Patrizia Imperatori

Weak charge-transfer polyoxoanion salts: the reaction of quinolin-8-ol (Hquin) with phosphotungstic acid and the crystal and molecular structure of [H2quin]3[PW12O40]·4EtOH·2H2O

Different solvated charge-transfer salts between quinolin-8-ol (Hquin) and phosphotungstic acid have been synthesized and characterized. Spectroscopic data support the presence of a sizeable electronic interaction between electron-rich aromatic organics and the inorganic acid, both in the solid state and in solution, provided that a large excess of the organic is present. This interaction is responsible for the formation of photosensitive compounds and provides a rationale for the subsequent facile photo-oxidation of the organic substrate. The crystal and molecular structure of [H2quin]3[PW12O40]·4EtOH·2H2O has been solved by the heavy-atom method and refined to a final R= 0.083, for 4 902 reflections with I 3σ(I): triclinic space group P; with a= 11.721(3), b= 12.818(3), c= 12.878(3)A, α= 89.20(2), β= 104.10(2), γ= 117.30(2)°, and Z= 1. The anion structure consists of an α-Keggin-type molecule in two-fold disorder. The 8-hydroxyquinolinium moieties (three per [PW12O40]3–) are stacked approximately along the x direction, with alternative interplanar spacings of 3.25 and 3.57 A. The crystal structure determination reveals the absence of any substantial, direct interaction between the organic cations and the phosphototungstate anions. Therefore no clear structural basis for the electronic interaction noted above can be given.

Sonochemical synthesis of versatile hydrophilic magnetite nanoparticles.

Hydrophilic magnetite nanoparticles in the size range 30-10nm are easily and rapidly prepared under ultrasonic irradiation of Fe(OH)(2) in di- and tri-ethylene glycol/water solution with volume ratio varying between 7:3 and 3:7. Structural (XRD) and morphological (SEM) characterization reveal good crystalline and homogeneous particles whereas, when solvothermally prepared, the particles are inhomogeneous and aggregated. The sonochemically prepared particles are versatile, i.e. well suited to covalently bind molecules because of the free glycol hydroxylic groups on their surface or exchange the diethylene or triethylene glycol ligand. They can be easily transferred in hydrophobic solvents too. Room-temperature magnetic hysteresis properties measured by means of Vibrating Sample Magnetometer (VSM) display a nearly superparamagnetic character. The sonochemical preparation is easily scalable to meet industrial demand.

High Yield Synthesis of Pure Alkanethiolate-Capped Silver Nanoparticles

One-phase, one-pot synthesis of Ag(0) nanoparticles capped with alkanethiolate molecules has been optimized to easily achieve a pure product in quantitative yield. We report the synthesis of dodecanethiolate-capped silver particles and the chemophysical, structural, and morphologic characterization performed by way of UV-vis, (1)H NMR, and X-ray photoelectron (XPS) spectroscopies, X-ray powder diffraction (XRD) and X-ray absorption fine structure analysis (XFAS), electron diffraction and high-resolution transmission electron microscopy (HR-TEM), and scanning and transmission electron microscopy (SEM and TEM). Depending on the molar ratio of the reagents (dodecylthiosulphate/Ag(+)), the mean Ag(0) particle size D(XRD) is tuned from 4 to 3 nm with a narrow size distribution. The particles are highly soluble, very stable in organic solvents (hexane, toluene, dichloromethane, etc.), and resistant to oxidation; the hexane solution after one year at room temperature does not show any precipitation or formation of oxidation byproducts.

Tetrathiafulvalenium salts of planar PtII, PdII, and CuII 1,2-dithio-oxalato-S,S′ anions. Synthesis, chemistry and molecular structures of bis(tetrathiafulvalenium) bis(1,2-dithio-oxalato-S,S′)palladate(II), [ttf]2[Pd(S2C2O2)2], and of bis(tetrathiafulvalenium)tetrathiafulvalene bis(1,2-dithio-oxalato-S,S′)platinate(II), [ttf]3[Pt(S2C2O2)2]

Tetrathiafulvalenium (ttf) salts with inorganic dithio-oxalato anions, [ttf]2[Pd(S2C2O2)2](1), [ttf]2[Pt(S2C2O2)2](2) and [ttf]1.0[Cu(S2C2O2)2](3) were prepared by reaction of [ttf]3[BF4]2 and the corresponding [A]2[M(S2C2O2)2](where A = NEt4 or AsPh4; M = PdII PtII or CuII) in acetonitrile, or by electrocrystallization of neutral ttf in acetonitrile containing [NEt4]2[Pt(S2C2O2)2] in the case of [ttf]3[Pt(S2C2O2)2](4). The crystal and molecular structures of compounds (1) and (4) were determined by single-crystal X-ray diffraction. Compound (1) crystallizes in the monoclinic space group P21/c with unit-cell dimensions a= 9.447(2), b= 11.044(4), c= 12.299(2)A, β= 113.52(2)°, and Z= 2. The ttf molecules exist as dimeric (ttf˙+)2 and form mixed stacks with the anions along the b axis of the unit cell. Compound (4) crystallizes in the monoclinic space group P21/c with unit-cell dimensions a= 9.754(2), b= 13.905(3), c= 13.733(3)A, β= 119.21 (1)°, and Z= 2. Two crystallographically independent ttf units are present: the first comprises dimerized (ttf˙+)2, and the Second is neutral (ttf0) and perpendicular to the dimer. The compound is better formulated as [(ttf˙+)2(ttf0)][Pt(S2C2O2)2]. Electron spin resonance, infrared and X-ray photoelectron spectroscopic studies of the palladium and platinum derivatives indicate that, in each compound, the metal ion is in the oxidation state +2 and that ttf is present as (ttf˙+)2and ttf0 as found in the crystal structure. The copper compound contains the metal ion in the uncommon oxidation state +3. Infrared, photoelectron, and electronic spectra suggest that the molecular structure of this compound consists of (ttf˙+)2dimers and planar diamagnetic [Cu(S2C2O2)2]–.

A Novel 1D-AF Hybrid Organic-Inorganic Chromium(II) Methyl Phosphonate Dihydrate: Synthesis, X-Ray Crystal and Molecular Structure, and Magnetic Properties

Light-blue crystals of chromium(II) methyl phosphonate dihydrate, [Cr(CH(3)PO(3))(H(2)O)].H(2)O, were obtained in water by mixing filtered solutions of methylphosphonic acid and chromium(II) chloride in the presence of urea in an inert atmosphere. The compound was characterized by elemental analysis, TGA-DSC, X-ray crystallography, magnetic measurements, and UV-visible and FT-IR spectroscopies. The crystal and molecular structures (orthorhombic Pnma (no. 62): a = 4.4714(5) A, b = 6.8762(7) A, c = 19.180(2) A, Z = 4) have been solved using single-crystal X-ray diffraction. The chromium(II) ion is six-coordinated by oxygens (4 + 2) to form an elongated octahedron, with the four equatorial oxygen atoms belonging to [-PO(3)](2-) phosphonate groups. This stereochemistry of the Cr(II) ion (high-spin d(4) electronic configuration) is ascribed to the Jahn-Teller effect. The [CrO(6)] chromophore, the [CH(3)PO(3)](2-) anions, and the water molecules build a novel one-dimensional (1D) metal(II) oxide chain, anchored to each other within the ab plane by two oxygens of the phosphonate ligand. Within the chain, each Cr(2+) ion is connected through double oxygen bridges to its two neighbors, forming edge-sharing octahedra running along the b axis. The chains are further connected with the adjacent chains by phosphonate [-PO(3)](2-) groups of the ligand, forming an inorganic layer that alternates along the c axis of the unit cell with bilayers, consisting of methyl groups and water of crystallization. The thermal variation of the magnetic susceptibility follows the Curie-Weiss law, with a large negative Weiss constant, theta = -60 K, indicating the presence of antiferromagnetic AF exchange interactions between neighboring Cr(II) ions. The magnetic behavior and the magnetic dimensionality have been analyzed in terms of Fishers classical limiting form of the Heisenberg chain theory, and a value of J = -9.3 cm(-1) was found. The negative value of the intra-chain exchange constant coupling J confirms the presence of an AF coupling. No sign of long-range magnetic ordering down to 2 K (the lowest measured temperature) is observed, in agreement with the predominant one-dimensional character of the exchange interactions.

Investigation of static and dynamic magnetic properties of Joule heated granular Co10Cu90 ribbons

Abstract The magnetic properties of a granular Co–Cu alloy (Co 10 Cu 90 ) produced by melt-spinning and annealed by Joule heating at different DC current densities have been investigated by magnetization, DC and AC susceptibility measurements. The increase of the heating current density has been found to promote grain growth and to enhance the strength of intergrain interactions, determining a change of magnetic behavior: from a collective freezing in random directions of moments of nanosized Co particles to an inhomogeneous and progressive blocking of moments of particles with increasing size. The effects of Joule heating on microstructure and magnetic properties are discussed in relation to the giant magnetoresistance properties exhibited by the system, which confirm the development of interparticle correlations with increasing the heating current density.

Reaction products of benzimidazole with tetracyanoethylene. Mechanism of formation and 13C NMR spectroscopy of the anions C16N8H5–, dicyano(3,4-dicyano-5-benzimidazol-1-yl-2H-pyrrol-2-ylideneamino)methanide (1) and C18N9H4–, 1,2,4,5-tetracyano-3,6,7,12,13-penta-aza-5H-indeno[1,2-d]-acenaphthylen-5-ide (2). Crystal and molecular structure of their tetraphenylarsonium salts

The anions (1) and (2) have been synthesized by the reaction of benzimidazole with tetracyano-ethylene. They have been characterized by X-ray crystallography and 13C NMR spectroscopy. The molecular structures of their tetraphenylarsonium salts have been determined. The charge delocalization and mechanism of formation are discussed.

Condensation reactions of tetracyanoethylene and its monoanion promoted by Lewis acids: synthesis and crystal, molecular, and electronic structure of a novel heterocycle, the 2,3,6,7-tetracyano-5-(tricyanoethenylimino)-3H-1,4,7b-triazabenzo[i,j]pentalenide ion

From the condensation reaction of tetracyanoethylene (C6N4, TCNE) with its radical monoanion (C6N4˙–) promoted by a Lewis acid [ZnCl2, AlCl3, or V(bpy)3+2], a novel heterocyclic carbanion (C17N11–) has been synthesized and characterized by X-ray, 13C NMR, IR, and UV spectroscopy and cyclic voltammetry measurements. The crystal and molecular structure of the title anion has been determined for the tetraphenylarsonium salt, and its electronic structure and the mechanism of formation are discussed.

Dithiolene-like platinum complexes of the methyl esters of N3-lsopropyl and t-butyl substituted dithiocarbazic acids. Crystal and molecular structures of [Pt{NPriNC(S)SMe}2] and [Pt{NButNC(S)SMe}2]

The crystal and molecular structures of dithiolene-like [Pt{NPriNC(S)SMe}2] and [Pt{N-ButNC(S)SMe}2] have been determined: both complexes have square-planar trans-PtN2S2 chromophores. Their electronic and i.r. spectra have been recorded, and electrochemical investigations performed.

Electronic and structural properties of novel cyanocarbon dyes based on tetracyanoethylene

Four novel cyanocarbon dyes derived from tetracyanoethylene (TCNE) have been studied. They are carbanions isolated as tetraphenylarsonium salts of formula C11N7H2–(1), C15N6H3–(2), C14N7H2–(3), and C13N8H–(4). Compound (1) was obtained by a condensation reaction of TCNE promoted by Ti(bpy)3 and its structure has already been reported. Compounds (2)–(4) are the 1,3-bistricyanovinyl derivatives of cyclopentadienyl, pyrrolyl, and imidazolyl anions, respectively. The tetraphenylarsonium salt of anion (3) gives crystals isomorphorus with the crystals of the analogous salts of anions (2) and (4), whose crystal structures are reported here. Structural and electronic properties of the four anions are discussed on the basis of 13C n.m.r., i.r., u.v., and electrochemical data; electrical and magnetic properties of their radical salts with the tetrathiafulvalenium cation (TTF˙+) are also reported and discussed.