8 research outputs found
Strong Cytotoxicity of Organometallic Platinum Complexes with Alkynyl Ligands
The synthesis, spectroscopy, structures,
and chemical reactivity
of the organometallic complexes [(COD)ÂPtÂ(Cî—¼CR)<sub>2</sub>]
and [(COD)ÂPtÂ(Cî—¼CR)Â(R′)] (COD = 1,5-cyclooctadiene, R
= Ph, (Me)ÂPh (2Me, 3Me, or 4Me), (NO<sub>2</sub>)ÂPh (2NO<sub>2</sub>, 3NO<sub>2</sub>, or 4NO<sub>2</sub>), (4F)ÂPh, (4OMe)ÂPh, 2Py (2-pyridyl);
R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl),
NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) has been explored.
The crystal structures reveal square-planar surroundings of the Pt
atoms with short Pt–CÂ(alkynyl) bonds (<2 Ã…) and almost
perpendicular orientation of the CC–aryl group to the
Pt coordination plane. Nonattractive π–π stacking
and C–H···F intermolecular interactions were
observed in the crystal structures. Multinuclear (<sup>1</sup>H, <sup>13</sup>C, <sup>195</sup>Pt, and <sup>19</sup>F) NMR spectroscopy
reveals structures in solution and Pt–ligand bond strength.
The thermal stability in organic solvents, the electrochemical stability,
and the reactivity of the complexes in organic or aquatic (water-containing)
solution toward the physiologically relevant species glutathione,
chloride, and protons was tested, revealing remarkable stability or
inertness of the complexes. Cytotoxicity experiments in HT-29 colon
carcinoma and MCF-7 breast adenocarcinoma cell lines revealed highly
promising activities for selected platinum alkynyl COD complexes
Interdependence of Structure, Morphology, and Phase Transitions in CVD Grown VO<sub>2</sub> and V<sub>2</sub>O<sub>3</sub> Nanostructures
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 [VÂ(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 [VÂ(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 °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
°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 °C (700 °C) and
65 °C (800 °C), much lower than the transition temperature
observed in single crystal material (68 °C). Precursors were
characterized in the solid state (XRD) and solution state (temperature
dependent EPR, NMR) to reveal an association–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
Strong Cytotoxicity of Organometallic Platinum Complexes with Alkynyl Ligands
The synthesis, spectroscopy, structures,
and chemical reactivity
of the organometallic complexes [(COD)ÂPtÂ(Cî—¼CR)<sub>2</sub>]
and [(COD)ÂPtÂ(Cî—¼CR)Â(R′)] (COD = 1,5-cyclooctadiene, R
= Ph, (Me)ÂPh (2Me, 3Me, or 4Me), (NO<sub>2</sub>)ÂPh (2NO<sub>2</sub>, 3NO<sub>2</sub>, or 4NO<sub>2</sub>), (4F)ÂPh, (4OMe)ÂPh, 2Py (2-pyridyl);
R′ = Me (methyl), Neop (neopentyl = 2,2-dimethyl-1-methyl),
NeoSi (neosilyl = trimethylsilylmethyl), Bz (benzyl)) has been explored.
The crystal structures reveal square-planar surroundings of the Pt
atoms with short Pt–CÂ(alkynyl) bonds (<2 Ã…) and almost
perpendicular orientation of the CC–aryl group to the
Pt coordination plane. Nonattractive π–π stacking
and C–H···F intermolecular interactions were
observed in the crystal structures. Multinuclear (<sup>1</sup>H, <sup>13</sup>C, <sup>195</sup>Pt, and <sup>19</sup>F) NMR spectroscopy
reveals structures in solution and Pt–ligand bond strength.
The thermal stability in organic solvents, the electrochemical stability,
and the reactivity of the complexes in organic or aquatic (water-containing)
solution toward the physiologically relevant species glutathione,
chloride, and protons was tested, revealing remarkable stability or
inertness of the complexes. Cytotoxicity experiments in HT-29 colon
carcinoma and MCF-7 breast adenocarcinoma cell lines revealed highly
promising activities for selected platinum alkynyl COD complexes
Linear Bis(perfluoroalkyl) Complexes of Nickel Bipyridine
Three new complexes were prepared: [(dtbpy)ÂNiÂ(CF<sub>3</sub>)<sub>2</sub>] (<b>1</b>), [(dtbpy)ÂNiÂ(CF<sub>2</sub>CF<sub>3</sub>)<sub>2</sub>] (<b>2</b>), and [(dtbpy)ÂNiÂ(CH<sub>3</sub>)<sub>2</sub>] (<b>3</b>) (dtbpy = 4,4′-di-<i>tert</i>-butyl-2,2′-bipyridine). Remarkable differences
in the structure,
electronics, reactivity, and absorption of visible light for the alkyl
versus perfluoroalkyl complexes were observed and are detailed in
this report
Nitrogen–Nitrogen Bond Formation via a Substrate-Bound Anion at a Mononuclear Nickel Platform
The
nickel-C<sub>4</sub>F<sub>8</sub> fragment coordinates an aminoaryl
N–H ketimine to form a stable complex, which upon treatment
with base and oxidant leads to an N–N bond-forming reaction
and the release of indazole product. A key and previously unidentified
intermediate in the formation of the indazole was a diimine complex
of nickel bearing significant charge on the aryl ring that initially
contained the amine substituent. The C<sub>4</sub>F<sub>8</sub> coligand
was key for the redox transformation and for stabilization of the
intermediate for characterization
CdS Nanoparticles Fabricated from the Single-Source Precursor [Cd{Et<sub>2</sub>NC(S)NP(S)(O<i>i</i>Pr)<sub>2</sub>}<sub>2</sub>]: In Depth Experimental and Theoretical Studies
Reaction
of the diethylammonium salt of <i>N</i>-thiophosphorylated
thioureate [Et<sub>2</sub>NCÂ(S)ÂNPÂ(S)Â(O<i>i</i>Pr)<sub>2</sub>]<sup>−</sup> (<b>L</b><sup><b>–</b></sup>) with CdCl<sub>2</sub> in aqueous ethanol leads to the complex <b>[CdL</b><sub><b>2</b></sub><b>]</b>. The compound
crystallizes in the triclinic space group <i>P</i>1Ì…
with <i>Z</i> = 2 and the metal cation is found in a tetrahedral <i>S</i><sub>2</sub><i>S</i>′<sub>2</sub> coordination
environment formed by the C–S and P–S sulfur atoms.
The Hirshfeld surface analysis showed that the structure of <b>[CdL</b><sub><b>2</b></sub><b>]</b> is dominated by
H···H, S···H, and O···H
contacts. According to charge and energy decomposition scheme ETS-NOCV,
topological noncovalent index (NCI) and quantum theory of atoms in
molecules (QTAIM) calculations, both inter- and intramolecular noncovalent
C–H···S and C–H···H–C
interactions are the main factors that stabilize <b>[CdL</b><sub><b>2</b></sub><b>]</b>. Calculated NMR data, based
on the GIAO approach, are in very good agreement with experimental
data. The complex <b>[CdL</b><sub><b>2</b></sub><b>]</b> is an efficient single-source precursor for the formation
of TOPO-capped CdS nanoparticles of about 5 nm diameter with wurtzite
structure (TOPO = tri-<i>n</i>-octylphosphine oxide). Their
growth was monitored over a period of time by means of UV–vis
spectroscopy. From ETS-NOCV modeling, the TOPO molecules were found
to strongly adhere to the CdS nanoparticles through dative-covalent
Cd–O bonds as well as through secondary noncovalent C–H···Cd
and C–H···S interactions. The characteristic
band edge luminescence was observed in the emission spectra of all
samples. The TEM microscopy showed well-dispersed spherical CdS nanoparticles;
the composition was supported by EDX
Unsymmetrical <i>N</i>‑Aryl-1-(pyridin-2-yl)methanimine Ligands in Organonickel(II) Complexes: More Than a Blend of 2,2′-Bipyridine and <i>N</i>,<i>N</i>‑Diaryl-α-diimines?
The
new organonickel complexes [(R-PyMA)ÂNiÂ(Mes)ÂX] [R-PyMA = <i>N</i>-aryl-1-(pyridin-2-yl)Âmethanimine; aryl = phenyl, 2,6-Me<sub>2</sub>-, 3,5-Me<sub>2</sub>-, 2,4,6-Me<sub>3</sub>-, 2,6-<sup><i>i</i></sup>Pr<sub>2</sub>-, 3,5-(OMe)<sub>2</sub>-, 2-NO<sub>2</sub>-4-Me-,
4-NO<sub>2</sub>-, 2-CF<sub>3</sub>-, and 2-CF<sub>3</sub>-6-F-phenyl;
Mes = 2,4,6-trimethylphenyl; X = F, Cl, Br, or I] were obtained as
approximate 1/1 cis and trans isomeric mixtures or pure cis isomers
depending on the PyMA ligand and X. The [(R-PyMA)ÂNiÂ(Mes)ÂX] complexes
with X = Br or Cl were directly synthesized from the precursors <i>trans</i>-[(PPh<sub>3</sub>)<sub>2</sub>NiÂ(Mes)ÂX], while [(PyMA)ÂNiÂ(Mes)ÂX]
derivatives with X = F or I were obtained from [(PyMA)ÂNiÂ(Mes)ÂBr] through
X exchange reactions. Although density functional theory (DFT) calculations
show a preference for the sterically favored cis isomers, both isomers
could be observed in many cases; in three cases, even single crystals
for X-ray diffraction could be obtained for the trans isomers. Possible
intermediates for the isomerization were investigated by DFT calculations.
All complexes were studied by multiple spectroscopic means, electrochemistry,
and spectroelectrochemistry (for the reduction processes). The long-wavelength
metal-to-ligand charge-transfer (MLCT) absorptions vary markedly with
the R substituent of the ligand and the cathodic electrochemical potentials
to a far smaller degree. Both are almost invariable upon variation
of X. All of this is in line with Ni-based and π*-based lowest
unoccupied molecular orbitals (LUMOs). In line with the unsymmetric
character of the N<sub>Py</sub>^N<sub>methanimine</sub> ligand, electrochemistry
and MLCT transitions seem to not correspond to the same type of π*
LUMO, making these PyMA ligands more interesting than the symmetric
heteroaromatic polypyridine ligands such as 2,2′-bipyridine
(bpy; N<sub>Py</sub>^N<sub>Py</sub>) and <i>N</i>,<i>N</i>-diaryl-substituted aliphatic α-diimines (N<sub>methanimine</sub>^N<sub>methanimine</sub>) such as the diaza-1,3-butadienes (DAB).
First attempts to use these complexes in Negishi-type cross-coupling
reactions were successful
A Five-Coordinate Nickel(II) Fluoroalkyl Complex as a Precursor to a Spectroscopically Detectable Ni(III) Species
Mechanistic proposals for nickel-catalyzed
coupling reactions often
invoke five-coordinate alkyl- or aryl-bound NiÂ(II) and/or high-valent
nickelÂ(III) species, but because of their reactive nature, they have
been difficult to study and fingerprint. In this work, we invoked
the stabilizing properties of fluoroalkyl ligands to access such nickel
species bearing ligands that are commonplace in organic coupling reactions.
We show that five-coordinate NiÂ(II) complexes containing nickel–carbon
bonds can readily be prepared given the appropriate precursor, and
we also present evidence for the formation of NiÂ(III) species upon
chemical and electrochemical oxidation of the five-coordinate complexes