33 research outputs found
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Synthesis, structural characterization, and luminescence properties of mono- and di-nuclear platinum(II) complexes containing 2-(2-pyridyl)benzimidazole
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Chelating and Bridging Roles of 2-(2-Pyridyl)benzimidazole and Bis(diphenylphosphino)acetylene in Stabilizing a Cyclic Tetranuclear Platinum(II) Complex.
The reaction of complex [Pt(Me)(DMSO)(pbz)], 1, (pbz = 2-(2-pyridyl)benzimidazolate) with [PtMe(Cl)(DMSO)2], B, followed by addition of bis(diphenylphosphino)acetylene (dppac), gave the novel tetranuclear platinum complex [Pt4Me4(μ-dppac)2(pbz)2Cl2], 2, bearing both the pbz and dppac ligands. In this structure, the pbz ligands are both chelating and bridging to stabilize the tetraplatinum framework. The tetranuclear Pt(II) complex was fully characterized by NMR spectroscopy, X-ray crystallography, and mass spectrometry, and its electronic structure was investigated and supported by DFT calculations
Functionalization and solubilization of inorganic nanostructures and carbon nanotubes by employing organosilicon and organotin reagents
Covalent functionalization of nanowires of TiO2, ZnO and Al2O3 has been carried out by employing the organosilicon reagents aminopropyltriethoxysilane and hexadecyltrimethoxysilane (HDTMS). The presence of the organosilane coating was confirmed by electron microscopy, energy dispersive X-ray analysis (EDXA) and IR spectroscopy. HDTMS-coated oxide nanowires give stable dispersions in CCl4 and toluene. Nanoparticles of these metal oxides as well as of CeO2 and Fe3O4 could be solubilized in non-polar solvents by functionalizing with HDTMS. Nanotubes and nanoparticles of BN could also be functionalized and solubilized with HDTMS. Organotin reagents have also been used to covalently functionalize oxide nanostructures and multi-walled carbon nanotubes, thereby producing stable dispersions in CCl4 and toluene. The organotin reagents used were dibutyldimethoxytin and trioctyltinchloride. Covalent functionalization of nanostructures using organosilane and organotin reagents provides a general method applicable to large class of inorganic materials as well as carbon nanotubes and is likely to be useful in practice
Substitution and Organohalide Oxidative Addition Reactions Involving a Dimethylplatinum(II) Complex in a Micelle Medium
Micellar
system of sodium dodecyl sulfate (SDS) in a mixture of water/ethanol
(1/1) is used as a new medium for stabilization of the platinum(II)
complex [PtMe<sub>2</sub>(bipy)], in which bipy = 2,2′-bipyridine,
knowing that the complex is unstable in water or ethanol in the absence
of SDS. Kinetic studies for oxidative addition reactions of complex
[PtMe<sub>2</sub>(bipy)] with methyl iodide, allyl bromide, or propargyl
bromide and also for substitution reactions of the chelate 2,2′-bipyridine
ligand in the complex [PtMe<sub>2</sub>(bipy)] by the P donor reagent
P(O-<sup>i</sup>Pr)<sub>3</sub>, L, to form the complex <i>cis</i>-[PtMe<sub>2</sub>L<sub>2</sub>], were successfully investigated
in the green and safe solvent micellar system of SDS by monitoring
the decay of the MLCT band in the UV–visible spectra
Enhanced Catalytic Performance and Tolerance to Carbon Monoxide Poisoning of CoO/PtPd/r‐GO Nanocomposite Thin Film for Methanol Fuel Cells
This study presents the facile synthesis of CoO/PtPd and CoO/PtPd/reducedgraphene
oxide (r-GO) nanocomposites, highlighting their significant role in
methanol fuel cells. To create a CoO/PtPd thin film at the toluene/water interface,
we employed NaBH4 to effectively reduce PtCl2(COD), PdCl2(COD), and
Co (acac)3 (COD = cis,cis-1,5- cyclooctadiene, acac = acetylacetonate). The
two nanocomposites were analyzed using XRD, FE-SEM, AFM, XPS, BET, and
TEM techniques. In the electrooxidation of methanol in the anodic part of fuel
cell, cobalt (II) oxide can serve as an oxygen source in the catalytic oxidation
of carbon monoxide (CO) or it can play a role in producing the HO-CoO intermediate
to facilitate the oxidation of CO-PtPd to carbon dioxide (CO2). This
reaction can help eliminate CO, which is a common poison for Pt-based catalysts
in methanol oxidation. Our research reveals significant improvements in
current densities and catalyst tolerance when using the CoO/PtPd/r-GO nanocomposite
thin film. The observed current density for CoO/PtPd/r-GO is
263.33 mA.cm2, surpassing the reported value of 30.00 mA.cm2 for PtPd/r-
GO. The jf/jb ratios, commonly used to evaluate catalyst tolerance, are approximately
2.80 for CoO/PtPd and 4.98 for CoO/PtPd/r-GO, in contrast to ratios
larger than 0.99 for ETEK Pt and 0.58 for other types of commercial
Pt/C. These findings indicate that the CoO/PtPd/r-GO thin film exhibits
enhanced catalytic performance and improved tolerance to CO poisoning. Furthermore,
the power output calculated for CoO/PtPd/r-GO is 104.5 mWcm2,
which is comparable to the reported value of 48.03 mWcm2 for commercial
Pt/C. These results demonstrate the potential of the CoO/PtPd/r-GO nanocomposite
thin film as a promising alternative to traditional catalyst materials in
methanol fuel cells
PtAu Thin Film as Anode Electrocatalyst in Methanol Fuel Cell
Expanding the application of methanol fuel cells in the energy economy is only feasible when a low-cost or highly COtolerant electrocatalyst replaces Pt catalysts to enhance the electrocatalytic properties of Pt. In this study, a PtAu thin film
was produced at the liquid-liquid interface through the simple reduction of [Pt(cod)Cl2] and [Au(PPh3)Cl] complexes. The resulting thin film was directly transferred onto a glassy carbon electrode (without the application of NafionTM) and used as an electrocatalyst in the methanol oxidation reaction. Experimental and theoretical results both confirmed that PtAu exhibits
lower CO poisoning compared to PtPd or Pt films. The high jf/jb ratio (where jf is the maximum current of the anodic peak in the forward route and jb is the maximum of peak current in the backward route), and theoretically calculated adsorption energies for PtAu thin film showed higher CO tolerance compared to Pt or PtPd thin film electrocatalysts
Luminescent mononuclear and dinuclear cycloplatinated (II) complexes comprising azide and phosphine ancillary ligands
A new series of cycloplatinated (II) complexes with general formulas of [Pt (bhq)(N-3)(P)] [bhq = deprotonated 7,8-benzo[h]quinoline, P = triphenyl phosphine (PPh3) and methyldiphenyl phosphine], [Pt (bhq)(PP)]N-3 [PP = 1,1-bis (diphenylphosphino)methane (dppm) and 1,2-bis (diphenylphosphino)ethane] and [Pt-2(bhq)(2)(mu-PP)(N-3)(2)] [PP = dppm and 1,2-bis (diphenylphosphino)acetylene] is reported in this investigation. A combination of azide (N-3(-)) and phosphine (monodentate and bidentate) was used as ancillary ligands to study their influences on the chromophoric cyclometalated ligand. All complexes were characterized by nuclear magnetic resonance spectroscopy. To confirm the presence of the N-3(-) ligand directly connected to the platinum center, complex [Pt (bhq)(N-3)(PPh3)] was further characterized by single-crystal X-ray crystallography. The photophysical properties of the new products were studied by UV-Vis spectroscopy in CH2Cl2 and photoluminescence spectroscopy in solid state (298 or 77 K) and in solution (77 K). Using density functional theory calculations, it was proved that, in addition to intraligand charge-transfer (ILCT) and metal-to-ligand charge-transfer (MLCT) transitions, the L ' LCT (L ' = N-3, L = CN) electronic transition has a remarkable contribution in low energy bands of the absorption spectra (for complexes [Pt (bhq)(N-3)(P)] and [Pt-2(bhq)(2)(mu-PP)(N-3)(2)]). It is indicative of the determining role of the N-3(-) ligand in electronic transitions of these complexes, specifically in the low energy region. In this regard, the photoluminescence studies indicated that the emissions in such complexes originate from a mixed (ILCT)-I-3/(MLCT)-M-3 (intramolecular) and also from aggregations (intermolecular)
Reactivity and Mechanism in the Oxidative Addition of Allylic Halides to a Dimethylplatinum(II) Complex
The complex [PtMe<sub>2</sub>(2,2′-bipyridine)], <b>1</b>, reacts with allyl chloride and allyl bromide, to give [PtXMe<sub>2</sub>(CH<sub>2</sub>CHCH<sub>2</sub>)(2,2′-bipyridine)], <b>2</b>, X = Cl; <b>3</b>, X = Br, with 2-methylallyl chloride
to give [PtClMe<sub>2</sub>(CH<sub>2</sub>CMeCH<sub>2</sub>)(2,2′-bipyridine)], <b>4</b>, and with crotyl chloride
(a mixture of <i>trans</i>- and <i>cis</i>-MeCHCHCH<sub>2</sub>Cl), to give a mixture of [PtClMe<sub>2</sub>(<i>trans-</i>CH<sub>2</sub>CHCHMe)(2,2′-bipyridine)], <b>5</b>, and [PtClMe<sub>2</sub>(<i>cis-</i>CH<sub>2</sub>CHCHMe)(2,2′-bipyridine)], <b>6</b>. The complexes are formed mostly by <i>trans</i> oxidative addition and, for the crotyl complexes, without allylic
rearrangement. Complex <b>1</b> reacts with CH<sub>2</sub>CHCHMeCl,
mostly with allylic rearrangement, to give complex <b>5</b>,
with complexes <b>6</b> and [PtClMe<sub>2</sub>(CHMeCHCH<sub>2</sub>)(2,2′-bipyridine)], <b>7</b>, as minor products.
The reactions of <b>1</b> with CH<sub>2</sub>CHCH<sub>2</sub>X (X = Cl or Br) and MeCHCHCH<sub>2</sub>Cl follow
second-order kinetics (first-order in both reagents), but <b>1</b> reacts with CH<sub>2</sub>CHCHMeCl by third-order kinetics
(first-order in <b>1</b>, second-order in CH<sub>2</sub>CHCHMeCl)
and with CH<sub>2</sub>CMeCH<sub>2</sub>Cl by a mixture of
second- and third-order kinetics. The second-order reactions are proposed
to occur by the S<sub>N</sub>2 mechanism, and potential mechanisms
of the third-order reactions are discussed
Recommended from our members
Chelating and Bridging Roles of 2-(2-Pyridyl)benzimidazole and Bis(diphenylphosphino)acetylene in Stabilizing a Cyclic Tetranuclear Platinum(II) Complex.
The reaction of complex [Pt(Me)(DMSO)(pbz)], 1, (pbz = 2-(2-pyridyl)benzimidazolate) with [PtMe(Cl)(DMSO)2], B, followed by addition of bis(diphenylphosphino)acetylene (dppac), gave the novel tetranuclear platinum complex [Pt4Me4(μ-dppac)2(pbz)2Cl2], 2, bearing both the pbz and dppac ligands. In this structure, the pbz ligands are both chelating and bridging to stabilize the tetraplatinum framework. The tetranuclear Pt(II) complex was fully characterized by NMR spectroscopy, X-ray crystallography, and mass spectrometry, and its electronic structure was investigated and supported by DFT calculations
Reactivity and Mechanism in the Oxidative Addition of Allylic Halides to a Dimethylplatinum(II) Complex
The complex [PtMe<sub>2</sub>(2,2′-bipyridine)], <b>1</b>, reacts with allyl chloride and allyl bromide, to give [PtXMe<sub>2</sub>(CH<sub>2</sub>CHCH<sub>2</sub>)(2,2′-bipyridine)], <b>2</b>, X = Cl; <b>3</b>, X = Br, with 2-methylallyl chloride
to give [PtClMe<sub>2</sub>(CH<sub>2</sub>CMeCH<sub>2</sub>)(2,2′-bipyridine)], <b>4</b>, and with crotyl chloride
(a mixture of <i>trans</i>- and <i>cis</i>-MeCHCHCH<sub>2</sub>Cl), to give a mixture of [PtClMe<sub>2</sub>(<i>trans-</i>CH<sub>2</sub>CHCHMe)(2,2′-bipyridine)], <b>5</b>, and [PtClMe<sub>2</sub>(<i>cis-</i>CH<sub>2</sub>CHCHMe)(2,2′-bipyridine)], <b>6</b>. The complexes are formed mostly by <i>trans</i> oxidative addition and, for the crotyl complexes, without allylic
rearrangement. Complex <b>1</b> reacts with CH<sub>2</sub>CHCHMeCl,
mostly with allylic rearrangement, to give complex <b>5</b>,
with complexes <b>6</b> and [PtClMe<sub>2</sub>(CHMeCHCH<sub>2</sub>)(2,2′-bipyridine)], <b>7</b>, as minor products.
The reactions of <b>1</b> with CH<sub>2</sub>CHCH<sub>2</sub>X (X = Cl or Br) and MeCHCHCH<sub>2</sub>Cl follow
second-order kinetics (first-order in both reagents), but <b>1</b> reacts with CH<sub>2</sub>CHCHMeCl by third-order kinetics
(first-order in <b>1</b>, second-order in CH<sub>2</sub>CHCHMeCl)
and with CH<sub>2</sub>CMeCH<sub>2</sub>Cl by a mixture of
second- and third-order kinetics. The second-order reactions are proposed
to occur by the S<sub>N</sub>2 mechanism, and potential mechanisms
of the third-order reactions are discussed