Unraveling the Structure of Iron(III) Oxalate Tetrahydrate and Its Reversible Li Insertion Capability
Hania AhouariGwenaëlle RousseJ. Rodrı́guez-CarvajalMoulay Tahar SougratiMatthieu SaubanèreMatthieu CourtyNadir RechamJean-Marie Tarascon
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In the search for better batteries, the quest for new positive electrode materials, which are derived from earth-abundant elements and synthesized through low energy demanding processes, has become an area of interest to the scientific community. Many Li–iron based polyanionic compounds have already been considered for Li ion batteries, but there still remain a large variety of Fe-based polyanionic carboxylate compounds (carbonates, oxalates, malonates, etc.) to be explored, among which Fe2(C2O4)3·nH2O is commercially available, but for which structure and electrochemical reactivity toward Li are lacking. By means of combined X-ray and neutron powder diffraction, we unravel for the first time the structure of Fe2(C2O4)3·4H2O. It adopts a triclinic unit cell with iron atoms being octahedrally coordinated by one water molecule and three oxalate groups, two of them being tetradentate. This arrangement translates into zigzag chains linked one to another through the third oxalate molecule to lead to an opened layered structure into which two additional water molecules are located. Moreover, we demonstrate that it reacts with lithium at an average potential of 3.35 V vs. Li leading to a sustainable capacity of 98 mAh/g. The insertion–extraction of the lithium process follows a biphasic process and involves the Fe3+/Fe2+ redox couple as deduced from in situ X-ray powder diffraction and operando Mössbauer spectroscopy measurements.Keywords:
Carboxylate
Triclinic crystal system
Two new bent bis(cyanophenyl)oxadiazole ligands, 2,5-bis(4-cyanophenyl)-1,3,4-oxadiazole (L7) and 2,5-bis(3-cyanophenyl)-1,3,4-oxadiazole (L8), were synthesized. The coordination chemistry of these ligands with various Ag(I) salts has been investigated. Seven new coordination polymers, namely, {[Ag(L7)(H2O)]ClO4}n (1) (triclinic, P1̄, a = 9.342(4) Å, b = 9.889(4) Å, c = 10.512(4) Å, α = 68.978(6)°, β = 78.217(6)°, γ = 81.851(7)°, Z = 2), {[Ag(L7)]SO3CF3}n (2) (monoclinic, P21/n, a = 7.559(2) Å, b = 23.739(6) Å, c = 10.426(3) Å, β = 108.071(4)°, Z = 4), {[Ag(L8)]BF4·0.5(C6H6)·H2O}n(3) (triclinic, P1̄, a = 7.498(3) Å, b = 10.649(4) Å, c = 13.673(5) Å, α = 98.602(5)°, β = 100.004(5)°, γ =110.232(5)°, Z = 2), {[Ag(L8)SbF6]·H2O}n (4) (triclinic, P1̄, a = 8.2621(9) Å, b = 10.6127(12) Å, c = 13.3685(15) Å, α = 98.012(2)°, β = 106.259(2)°, γ = 112.362(2)°, Z = 2), {[Ag2(L8)2(SO3CF3)]·H2O}n (5) (triclinic, P1̄, a = 10.713(4) Å, b = 13.449(5) Å, c = 15.423(5) Å, α = 65.908(5)°, β = 74.231(5)°, γ = 83.255(5)°, Z = 2), {[Ag2(L8)(C6H6)(ClO4)]·ClO4}n (6) (monoclinic, P21/n, a = 6.9681(17) Å, b = 20.627(5) Å, c = 17.437(4) Å, β = 95.880(4)°, Z = 4), and {[Ag2(L8)(H2PO4)2]}n (7) (triclinic, P1̄, a = 7.956(2) Å, b = 9.938(3) Å, c = 14.242(4) Å, α = 106.191(4)°, β = 97.322(4)°, γ = 107.392(4)°, Z = 1), were obtained by the combination of L7 and L8 with Ag(I) salts in a benzene/methylene chloride mixed-solvent system and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. In addition, the luminescence and electrical conductance properties of compounds 1−6 and the host−guest chemistry of compound 3 were investigated.
Triclinic crystal system
Monoclinic crystal system
Oxadiazole
Coordination polymer
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Triclinic crystal system
Monoclinic crystal system
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Triclinic crystal system
Monoclinic crystal system
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Triclinic crystal system
Monoclinic crystal system
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The title compound, C18H18O4, is a triclinic polymorph of the previously reported monoclinic polymorph [Han & Zhen (2005 ▶). Acta Cryst. E61, o4358-o4359]. In the crystal of the triclinic polymorph, molecules are linked by two pairs of C-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (102), and enclosing loops with graph set motifs of R2(2)(8) and R2(2)(6).
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Abstract The crystal structures of three N -(arenecarbonyl)- N , N ′-dicyclohexylureas, [ 1 : ArCO-N(cyclohexyl)-CO-NH-cyclohexyl: (R = Ph ( 1a ), pyridin-3-yl ( 1c ) and pyrazinyl ( 1e )] are reported from data collected at 120K. Comparison of the new findings with published data for the three compounds indicates three forms have been recognized for this group of compounds: an orthorhombic -form [P2 1 2 1 2 1 ] and two triclinic [ P -1] forms – triclinic - I and triclinic - II . Orthorhombic and triclinic - II phases have been determined for compound, 1a , triclinic - I and triclinic - II forms for compound 1c , and just the orthorhombic form for compound, 1e . O rthorhombic 1a and 1e are isostructural, as are triclinic - II 1a and 1c . The asymmetric unit for the orthorhombic form contains just a single molecule, while the molecules are linked into chains, C(7)R 2 2 (11) , via strong N—H ··· O and weaker C—H ··· O intermolecular hydrogen bonds. The asymmetric unit for triclinic - I consists of two independent molecules, molecules A and B, which are linked alternatively into chains, C(8)R 2 2 (16) , via N—H ··· N and C—H ··· O intermolecular hydrogen bonds in the direction of the a axis: such chains are linked via C—H ··· O hydrogen bonds. The asymmetric unit of the triclinic - II phase also comprises two independent molecules, molecules A and B, which are also linked alternatively into chains, C(8) , but only via N—H ··· O hydrogen bonds, with other intermolecular interactions of the C—H ··· π type also present.
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Hexachlorethane.-C 2 Cl 6 . Molecular weight, 236·76. This substance is typical of the halogen derivatives of ethane and will therefore be considered in some detail. Trimorphism .-C 2 Cl 6 is orthorhombic at ordinary temperatures, but at about 46°C, it changes over to a triclinic form and at 71° the triclinic form becomes cubic. The process is reversible:— Rhombic 45·1 - 46·6 ⇄ 43·1 triclinic 71·1 ⇄ 71·1 cubic.
Triclinic crystal system
Orthorhombic crystal system
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In the title complex, {[Ho(C2O4)(C6H4NO3)(H2O)]·(H2O)}n, the HoIII ion is coordinated by three O atoms from two 2-oxidopyridinium-3-carboxylate ligands, four O atoms from two oxalate ligands and one water molecule in a distorted bicapped trigonal-prismatic geometry. The 2-oxidopyridinium-3-carboxylate and oxalate ligands link the HoIII ions into a layer in (100). These layers are further connected by intermolecular O—H⋯O hydrogen bonds involving the coordinated water molecules to assemble a three-dimensional supramolecular network. The uncoordinated water molecule is involved in N—H⋯O and O—H⋯O hydrogen bonds within the layer.
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Trigonal crystal system
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The triclinic form of (PC6H5)6 contains two independent molecules lying on different centres of symmetry in the unit cell. The two molecules are very similar to one another and also to the molecule of (PC6H5)6 in the trigonal form of this substance. The six-membered phosphorus rings in the triclinic form both have the chair configuration with phenyl groups lying in the equatorial positions.
Triclinic crystal system
Trigonal crystal system
Crystal (programming language)
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