Pyrazolate-supported Cr(μ-O) cores; homovalent CrIII3 and mixed-valent CrIII2Cr.

The thermally assisted reaction of Cr(NO)·9HO, 4-Cl-pzH, and EtN yielded electrochemically active trinuclear Cr-oxo-pyrazolate complexes with formula (PhP)[Cr(μ-O)(μ-4-Cl-pz)X], X = Cl (1) and Br (2). Magnetic susceptibility measurements and EPR spectroscopy show that 1 has an antiferromagnetically coupled CrO-core with an = 1/2 ground state and isotropic exchange of = -12.7 cm.

"Antibacterial properties of nine indium(III) complexes of substituted pyrazoles/pyrazolate and the structural and solution characterization of the mer- and trans‑indium(III) complexes of 4-Me-pzH".

Two indium(III) complexes of formula mer-[InCl(4-Me-pzH)] and trans-[InCl(4-Me-pzH)]Cl·(4-Me-pzH)·(HO) were isolated from the same reaction mixture and crystallographically characterized. The two complexes exist in dynamic equilibrium and their dynamic behavior was probed by variable temperature H NMR spectroscopy in the 202 to 296 K range. Powder X-ray diffraction of the batch confirmed existence of both complexes in a 1:2 ratio.

Mononuclear, hexanuclear and polymeric indium(III) pyrazolido complexes; structural characterization, dynamic solution studies and luminescent properties.

A new family of six mononuclear indium(III) complexes of formula -[InCl(pz*H)]-pz*H = pyrazole (pzH), or substituted pyrazoles: 4-Cl-pzH, 4-Br-pzH, 4-I-pzH, 4-Ph-pzH and 3,5-Me-pzH-were synthesized by addition reactions of InCl and pz*H and crystallographically characterized. The fluxional behaviour of the complexes, probed by variable temperature H NMR spectroscopy in the 328 K to 173 K range, was attributed to (at least) four simultaneous processes: pyrazole N-H proton dissociation/association, /-pyrazole exchange, and N/N tautomerization of the - and of the -pyrazoles. Three novel trianionic hexanuclear complexes of general formula (pipH)[InCl(μ-OH)(μ-OH)(μ-pz*)]-pz* = pz, 4-Cl-pz and 4-Ph-pz-showing μ-hydroxo and μ-oxo bridges were synthesized from the corresponding -[InCl(pz*H)] and characterized by single crystal X-ray diffraction and H NMR.

Crystal Structure Determination and Hirshfeld Analysis of a New Alternariol Packing Polymorph.

A new polymorph of the mycotoxin alternariol is reported and characterized by single crystal X-ray diffraction. Structural data, Hirshfeld surface analysis, and 2D fingerprint plots are used to compare differences in the intermolecular interactions of the orthorhombic 2 Form I (previously reported) and the monoclinic 2/ Form II (herein reported). The polymorphs have small differences in planarity-7.

Low-temperature crystal structure of 4-chloro-1-pyrazole.

The structure of 4-chloro-1-pyrazole, CHClN, at 170 K has ortho-rhom-bic () symmetry and is isostructural to its bromo analogue. Data were collected at low temperature since 4-chloro-1-pyrazole sublimes when subjected to the localized heat produced by X-rays. The structure displays inter-molecular N-H⋯N hydrogen bonding and the packing features a trimeric mol-ecular assembly bis-ected by a mirror plane ( normal to ) running through one chlorine atom, one carbon atom and one N-N bond.

Observation and deconvolution of a unique EPR signal from two cocrystallized spin triangles.

A 16-line pattern has been theoretically predicted, but hitherto not reported, for the Electron Paramagnetic Resonance (EPR) spectrum of antiferromagnetically coupled CuII triangles experiencing isotropic exchange of isosceles magnetic symmetry. Now, the crystallization of such a triangular species and its X-ray structure determination in a polar space group, R3 (No. 146), has enabled its single crystal EPR study.

A novel fungal metabolite inhibits Plasmodium falciparum transmission and infection.

Background: Malaria transmission depends on infected mosquitoes and can be controlled by transmission-blocking drugs. The recently discovered FREP1-mediated malaria transmission pathway is an excellent target to screen drugs for limiting transmission.

Methods: To identify candidate small molecules, we used an ELISA-based approach to analyze extracts from a fungal library for inhibition of the FREP1-parasite interaction.

Origin of Ferromagnetism and Magnetic Anisotropy in a Family of Copper(II) Triangles.

Previously reported ferromagnetic triangles (NnBu ) [Cu (μ -Cl) (μ-4-NO -pz) Cl ] (1), (PPN) [Cu (μ -Cl) (μ-pz) Cl ] (2), (bmim) [Cu (μ -Cl) (μ-pz) Cl ] (3) and newly reported (PPh ) [Cu (μ -Cl) (μ-4-Ph-pz) Cl ] (4) were studied by magnetic susceptometry, electron paramagnetic resonance (EPR) spectroscopy and ab initio calculations to assess the origins of their ferromagnetism and of the magnetic anisotropy of their ground S=3/2 state (PPN =bis(triphenylphosphine)iminium, bmim =1-butyl-3-methylbenzimidazolium, pz =pyrazolate). Ab initio studies revealed the d character of the magnetic orbitals of the compressed trigonal bipyramidal copper(II) ions. Ferromagnetic interactions were attributed to weak orbital overlap via the pyrazolate bridges.

Coordination polymers of Cd and Pb with croconate show remarkable differences in coordination patterns: a structural and spectroscopic study.

The croconate dianion is a highly versatile ligand with two tautomeric forms making it useful for building large superstructures in the solid state. The single-crystal X-ray structures of Pb- and Cd-croconate coordination polymers, namely catena-poly[[[diaqualead(II)]-μ-croconato-κO,O:O,O] monohydrate], {[Pb(CO)(HO)]·HO}, 1, and catena-poly[[triaquacadmium(II)]-μ-croconato-κO,O:O,O], [Cd(CO)(HO)], 2, have been determined. Both polymers form one-dimensional (1D) structures; 1 is a nonplanar 1D zigzag coordination polymer extended along the crystallographic b axis, whereas 2 is a planar 1D ribbon parallel to the [101] direction.

Nitrite Reduction by Trinuclear Copper Pyrazolate Complexes: An Example of a Catalytic, Synthetic Polynuclear NO Releasing System.

Two trinuclear Cu pyrazolato complexes with a Cu(μ-E)-core (E = O or OH) and terminal nitrite ligands in two coordination modes were characterized crystallographically, spectroscopically, and electrochemically. One-electron oxidation of the μ-O species produces a delocalized, mixed-valent, formally CuCu-nitrite, but no nitrate. In contrast, under reducing conditions-addition of PhSH as an electron and proton donor-both complexes mediate the reduction of nitrite, releasing NO.

Spontaneous Resolution by Crystallization of an Octanuclear Iron(III) Complex Using Only Racemic Reagents.

The P and M enantiomers of the octanuclear [Fe (μ -O) (μ-4-Cl-pz) Cl ] complex, having T symmetry, were resolved by temporary substitution of chloride ligands by racemic 4- Bu-phenolates and subsequent crystallization, where the (S)- and (R)-phenolates coordinate selectively to the M and P complexes, respectively. The complexes were characterized by circular dichroism analysis and X-ray structure determination. This work constitutes a rare example of enantiomeric recognition resulting in spontaneous resolution upon crystallization.

Magnetic resonance imaging contrast enhancement in vitro and in vivo by octanuclear iron-oxo cluster-based agents.

A water-soluble octanuclear cluster, [Fe], was studied with regard to its properties as a potential contrast enhancing agent in magnetic resonance imaging (MRI) in magnetic fields of 1.3, 7.2 and 11.

Interactions between H-bonded [Cu(μ-OH)] triangles; a combined magnetic susceptibility and EPR study.

The X-ray crystal structure of the CuII complex [Cu3(μ3-OH)(μ-pz)3(PhCOO)3]- (pz- = pyrazolato anion) shows an isosceles triangular core, further forming a hexanuclear H-bonded aggregate. Cleavage of the H-bonds in solution results in isolated trinuclear species. Analysis of variable temperature magnetic susceptibility data of a powder sample shows an antiferromagnetically-coupled Cu3-core with a doublet ground state and isotropic exchange parameters (Jave = -355 cm-1, Hiso = -JijSiSj).

Crystal structure and conformational analysis of doxorubicin nitrate.

Crystal structure determination of doxorubicin nitrate, (DoxH)NO, systematic name (7,9)-7-{[(2,4,5,6)-4-azaniumyl-5-hy-droxy-6-methyl-oxan-2-yl]-oxy}-6,9,11-trihy-droxy-9-(2-hy-droxy-acet-yl)-4-meth-oxy-8,10-di-hydro-7-tetra-cen-5,12-dione nitrate, shows two formula units present in the asymmetric unit. In the crystal lattice, hydrogen-bonded pairs of (DoxH) cations and segregation of the aglycone and sugar moieties are observed. Inspection of mol-ecular overlays reveals that the conformation of (DoxH)NO resembles that of DNA-inter-calated, but not of protein-docked (DoxH).

Towards ionic liquids with tailored magnetic properties: bmim salts of ferro- and antiferromagnetic Cu triangles.

Complexes (bmim)[Cu(μ-Cl)(μ-pz)Cl] (1), (bmim)[Cu(μ-OH)(μ-pz)Cl] (2) and (bmim)[Cu(μ-OH)(μ-Cl)(μ-pz)Cl] (3) were synthesized (bmim = 1-butyl-3-methylimidazolium, pz = pyrazolato anion). Dianionic complexes 1 and 3 were obtained as crystalline solids, whereas the monoanionic complex 2 was obtained as a viscous paste. Magnetic susceptibility and X-band EPR studies revealed intramolecular ferromagnetic interactions for 1 with small magnetoanisotropy in its ground state (D∼ 10 cm) and intramolecular antiferromagnetic interactions for 2 and 3 (-285 and -98 cm average J, respectively) with important magnetic anisotropy in their ground states stemming from a combination of low magnetic symmetry and antisymmetric exchange interactions.

Synthesis of 8-(1,2,3-triazol-1-yl)-7-deazapurine nucleosides by azide-alkyne click reactions and direct C-H bond functionalization.

Treatment of toyocamycin or sangivamycin with 1,3-dibromo-5,5-dimethylhydantoin in MeOH (r.t./30 min) gave 8-bromotoyocamycin and 8-bromosangivamycin in good yields.

Crystal structure of μ-chlorido-nona-kis-(μ-4-chloro-pyrazolato)bis-μ-methoxo-hexa-copper(II).

The hexa-nuclear title compound, [{Cu(μ-OCH)(μ-CHClN)}(μ-CHClN)(μ-Cl)] or [Cu(CHClN)(CHO)Cl], crystallizes in the space group , with individual mol-ecules being located on a twofold rotation axis. The mol-ecule adopts a trigonal prismatic shape, with two trinuclear units linked by three 4-chloro-pyrazolate ligand bridges by encapsulating a Cl anion in a μ-coordination mode. In the crystal, individual mol-ecules are stacked into rods parallel to [1-10] that are arranged in a pseudo-hexa-gonal packing.

A Redox-Induced Spin-State Cascade in a Mixed-Valent Fe (μ -O) Triangle.

One-electron reduction of a pyrazolate-bridged triangular Fe (μ -O) core induces a cascade wherein all three metal centers switch from high-spin Fe to low-spin Fe . This hypothesis is supported by spectroscopic data ( H-NMR, UV-vis-NIR, infra-red, Fe-Mössbauer, EPR), X-ray crystallographic characterization of the cluster in both oxidation states and also density functional theory. The reduction induces substantial contraction in all bond lengths around the metal centers, along with diagnostic shifts in the spectroscopic parameters.

A [Cu3(μ3-O)]-pyrazolate metallacycle with terminal nitrate ligands exhibiting point group symmetry 3.

The trinuclear triangular cuprate anion of the title compound, tris-[bis-(tri-phenyl-phospho-ranyl-idene)ammonium] tris-(μ2-4-chloro-pyrazolato-κ(2) N:N')-μ3-oxido-tris-[(nitrato-κ(2) O,O')cuprate(II)] nitrate monohydrate, (C36H30P2N)[Cu3(C3H2ClN2)3(NO3)3O]NO3·H2O, has point group symmetry 3., with the μ3-O atom located on the threefold rotation axis. The distorted square-pyramidal coordination sphere of the Cu(II) atom is completed by two N atoms of trans-bridging pyrazolate groups and a chelating nitrate anion.

Uracil Nucleosides with Reactive Group at C5 Position: 5-(1-Halo-2-sulfonylvinyl)uridine Analogues.

The transition-metal-catalyzed or radical-mediated halosulfonylation of 5-ethynyluridine provided (E)-(1-halo-2-tosylvinyl)uridines. These (β-halo)vinyl sulfones undergo efficient stereoselective addition-elimination with amines or thiols to provide Z-β-aminovinyl or E-β-thiovinyl sulfones tethered to the C5 position of the uracil ring.

A trigonal prismatic Cu6-pyrazolato complex containing a μ6-F ligand.

The encapsulation of a fluoride ion in a trigonal prismatic CuII6-pyrazolato cage results in a small expansion of the Cu6-host. The structural, electronic and magnetic features of the Cu6-complex, containing an endohedral fluoride in the rare μ6-F coordination mode, are compared with those of the parent complex with a vacant Cu6-cage.

Spin-glass behavior of a hierarchically-organized, hybrid microporous material, based on an extended framework of octanuclear iron-oxo units.

Inspired by the stepwise addition of octanuclear iron units into mammalian ferritin, a "stop-and-go" synthesis strategy was used to prepare two microporous (Langmuir surface area, 490 m(2) g(-1); effective pore size, 4-5 Å) hierarchical materials {[Fe8(μ4-O)4(μ-pz)12Cl0.3(μ-O)1.85}n () and {[Fe8(μ4-O)4(μ-4-Me-pz)12Cl0.

Double exchange in a mixed-valent octanuclear iron cluster, [Fe8(μ4-O)4(μ-4-Cl-pz)12Cl4](-).

A combination of SQUID and pulsed high-field magnetometry is used to probe the nature of mixed valency in an Fe(II)Fe7(III) cluster. DFT-computed spin Hamiltonian parameters suggest that antiferromagnetic coupling dominates, and that electron transfer both between the four irons of the cubane core (t1) and between a cubane and three neighboring irons (t2) is significant. Simulations using the computed parameters are able to reproduce the key features of the measured effective magnetic moment, μeff(T), over the 2 < T < 300 K temperature range.

Synthesis and characterization of palladium and palladium-cobalt nanoparticles on Vulcan XC-72R for the oxygen reduction reaction.

A single-source approach was used to synthesize bimetallic nanoparticles on a high-surface-area carbon-support surface. The synthesis of palladium and palladium-cobalt nanoparticles on carbon black (Vulcan XC-72R) by chemical and thermal reduction using organometallic complexes as precursors is described. The electrocatalysts studied were Pd/C, Pd2Co/C, and PdCo2/C.

Trigonal prismatic Cu(I) and Ag(I) pyrazolato nanocage hosts: encapsulation of S8 and hydrocarbon guests.

Two neutral hexanuclear trigonal prismatic cage molecules have been synthesized by coupling two planar triangular M3pz3-panels, M = Cu(I) and Ag(I), in eclipsed geometry. The ~230 Å(3) cage volume can be either vacant or occupied by neutral guests. The crystal structures of the M6-cyclohexane and Ag6-S8 host-guest species have been determined.