Magnetic anisotropy of two tetrahedral Co(II)-halide complexes with triphenylphosphine ligands

Recently, the choice of ligand and geometric control of mononuclear complexes, which can affect the relaxation pathways and blocking temperature, have received wide attention in the field of single-ion magnets (SIMs). To find out the influence of the coordination environment on SIMs, two four-coordinate mononuclear Co(II) complexes [NEt₄][Co(PPh₃)X₃] (X = Cl^-, 1; Br^-, 2) have been synthesized and studied by X-ray single crystallography, magnetic measurements, high-frequency and -field EPR (HF-EPR) spectroscopy and theoretical calculations. Both complexes are in a cubic space group Pa3̄ (No. 205), containing a slightly distorted tetrahedral moiety with crystallographically imposed C_3v symmetry through the [Co(PPh₃)X₃]^- anion. The direct-current (dc) magnetic data and HF-EPR spectroscopy indicated the anisotropic S = 3/2 spin ground states of the Co(II) ions with the easy-plane anisotropy for 1 and 2. Ab initio calculations were performed to confirm the positive magnetic anisotropies of 1 and 2. Frequency- and temperature-dependent alternating-current (ac) magnetic susceptibility measurements revealed slow magnetic relaxation for 1 and 2 at an applied dc field. Finally, the magnetic properties of 1 and 2 were compared to those of other Co(II) complexes with a [CoAB₃] moiety.

Molecular Engineering of Metal Alkoxides for Solution Phase Synthesis of High-Tech Metal Oxide Nanomaterials

The 'bottom-up' synthesis of inorganic nanomaterials with precision at the atomic/molecular level offers many opportunities for the design and improvement of the nanomaterials for various applications. Molecular engineering during soft chemical processing for the synthesis of functional nanomaterials enables the desired chemical and physical properties of the precursors, such as solubility or volatility, clean decomposition, control of stoichiometry for multimetallic species to name a few, and leads to easy control of uniform particle size distribution, stoichiometry…. This Minireview illustrates some important aspects of the molecular engineering in light of some recent developments from the molecular synthesis of nanomaterials involving non-silicon metal alkoxide systems for high-tech applications.

The use of mixed-metal single source precursors for the synthesis of complex metal oxides

This Feature Article highlights the use of mixed-metal single source precursors to directly access useful complex metal oxide materials.

Synthetic strategies, diverse structures and tuneable properties of polyoxo-titanium clusters

A review of polyoxo-titanium clusters (PTCs), with an emphasis on synthetic methodologies, diverse structures, tuneable optical properties and potential applications.

Hydrolysis of organometallic and metal–amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles

Organometallic and metal amide reagents react with –OH groups to generate metal–oxygen connectivity, yielding metal-oxo heterobimetallics, clusters and nanoparticles.

From nanoparticles to bulk crystalline solid: nucleation, growth kinetics and crystallisation of mixed oxide ZrxTi1−xO2 nanoparticles

We describe the preparation of mixed metal oxide nanoparticles of a desirable composition and their transformation to the crystalline solids Zr_xTi_1−xO₂ (0.0 ≤ x ≤ 1.0) after heat treatment.

A new cadmium-doped titanium–oxo cluster with stable photocatalytic H2 evolution properties

A new Cd-doped titanium–oxo cluster (TOC) with good H₂ evolution ability and high catalytic stability has been prepared and characterized.

Nucleation and growth kinetics of zirconium-oxo-alkoxy nanoparticles

Nucleation and growth of zirconium-oxo-alkoxy nanoparticles were studied in a sol–gel process in n-propanol solution in quasi-perfect micromixing conditions.

General facile approach to transition-metal oxides with highly uniform mesoporosity and their application as adsorbents for heavy-metal-ion sequestration

Mesoporous powders of transition-metal oxides, TiO2, ZrO2, HfO2, Nb2O5, and Ta2O5, pure from organic impurities were produced by a rapid single-step thermohydrolytic approach. The obtained materials display an impressively large active surface area and sharp pore-size distribution, being composed of partially coalesced uniform nanoparticles with crystalline cores and amorphous shells. They reveal extremely high adsorption capacity in removal of Cr(VI) anions from solutions (25.8 for TiO2, 73.0 for ZrO2, and 74.7 mg g(-1) for Nb2O5 in relation to the Cr2O7(2-) anion), making them very attractive as adsorbents in water remediation applications. The difference in adsorption capacities for the studied oxides may be explained by variation in surface hydration and surface-charge distribution.

Precursor directed synthesis--"molecular" mechanisms in the Soft Chemistry approaches and their use for template-free synthesis of metal, metal oxide and metal chalcogenide nanoparticles and nanostructures

This review provides an insight into the common reaction mechanisms in Soft Chemistry processes involved in nucleation, growth and aggregation of metal, metal oxide and chalcogenide nanoparticles starting from metal-organic precursors such as metal alkoxides, beta-diketonates, carboxylates and their chalcogene analogues and demonstrates how mastering the precursor chemistry permits us to control the chemical and phase composition, crystallinity, morphology, porosity and surface characteristics of produced nanomaterials.

Local structural investigation of Eu(3+)-doped BaTiO3 nanocrystals

A structural investigation of sub-15 nm xEu:BaTiO3 nanocrystals (x = 0-5 mol%) was conducted to determine the distribution of the Eu(3+) ion in the BaTiO3 lattice. Pair distribution function analysis of X-ray total scattering data (PDF), steady-state photoluminescence, and X-ray absorption spectroscopy (XANES/EXAFS) were employed to interrogate the crystal structure of the nanocrystals and the local atomic environment of the Eu(3+) ion. The solubility limit of the Eu(3+) ion in the nanocrystalline BaTiO3 host synthesized via the vapor diffusion sol-gel method was estimated to be ∼4 mol%. A contraction of the perovskite unit cell volume was observed upon incorporation of 1 mol% of europium, while an expansion was observed for nominal concentrations between 1 and 3 mol%. The average Eu-O distance and europium coordination number decreased from 2.46 Å and 9.9 to 2.42 Å and 8.6 for europium concentrations of 1 and 5 mol%, respectively. Structural trends were found to be consistent with the substitution of Eu(3+) for Ba(2+)via creation of a Ti(4+) vacancy at low europium concentrations (<1 mol%), and with the substitution of Eu(3+) for both Ba(2+) and Ti(4+) at high europium concentrations (1-3 mol%). The significance of accounting for local structural distortions to rationalize the distribution of lanthanide ions in the perovskite host is highlighted.

Precursor-directed assembly of complex oxide nanobeads: the role of strongly coordinated inorganic anions

The use of an inorganic perrhenate ligand in the structure of early-transition-metal alkoxide precursors permits to achieve uniform self-assembly of the primary nanoparticles produced by their hydrolysis. The latter has been carried out in a hydrocarbon reaction medium by the addition of water with vigorous stirring, either in the pure form or in solutions in parent alcohols. The self-assembly is guided by the surface charge enhanced by the presence of strongly coordinated anions as determined by zeta potential measurements. The aggregation process has been followed in real time by nanoparticle tracking analysis (NanoSight technique). The reaction products are spherical aggregates with a size that can be efficiently controlled through the polarity of the reaction medium. The produced nanobeads have been characterized by TEM, SEM-EDS, DLS, nitrogen adsorption, and FTIR. The coordination of metal centers has been investigated using EXAFS spectroscopy. The aggregates remain amorphous on thermal treatment of up to 700 °C (24 h treatment) but crystallize when treated at 1000 °C. This latter process is associated with the total loss of rhenium content and offers early-transition-metal oxides as products.

Synthesis of CuAl2(acac)4(O(i)Pr)4, its hydrolysis and formation of bulk CuAl2O4 from the hydrolyzed gels; a case study of molecules to materials

CuAl(2)(acac)(4)(O(i)Pr)(4) was obtained by the reaction driven by the ligand rearrangement between anhydrous Cu(acac)(2) and Al(OPr(i))(3) in toluene under refluxing conditions. The single molecular nature and the stability of the precursor were evidenced by the presence of the molecular ion peak at m/z 749 in the EI mass spectrum. The FT-IR spectrum also confirmed the formation of the molecular precursor with strong bands appearing at 961, 1021, 1289, 1394, 1527 and 1594 cm(-1). Very low solubility as well as low stability of the precursor in common solvents hindered the growth of single crystals. The stability could be improved in acetic acid medium which was further used for the controlled hydrolysis of the precursor. A blue gel obtained on hydrolysis for 11 days showed the presence of acetate, isopropoxy and acac moieties in addition to the hydroxide group in the FT-IR spectrum. Fast hydrolysis assisted by ultrasonication with 1.5 ml of the hydrolyzing agent for 6 h resulted in a blue colored gel, the FT-IR spectrum of which also indicated the presence of acetate, isopropoxy, acac and hydroxide moieties. Both the gels showed a mass loss up to 78% according to thermal analysis in air up to 900 degrees C. While the PXRD pattern of the gel from the controlled hydrolysis yielded monophasic cubic CuAl(2)O(4) on heating at 900 degrees C in air for 12 h, phase pure product could be obtained within 12 h at 700 degrees C from the sonicated gel. Both the oxides were nanosized as observed in the TEM images. The particle size distribution obtained from the laser light scattering method showed monodispersity. The room-temperature Raman spectrum of CuAl(2)O(4) exhibited broad bands at 476, 505, 610, 712, 792 cm(-1) typical of nanosized crystallites and were assigned based on group theoretical analysis. The (27)Al NMR spectrum of CuAl(2)O(4) showed a sharp and intense resonance signal at around delta = 0.112 ppm characteristic of aluminium in octahedral coordination and one sharp signal at delta = 69 ppm corresponding to tetrahedrally coordinated aluminium. Heterogeneous catalytic reduction of p-nitrophenol using CuAl(2)O(4) was followed by UV/visible spectroscopy. CuAl(2)O(4) from the present procedure proved to be an effective catalyst for the reduction of p-nitrophenol.

Photooxidation of water by NiTiO3 deposited from single source precursor [Ni2Ti2(OEt)2(micro-OEt)6(acac)4] by AACVD

A single-source heterobimetallic complex Ni2Ti2(OEt)2(mu-OEt)6(acac)4 (1) (acac=2,4-pentanedionate), having a low decomposition temperature and sufficient solubility in organic solvents, was synthesized by simple chemical techniques in high yield and analyzed by melting point, FTIR, single crystal X-ray analysis and thermal analysis. The TGA analysis proved that complex (1) underwent facile thermal decomposition at 500 degrees C to give NiTiO3 residue. In-house designed aerosol assisted chemical vapor deposition equipment was used to deposit high quality thin films of NiTiO3 on a SnO2 coated conducting glass substrate at 500 degrees C. An XRD analysis of the thin films proved the formation of crystalline NiTiO3 with average grain size 42 nm. Scanning electron microscopic studies (SEM) show that the thin films consist of flat, plate-like nanoparticles. The current-potential characteristics recorded under AM1.5 illumination indicate that NiTiO3 thin films are anodic and the photocurrent density at 1.23 V vs RHE (Reversible Hydrogen Electrode) is about 40 microA cm(-2).