Structures from powders: Diflorasone diacetate

Diflorasone diacetate, a steroid anti-inflammatory drug (marketed as Diacort^® or Florone^® by Pfizer) and used in the treatment of skin disorders, can be prepared as anhydrous form, DD1 (as deposited in the US pharmacopoeia), or as a monohydrated phase, DDW. Heating the DDW form above 90 °C, a mixture of DD1 and of a new anhydrous polymorph, DD2 is obtained. Further heating of this mixture, or of pure DD1, up to 230 °C (only a few degrees before melting!), generates an elusive anhydrous DD3 polymorph. Their crystal structures, determined uniquely from laboratory powder diffraction data, show the isomorphous character of the DDW and DD1 forms, while the DD2 and DD3 polymorphs crystallize with markedly different unit cells. Crystals of the DD1, DD2 and DDW forms are orthorhombic, P2₁2₁2₁, a = 29.386(1) Å; b = 10.4310(9) Å, c = 8.1422(7) Å, V = 2495.8(3) Å³ for DD1; a = 15.2639(10) Å; b = 11.7506(7) Å, c = 13.8931(11) Å, V = 2491.9(3) Å³ for DD2; a = 30.311(2) Å; b = 10.6150(9) Å, c = 7.9337(7) Å, V = 2552.7(4) Å³ for DDW; while the lattice parameters for the monoclinic P2₁DD3 species are a = 11.5276(10) Å; b = 13.8135(11) Å, c = 7.8973(7) Å, β = 103.053(6)°, V = 1225.0(2) Å³. These compounds have also been fully characterized by thermo analytical methods, as well by ¹³C, ¹⁹F, and ¹H NMR spectroscopy.     

Two cadmium-thiocyanate coordination polymers with organic cations: Synthesis, crystal structures and luminescent properties

Two new inorganic-organic hybrid polymers [ClBzQl]₂[Cd(SCN)_3.5Br_0.5]·0.25H₂O (1) and [ClBzMePy][Cd(SCN)₃] (2) (ClBzQl = 1-(4′-Cl-benzyl)quinolinium cation and ClBzMePy = 1-(4′-Cl-benzyl)-2-methylpyridinium cation) have been synthesized and characterized by IR, UV, elemental analysis and X-ray crystallography. Crystal structure analyses show that two polymers belong to the monoclinic space group P2/n (1) and P2₁/c (2) with a = 18.548(2) Å, b = 9.526(1) Å, c = 20.689(2) Å, β = 94.008(1)°, V = 3646.6(5) Å³ for 1, and a = 11.195(2) Å, b = 16.415(3) Å, c = 10.751(2) Å, β = 102.930(3)°, V = 1925.7(7) Å³ for 2. The Cd atom exhibits a distorted octahedral coordination geometry for 1 and 2. For 1, a pair of 1,1-μ-SCN⁻ anions and a pair of 1,3-μ-SCN⁻ anions are alternately bridge adjacent Cd centers to form infinite polymeric chains. For 2, adjacent Cd atoms are linked by three 1,3-μ-SCN⁻ anions to form infinite [Cd(SCN)₃⁻]_∞ polymeric chains. The luminescent properties of the two polymers in the solid state at room temperature were investigated.     

Homochiral metal-organic coordination networks from l-typtophan

Three homochiral metal-organic coordination networks [Co₂(l-Trp)₂(Py)₆] · Py · (ClO₄)₂ (1), [Ni(l-Trp)(Py)₃] · H₂O · ClO₄ (2) and [Co₂(l-Trp)(INT)₂(H₂O)₂(ClO₄)] (3), all containing natural amino acid l-HTrp (l-typtophan), were hydrothermally synthesized and structurally characterized. The compounds 1 and 2 crystallize in the orthorhombic space group C222₁, with a = 10.731(2) Å, b = 19.709(4) Å, c = 27.365(6) Å and Z = 4 for 1 and a = 10.710(10) Å, b = 20.088(18) Å, c = 27.63(3) Å and Z = 8 for 2, respectively. The compound 3 has the monoclinic space group P2₁, with a = 8.1934(14) Å, b = 13.209(2) Å, c = 12.464(2) Å, β = 104.107(3)° and Z = 2. Both 1 and 2 consist of 1D helical chains. Compound 3 is composed of 2D networks, which further assemble into a 3D supramolecular structure via weak interlayer interactions. The optically pure amino acid l-HTrp plays an important role leading to homochiral structures reported here.     

Syntheses, structures, and magnetic properties of two new μ-alkoxo-μ-pyrazolato bridged dicopper(II) complexes

The syntheses, structures, and magnetic properties of two new μ-alkoxo-μ-pyrazolato heterobridged compounds, [Cu ^II₂(L¹-F)(μ-prz)] (1) and [Cu ^II₂(L¹-2OMe) (μ-prz)] · 0.5 CH₃CN (2) (prz=pyrazolato; H₂L¹-F=1,3-bis(3-fluorosalicylideneamino)-2-propanol; H₂L¹-2OMe=1,3-bis(4,6-dimethoxy salicylideneamino)-2-propanol) have been reported. Compound 1 crystallizes in triclinic space group with a=8.6392(10) Å, b=10.6431(9) Å, c=11.6809(13) Å, α=85.972(8)°, β=71.492(9)°, and γ=72.221(9)°, while the unit cell parameters of 2 are as follows: space group: monoclinic C2/c, a=28.2948(5) Å, b=7.3033(2) Å, c=26.3933(5) Å, and β=96.243(1)°. The variable-temperature magnetic susceptibility measurements reveal that the metal centers in both the compounds are antiferromagnetically coupled with J=−200 cm⁻¹ for 1 and J=−175 cm⁻¹ for 2. The magnetic behaviors have been explained on the basis of two opposing factors, complementarity and countercomplementarity of magnetic orbitals.     

Synthesis, crystal structure, magnetic properties and electrochemical behaviour of the mixed valence compound [Cu(CN)3Cu(C3H10N2)2]

The binuclear mixed valence copper(I/II) compound [Cu^I(CN)₃Cu^II(tn)₂] (1) (tn = propane-1,3-diamine) and its acetonitrile adduct [Cu^I(CN)₃Cu^II(tn)₂] · 2MeCN (2) have been synthesized. Complex 1 crystallizes triclinic, space group , a = 8.117(2) Å, b = 8.389(2) Å, c = 11.920(2) Å, α = 108.728(3)°, β = 100.024(3)°, γ = 104.888(4)°, Z = 2, and compound 2 monoclinic, space group P2₁/m, a = 8.752(2) Å, b = 13.243(3) Å, c = 9.549(2) Å, β = 114.678(4)°, Z = 2. In both crystal structures, the binuclear [Cu^I(CN)₃Cu^II(tn)₂] complex with slightly different bonding geometries is formed. One of the three nitrogen atoms of a Cu^I(CN)₃ moiety is coordinated to Cu(II) at the apex of a square-pyramid with two chelating ligands tn on its base. The shortest intramolecular Cu^II?Cu^II distance in 1 is 5.640(7) Å. The EPR behaviour of 1 has been investigated at room temperature and at 77 K. The magnetic properties were measured in the temperature range 1.8-300 K.     

Octahedral cyanohydroxo cluster complex trans-[Re6Se8(CN)4(OH)2]: Synthesis, crystal structure, and properties

A hexarhenium cyanohydroxo anionic cluster complex [Re₆Se₈(CN)₄(OH)₂]⁴⁻ was synthesized for the first time starting from [Re₆Se₈(OH)₆]⁴⁻, which was crystallized as a salt of the composition Cs_2.75K_1.25[Re₆Se₈(CN)₄(OH)₂]·H₂O (1). The reaction of the complex with Cu²⁺ in an aqueous ammonia or methylamine solutions afforded [Cu(NH₃)₅]₂[Re₆Se₈(CN)₄(OH)₂]·8H₂O (2) or [{Cu(CH₃NH₂)₄}₂Re₆Se₈(CN)₄(OH)₂] (3), respectively. All of these three compounds were characterized by a single-crystal X-ray diffraction method. Compound 1 is crystallized in the tetragonal space group I4/m with eight formula units per cell (a = b = 17.4823(14) Å, c = 19.430(2) Å, V = 5938.3(10) Å³); compound 2 is crystallized in the monoclinic space group P2₁/n with two formula units per cell (a = 12.1845(13) Å, b = 8.6554(9) Å, c = 19.2568(19) Å, β = 91.081(2)°, V = 2030.5(4) Å³); compound 3 is crystallized in the orthorhombic space group Cmcm with four formula units per cell (a = 19.816(4) Å, b = 14.611(3) Å, c = 13.751(3) Å, V = 3981.2(13) Å³). The luminescence properties of 1 were studied in both aqueous solution and solid state. In addition, the electronic structure of [Re₆Se₈(CN)₄(OH)₂]⁴⁻ was elucidated by DFT calculations.     

Organolanthanide constrained geometry complexes modified for catalysis: synthesis, structure, and aminoalkene hydroamination properties of a pyrrolidine-substituted constrained geometry organolutetium complex

The reaction of the organolutetium complex (CGC′)LuCl₃Li₂(THF), (1; CGC′ = [Me₂Si(3-pyrrolidinyl-1-η⁵-indenyl)(^tBuN)]²⁻) with NaN(TMS)₂ provides a straightforward route to the halide-free organolutetium amido complex, (CGC′)LuN(TMS)₂(THF) (2). These new complexes were characterized by standard analytical methodology. The monomeric complex 2 crystallizes in the monoclinic space group P2₁/c with four molecules in a cell of dimensions a = 11.1566(6) Å, b = 14.9805(8) Å, c = 22.18007(12) Å, and β = 90.0620(10)°. Complex 2 is an active precatalyst for the intramolecular hydroamination/cyclization of representative aminoalkenes with turnover frequencies as high as 205 h⁻¹ at room temperature.     

Synthesis and characterization of new coordination polymers generated from oxadiazole-containing ligands and IIB metal ions

The coordination chemistry of the oxadiazole-containing rigid bidentate ligands 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (L1) and 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (L2) with inorganic IIB metal salts have been investigated. Five new coordination polymers (1-5) were prepared by solution reactions and fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Cd(L1)₂(CH₃CN)₂](ClO₄)₂ · (CH₃CN)₂ (1) crystallized in the monoclinic space group P2₁/c, a = 8.4028(5) Å, b = 21.3726(13) Å, c = 10.5617(7) Å, β = 95.1200(10)°, and Z = 2. In the solid state, it adopts an infinite two-dimensional polymeric structural motif with effective cross section of ca. 14.31 × 14.31 Å. Cd(L2)(H₂O)(NO₃)₂ (2) crystallized in the monoclinic space group Ia, a = 7.1203(5) Å, b = 22.2475(15) Å, c = 20.2652(16) Å, β = 90.6080(10)°, and Z = 8. In the solid state, the two Cd(II) centers are connected to each other by L2 ligands and bridging nitrates into a two-dimensional network. [ZnCl₂(L1)] (3) and [HgI₂(L1)] · CH₃CN (4) crystallized in the monoclinic crystal system (3: P2₁/c, a = 5.3702(3) Å, b = 20.4800(11) Å, c = 12.4093(7) Å, β = 94.7930(10)°, and Z = 4; 4: P2/n, a = 17.2733(11) Å, b = 5.2173(3) Å, c = 20.4069(13) Å, β = 102.8690(10)°, and Z = 4). In the solid state, Zn(II) and Hg(II) metal centers are connected to each other by L1 ligands into a zigzag chain motif. Compound 5 (HgBr₂(L2) is different from 3 and 4, monoclinic, P2(1)/n, a = 5.470(4) Å, b = 16.271(13) Å, c = 16.486(12) Å, β = 93.197(15)°, and Z = 4) adopts a novel one-dimensional helical chain motif which resulted from the relative different coordinated orientation of the two N-donors on L2 ligand.     

Novel 2D supramolecular array based on antibacterial drug norfloxacin

Self-assembly reaction of Cd(ClO₄)₂ · 6H₂O with Norfloxacin (H-Norf) affords a novel 2D rectangular grid framework [Cd(Norf)(ClO₄)(H₂O)] (1) with strong blue luminescent emission (λ_em=425 nm), while Norf⁻ acts as a tetradentate bridging linker to connect three Cd centers and ClO₄ ⁻ completes Cd center octahedron coordination geometry. The compound 1 has crystallographic data of triclinic, space group , a=9.4577(1) Å, b=9.5012(2) Å, c=12.2805(1) Å, V=3624.4(3) ų, Z=2.     

Syntheses and characterization of novel binuclear chromium (III) complexes of 1,4,8,11-tetraazacyclotetradecane (cyclam)

The syntheses and characterization of novel binuclear chromium (III) complexes of 1,4,8,11-tetraazacyclotetradecane (cyclam) are described. The complex [(cyclam)Cr(OH)]₂Cl₄ · 7H₂O (1) crystallizes in the monoclinic space group C2/c with four binuclear formula units in a cell of dimensions a = 17.403 (2), b = 16.803 (3), c = 12.708 (2) Å, and β = 100.83 (1)°. The cation in 1 consists of di-μ-hydroxodichromium (III) units. The bridging OH groups lie on a twofold axis, which relates one end of the dimer to the other and gives rise to a rigorously planar Cr₂O₂ bridging unit. The Cr?Cr separation is 3.122 (1) Å and the average bridging Cr-O-Cr angle is 104.6 (4)°. The complex [(cyclam)Cr(SO₄)]₂ (ClO₄) · H₂O (5) crystallizes in the monoclinic space group P2₁/c with two binuclear formula units in a cell of dimensions a = 9.516 (2), b = 13.263 (3), c = 14.870 (3) Å, and β = 104.08 (3)°. This cation consists of bis-μ-sulfato-di-chromium (III) units, in which the two chromium centers are bridged by two bridging sulfate groups leading to an eight-membered {Cr-O-S-O}₂ bridging framework. Both dimers exhibit antiferromagnetic interactions, with J = 27.7 cm⁻¹ for complex 1 and J = 4.7 cm⁻¹ for complex 5. The EPR spectrum of the complex 1 has been simulated, demonstrating that the spectrum almost entirely originates from the quintet state, while a few lines can be attributed as triplet and septet transitions.     

Water dimers connect [Cu(cda)(py)3] (cda = pyridine-4-hydroxy-2,6-dicarboxylate, py = pyridine) complex units to left- and right-handed helices that form a tubular coordination polymer through supramolecular bonding

The reaction between pyridine-4-hydroxy-2,6-dicarboxylic acid (cdaH₂) and Cu(NO₃)₂ · 3H₂O afford products that depend on the reaction conditions applied. In presence of excess of aqueous pyridine (1:2 v/v), equimolar amounts of the reactants form {[Cu(cda)(py)₃]₂ · 5H₂O}_n (1). In this complex, dimeric water clusters are H-bonded to carboxylate O atoms forming both left- and right-handed helices. These helices are further H-bonded to form a tubular coordination polymer. It crystallizes in the monoclinic space group P2₁/a with a = 14.235(5), b = 23.097(4), c = 15.542(6) Å, β = 114.392(5)°, V = 4654(2) Å³, Z = 4, R₁ = 0.0422, wR₂ = 0.0992, S = 0.899. When pyridine is used in place of aqueous pyridine, a new coordination polymer, {Cu(cda)(py)}_n(2) is formed that crystallizes in the monoclinic space group P2₁/c with a = 12.391(5), b = 12.770(5), c = 7.135(5) Å, β = 95.155(5)°, V = 1124(1) Å³, Z = 4, R₁ = 0.0415, wR₂ = 0.0882, S = 1.190. The structure of 2 consists of carboxylate-bridged [Cu(cda)(py)] units extending as a zigzag infinite chain where each metal ion shows square-pyramidal geometry. Variable temperature magnetic susceptibility measurements in the temperature range, 2-300 K for 2 is also reported.     

Hydrothermal synthesis and structure characterization of the first organically templated metal iodates

The first organically templated molybdenum iodates (C₅H₆N)₂Mo₂O₅(IO₃)₄(H₂O)₂ (1), (C₁₀H₈N₂)[MoO₂(IO₃)₃] · H₃O (2), and uranium iodate (C₅H₅N)₂[(UO₂)(IO₃)₃](IO₃) (3), have been successfully synthesized under mild hydrothermal conditions. Compound 1 is simple zero-dimensional units consisting of [(Mo₂O₅(IO₃)₄)]²⁻ anions, which can be described as a tetranuclear unit hanged on either side by two [IO₃] groups. The [Mo₂O₅(IO₃)₄]²⁻ anions are in a close connection through the water molecules and protonated pyridine cations, via hydrogen bonds and intermolecular actions. Compound 2 is built up from [MoO₆] octahedra and [IO₃] pyramids to two-dimensional layers, in which 4,4′-bipy molecules and water cations are located, forming strong hydrogen bonds with the inorganic framework, leading to pseudo three-dimensional structure. Compound 3 is one-dimensional ribbons containing {[(UO₂)(IO₃)₃](IO₃)}²⁻ anions and charge neutrality is achieved by the protonated 4,4′-bipy cations, which reside between two ribbons, forming hydrogen bonds with the inorganic framework and resulting in pseudo two-dimensional structure. Crystal data are as follows: (C₅H₆N)₂Mo₂O₅(IO₃)₄(H₂O)₂ (1), orthorhombic, Pnma, a = 24.097(5) Å, b = 13.532(3) Å, c = 7.836(16) Å, Z = 4, V = 2555.2(9) Å³; (C₁₀H₈N₂)[MoO₂(IO₃)₃] · H₃O (2), monoclinic, C2/c, a = 24.176(5) Å, b = 10.751(2) Å, c = 7.5074(15) Å, β = 107.44(3)°, Z = 8, V = 1861.6(6) Å³; (C₅H₅N)₂[(UO₂)(IO₃)₃](IO₃) (3), monoclinic, P2₁/n, a = 14.430(3) Å, b = 7.3459(15) Å, c = 19.811(4) Å, β = 106.70(3)°, Z = 4, V = 2011.3(7) Å³.     

An unprecedented (3,4)-connected self-penetrating network of zinc complex: In situ formation of a tetradentate N-heterocyclic ligand under POMs-mediated hydrothermal conditions

The reaction of lacunary polyanion [α-H₂P₂W₁₂O₄₈]¹²⁻, zinc acetate, bpp (1,3-bis(4-pyridyl)propane) and BTC (1,3,5-benzenetricarboxylate) in an acidic aqueous solution led to the isolation of a new complex [Zn₃(BTC)₂(chtpy)(H₂O)₂] · 2H₂O (1), which crystallizes in the space group C2/c with a = 28.988(6) Å, b = 11.254(2) Å, c = 17.347(4) Å, V = 4682.5(2) Å³, Z = 4. X-ray diffraction analysis reveals that there exists the generation of in situ ligand through simultaneous dehydrogenative coupling and hydroxylation of an N-heterocyclic ligand in complex 1. More interestingly, it exhibits an unprecedented (3,4)-connected (8².10)₂(8³)₂(8⁴.10.12)(8⁵.10) topology which has been reported for the first time and shows self-penetrating nature at the same time.     

Synthesis, characterization and magnetic properties of a novel fluorinated iron phosphite Fe2(HPO3)F2 with infinite -Fe-F-Fe-O-Fe- linkage and -Fe-F-Fe- layer

A novel fluorinated iron phosphite Fe₂(HPO₃)F₂ (1) has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic space group Pnma (No. 51) with a = 7.3458(15) Å, b = 10.038(2) Å, c = 5.4947(11) Å, V = 405.16(14) Å³, Z = 4. Its structure is built up from iron(II) oxygen-fluorine FeO₃F₃ octahedra and HPO₃ pseudo-tetrahedra, giving rise to a 3D inorganic framework. The infinite -Fe-O-Fe-F-Fe- linkage and -Fe-F-Fe- layer in the framework are the noteworthy structural features. Mössbauer spectrum shows the presence of Fe²⁺ in the octahedral coordination. Magnetic measurements indicate the existence of antiferromagnetic interactions.     

Synthesis, single crystal structure and DNA cleavage studies on first N-ethyl substituted three coordinate copper(I) complex of thiosemicarbazone

A copper(I) complex [Cu(CETH)₂Cl] (Ia), where CETH = cuminaldehyde-4-ethyl-3-thiosemicarbazone (I), is prepared and structurally characterised. The complex crystallizes in orthorhombic space group pna2(1) with the unit cell parameters; a = 9.8598(14) Å, b = 15.411(2) Å, c = 0.817(3) Å, V = 2055.9(4) Å³ and Z = 4. The neutral complex has the copper(I) centre bonded to two thioketonic sulphur donor in η¹-S bonding mode and one chloride giving ‘Y’ shape geometry. The complex is diamagnetic and exhibits a copper to ligand charge transfer bands at 351 and 398 nm in dimethylformamide. The complex shows quasireversible cyclic voltammetric response at 0.41 V (ΔEp = 300 mV) at 50 mVS⁻¹ in DMF for the Cu(II)/Cu(I) oxidation couple. Complex Ia shows marginal nuclease activity with pUC18 DNA in the presence of reducing agent (Dithiotretal) and hydrogen peroxide.     

Bifunctional chelates with mixed aromatic and aliphatic amine donors for labeling of biomolecules with the {Tc(CO)3} and {Re(CO)3} cores

A series of tridentate ligands consisting of mixed aromatic and aliphatic amine derivatives of single amino acid chelates and phenylpiperazine have been developed, and their reactions with [NEt₄]₂[ReBr₃(CO)₃] have been investigated. The compounds [Re(CO)₃{(NC₅H₄CH₂)NCH₃(C₂H₄)NHCH₃}]Br (4), [Re(CO)₃{(NC₅H₄CH₂)NCH₃(C₂H₄)NCH₃(CH₂)_xCOOC₂H₅}]Br (x = 1, 5; x = 4, 6) [Re(CO)₃{(NC₅H₄CH₂)NH(C₂H₄)N(CH₃)₂}]Br (7), [Re(CO)₃{(NC₅H₄CH₂)N(CH ₂COOC₂H₅)(C₂H₄)N(CH₃)₂}]Br (8) and [Re(CO)₃(NC₅H₄CH₂)(C₂H₄NH₂)N(CH₂)₃-CH₃Ophenpip]Br (9) (phenpip: phenylpiperazine, -C₆H₄-(CH₂CH₂)₂N-) were prepared and characterized by elemental analysis, NMR, IR, HSMS and X-ray crystallography. All complexes exhibit fac-{Re(CO)₃N₃} coordination geometry in the cationic molecular unit. Crystal data for C₁₃H₁₇BrN₃O₃Re (4): orthorhombic, Pbca, a = 13.4510(8) Å, b = 10.5728(6) Å, c = 22.5378(13) Å, V = 3205.2(3) ų, Z = 8; C₁₇H₂₃BrN₃O₅Re (5): orthorhombic, Pcca, a = 16.5907(7) Å,b = 14.8387(6) Å, c = 16.7075(7) Å, V = 4113.1(3) ų, Z = 8; C₁₃H₂₅BrN₃O₇Re (7 · 4H₂O): monoclinic, P2₁/n, a = 14.0698(17) Å, b = 9.6760(12) Å, c = 15.6099 (19) Å, β = 114.930(2)°, V = 1927.1(4) ų, Z = 4; C₁₇H₂₃BrN₃O₅Re (8): monoclinic, P2₁/n, a = 7.5312(5) Å, b = 16.0366(10) Å, c = 16.8741(10) Å, β = 98.9990(10)°, V = 2012.9(2) ų, Z = 4.     

Extended molecular networks based on Zn and Cd imparting N-substituted imidazole

Synthesis of complexes with the formulations [M(CPI)₂Cl₂] (M = Zn, 1; M = Cd, 4) and [M(CPI)₆](X)₂ (M = Zn, X = NO₃⁻, 2; X = ClO₄⁻, 3; M = Cd, X = NO₃⁻, 5; X = ClO₄⁻, 6) have been achieved from the reactions of MCl₂, M(NO₃)₂·xH₂O and M(ClO₄)₂·xH₂O (M = Zn, Cd) with 1-(4-cyanophenyl)-imidazole (CPI). Complexes 1-6 have been characterized by elemental analyses and spectral studies (IR, ¹H, ¹³C NMR, electronic absorption and emission). Molecular structures of 1, 2, 3 and 6 have been determined crystallographically. Weak interaction studies on the complexes revealed presence of various interesting motifs resulting from C-H···N, C-H···Cl and π-π stacking interactions. The complexes under study exhibit strong luminescence at ∼450 nm in DMSO at room temperature.     

Mononuclear single helices of lanthanum(III) and europium(III). Metal dependent diastereomeric excess

Using the 1:2 condensate of benzildihydrazone and 2-acetylpyridine as a tetradentate N donor ligand L, LaL(NO₃)₃ (1) and EuL(NO₃)₃ (2), which are pale yellow in colour, are synthesized. While single crystals of 1 could not be obtained, 2 crystallises as a monodichloromethane solvate, 2·CH₂Cl₂ in the space group Cc with a = 11.7099(5) Å, b = 16.4872(5) Å, c = 17.9224(6) Å and β = 104.048(4)°. From the X-ray crystal structure, 2 is found to be a rare example of monohelical complex of Eu(III). Complex 1 is diamagnetic. The magnetic moment of 2 at room temperature is 3.32 BM. Comparing the FT-IR spectra of 1 and 2, it is concluded that 1 also is a mononuclear single helix. ¹H NMR reveals that both 1 and 2 are mixtures of two diastereomers. In the case of the La(III) complex (1), the diastereomeric excess is only 10% but in the Eu(III) complex 2 it is 80%. The occurrence of diastereomerism is explained by the chiralities of the helical motif and the type of pentakis chelates present in 1 and 2.     

Synthesis, structure and magnetic property of a 2D grid-like copper(II) complex with end-on azido and pyrazine bridges

A 2D grid-like copper(II) complex [Cu(N₃)₂(pyz)](pyz = pyrazine) (1) has been synthesized and characterized by single crystal X-ray analysis and magnetic measurements. The 2D grid-like network of 1 consists of 1D chain of Cu-pyz units connected by end-on azido bridge. 1 crystallizes in the monoclinic space group C2 with a = 15.148(6) Å, b = 6.877(2) Å, c = 3.4591(12) Å and Z = 2. The magnetic investigation showed the presence of an antiferromagnetic interaction between the copper(II) ions mainly mediated through pyrazine bridge.     

Synthesis, crystal structure and magnetism of a new mixed germanium-polyoxovanadate cluster

A new germanium-polyoxovanadate, (H₃aep)₄[V₁₄Ge₈O₅₀]·2(aep)·13H₂O (1), has been synthesized under solvothermal conditions applying GeO₂, NH₄VO₃, Cu(NO₃)₂·3H₂O and an aqueous solution of 1-(2-aminoethyl)-piperazine (aep, C₆H₁₈N₃) in the temperature range from 110 to 150 °C. The compound crystallizes in the non-centrosymmetric tetragonal space group P-42₁c with a = 17.193(1) Å, c = 16.501(1) Å, V = 4877.9(5) Å³ and Z = 2. The structure consists of isolated spherical [V^IV₁₄Ge^IV₈O₅₀]¹²⁻ cluster anions and protonated amine molecules as counterions. The cluster anion can be viewed as a derivative of the [V₁₈O₄₂] archetype by replacing four VO₅ pyramids by four Ge₂O₇ units. The latter are formed by corner-sharing of two [GeO₄]⁴⁻ tetrahedra. At temperatures above 150 °C the compound (H₂pip)₄(Hpip)₄[V^IV₁₄Ge^IV₈O₅₀(H₂O)] (2) (pip = piperazine, C₄N₂H₁₀) is formed and during the reaction Cu²⁺ is reduced to elemental copper. This redox reaction is essential for the formation of 2. The crystal water molecules in the structure of 1 are emitted at low temperatures. The magnetic properties are dominated by strong intra-cluster antiferromagnetic coupling and the strongest exchange between edge- and corner-sharing VO₅ square pyramids results in an eight-membered spin ring to which two three-membered spin bridges are joined. The magnetic susceptibility data suggest that even at the low temperature of 2 K several multiplet states are still significantly populated.