Monoclinic System P2 Research Articles

Investigation of the new ammonium phosphate protonic conductor: Crystal structure, vibrational study, electric and dielectric properties

• Investigation of NPTe material has been regarded technologically significant. • Thermal analyses highlight one phase transition before the decomposition. • Electrical properties prove that this material is a typical relaxer and a super-ionic protonic conductor. • The fundamental conduction mechanism is the overlapping large‒polaron tunneling (OLPT) model. The hydrothermal preparation yielded a new super ionic-protonic conductor. The (NH 4 ) 2 HPO 4 .Te(OH) 6 (NPTe) which crystallizes in the monoclinic system P2 1 /c. its crystal structure, is built up from isolated (HPO 4 2- ), (H 6 TeO 6 ) and (NH 4 + ) groups connected by two types of hydrogen bonds: O-H…O and N-H…O, which make up the building of the crystal. IR study highlighted the presence and the independence of the ionic groups and provided detailed information on hydrogen bonds. DSC, DTA and TG, corroborate that the phase transition related to the decomposition, starts at about T= 475K, manifested through the release of water and ammoniac gas. The (NPTe) compound was characterized by complex impedance spectroscopy in the selected temperature and frequency ranges. In fact, the adjustments of the Nyquist plots were performed using an equivalent circuit consisting of two cells. However, the thermal evolution of the conductivity σ dc for this compound displays an Arrhenius – type behavior and suggests that the electrical conduction of our material is provided by a hopping mechanism. Furthermore, the frequency behavior of the conductivity σ ac suggests that the conduction of the title compound is ensured by a mechanism of overlapping large‒polaron tunneling (OLPT) model.

Structural single crystal, thermal analysis and vibrational studies of the new rubidium phosphate tellurate Rb2HPO4RbH2PO4·Te(OH)6

The determination of the crystalline structure of rubidium phosphate tellurate Rb2HPO4RbH2PO4·Te(OH)6 [RbPTe] is performed from single crystal X-ray diffraction data. The title compound crystallizes in the monoclinic system P2. The unit cell parameters are as follows: a=7.9500(7)Å, b=6.3085(6)Å, c=9.5008(9)Å, β=109.783(4)°, Z=2 and V=448.37(7)Å3.The crystal structure is constituted from isolated (PO43-) tetrahedra and (TeO66-) octahedra and two nonequivalent Rb+ cations. Material cohesion is built of O–H⋯O bondings and ionic interactions.The new synthesized material has been characterized using the differential scanning calorimetry (DSC), thermal analysis [differential thermogravimetric analysis (TG), thermodifference analysis (DTA) and the mass spectrometric analysis], FT-IR and Raman techniques.Thermal analysis, in the temperature range of 300–900K, confirms that the decomposition of this material took place in two steps. The differential scanning calorimetry analysis shows three endothermic peaks at 451, 463 and 481K.The existence of anionic groups in the structure has been confirmed by IR and Raman spectroscopy in the frequency ranges 3000–600cm−1 and 1300–50cm−1, respectively.

Purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies of catfish (Clarias magur) haemoglobin

Haemoglobin is an interesting physiologically significant protein composed of specific functional prosthetic haem and globin moieties. In recent decades, there has been substantial interest in attempting to understand the structural basis and functional diversity of fish haemoglobins (Hbs). Towards this end, purification, crystallization, preliminary X-ray diffraction and molecular-replacement studies have been carried out on Clarias magur Hb. Crystals were grown by the hanging-drop vapour-diffusion method using PEG 2000 and NaCl as precipitants. The crystals belonged to the primitive monoclinic system P2, with unit-cell parameters a=98.35, b=56.63, c=112.88 Å, β=100.22°; a complete data set was collected to a resolution of 2.4 Å. The Matthews coefficient of 2.42 Å3 Da(-1) for the crystal indicated the presence of two α2β2 tetramers in the asymmetric unit.

ChemInform Abstract: Fluoride Ion Donor Properties of TcO2F3 and ReO2F3: X-Ray Crystal Structures of MO2F3×SbF5 (M: Tc, Re) and TcO2F3×XeO2F2 and Raman and NMR Spectroscopic Characterization of MO2F3×PnF5 (Pn: As, Sb), [ReO2F2(CH3CN)2] [SbF6], and [Re2O4F

The fluoride ion donor properties of TcO2F3 and ReO2F3 toward AsF5, SbF5, and XeO2F2 have been investigated, leading to the formation of TcO2F3.PnF5 and ReO2F3.PnF5 (Pn = As, Sb) and TcO2F3.XeO2F2, which were characterized in the solid state by Raman spectroscopy and X-ray crystallography. TcO2F3.SbF5 crystallizes in the monoclinic system P2(1)/n, with a = 7.366(2) A, b = 10.441(2) A, c = 9.398(2) A, beta = 93.32(3) degrees, V = 721.6(3) A3, and Z = 4 at 24 degrees C, R1 = 0.0649, and wR2 = 0.1112. ReO2F3.SbF5 crystallizes in the monoclinic system P2(1)/c, with a = 5.479(1) A, b = 10.040(2) A, c = 12.426(2) A, beta = 99.01(3) degrees, V = 675.1(2) A3, and Z = 4 at -50 degrees C, R1 = 0.0533, and wR2 = 0.1158. TcO2F3.XeO2F2 crystallizes in the orthorhombic system Cmc2(1), with a = 7.895(2) A, b = 16.204(3) A, c = 5.198(1) A, beta = 90 degrees, V = 665.0(2) A3, and Z = 4 at 24 degrees C, R1 = 0.0402, and wR2 = 0.0822. The structures of TcO2F3.SbF5 and ReO2F3.SbF5 consist of infinite chains of alternating MO2F4 and SbF6 units in which the bridging fluorine atoms on the antimony are trans to each other. The structure of TcO2F3.XeO2F2 comprises two distinct fluorine-bridged chains, one of TcO2F3 and the other of XeO2F2 bridged by long Tc-F...Xe contacts. The oxygen atoms of the group 7 metals in the three structures are cis to each other and to two terminal fluorine atoms and trans to the bridging fluorine atoms. The 19F NMR and Raman spectra of TcO2F3.PnF5 and ReO2F3.PnF5 in SbF5 and PnF5-acidified HF solvents are consistent with dissociation of the adducts into cis-MO2F2(HF)2+ cations and PnF6- anions. The energy-minimized geometries of the free MO2F2+ cations and their HF adducts, cis-MO2F2(HF)2+, have been calculated by local density functional theory (LDFT), and the calculated vibrational frequencies have been used as an aid in the assignment of the Raman spectra of the solid MO2F3.PnF5 adducts and their PnF5-acidified HF solutions. In contrast, ReO2F3.SbF5 ionizes in SO2ClF solvent to give the novel Re2O4F5+ cation and Sb2F11- anion. The 19F NMR spectrum of the cation is consistent with two ReO2F2 units joined by a fluorine bridge in which the oxygen atoms are assumed to lie in the equatorial plane. The [ReO2F2(CH3CN)2][SbF6] salt was formed upon dissolution of ReO2F3.SbF5 in CH3CN and was characterized by 1H, 13C, and 19F NMR and Raman spectroscopies. The ReO2F2(CH3CN)2+ cation is a pseudooctahedral cis-dioxo arrangement in which the CH3CN ligands are trans to the oxygens and the fluorines are trans to each other.

Synthesis, crystal structure, and properties of a binuclear Zn(II) macroheterocyclic complex based on ferrocene-thiocarbazide ligand

A binuclear macroheterocyclic complex Zn2(FcL)2 based on ferrocene-thiocarbazide (FcL) was synthesized. X-ray diffraction analysis shows that it belongs to the monoclinic system P2(1)/n space group, with a = 1.35379(17) nm, b = 2.6026(3) nm, c = 1.8693(2) nm, β = 95.687(2)° and final R indices R = 0.0796 and Rw = 0.2119. Two Zn(II) ions and two FcL ligands form a 22-membered macroheterocycle, further extended to an infinite 1-D helical chain by intermolecular hydrogen bonding. Spectral properties of the title complex and electrochemical properties of the ligand FcL are also discussed.

Fluoride ion donor properties of TcO2F3 and ReO2F3: X-ray crystal structures of MO2F3.SbF5 (M = Tc, Re) and TcO2F3.XeO2F2 and Raman and NMR spectroscopic characterization of MO2F3.PnF5 (Pn = As, Sb), [ReO2F2(CH3CN)2][SbF6], and [Re2O4F5][Sb2F11

The fluoride ion donor properties of TcO2F3 and ReO2F3 toward AsF5, SbF5, and XeO2F2 have been investigated, leading to the formation of TcO2F3.PnF5 and ReO2F3.PnF5 (Pn = As, Sb) and TcO2F3.XeO2F2, which were characterized in the solid state by Raman spectroscopy and X-ray crystallography. TcO2F3.SbF5 crystallizes in the monoclinic system P2(1)/n, with a = 7.366(2) A, b = 10.441(2) A, c = 9.398(2) A, beta = 93.32(3) degrees, V = 721.6(3) A3, and Z = 4 at 24 degrees C, R1 = 0.0649, and wR2 = 0.1112. ReO2F3.SbF5 crystallizes in the monoclinic system P2(1)/c, with a = 5.479(1) A, b = 10.040(2) A, c = 12.426(2) A, beta = 99.01(3) degrees, V = 675.1(2) A3, and Z = 4 at -50 degrees C, R1 = 0.0533, and wR2 = 0.1158. TcO2F3.XeO2F2 crystallizes in the orthorhombic system Cmc2(1), with a = 7.895(2) A, b = 16.204(3) A, c = 5.198(1) A, beta = 90 degrees, V = 665.0(2) A3, and Z = 4 at 24 degrees C, R1 = 0.0402, and wR2 = 0.0822. The structures of TcO2F3.SbF5 and ReO2F3.SbF5 consist of infinite chains of alternating MO2F4 and SbF6 units in which the bridging fluorine atoms on the antimony are trans to each other. The structure of TcO2F3.XeO2F2 comprises two distinct fluorine-bridged chains, one of TcO2F3 and the other of XeO2F2 bridged by long Tc-F...Xe contacts. The oxygen atoms of the group 7 metals in the three structures are cis to each other and to two terminal fluorine atoms and trans to the bridging fluorine atoms. The 19F NMR and Raman spectra of TcO2F3.PnF5 and ReO2F3.PnF5 in SbF5 and PnF5-acidified HF solvents are consistent with dissociation of the adducts into cis-MO2F2(HF)2+ cations and PnF6- anions. The energy-minimized geometries of the free MO2F2+ cations and their HF adducts, cis-MO2F2(HF)2+, have been calculated by local density functional theory (LDFT), and the calculated vibrational frequencies have been used as an aid in the assignment of the Raman spectra of the solid MO2F3.PnF5 adducts and their PnF5-acidified HF solutions. In contrast, ReO2F3.SbF5 ionizes in SO2ClF solvent to give the novel Re2O4F5+ cation and Sb2F11- anion. The 19F NMR spectrum of the cation is consistent with two ReO2F2 units joined by a fluorine bridge in which the oxygen atoms are assumed to lie in the equatorial plane. The [ReO2F2(CH3CN)2][SbF6] salt was formed upon dissolution of ReO2F3.SbF5 in CH3CN and was characterized by 1H, 13C, and 19F NMR and Raman spectroscopies. The ReO2F2(CH3CN)2+ cation is a pseudooctahedral cis-dioxo arrangement in which the CH3CN ligands are trans to the oxygens and the fluorines are trans to each other.

Conductivity and dielectric studies in Cs 0.4Rb 0.6H 2PO 4 mixed crystals

The mixed caesium rubidium dihydrogen phosphate, Cs 0.4Rb 0.6H 2PO 4 (CRDP) crystallises in the monoclinic system P2 1/m at room temperature with the following parameters: a=4.8183(9); b=6.2671(6); c=7.7620(10) A ̊ and β=108.26°(10); Z=2. A calorimetric study of the title compound shows two distinct endothermal peaks which are detected at 293 and 525 K. Samples were examined by impedance and modulus spectroscopy techniques. The first transition (293 K) is attributed to a ferroelectric–paraelectric type. A high temperature phase transition (525 K) leading to a superionic–protonic phase was found, characterised by an unusual high conductivity. The conductivity relaxation parameters associated with the high-disorder protonic conduction have been determined from analysis of the M″/ M″ max spectrum measured in a wide temperature range. Transport properties in this material appear to be due to proton hopping mechanism.

Dinuclear Oxovanadium(IV) N-(Phosphonomethyl)iminodiacetate Complexes: Na(4)[V(2)O(2){(O)(2)P(O)CH(2)N(CH(2)COO)(2)}(2)].10H(2)O and Na(8)[V(2)O(2){(O)(2)P(O)CH(2)N(CH(2)COO)(2)}(2)](2).16H(2)O(1).

The dioxovanadium(IV) complexes with pida(4)(-) ligands (H(4)pida) = N-(phosphonomethyl)iminodiacetic acid), Na(4)[V(2)O(2){(O)(2)P(O)CH(2)N(CH(2)COO)(2)}(2)].10H(2)O (1) and Na(8)[V(2)O(2){(O)(2)P(O)CH(2)N(CH(2)COO)(2)}(2)](2).16H(2)O (2), were isolated from reactions of H(4)pida with either oxovanadium(V) (i.e., NaVO(3)) or oxovanadium(IV) precursors within the pH range of 2-8. The structures of complexes 1 and 2 were investigated by X-ray diffraction methods and in contrast to expectation were both found to be dinuclear. Complex 1 crystallized in the monoclinic system: P2(1)/n, a = 10.5632(1) Å, b = 11.1868(1) Å, c = 12.6921(1) Å, beta = 106.45 degrees, V = 1438.44(2) Å(3), Z = 4, and R (wR2) = 0.0781 (0.2017). Complex 2 crystallized in the monoclinic system P2(1)/c: a = 13.9822(2) Å, b = 11.1888(2) Å, c = 18.6519(3) Å, beta = 100.88 degrees, V = 2865.51(8) Å(3), Z = 4, and R (wR2) = 0.046 (0.125). Both complexes 1 and 2 have similar dimeric frameworks where two vanadium centers are linked by two phosphonate groups of two pida(4)(-) ligands (quadridentate binucleating), bridging through their four oxygen atoms to form a V(2)O(4)P(2) eight-membered ring which possesses a crystallographic inversion center. In contrast to their solid-state features, in aqueous solution both dinuclear crystalline compounds immediately dissociate to monomeric species, as observed by EPR and UV/vis spectroscopy. Both solution-state EPR and NMR spectroscopy confirmed that redox chemistry is involved in the reaction between vanadate and H(4)pida. Studies in mixed solvent systems showed that the dinuclear complex would remain intact in the presence of sufficient organic solvent. In the absence of oxygen the mononuclear and the dinuclear complexes will reversibly interconvert, whereas, in the presence of oxygen, the complexes will oxidize. These studies document the existence of higher oligomeric vanadium compounds and surprisingly, in general, lend credibility to several emerging mechanistic proposals involving oligomeric species of vanadium compounds in catalytic processes.

Spin crossover in six-coordinate [Fe(L) 2(NCX) 2] compounds with L = DPQ = 2,3-bis-(2′-pyridyl)-quinoxaline, ABPT = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole and X = S, Se: synthesis, magnetic properties and single crystal studies

The iron(II) compounds of formulae [Fe(DPQ) 2(NCS) 2]·CO(CH) 3) 2(DPQ = 2,3-bis-(2′-pyridyl)-quinoxaline) ( 1) and [Fe(ABPT) 2-(NCX) 2] (ABPT = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) X = S ( 2) and Se ( 3) were synthesized and the crystal structure of 1 determined by X-ray diffraction methods. It crystallizes in the monoclinic system P2 1/n, a = 12.057(2), b = 22.474(5), c = 15.004(7) A ̊ , β = 109.76(3)°, V = 3826 A ̊ 3, Z = 4 and T = 293 K . The structure is made up of discrete [Fe(DPQ) 2(NCS) 2] units. Each metal atom is in a distorted FeN 6 octahedral environment, the FeN bonds ranging from 2.013(8) Å to 2.425(8) Å. Variable-temperature magnetic susceptibility data in the temperature range 290–4.2 K revealed that 1 is high spin, in contrast to 2 and 3 which show a moderately cooperative high spin ↔ low spin (HS ↔ LS) transition, centred at T 1 2 = 186 K and 224 K for 2 and 3 respectively. The thermodynamic model of Slichter and Drickamer was applied to account for the magnetic data. The intermolecular interaction parameter, the enthalpy and entropy changes associated with the spin transition of 2 were estimated as Γ = 2.3 kJ mol −1, ΔH = 10.7 kJ mol −1 and ΔS = 58 J mol −1K −1 respectively.

Hydrothermal synthesis and structure refinements of alkali-metal trivanadates AV 3O 8 ( A = K, Rb, Cs)

Hydrothermal methods for growing single crystals of alkali-metal trivanadates AV 3O 8 for A = K, Rb, Cs and their single-crystal structural studies are presented. Plate-shaped orange crystals were hydrothermally grown at 250 °C from V 2O 5 powders dispersed A(NO) 3 solutions. RbV 3O 8, the structure of which has remained undetermined, was found to be isostructural with KV 3O 8 and CsV 3O 8: the monoclinic system P2 1 m with a = 4.9864(8) A ̊ , b = 8.442(1) A ̊ , c = 7.8621(7) A ̊ , β = 96.064(9) °, and Z ≖ 2. The crystallographic data for KV 3O 8 and CsV 3O 8 have been revised; in particular, the data of KV 3O 8 has been greatly improved. AV 3O 8 adopts a layered structure with V 3O 8 layers consisting of VO 6 octahedra and VO 5 square pyramids. The oxygen coordination around interlayer A atom is AO 8 for A = Rb, Cs but is regarded as AO 6 for A = K from the anomalous variation of A − O distances with A + ionic radii.

Structures of charge-perturbed or sterically overcrowded molecules. 16. The cesium tetracyanoethylenide radical salt

The electron-acceptor molecule tetracyanoethylene, characterized by a multitude of data, is considered to be prototype charge-transfer complex ligand and is of actual interest as a counteranion in organic conductors and ferromagnets. Tetracyanoethylene (TCNE) reacts in aprotic dimethoxyethane solution with a cesium metal mirror to yield black crystals of [TCNE[sup [sm bullet][minus]]Cs[sup +]][sup [sm bullet]][sub [infinity]]. The solvent-free radical salt C[sub 6]N[sub 4]Cs crystallizes in the monoclinic system P2[sub 1]/n with Z = 8, fw 261.0, a = 858.39 (40) pm, b = 1762.76 (90) pm, c = 1030.49 (50) pm, and [beta] = 93.43 (4)[degrees], R[sub w] = 3.6%. It contains staples of two differently structured TCNE[sup [sm bullet][minus]] radical anions with two different cesium countercations, which are coordinated to eight and nine nitrogens. The crystal structure is compared to those of the respective sodium and potassium salts as well as to cesium pentacyanopropenide and cesium tetracyanoquinodimethanide.