenylborate ions are now completely ordered. 5b crystallizes in the monoclinic space group P21/c (a = 10.8010(3), b = 14.1502(5), c = 20.9867(9) A° , β = 94.322(1)◦). In the crystal structure the guanidinium ions are linked via chloride ions through N-H· · ·Cl hydrogen bonds, but in contrast to 5a two infinite strands are formed along the a axis with the tetraphenylborate ions interspersed between them for charge compensation.

Similarities and peculiarities between the crystal structures of the hydrates of sodium sulfate and selenate

2014 ◽  
Vol 70 (4) ◽  
pp. 714-722 ◽  
Author(s):  
Stoyan Kamburov ◽  
Horst Schmidt ◽  
Wolfgang Voigt ◽  
Christo Balarew
Keyword(s):  
Temperature Dependence ◽  
Crystal Structures ◽  
Sodium Sulfate ◽  
Room Temperature ◽  
Site Occupancy ◽  
Monoclinic Space Group ◽  
Chemical Compositions ◽  
Crystal Nucleus ◽  
Space Group ◽  
First Time

The crystal structures of the two hydrates Na2SeO4·10H2O and Na2SeO4·7.5H2O are studied for the first time. The structures of Na2SO4·10H2O and Na2SO4·7H2O are reinvestigated as a function of temperature with respect to the degree of disorder of the O atoms of {\rm SO}_{4}^{2-} in the decahydrate and the O atom of water in the heptahydrate. For Na2SO4·10H2O, the unit site occupancy factor (SOF) of O atoms of {\rm SO}_{4}^{2-} was determined at 120 K. After the temperature dependence of the lattice parameters was studied from 120 to 260 K, it was shown that SOF decreased from 1.0 at 120 K to 0.247 at room temperature. The interesting fact that two salts with different chemical compositions and different crystal structures (Na2SO4·7H2O, tetragonal, space groupP41212 and Na2SeO4·7.5H2O, monoclinic, space groupC2/c) can act mutually as a crystal nucleus is accounted for by similarities in certain fragments of their crystal structures. This phenomenon is attributed to similarities between particular elements of their structures.

An Unusual Geometry of Five-Coordinate Copper(II): The Structure of Cu(terpy)I2 and Spectroscopic Investigations of Complexes Cu(terpy)X2 (X: I, NCS)

1991 ◽  
Vol 46 (9) ◽  
pp. 1193-1199 ◽  
Author(s):  
Ali Kutoglu ◽  
Rudolf Allmann ◽  
José-Vicente Folgado ◽  
Michail Atanasovc ◽  
Dirk Reinen
Keyword(s):  
Single Crystal ◽  
Room Temperature ◽  
Monoclinic Space Group ◽  
Space Group ◽  
Spectroscopic Investigations ◽  
Epr Measurements

The structure of the compound Cu(terpy)I2 (terpy 2,2′: 6′, 2″ terpyridine) was determined at room temperature. It is monoclinic, space group I2/c with a = 13.689(3), b = 9.510(2), c = 11.605(3) Å, β = 97.59(4)° and Ζ = 4. The copper(II) ions are five-coordinated by the three nitrogen atoms from the terpy ligand and the two iodine atoms. The CuN3I2 polyhedron exhibits the same unusual “reverse” geometry as is observed for Cu(terpy)(NCS)2. Single crystal EPR measurements of the iodide and the isothio-cyanate complexes confirmed the structural results, excluding the possibility of a dynamically averaged geometry.

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