7 research outputs found

    Octakis(<i>tert</i>-butoxo)dicerium(IV) [Ce<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>8</sub>]: Synthesis, Characterization, Decomposition, and Reactivity

    No full text
    An advanced synthesis for the homometallic derivative [Ce<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>8</sub>] (<b>1</b>) starting from [CeĀ­(O<sup><i>t</i></sup>Bu)<sub>2</sub>{NĀ­(SiMe<sub>3</sub>)<sub>2</sub>}<sub>2</sub>] was developed. Structural characterization of a ceriumĀ­(IV) complex and its decomposition products confirmed the coexistence of both ether elimination and Ceā€“O bond cleavage processes, which lead to the formation of [Ce<sub>3</sub>OĀ­(O<sup><i>t</i></sup>Bu)<sub>10</sub>] and [Ce<sub>3</sub>(O<sup><i>t</i></sup>Bu)<sub>11</sub>] (<b>2</b>) derivatives, respectively. Variable-temperature NMR spectroscopy under strict exclusion of moisture enabled insight into the decomposition processes in noncoordinating solvents and at elevated temperature. In addition, structural analysis of the heterovalent <b>2</b> and of two new complexes of the general formula [Ce<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>8</sub>(L)] [L = HO<sup><i>t</i></sup>Bu (<b>3</b>), OCPh<sub>2</sub> (<b>4</b>)] is described

    Heterobi- and Trimetallic Cerium(IV) <i>tert</i>-Butoxides with Monoā€‘, Diā€‘, and Trivalent Metals (<i>M</i> = K(I), Ge(II), Sn(II), Pb(II), Al(III), Fe(III))

    No full text
    The reaction of <i>C</i>erium <i>A</i>mmonium <i>N</i>itrate (CAN) with varying amounts of KO<sup><i>t</i></sup>Bu produced homometallic CeĀ­(O<sup><i>t</i></sup>Bu)<sub>4</sub>(NC<sub>5</sub>H<sub>5</sub>)<sub>2</sub> (<b>1</b>) and the heterometallic derivative KCe<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>10</sub> (<b>3</b>) characterized by X-ray diffraction and NMR spectroscopy. The oxo-alkoxide cluster Ce<sub>3</sub>OĀ­(O<sup><i>t</i></sup>Bu)<sub>9</sub> (<b>2</b>) was obtained from a solution of ceriumĀ­(IV) tetrakisĀ­(<i>tert</i>-butoxide) in <i>n</i>-heptane under stringent precautions to avoid any adventitious hydrolysis. Lewis acid-base reactions of in situ generated CeĀ­(O<sup><i>t</i></sup>Bu)<sub>4</sub>(THF)<sub>2</sub> (THF = tetrahydrofuran) with bi- and trivalent metal alkoxides [<i>M</i>(O<sup><i>t</i></sup>Bu)<sub><i>x</i></sub>]<sub><i>n</i></sub> (<i>M</i> = Ge, Sn; <i>x</i> = 2; <i>n</i> = 2; <i>M</i> = Pb, <i>x</i> = 2; <i>n</i> = 3; <i>M</i> = Al, Fe; <i>x</i> = 3; <i>n</i> = 2) resulted in volatile products of the general formula <i>M</i>CeĀ­(O<sup><i>t</i></sup>Bu)<sub>4+<i>x</i></sub> (<i>M</i> = Al (<b>4</b>), Fe (<b>5</b>); <i>x</i> = 3; <i>M</i> = Ge (<b>8</b>), Sn (<b>9</b>), Pb (<b>10</b>); <i>x</i> = 2) in high yields. By dissolving <b>4</b> and <b>5</b> in pyridine the solvent adducts <i>M</i>CeĀ­(O<sup><i>t</i></sup>Bu)<sub>7</sub>(NC<sub>5</sub>H<sub>5</sub>) (<i>M</i> = Al (<b>6</b>), Fe (<b>7</b>)) were formed, whereas <b>8</b> and <b>9</b> reacted with MoĀ­(CO)<sub>6</sub> in boiling toluene to yield the termetallic complexes (CO)<sub>5</sub>Mo<i>M</i>(Ī¼<sub>2</sub>-O<sup><i>t</i></sup>Bu)<sub>3</sub>CeĀ­(O<sup><i>t</i></sup>Bu)<sub>3</sub> (<i>M</i> = Ge (<b>11</b>), Sn (<b>12</b>)). The new compounds were characterized by comprehensive spectral studies, mass spectroscopy, and single crystal X-ray diffraction analysis

    Heterobi- and Trimetallic Cerium(IV) <i>tert</i>-Butoxides with Monoā€‘, Diā€‘, and Trivalent Metals (<i>M</i> = K(I), Ge(II), Sn(II), Pb(II), Al(III), Fe(III))

    No full text
    The reaction of <i>C</i>erium <i>A</i>mmonium <i>N</i>itrate (CAN) with varying amounts of KO<sup><i>t</i></sup>Bu produced homometallic CeĀ­(O<sup><i>t</i></sup>Bu)<sub>4</sub>(NC<sub>5</sub>H<sub>5</sub>)<sub>2</sub> (<b>1</b>) and the heterometallic derivative KCe<sub>2</sub>(O<sup><i>t</i></sup>Bu)<sub>10</sub> (<b>3</b>) characterized by X-ray diffraction and NMR spectroscopy. The oxo-alkoxide cluster Ce<sub>3</sub>OĀ­(O<sup><i>t</i></sup>Bu)<sub>9</sub> (<b>2</b>) was obtained from a solution of ceriumĀ­(IV) tetrakisĀ­(<i>tert</i>-butoxide) in <i>n</i>-heptane under stringent precautions to avoid any adventitious hydrolysis. Lewis acid-base reactions of in situ generated CeĀ­(O<sup><i>t</i></sup>Bu)<sub>4</sub>(THF)<sub>2</sub> (THF = tetrahydrofuran) with bi- and trivalent metal alkoxides [<i>M</i>(O<sup><i>t</i></sup>Bu)<sub><i>x</i></sub>]<sub><i>n</i></sub> (<i>M</i> = Ge, Sn; <i>x</i> = 2; <i>n</i> = 2; <i>M</i> = Pb, <i>x</i> = 2; <i>n</i> = 3; <i>M</i> = Al, Fe; <i>x</i> = 3; <i>n</i> = 2) resulted in volatile products of the general formula <i>M</i>CeĀ­(O<sup><i>t</i></sup>Bu)<sub>4+<i>x</i></sub> (<i>M</i> = Al (<b>4</b>), Fe (<b>5</b>); <i>x</i> = 3; <i>M</i> = Ge (<b>8</b>), Sn (<b>9</b>), Pb (<b>10</b>); <i>x</i> = 2) in high yields. By dissolving <b>4</b> and <b>5</b> in pyridine the solvent adducts <i>M</i>CeĀ­(O<sup><i>t</i></sup>Bu)<sub>7</sub>(NC<sub>5</sub>H<sub>5</sub>) (<i>M</i> = Al (<b>6</b>), Fe (<b>7</b>)) were formed, whereas <b>8</b> and <b>9</b> reacted with MoĀ­(CO)<sub>6</sub> in boiling toluene to yield the termetallic complexes (CO)<sub>5</sub>Mo<i>M</i>(Ī¼<sub>2</sub>-O<sup><i>t</i></sup>Bu)<sub>3</sub>CeĀ­(O<sup><i>t</i></sup>Bu)<sub>3</sub> (<i>M</i> = Ge (<b>11</b>), Sn (<b>12</b>)). The new compounds were characterized by comprehensive spectral studies, mass spectroscopy, and single crystal X-ray diffraction analysis

    Single-Source Precursors for Alloyed Goldā€“Silver Nanocrystals - A Molecular Metallurgy Approach

    No full text
    Multiple silverĀ­(I)-auratesĀ­(I) have been prepared by salt metathesis reactions that act as efficient single-source precursors to colloidal gold silver alloys with the highest possible atom economy in the chemical synthesis of nanostructures. The CF<sub>3</sub> group present on the Au cation acts as an in situ reducing agent and can be converted into CO ligands by simple hydrolysis. This ligand-mediated activation and subsequent decomposition of metalā€“organic precursors impose a molecular control over the nucleation process, producing homogeneously alloyed (Agā€“Au) nanoparticles with an atomic Au:Ag ratio of 1:1. The concept also works for the Auā€“Cu system and acts as a pointer to replace Au (Ag) with less expensive (Cu) metals

    Interdependence of Structure, Morphology, and Phase Transitions in CVD Grown VO<sub>2</sub> and V<sub>2</sub>O<sub>3</sub> Nanostructures

    No full text
    Phase selective chemical vapor deposition of nanostructured vanadium dioxide (VO<sub>2</sub>) and sesquioxide (V<sub>2</sub>O<sub>3</sub>) was achieved by deploying [VĀ­(O<i>R</i>)<sub>4</sub>]<sub><i>n</i></sub> (<i>R</i> = <sup><i>t</i></sup>Bu, <i>n</i> = 1 (<b>1</b>), <i>R</i> = Et, <i>n</i> = 3 (<b>2</b>), <i>R</i> = Me, <i>n</i> = 4 (<b>3</b>)). Use of [VĀ­(O<sup><i>t</i></sup>Bu)<sub>4</sub>] (<b>1</b>) produced thin films of monoclinic VO<sub>2</sub> (M1) at 700 and 800 Ā°C consisting of anisotropic nanostructures with high crystallinity and small hysteresis in the metal-to-semiconductor transition (MST). Film morphologies manifested strong dependence on growth temperatures and exhibited pronounced texturing effects at high temperatures (>700 Ā°C). The microstructure of the films was found to significantly affect the MST behavior of VO<sub>2</sub> films. DTA measurements of VO<sub>2</sub> films showed MST at 63 Ā°C (700 Ā°C) and 65 Ā°C (800 Ā°C), much lower than the transition temperature observed in single crystal material (68 Ā°C). Precursors were characterized in the solid state (XRD) and solution state (temperature dependent EPR, NMR) to reveal an associationā€“dissociation equilibrium in solution (complexes <b>2</b> and <b>3</b>), involving monomeric, dimeric, and oligomeric species. Use of <b>2</b> and <b>3</b> as single precursors produced thin films of crystalline V<sub>2</sub>O<sub>3</sub> consisting of nanosheets (5 nm) with a flower-like morphology

    Single-Source Precursors for Alloyed Goldā€“Silver Nanocrystals - A Molecular Metallurgy Approach

    No full text
    Multiple silverĀ­(I)-auratesĀ­(I) have been prepared by salt metathesis reactions that act as efficient single-source precursors to colloidal gold silver alloys with the highest possible atom economy in the chemical synthesis of nanostructures. The CF<sub>3</sub> group present on the Au cation acts as an in situ reducing agent and can be converted into CO ligands by simple hydrolysis. This ligand-mediated activation and subsequent decomposition of metalā€“organic precursors impose a molecular control over the nucleation process, producing homogeneously alloyed (Agā€“Au) nanoparticles with an atomic Au:Ag ratio of 1:1. The concept also works for the Auā€“Cu system and acts as a pointer to replace Au (Ag) with less expensive (Cu) metals

    Air-Stable Gadolinium Precursors for the Facile Microwave-Assisted Synthesis of Gd<sub>2</sub>O<sub>3</sub> Nanocontrast Agents for Magnetic Resonance Imaging

    No full text
    Using metal organic precursors in materials synthesis remains a challenge due to their high moisture susceptibility. In this work, we describe a facile methodology for the synthesis of Gd<sub>2</sub>O<sub>3</sub>-based contrast agents from two new gadolinium-based complexes. [GdĀ­(PyTFP)<sub>4</sub>] (PyH) <b>1</b> (PyTFP = C<sub>8</sub>H<sub>5</sub>NOF<sub>3</sub>, Py = C<sub>5</sub>H<sub>5</sub>N) and [GdĀ­(DMOTFP)<sub>3</sub>Py] <b>2</b> (DMOTFP = C<sub>8</sub>H<sub>7</sub>NO<sub>2</sub>F<sub>3</sub>) were synthesized via a classical ligand exchange reaction of [GdĀ­{NĀ­(SiMe<sub>3</sub>)<sub>2</sub>}<sub>3</sub>] under inert conditions. As a result, X-ray diffraction analysis revealed a distorted square antiprismatic coordination and an augmented triangular prismatic arrangement of ligands around gadolinium atoms in <b>1</b> and <b>2</b>, respectively. It also showed that <b>1</b> is an anionic complex of formula [GdĀ­(PyTFP)<sub>4</sub>]Ā­(PyH), while a neutral tris-compound, [GdĀ­(DMOTFP)<sub>3</sub>Py], was obtained as a pyridine adduct in <b>2</b>. Fast and reproducible microwave-assisted decomposition of <b>1</b> and <b>2</b> provided homogeneous GdĀ­(OH)<sub>3</sub> nanorods at mild temperature without using any surfactant or capping reagent. As-synthesized nanorods were easily transformed into a cubic phase of Gd<sub>2</sub>O<sub>3</sub> nanoparticles by thermal treatment under ambient conditions. The magnetic measurement showed the typical paramagnetic behavior of the Gd<sub>2</sub>O<sub>3</sub> nanoparticles (NPs). The cytotoxicity profile demonstrates the biocompatibility and negligible toxicity of the as-synthesized nanoprobes. The suggested approach provides a new class of gadolinium-based precursors which allows facile synthesis of highly crystalline Gd<sub>2</sub>O<sub>3</sub> NPs
    corecore