10 research outputs found
Relieving Steric Strain at Octahedral Platinum(IV): Isomerization and Reductive Coupling of Alkyl and Aryl Chlorides
Oxidation of monocyclometalated platinum(II) complexes
results
in octahedral platinum(IV) complexes. Depending on the substitution,
two different reactions occur: either a simple isomerization, resulting
in the exchange of ligand positions, or a reductive coupling of aryl
chloride. With a doubly cyclometalated complex, stability of the oxidized
form is dependent on isomeric form: whereas the <i>trans</i> isomer is robust, being manipulable in air at room temperature,
the <i>cis</i> isomer decomposes at −20 °C and
above. Reductive coupling at this <i>cis</i> isomer is 100%
selective for alkyl chloride over aryl chloride and is suggested to
be a concerted process
Relieving Steric Strain at Octahedral Platinum(IV): Isomerization and Reductive Coupling of Alkyl and Aryl Chlorides
Oxidation of monocyclometalated platinum(II) complexes
results
in octahedral platinum(IV) complexes. Depending on the substitution,
two different reactions occur: either a simple isomerization, resulting
in the exchange of ligand positions, or a reductive coupling of aryl
chloride. With a doubly cyclometalated complex, stability of the oxidized
form is dependent on isomeric form: whereas the <i>trans</i> isomer is robust, being manipulable in air at room temperature,
the <i>cis</i> isomer decomposes at −20 °C and
above. Reductive coupling at this <i>cis</i> isomer is 100%
selective for alkyl chloride over aryl chloride and is suggested to
be a concerted process
Oxidative Addition of MeI to a Rollover Complex of Platinum(II): Isolation of the Kinetic Product
A pair of new Pt(II)/Pt(IV) 2,2′-bipyridine
cyclometalated
rollover complexes have been synthesized and characterized. [Pt(bpy-H)(CH<sub>3</sub>)(PMe<sub>3</sub>)] (<b>1</b>), where bpy-H = κ<sup>2</sup><i>N</i>,<i>C</i>-2,2′-bipyridine,
was
obtained from the electron-rich precursor <i>cis</i>-[Pt(CH<sub>3</sub>)<sub>2</sub>(DMSO)<sub>2</sub>] with a one-pot, two step
synthesis; its reactivity has been tested with CH<sub>3</sub>I, giving
the corresponding Pt(IV) complex <i>cis</i>-[Pt(bpy-H)(CH<sub>3</sub>)<sub>2</sub>(I)(PMe<sub>3</sub>)] (<b>2</b>), which
was fully characterized. Crystals suitable for X-ray analysis were
obtained and allowed the determination of the structure of isomer <b>2A</b> which is the product of the <i>trans</i> addition
of CH<sub>3</sub>I, usually thought of as the <i>kinetic</i> product
Oxidative Addition of MeI to a Rollover Complex of Platinum(II): Isolation of the Kinetic Product
A pair of new Pt(II)/Pt(IV) 2,2′-bipyridine
cyclometalated
rollover complexes have been synthesized and characterized. [Pt(bpy-H)(CH<sub>3</sub>)(PMe<sub>3</sub>)] (<b>1</b>), where bpy-H = κ<sup>2</sup><i>N</i>,<i>C</i>-2,2′-bipyridine,
was
obtained from the electron-rich precursor <i>cis</i>-[Pt(CH<sub>3</sub>)<sub>2</sub>(DMSO)<sub>2</sub>] with a one-pot, two step
synthesis; its reactivity has been tested with CH<sub>3</sub>I, giving
the corresponding Pt(IV) complex <i>cis</i>-[Pt(bpy-H)(CH<sub>3</sub>)<sub>2</sub>(I)(PMe<sub>3</sub>)] (<b>2</b>), which
was fully characterized. Crystals suitable for X-ray analysis were
obtained and allowed the determination of the structure of isomer <b>2A</b> which is the product of the <i>trans</i> addition
of CH<sub>3</sub>I, usually thought of as the <i>kinetic</i> product
Selective Imaging of Discrete Polyoxometalate Ions on Graphene Oxide under Variable Voltage Conditions
Monosubstituted lacunary Keggin [CoSiW<sub>11</sub>O<sub>39</sub>]<sup>6–</sup> ions on graphene oxide
(GO) were used in a
comparative imaging study using aberration corrected transmission
electron microscopy at two different acceleration voltages, 80 and
200 kV. By performing a set of static and dynamical studies, together
with image simulations, we show how the use of lower voltages results
in better stability and resolution of the underlying GO support while
the use of higher voltages permits better resolution of the individual
tungsten atoms and leads to less kinetic motion of the cluster, thus
leading to a more accurate identification of cluster orientation and
better stability under dynamical imaging conditions. Applying different
voltages also influences the visibility of both GO and the lighter
Co at lower or higher voltages, respectively
Acclimatization study of <i>Tagetes lucida</i> L. in Egypt and the chemical characterization of its essential oils
<p>Seeds of <i>Tagetes lucida</i> were imported to Egypt from Canada and propagated under greenhouse conditions in peat moss media. Soil was sandy in texture and the irrigation system was dripping irrigation. The growth parameters were determined at five successive plant ages, fresh and dry weights of herb were determined at three successive plant ages. The yield of aerial parts after 175 days, was about 7.5 Mg/ha. The essential oil (EO) was extracted by hydro-distillation for three hours with a yield of about 0.5% (w/v). The EO of each sample was subjected to gas-chromatography/mass spectrometry analyses to study the chemical composition. The main component of the EO was identified as methyl chavicol which matched over 90% of the whole composition. Chlorophyll a and carotenes increased with increasing plant age in both sites and seasons. Flavonoids decreased with the development of plant age, while the opposite was true with coumarines content.</p
Resolving the Nanoscale Morphology and Crystallographic Structure of Molecular Thin Films: F<sub>16</sub>CuPc on Graphene Oxide
Electron microscopy and diffraction are used to examine
the nanoscale structure and molecular orientation in molecular films
down to nominally monolayer thickness. The films studied consist of
the planar n-type molecular semiconductor copper hexadecafluorophthalocyanine
(F<sub>16</sub>CuPc) directly deposited onto graphene oxide (GO) membranes
by organic molecular beam deposition. The graphene oxide support crucially
provides the strength and low background required to analyze the crystal
structure and morphology of even nominally monolayer thick films and
is of relevance for molecular electronic applications. The crystal
structure of the F<sub>16</sub>CuPc polymorph is solved by X-ray diffraction
of single crystals and used to analyze the electron diffraction patterns
from the thin-films, revealing that the F<sub>16</sub>CuPc molecules
assemble with their molecular plane oriented perpendicular to the
GO. There is no evidence for changes in the unit cell with film thickness,
although the thinnest films show the greatest disorder in molecular
packing. Direct deposition of molecular materials on low contrast
and relevant substrates combined with electron and scanning probe
microscopy is thus shown to be a powerful technique for elucidating
structure in nanostructured organic thin films
Heterobimetallic Rollover Derivatives
Heterobimetallic complexes with metal centers connected
by a small
delocalized ligand constitute an interesting class of compounds. Here
we report that starting from the mononuclear platinum(II) rollover
complexes [Pt(bipy-H)(L)Cl] (bipy-H = 2,2′-bipyridine C(3′)-N
cyclometalated, L= DMSO, PPh<sub>3</sub>) a second rollover cyclometalation
may produce a series of Pt(II)/Pd(II) heterobimetallic complexes where
the two metals are linked by the planar, highly delocalized, doubly
deprotonated 2,2′-bipyridine
Heterobimetallic Rollover Derivatives
Heterobimetallic complexes with metal centers connected
by a small
delocalized ligand constitute an interesting class of compounds. Here
we report that starting from the mononuclear platinum(II) rollover
complexes [Pt(bipy-H)(L)Cl] (bipy-H = 2,2′-bipyridine C(3′)-N
cyclometalated, L= DMSO, PPh<sub>3</sub>) a second rollover cyclometalation
may produce a series of Pt(II)/Pd(II) heterobimetallic complexes where
the two metals are linked by the planar, highly delocalized, doubly
deprotonated 2,2′-bipyridine
Deoxygenation of Graphene Oxide: Reduction or Cleaning?
We show that the two-component model
of graphene oxide (GO), that
is, composed of highly oxidized carbonaceous debris complexed to oxygen
functionalized graphene sheets, is a generic feature of the synthesis
of GO, independent of oxidant or protocol used. The debris present,
roughly one-third by mass, can be removed by a base wash. A number
of techniques, including solid state NMR, demonstrate that the properties
of the base-washed material are independent of the base used and that
it contains similar functional groups to those present in the debris
but at a lower concentration. Removal of the oxidation debris cleans
the GO, revealing its true monolayer nature and in the process increases
the C/O ratio (i.e., a deoxygenation). By contrast, treating GO with
hydrazine both removes the debris and reduces (both deoxygenations)
the graphene sheets