Imidazolium based ionic liquid crystals: structure,photophysical and thermal behaviour of [Cnmim]Br·xH2O (n = 12, 14; x=0, 1)

The long chain imidazolium halides [C_nmim]Br·xH₂O (n = 10, 12; x = 0, 1) have been synthesized and their structural and thermal behaviour together with their photophysical properties characterized. X‐ray structure analyses of the monohydrates ([C₁₂mim]Br·H₂O: triclinic, P1, no. 2, Z = 2, Pearson code aP112, a = 550.0(5) pm, b = 779.4(5) pm, c = 2296.1(5) pm, α = 81.89(5)°, β = 83.76(5)°, γ = 78.102(5)°, 3523 unique reflections with I_o > 2σ(I_o), R₁ = 0.0263, wR₂ = 0.0652, GooF = 1.037, T = 263(2) K; [C₁₄mim]Br•H₂O: triclinic, P1, no. 2, Z = 12, Pearson code aP11, a = 549.86(8) pm, 782.09(13) pm, c = 2511.3(4) pm, α = 94.86(2)°, β = 94.39(2)°, γ = 101.83(2)°, 2063 unique reflections with I_o > 2σ(I_o), R₁ = 0.0429, wR₂ = 0.0690, GooF = 0.770, T = 293(2) K) show for both compounds similar bilayered structures. Sheets composed of hydrophilic structure regions constituted by positively charged imidazolium head groups, bromide anions and hydrogen bonded water alternate with hydrophobic areas formed by interdigitated long alkyl chains belonging to imidazolium cations with different orientation. Combined differential scanning calorimetry and polarizing optical microscopy shows that the monohydrates as well as the anhydrous imidazolium salts are thermotropic liquid crystals which adopt smectic mesophases. The mesophase region is larger in case of the monohydrates when compared to the anhydrous compounds indicating that water obviously stabilizes the mesophase. All compounds show an intense whitish photoluminescence with short lived (¹π←¹π*) and long lived (¹π←³π*) transitions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electrical Conductivity and Crystal Structure of Pure and SrCO3-doped K2CO3

Electrical conductivity of pure and SrCO₃ doped potassium carbonate has been investigated in the temperature range between 350 and 800 °C. Sintered carbonate mixtures were analysed by X-ray powder diffraction techniques at room temperatures. The conductivity of SrCO₃ doped K₂CO₃ increases nearly linear up to 10 mol.% and decreases in the range between 20 and 50 mol.% continously. X-ray diffraction patterns do not show changes up to 10 mol.% SrCO₃ in the host lattice. The compound K₂Sr(CO₃)₂ was found for samples containing 15–50 mol.% SrCO₃. The lattice constants of hexagonal crystals which are isotypic with K₂Ca(CO₃)₂ are a₀ = (534 ± 1) pm and c₀ = (1352 ± 2) pm.     

Molecular iodine catenation in the anionic chains [Pd2I6(I2)]2–

In the easily accessible salt [(H₅O₂)(db24c8)]₂[Pd₂I₆(I₂)], iodine molecules are catenated in linear anionic chains [^…I₂PdI₂PdI₂^…I–I^…]^2– which are separated by bulky cations consisting of two (H₅O₂)⁺ cations sequestered in dibenzo‐24‐crown‐8 (db24c8) molecules. The new compound is obtained as black single crystals (triclinic, P1, a = 1001.8(2), b = 1185.8(2), c = 1503.7(3) pm, α = 102.97(1), β = 107.65(1), γ = 90.85(1)°, V = 1652.3(5) 10⁶·pm³, Z = 1) from a moist 1:1 dichloromethane/ethanol solution of PdCl₂, iodine and db24c8. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The Crystal and Molecular Structure of Mesogenic Malonates

The crystal and molecular structures of diethylene-6-[4-(4′-nitrophenylazo)phenoxy]dodecylmalonate (12 PhNO₂) and -propylmalonate (3 PhNO₂) were determined with CuK_α to a = 19.235(5) Å, b = 7.620(1) Å, c = 22.400(4) Å; α = 90°, β = 103.27(1)°, γ = 90°; space group P2₁/c for 12 PhNO₂ and a = 6.797 (6) Å, b = 7.756 (8) Å, c = 22.74(2) Å; α = 81.48(7)°, β = 88.29(7)°, γ = 68.10(9)°; space group P1 for 3 PhNO₂. Refinement with 1130 observed reflections (> 3σ) for 12 PhNO₂ and 1615 for 3 PhNO₂ leads to R (12 PhNO₂) = 5.8% and R(3 PhNO₂) = 4.4%. The molecular conformation in the crystalline state is the most extended trans conformation for both compounds. On rapidly cooling from the isotropic melt, 12 PhNO₂ shows a smectic A-phase. In agreement with prior investigations on polar mesogens, the molecules arrange in an antiparallel packing. The azo-mesogen is nearly coplanar with the alkoxy spacer up to the branching atom. The low molecular weight malonates investigated may serve as model compounds for side-group liquid crystalline polymers.     

The Crystal and Molecular Structure of Mesogenic Malonates (II)

The crystal and molecular structures of three diethyl-2-{n-[4-(4-nitrophenylazo)-phenoxy]alkyl}malonate with n = 5 (5 PhNO₂), 7 (7PhNO₂), 9 (9 PhNO₂) and an analogous diethyl-2-[4(4-cyanophenylazo)phenoxy]pentylmalonate (5 PhCN) have been determined with CuK_a or MoK_a: 5 PhNO₂: a = 8.007(6) Å, b = 11.960(8) Å, c = 13.516(9) Å, α = 77.10(6)°, β = 81.80(5)°, γ = 83.15(5)°; R = 0.053; 7PhNO₂: a = 8.074(4) Å, b = 11.592(5) Å, c = 14.422(7) Å, α = 87.43(3)°, β = 82.46(3)°, γ = 85.43(3)°; R = 0.072; 9 PhNO₂: a = 5.520(5) Å, b = 13.628(9) Å, c = 20.220(11) Å, α = 100.02(4)°, β = 95.49(4)°, γ = 101.02(4)°; R = 0.042; 5 PhCN: a = 8.018(6) Å, b = 11.960(8) Å, c = 13.566(7) Å, α = 77.82(5)°, β = 81.89(5)°, γ = 82.69(5)°; R = 0.067 (isotropically refined). All these structures belong to the triclinic space groups P1 . The arrangements of the molecules in the crystal of the homologous series of nPhNO₂ suggest two different types of packing independent of n even, odd or large, small. 5 PhCN represents an isomorphous structure to 5 PhNO₂. Isomophism between 7 PhNO₂ and 7 PhCN was confirmed by cocrystallization of these two compounds whose crystal structure was also determined.     

Effective electro‐optic coefficient of (1–x)Pb(Zn1/3Nb2/3)O3–xPbTiO3 single crystals

Refractive indices and effective electro‐optic coefficient γ_c of (1–x)Pb(Zn_1/3Nb_2/3)O₃–xPbTiO₃ (PZN‐xPT, x = 0.05, 0.09 and 0.12) single crystals were measured at 532 nm wavelength. Orientation and temperature dependences of the electro‐optic coefficient were investigated. Large electro‐optic coefficient (γ_c = 470 pm/V) was observed in [001]‐poled PZN‐0.09PT crystal. More importantly, γ_c of tetragonal PZN‐0.12PT is almost unchanged in a temperature range −20 ∼ 80 °C. The γ_c of PZN‐xPT single crystals are much higher than that of widely used electro‐optic crystal LiNbO₃ (γ_c = 20 pm/V). These results show that PZN‐xPT single crystals are very promising materials for electro‐optic modulators in optical communications.     

The molecular and crystal structure of 2-oxo-1-pyrrolidine-acetamide

C₆H₁₀N₂O₂, P1 , a = 6,607(2) Å, b = 8,538(2) Å, c = 6,392(2) Å, α = 102,43(2)°, β = 91,11(2)°, y = 79,82(2)°, V = 349,1 ų, Z = 2, D_m = 1,36 g × cm⁻³, D_x = 1,35 g × × cm⁻³, MoKα radiation, λ = 1.71069 Å, μ(MoKα) = 1.11 cm⁻¹. The structure was solved by direct methods. The parameters were refined by full matrix least squares technique to a final R = 0.088 for 834 reflections with ∥F₀∥ > 4σ(F₀). The dihedral angle between the least-squares plane through the pyrrolidine ring and that through the acetamide group is 90.4°. The N H … O hydrogen bonds connect molecules to form bands parallel to the z axis.     

X-ray Diffraction Study on MgSeO4. 6 H2O at Elevated Temperatures

The dehydration of MgSeO₄. 6 H₂O has been studied using an X-ray powder diffraction method at elevated temperatures. Five different solid phases have been identified in the temperature interval of 20–450 °C: MgSeO₄. 6 H₂O; MgSeO₄. 5 H₂O (with a small amount of MgSeO₄. 4 H₂O), MgSeO₄. 2 H₂O, amorphous MgSeO₄ and crystalline MgSeO₄. MgSeO₄. 5 H₂O crystallizes in the triclinic system with the lattice parameters: a = 6.403(2) Å, b = 10.576(5) Å, c = 6.196(3) Å, α = 98.63(2)°, β = 110.36(2)°, γ = 75.25(3)°, SG P1 . MgSeO₄. 2 H₂O forms orthorhombic crystals with lattice parameters: a = 10.304(1) Å, b = 10.351(9) Å, c = 9.138(9) Å. The crystalline anhydrous magnesium selenate crystallizes in the orthorhombic system with the lattice parameters: a = 4.925(2) Å, b = 9.026(5) Å, c = 6.816(6) Å. Additionally MgSeO₄. 4 H₂O has been prepared and studied roentgenographically: monoclinic system with the lattice constants: a = 6.064(4) Å, b = 13.773(7) Å, c = 8.062(6) Å, β = 91.82(7)°, SG P2₁/n. According to expectation the magnesium selenate hydrates are isomorphous with the corresponding magnesium sulphate hydrates.     

Electrical conductivity and crystal structure of pure and SrCO3-doped Na2CO3

The electrical conductivity of pure and SrCO₃-doped sodium carbonate has been measured in the temperature range 310–800 °C in air using a dc technique. Its concentration dependency is similar to that of the K₂CO₃–SrCO₃ system described recently (GUTH et al. 1986). The maximum conductivity could be observed at ≈ 20 mol.% SrCO₃. At temperatures > 440 °C, the conductivity of Na₂CO₃–SrCO₃ mixtures containing up to 80 mol.% SrCO₃ is larger than that of pure Na₂CO₃. X-ray investigations of slowly cooled samples show the mixtures to be heterogeneous. X-ray diffraction patterns of quenched mixtures containing 10 mol.% SrCO₃ show reflexes of a high temperature compound. SrCO₃, however, could not be detected. The lattice constants of this hexagonal compound Na₂Sr₄(CO₃)₅ which is isotyp with Na₂Ca₂Sr₂(CO₃)₅ described by CHEN and CHAO are a₀ = (1066.1 ± 0.4) pm and c₀ = (653.2 ± 0.2) pm.     

Synthesis and structure of a new one‐dimensional cobalt complex with dicyanamide and 4‐picolyl choride bridges

The synthesis and structure of the 1D cobalt (II) complex, [Co( L )₂(dca)₂] ( 1 ) (dca = dicyanamide, C₂N₃^–, L = 4‐picolyl choride) is reported. Complex 1 crystallized in triclinic system, space group P ‐1, with cell dimensions of a = 7.291(2) Å, b = 7.481(2) Å, c = 9.007(3) Å, α =104.444(4)°, β = 96.971(4)°, γ =102.618(4)°, V = 456.1(2) ų, Z = 1, Dc = 1.624 Mg/m³. In complex 1 , Co (II) is 6‐coordinated by N atoms of four dca ligands and two L ligands. The centrosymmetric CoN6 chromophore is an axially elongated octahedron that has Co‐N distances ranging from 2.122(3) to 2.154(3) Å. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,characterization and crystal structure of a 3‐D supramolecular Cu/Mn complex with pydc

A supramolecular compound, {[CuMn(pydc)₂(H₂O)₅]·2H₂O} ( 1 ) (pydc = pyridine‐2,6‐dicarboxylate dianion), has been synthesized and characterized by single‐crystal X‐ray diffraction. Single‐crystal X‐ray analysis reveals that it crystallizes in the triclinic space group P‐1, a = 8.4763(17) Å, b = 9.7715(19) Å, c = 13.909(3) Å, α =101.234(3)°, β =102.520(3)°, γ= 97.375(4)°. Two mixed‐metal ions exhibit similar coordinated geometries with octahedron. 1 possesses a 3‐D unusual supramolecular network featuring 1D water tape. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and crystal structure of Mn(II) and Zn(II) complexes with 1,3,5-tris(carboxymethoxyl)benzene ligand

Two complexes (H₂bipy)[M₂(TB)₂(H₂O)₈]·5H₂O (M = Mn 1, Zn 2) (bipy = 4,4′-bipyridine, H₃TB = 1,3,5-tris(carboxymethoxyl)benzene) were synthesized by the reaction of the corresponding metal salt with ligand H₃TB and 4,4′-bipy in an aqueous methanol solution at room temperature, respectively. Their structures were determined by single crystal X-ray diffraction analysis. Both complexes 1 and 2 crystallize in the triclinic space group with the crystal parameters of 1: a = 9.725(12) ?, b = 10.651(13) ?, c = 10.882(13) ?, α = 91.72(2)°, β = 96.41(2)°, γ = 97.72(2)°, V = 1109(2) ?³, Z = 1 and 2: a = 9.610(10) ?, b = 10.55(2) ?, c = 10.83(2) ?, α = 91.60(4)°, β = 95.32(2)°, γ = 97.73(4)°, V = 1082(3) ?³, Z = 1. Complexes 1 and 2 have the same dinuclear structure, in which each metal atom is six coordinated with distorted octahedral geometry by two oxygen atoms from two different TB³⁻ ligands and four ones from four coordinated water molecules. The dinuclear units are further linked by hydrogen bonding and π–π interactions to form the three-dimensional framework structure.     

Crystal structure of 2‐(2'‐hydroxyphenyl)‐6‐tributylstannyl‐4‐(3H )‐quinazolinone and 2‐(2'‐hydroxyphenyl)‐6‐iodo‐4‐(3H)‐quinazolinone

The structures of the title compounds C₂₆H₃₇N₂O₂Sn ( I ) and C₁₄H₉IN₂O₂ ( II ) were determined by single‐crystal X‐ray diffraction technique. Compound I crystallizes in the triclinic space group P1 with a = 9.560(3) Å, b = 16.899(6) Å, c = 17.872(5) Å, α = 65.957(7)°, β = 83.603(5)°, γ ( = 75.242(5)°, V = 2549.8(13) ų, Z = 4, and D =1.374 g/cm³. The compound consists of a quinazolinone ring with phenol and tributylstannyl moieties. Compound II crystallizes in the monoclinic space group P2₁/c with a = 7.6454(12) Å, b = 5.9270(9) Å, c = 27.975(4) Å; α = 90°, β = 95.081(3)°, γ = 90°, V = 1262.7(3) ų, Z = 4, and D = 1.915 g/cm³. The compound consists of a quinazolinone ring with phenol and iodine substituents. For both I and II , the short intramolecular O–H…N and two long intermolecular N–H…O hydrogen bonds are highly effective in holding the molecular system in a stable state. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The crystal and molecular structure of three homologue 1,4-dialkanoyloxy-biphenyls (SYM-n)

The three homologue compounds with the general formula C_nH_2n+1 COO C₆H₄ C₆H₄ OOC C_nH_2n+1 (SYM-n) crystallize in the following space groups: SYM-1: triclinic, P1 , a = 7.400(6), b = 9.227(3), c = 10.579(3) Å, α = 85.97(3), β = 89.09(3), γ = 71.47(3)°; SYM-2; monoclinic, P2₁/c, a = 11.712(7), b = 5.648(1), c = 12.408(6), Å, β = 103.84(3)°; SYM-5: triclinic, P1, a = 5.505(4), b = 8.342(8), c = 24.79(2) Å, α = 86.67(3), β = 85.45(6), γ = 71.74(7)°. The structures have been solved by direct methods and refined to R = 0.075, 0.061 and 0.053, respectively. The packing arrangements show a layer-like structure. The layers are almost separated for SYM-1 as well as for SYM-2 and interdigitated for the structure of SYM-5.     

Structural Properties of S-alkylated Dithiolene Chelates (I). Crystal and Molecular Structures of Bis(S-ethyl-ethene-1,2- dithiolato)palladium (II) and Bis(S-ethyl-ethene-1,2-dithiolato) platinum (II)

Bis(S-ethyl-ethene-1,2-dithiolato)palladium(II), Pd(S₂C₄H₇)₂, is monoclinic, P 2₁/n, with a = 7.598(1) Å, b = 10.445(2) Å, c = 8.031(1) Å, β = 95.3(1)° and Z = 2. The structure was determined by 893 independent reflections and refined by the block-diagonal leastsquares method to R = 0.12. The chelate molecule is nearly planar and the palladiumsulfur distances are 2.278(6) Å and 2.403(6) Å. Bis(S-ethyl-ethene-1,2-dithiolato)platinum(II), Pt(S₂C₄H₇)₂, is monoclinic, P 2₁/a, with a 13.114(2) Å, b = 12.873(2) Å, c = 7.446(2) Å, β = 96.1(1)° and Z = 4. The structure was solved from 2040 independent reflections. The compound is not isomorphic with the isomeric palladium complex. In the unit cell there exist two symmetry independent molecules. The platinum-sulfur distance is 2.280 (6) Å.     

Syntheses and crystal structures of an organometallic thiosemicarbazone and an organometallic enehydrazide

Reactions of ferrocenoylacetone with thiosemicarbazide and isonicotinic acid hydrazide generate an organometallic thiosemicarbazone 1 and enehydrazide 2, respectively. The complexes 1 and 2, which can be formulated as [C₅H₅FeC₅H₄C(O)CH₂C(=NNHCSNH₂)CH₃] and [C₅H₅FeC₅H₄C(O)CH=C(NHNHCOC₅H₄N-4)CH₃], have been characterized by elemental analyses, IR, NMR, UV and were structurally characterized by single-crystal X-ray crystallography. Complex 1 (C₁₅H₁₇FeN₃OS) crystallizes in the monoclinic space group P2₁/c, with lattice constants: a = 13.939(3) ?, b = 8.2600(17) ?, c = 13.176(3) ?, β = 94.83(3)°, V = 1511.7(6) ?³, Z = 4, D _c = 1.508 g cm⁻³, F(000) = 712, R ₁ = 0.0602, wR ₂ = 0.1526. Two intermolecular hydrogen bonds N–H···S (N···S = 3.356(8) and 3.499(7) ?, N–H···S = 168 and 170°) form a chain in the [010] direction. The intermolecular hydrogen bond C–H···O (C···O = 3.432(10) ?, C–H···O = 151°) leads to a [010] double-chain through each unit cell. The intermolecular hydrogen bond C–H···O (C···O = 3.359(10) ?, C–H···O = 173°) makes the [010] double-chain pack along the c axis to result in a two-dimensional network. Complex 2 (C₂₀H₁₉FeN₃O₂) crystallizes in the monoclinic space group P2₁/c, with lattice constants: a = 14.091(2) ?, b = 10.024(2) ?, c = 13.806(2) ?, β = 112.41(2)°, V = 1802.8(6) ?³, Z = 4, D _c = 1.434 g cm⁻³, F(000) = 808, R ₁ = 0.0576, wR ₂ = 0.1593. The strong intramolecular hydrogen bond N–H···O from the enamine N atom and carbonyl O atom stabilizes the enehydrazide. The intermolecular hydrogen bonds N–H···O and C–H···O (N···O = 2.906(6) ?, N–H···O = 155° C···O = 3.364(6) ?, C–H···O = 153°) generate a [010] chain. The intermolecular hydrogen bond N–H···O (N···O = 2.989(6) ?, N–H···O = 128°) forms a [010] double-chain through each unit cell. The π···π stacking interation involving the pyridyl groups makes the [010] double-chain pack along the c axis to lead to a two-dimensional network.     

An X-ray Crystallographic Study of the Related Triazenes, 1,4-Di[(<Emphasis Type="Italic">E</Emphasis>)-2-(2-nitrophenyl)-1-diazenyl]piperazine and Methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate

Abstract The crystal structures of methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate (2a) and 1,4-di[(E)-2-(2-nitrophenyl)-1-diazenyl]piperazine (3a) have been determined by single crystal X-ray diffraction analysis. The bis-triazene (3a) adopts an unusual pseudo-boat conformation in the piperazine ring, with a dihedral angle of 52.20(0.06)° between the two planes defined within the piperazine ring. The crystal structures of 2a and 3a are compared with the structure of the triazene (4) and the closely related bis-triazene (5). The piperazine ring of 2a adopts a typical chair conformation, whereas the piperazine ring of 3a adopts an unusual boat conformation. Crystal data: 2a C₁₃H₁₈N₄O₂, monoclinic, space group P2₁ /n, a = 13.849(3) ?, b = 6.577(1) ?, c = 14.904(3) ?, α = 90°, β = 96.098(3)°, γ = 90° and V = 1,349.8(4) ?³, for Z = 4. 3a C₁₆H₁₆N₈O₄, triclinic, space group P-1, a = 7.6066(6) ?, b = 8.3741(7) ?, c = 14.507(1) ?, α = 78.673(1)°, β = 81.877(1)°, γ = 73.445(1)° and V = 865.0(1) ?³, for Z = 2. Index abstract The crystal structures of methyl 4-{(E)-2-(4-methylpiperazino)-1-diazenyl}benzoate (2a) and 1,4-di[(E)-2-(2-nitrophenyl)-1-diazenyl]piperazine (3a) have been determined by single crystal X-ray diffraction analysis.     

<Emphasis Type="Italic">Trans</Emphasis>-dibromodioxodimethylformamide molybdenum(VI) MoO<Subscript>2</Subscript>Br<Subscript>2</Subscript>(OCHNMe<Subscript>2</Subscript>)<Subscript>2</Subscript>

The molecular structure of trans-dibromodioxodimethylformamide molybdenum(VI), MoO₂Br₂(OCHNMe₂)₂ has been determined. Crystal data: Triclinic, P-1, a = 12.3005(2), b = 15.8763(4), c = 21.1653(6) ?, α = 71.992(1)°, β = 88.966(2)°, γ = 89.999(1)°, V = 3930.1(2) ?, Z = 12. Trans-dibromodioxodimethylformamide molybdenum(VI) was obtained by the reaction of sodium molybdate, HBr and dimethylformamide and was characterized by IR, and ¹H NMR spectroscopy and elemental analysis.     

Solvent-controlled structures. Synthesis and characterization of complexes Cu(L)2(CH3COO)2 and [Cu2(μ-CH3COO)4(L)2](L)2 [L = N-(4′-methylaniline)-4-pyridinecarboxamide]

Two complexes Cu(L)₂(CH₃COO)₂ (1) and [Cu₂(μ-CH₃COO)₄(L)₂](L)₂ (2) (L = N-(4′-methylaniline)-4-pyridinecarboxamide) have been prepared and their crystal structures have been determined by single-crystal X-ray diffraction. The complexes are obtained by using the same raw materials and reaction conditions except solvents. The presence or absence of water controls the coordination mode to give rise to different structures. The structure of 1 has a triclinic space group P-1 with a = 8.381(3) ?, b = 8.545(4) ?, c = 11.357(5) ?, α = 110.654(6)°, β = 102.388(7)°, γ = 97.889(7)°, V = 722.9(5) ?³, and Z = 1. The structure of 2 has a triclinic space group P-1 with a = 9.121(3) ?, b = 9.454(3) ?, c = 17.233(5) ?, α = 77.374(5)°, β = 89.827(6)°, γ = 74.342(6)°, V = 1393.8(7) ?³, and Z = 1. Supramolecular assemblies have also been found via noncovalent bonds such as hydrogen bonds, π–π stacking interactions.     

A Novel Coordination Structure of Dichromates Bonding to Copper (II): [Cu(bipy)2(Cr2O7)] · 2 H2O

Dark-green multimetal compound crystal [Cu(bipy)₂(Cr₂O₇)]· 2 H₂O was obtained from aqueous solution of Cu(NO₃)₂, K₂Cr₂O₇ and bipyridine. The crystal structure was determined by X-ray crystallography: triclinic P1 , a = 7.716(3) Å, b = 9.656(3) Å, c = 15.517(5)Å, α = 77.41(3)°, β = 81.04(3)°, γ = 82.33(3)°, Z = 2. In this compound, two chromium atoms and a copper atom are linked by two oxo bridges (Cu(II) O Cr(VI) O Cr(VI)). The copper coordination polyhedron corresponds to a five-coordinated distorted trigonal bipyramid.