Funding was received from the European Research Council under the European Community&#39;s Seventh Framework Programme (FP7/2007-2013) / ERC Grant agreement no&#160;[239603]

<ol>
	<li>Preparation of the V (V) complex (Figure 2);18 conduct steps 1.1-1.4 in a glove-box; if a glove-box is not available, skip to the alternative steps 2 (2.1-2.6).
	<ol>
		<li>Dissolve 0.42 mmol of the ligands H2L in dry THF and add it to a stirring solution of equivalent amounts of VO(OiPr)3 in THF.</li>
		<li>Stir the reaction mixture at room temperature for 15 min, and remove the volatiles under vacuum.</li>
		<li>Add cold hexane and remove it under vacuum. A dark purple powder should be obtained in a quantitative yield.</li>
		<li>Weigh 8 mg of the obtained compound in an Eppendorf vial. Skip to step 3.</li>
	</ol>
	</li>
	<li>Prepare the V (V) complex using a Schlenk line.
	<ol>
		<li>Dissolve 0.42 mmol of the ligand H2L in dry THF in a dry Schlenk flask with a septum cap, attach to a Schlenk line and apply alternating vacuum/inert gas (N2 or Ar) environments; it is recommended to apply three such rounds and wait 2-5 min on the vacuum stages.</li>
		<li>Add dry THF via syringe through the septum cap.</li>
		<li>Add equivalent amounts of VO(OiPr)3 in a THF solution, which had been prepared similarly by hooking a proper dry Schlenk flask to the line, applying an inert environment&#160;and adding the reagents through a syringe from the vanadium solution to that of the ligand.</li>
		<li>Stir the reaction mixture at room temperature for 15 min&#160;and remove the volatiles under vacuum; if there is a concern of unstable products, perform Schlenk type distillation of the volatiles under inert atmosphere; use inert gas flow to attach the required glassware that had been predried.</li>
		<li>Add cold hexane and remove it under vacuum. A dark purple powder should be obtained in a quantitative yield.</li>
		<li>Weigh 8 mg of the obtained compound in an Eppendorf vial.</li>
	</ol>
	</li>
	<li>Preparation of the Ti (IV) complex (Figure 2);28 conduct steps 3.1-3.3 in a glove-box; if a glove-box is not available, adjust the alternative steps discussed for the vanadium analogue (step&#160;2) that employ a Schlenk line instead.
	<ol>
		<li>Dissolve 0.35 mmol of the ligand H2L in dry THF and add it to a stirring solution of equivalent amounts of Ti(OiPr)4 in THF.</li>
		<li>Stir the reaction mixture at room temperature for 2 hr. Remove the volatiles under vacuum to give a yellow product in a quantitative yield.</li>
		<li>Weigh 8 mg of the obtained compound in Eppendorf vial.</li>
	</ol>
	</li>
	<li>Preparation of HT-29 cells 96-well plate
	<ol>
		<li>Culture HT-29 cells in a 75 cm2 flask with RPMI-1640 medium that contains 1% penicillin/streptomycin antibiotics, 1% L-glutamine, and 10% fetal bovine serum (FBS), at 37 &#176;C with 5% CO2.</li>
		<li>Remove the medium when the HT-29 cells reach maximal confluency (90-100%, every 3-4 days without subculture). Wash with 1 ml of trypsin (0.25%)/EDTA (0.05%) solution and remove it.</li>
		<li>Add 1 ml of trypsin (0.25%)/EDTA (0.05%) solution and incubate for 5 min.</li>
		<li>Detach the HT-29 cells from the flask and add 10 ml of the medium to disable the trypsin activity. Transfer 5 ml of the cells mixture to a tube.</li>
		<li>Use pipette to transfer a few drops of the cells mixture into counter chamber. The counter chamber includes 5 x&#160;5 squares.</li>
		<li>Count the cells in 5 representative squares using a microscope: the 4 squares in the corners and the one that is in the middle.</li>
		<li>Calculate the estimated amount of cells present. Sum the cells in the 5 representative squares and divide by 20.</li>
		<li>Divide 0.6 by the result of step 4.7. The received number is the amount of cell mixture required per plate. This calculation refers to a plate that contains 0.6 x&#160;106 cells (9,000 cells per well).</li>
		<li>Use pipette to transfer the amount of cell mixture required per plate (as calculated in section 4.8) and add 13.2 ml of the medium (200 &#956;l per well &#215; 66 wells).</li>
		<li>Add the mixture to 96-well plate by 11-channel pipette (200 &#956;l per well, 6 lines, 66 wells in total). One well of each line should remain empty for blank control.</li>
		<li>Incubate the plate at 37 &#176;C with 5% CO2 for 24 hr to allow the cells to attach to the plate.</li>
	</ol>
	</li>
	<li>Insertion of the compounds
	<ol>
		<li>Add 200 &#956;l (or different amount according to the desired concentration range) of dry THF to 8 mg of each compound weighed as described in step 1.4 (or 2.6) or 3.3. Weigh 8 mg of the ligand H2L, too.</li>
		<li>Dilute each compound solution further by adding 60 &#956;l of THF in 9 different Eppendorf vials.</li>
		<li>Transfer with a pipette 60 &#956;l from the mixture in section 5.1 to the first Eppendorf vial, resuspend and transfer 60 &#956;l to the next vial, and so on until 10 different concentrations are obtained (including the parent mixture in section 5.1).</li>
		<li>Dilute 20 &#956;l of each concentration in THF with 180 &#956;l of medium.</li>
		<li>Prepare a control solution with THF only; 20 &#956;l of THF with 180 &#956;l of medium in each measurement.</li>
		<li>Add 10 &#956;l from the resulting solution (including the THF control), to each well that already contains 200 &#956;l of the aforementioned solution of cells in the medium to give final concentrations of the compound of up to 200 mg/L (the concentration range can be changed according to the compound activity).</li>
		<li>You may observe some precipitation at the highest concentration applied depending on the compound solubility.</li>
		<li>Repeat each measurement of the compound 3x (3 lines in the plate of the same compound); each line contains: cells treated with the compound in 10 different concentrations, 1 well containing cells treated with solvent only for control and 1 well without cells for blank control.</li>
		<li>Incubate the loaded plate for 3 days at 37 &#176;C in 5% CO2 atmosphere.</li>
	</ol>
	</li>
	<li>Cytotoxicity measurement using the MTT assay
	<ol>
		<li>Prepare the MTT solution by adding 1 g of MTT powder to a 200 ml solution of RPMI-1640 medium without phenol red. The stock solution can be divided to 15 ml tubes and stored in -20 &#176;C.</li>
		<li>Add 20 &#956;l of MTT solution to each well using 11-channel pipette (except to the blank control wells without the cells from step 4.10), and incubate the plate for additional 3 hr.</li>
		<li>Remove the medium solution from each well.</li>
		<li>Add 200 &#956;l of isopropanol to each well to dissolve formazan. Stir the plate for 0.5 hr until homogeneousness is reached.</li>
		<li>Measure the absorbance at 550 nm for 200 &#956;l of the aforementioned solution by a microplate reader spectrophotometer.</li>
		<li>Repeat each measurement (that includes 3 repetitions, see step 5.8) on 3 different days.</li>
		<li>Calculate the percentage of cell viability by deducting the blank control absorbance value from the measured value, dividing the result by the absorbance of the THF solvent control value and multiplying by 100%.</li>
		<li>Calculate IC50 values using GraphPad Prism software (or equivalent).</li>
		<li>The reported IC50 is the average of all IC50 values collected on at least three different days, and the error value is the standard deviation.</li>
	</ol>
	</li>
</ol>

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A., Fakhree, M. A. A., Omidi, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+Toxicity+of+Nanogenomedicine+in+MCF-7+Cell+Line:+MTT+assay.">Cellular Toxicity of Nanogenomedicine in MCF-7 Cell Line: MTT assay.</a> Journal of Visualized Experiments. (26), e1191 (2009).</li><li>Gonzalez, R. J., Tarloff, J. 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The authors declare they have no competing financial interests.

The method described in this manuscript combines chemical synthesis with biological cell viability assay. As with any biological methods concerning viable cells, it is vital to work in a laminar hood, and maintain sterile conditions, including the use of sterile organic solvents. Also, preparation and storage of hydrolytically unstable metal based drugs should be carried out under inert conditions, for which glove box or Schlenk line techniques should be utilized.
The selection of the techniqu...

Chemotherapy is still one of the main courses of treatments employed in the clinic for various cancer diseases, and thus vast amount of research is conducted worldwide with the aim to develop new and improved anticancer drugs. Such studies mostly begin at the chemical level, with the design and preparation of compounds, followed by biological evaluation of the cytotoxic properties in vitro. Cell viability may be assessed by various assays that provide information on cellular activity1-2.
Cisplatin is an example of a platinum complex that is widely used as a chemotherapeutic drug, which is considered an efficient treatment mainly for testicular and ovarian cancers3-4. However, its narrow activity range and severe side effects trigger studies of other potent transition metal complexes5-8. Among others, titanium (IV) and vanadium (V) complexes showed promising results of high activity and reduced toxicity9-16. Ti (IV) complexes were the first to enter clinical trials after cisplatin due to these properties; however, they have failed the trials due to formulation difficulties and hydrolytic instability. There is thus a current need to develop improved derivatives of these metal complexes that may combine high anticancer activity with water resistance15,17-21.
A challenge in the preparation of Ti (IV) and V (V) complexes refers to the hydrolytic instability of the precursor reagents; therefore, inert atmosphere should be maintained. The preparation of Ti (IV) and V (V) compounds is conducted under N2 or Ar conditions in a glove box or using Schlenk line techniques.
One common method for evaluation of the anti-cancer activity is based on the MTT (3-(4,5-dimethylthiazolyl)-2,5-diphenyltetrazolium bromide) assay. This assay is a colorimetric viability assay that was presented in 1983 by Mosmann22. It is extremely well studied and characterized, and it is considered highly efficient when evaluating the effectiveness of new cytotoxic compounds due to its precision, rapidity, and its capability to be applied on variety of cell lines. This viability assay is based on the color change of the MTT molecule when it is exposed to viable cells. Measurement of the absorbance, which is proportional to the number of viable cells, and comparison to untreated controls, enables assessment of the cell growth inhibition capabilities of the compound tested.
The MTT colorimetric assay is conducted in a 96-well plate format23.&#160;The cells may require preincubation in the wells before the addition of the tested drug. The preincubation times may vary from 0-24 hr according to the cell line properties. Cells are usually exposed to the drug for 24-96 hr depending on the drug activity. MTT solution is then added to the treated cells, where the yellow MTT is reduced to purple formazan by a variety of mitochondrial and cytosolic enzymes that are operational in viable cells (Figure 1)24. The MTT molecule is not reduced by dead cells or red blood cells (metabolically inactive cells), spleen cells (resting cells) and concanavalin A-stimulated lymphocytes (activated cells)22. After 3-4 hr of incubation with MTT the formazan precipitates. The formation of the formazan begins after 0.5 hr of incubation but for optimal results it is best to expose the cells to MTT for at least 3 hr22. Consequently, the growing medium is removed and the formazan is dissolved in an organic solvent, preferably isopropanol25, although DMSO can also be used26. The elimination of the medium is crucial for achieving accurate results since phenol red, which is widely common in growth medium, and precipitating proteins can interfere with the absorbance measurement25. When the formazan solution reaches homogeneous, the absorbance of the solution is measured using a microplate reader spectrophotometer. The absorbance at 550 nm is directly proportional to the number of cells in range of 200-50,000 cells per well, and thus very small amounts of cells can be detected22. The absorbance indicates the amount of viable cells that remained after treatment with the drug, and is compared to the absorbance of control cells that were not exposed to the drug. Analysis of the results by proper software provides the IC50 (inhibition concentration; 50%) values and their statistical errors based on several repetitions of the measurement.
The MTT assay is widely common in cytotoxicity studies for screening new anticancer compounds, due to its accuracy and relative simplicity. However, when using the MTT assay, which is depended on enzymatic reaction, one must consider that various enzyme inhibitors can affect the reduction of MTT and lead to false results27. In addition, the MTT assay does not provide any information on the molecular mechanism of the cytotoxic activity of the drug2.

<table border="1">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Reagent/Material</td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Biological Industries</td>
			<td>04-007-1A</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexane AR</td>
			<td>Gadot</td>
			<td>830122313</td>
			<td>Dried using a solvent drying system</td>
		</tr>
		<tr>
			<td>HT-29 cell line</td>
			<td>ATCC</td>
			<td>HTB-38</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropanol AR</td>
			<td>Gadot</td>
			<td>830111370</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Biological Industries</td>
			<td>03-020-1B</td>
			<td></td>
		</tr>
		<tr>
			<td>MTT</td>
			<td>Sigma-Aldrich</td>
			<td>M5655-1G</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/streptomycin antibiotics</td>
			<td>Biological Industries</td>
			<td>03-031-1B</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI-1640 with phenol red with L-glutamine</td>
			<td>Sigma-Aldrich</td>
			<td>R8758</td>
			<td></td>
		</tr>
		<tr>
			<td>RPMI without phenol red</td>
			<td>Biological Industries</td>
			<td>01-103-1A</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF) AR</td>
			<td>Gadot</td>
			<td>830156391</td>
			<td>dried using a solvent drying system</td>
		</tr>
		<tr>
			<td>Ti(OiPr)4</td>
			<td>Sigma-Aldrich</td>
			<td>205273-500ML</td>
			<td>moisture sensitive</td>
		</tr>
		<tr>
			<td>Trypsin/EDTA</td>
			<td>Biological Industries</td>
			<td>03-052-1B</td>
			<td></td>
		</tr>
		<tr>
			<td>VO(OiPr)3</td>
			<td>Sigma-Aldrich</td>
			<td>404926-10G</td>
			<td>moisture sensitive</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>12-channel pipette 30-300 &#956;l</td>
			<td>Thermo Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>12-channel pipette 5-50 &#956;l</td>
			<td>Finnpipette</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>75 cm2 flask</td>
			<td>NUNC</td>
			<td>156472</td>
			<td></td>
		</tr>
		<tr>
			<td>96-well plate with lid (flat bottom)</td>
			<td>NUNC</td>
			<td>167008</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 Incubator</td>
			<td>Binder</td>
			<td>APT.line C150</td>
			<td></td>
		</tr>
		<tr>
			<td>Counter chamber</td>
			<td>Marienfeld-Superior</td>
			<td>650030</td>
			<td></td>
		</tr>
		<tr>
			<td>Eppendorf vial</td>
			<td>KARTELL</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glove box</td>
			<td>M. Braun</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Laminar flow hood</td>
			<td>ADS LAMINAIRE</td>
			<td>OPTIMALE 12</td>
			<td></td>
		</tr>
		<tr>
			<td>Microplate reader spectrophotometer</td>
			<td>Bio-Tek</td>
			<td>El-800</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Nikon</td>
			<td>Eclipse TS100</td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette 20-200 &#956;l</td>
			<td>Finnpipette</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pipette 5-50 &#956;l</td>
			<td>Finnpipette</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

anticancer metal complexes: synthesis and cytotoxicity evaluation by the mtt assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

The complexes were prepared based on established procedures18,28 and their purity may be evaluated by NMR and elemental analysis.
The data received from the MTT assay is analyzed to evaluate the cytotoxicity of the compound18,21. First, subtraction of the blank control absorbance value from all the other values is performed. Second, the THF solvent control value is set to 100% viability, as no growth inhibiting compound was added. All other values are transformed into per...

Watch this Scientific Journal Video about Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay at JoVE.com

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

anticancer-metal-complexes-synthesis-cytotoxicity-evaluation-mtt

Research

JoVE Journal

Chemistry

57.0K Views.  The Hebrew University of Jerusalem. A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Video: Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox reactions. The Cu (I) complex of the peptide model of a Cu (I) binding metallochaperone protein, which includes the sequence MTCSGCSRPG (underlined is conserved), was determined in solution under inert conditions by NMR spectroscopy.
NMR is a widely accepted technique for the determination of solution structures of proteins and peptides. Due to difficulty in crystallization to provide single crystals suitable for X-ray crystallography, the NMR technique is extremely valuable, especially as it provides information on the solution state rather than the solid state. Herein we describe all steps that are required for full three-dimensional structure determinations by NMR. The protocol includes sample preparation in an NMR tube, 1D and 2D data collection and processing, peak assignment and integration, molecular mechanics calculations, and structure analysis. Importantly, the analysis was first conducted without any preset metal-ligand bonds, to assure a reliable structure determination in an unbiased manner.

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

The NMR-solution structure of a metallochaperone model peptide with Cu (I) was determined, and a detailed protocol from sample preparation and 1D and 2D data collection to a three-dimensional structure is described.

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox ...

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Metal-free Synthesis of Ynones from Acyl Chlorides and Potassium Alkynyltrifluoroborate Salts

Ynones are a valuable functional group and building block in organic synthesis. Ynones serve as a precursor to many important organic functional groups and scaffolds. Traditional methods for the preparation of ynones are associated with drawbacks including harsh conditions, multiple purification steps, and the presence of unwanted byproducts. An alternative method for the straightforward preparation of ynones from acyl chlorides and potassium alkynyltrifluoroborate salts is described herein. The adoption of organotrifluoroborate salts as an alternative to organometallic reagents for the formation of new carbon-carbon bonds has a number of advantages. Potassium organotrifluoroborate salts are shelf stable, have good functional group tolerance, low toxicity, and a wide variety are straightforward to prepare. The title reaction proceeds rapidly at ambient temperature in the presence of a Lewis acid without the exclusion of air and moisture. Fair to excellent yields may be obtained via reaction of various aryl and alkyl acid chlorides with alkynyltrifluoroborate salts in the presence of boron trichloride.

The goal of this manuscript is to demonstrate a straightforward method for the preparation of ynones from acyl chloride and potassium alkynyltrifluoroborate salt starting materials. The one-pot reaction proceeds rapidly in the presence of boron trichloride without exclusion of air and moisture.

Ynones are a valuable functional group and building block in organic synthesis. Ynones serve as a precursor to many important organic functional groups ...

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the hydroxylmethylene phosphine precursor with ammonia in methanol under a nitrogen atmosphere. The N-triphosPh ligand precipitates from the solution after approximately 1 hr of reflux and can be isolated analytically pure via simple cannula filtration procedure under nitrogen. Reaction of the N-triphosPh ligand with [Ru3(CO)12] under reflux affords a deep red solution that show evolution of CO gas on ligand complexation. Orange crystals of the complex [Ru(CO)2{N(CH2PPh2)3}-&#954;3P] (2) were isolated on cooling to RT. The 31P{1H} NMR spectrum showed a characteristic single peak at lower frequency compared to the free ligand. Reaction of a toluene solution of complex 2 with oxygen resulted in the instantaneous precipitation of the carbonate complex [Ru(CO3)(CO){N(CH2PPh2)3}-&#954;3P] (3) as an air stable orange solid. Subsequent hydrogenation of 3 under 15 bar of hydrogen in a high-pressure reactor gave the dihydride complex [RuH2(CO){N(CH2PPh2)3}-&#954;3P] (4), which was fully characterized by X-ray crystallography and NMR spectroscopy. Complexes 3 and 4 are potentially useful catalyst precursors for a range of hydrogenation reactions, including biomass-derived products such as levulinic acid (LA). Complex 4 was found to cleanly react with LA in the presence of the proton source additive NH4PF6 to give [Ru(CO){N(CH2PPh2)3}-&#954;3P{CH3CO(CH2)2CO2H}-&#954;2O](PF6) (6).

The Synthesis, Characterization and Reactivity of a Series of Ruthenium N-triphosPh Complexes

Ruthenium phosphine complexes are widely used for homogeneous catalytic reactions such as hydrogenations. The synthesis of a series of novel tridentate ruthenium complexes bearing the N-triphos ligand N(CH2PPh2)3 is reported. Additionally, the stoichiometric reaction of a dihydride Ru&#8211;N-triphos complex with levulinic acid is described.

Herein we report the synthesis of a tridentate phosphine ligand N(CH2PPh2)3 (N-triphosPh) (1) via a phosphorus based Mannich reaction of the ...

Reverse Microemulsion-mediated Synthesis of Monometallic and Bimetallic Early Transition Metal Carbide and Nitride Nanoparticles

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The silica-encapsulated metal oxide nanoparticles are then carburized in a methane/hydrogen atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal carbide nanoparticles. During the carburization process, the silica shells prevent the sintering of adjacent carbide nanoparticles while also preventing the deposition of excess surface carbon. Alternatively, the silica-encapsulated metal oxide nanoparticles can be nitridized in an ammonia atmosphere at temperatures over 800 &#176;C to form silica-encapsulated early transition metal nitride nanoparticles. By adjusting the reverse microemulsion parameters, the thickness of the silica shells, and the carburization/nitridation conditions, the transition metal carbide or nitride nanoparticles can be tuned to various sizes, compositions, and crystal phases. After carburization or nitridation, the silica shells are then removed using either a room-temperature aqueous ammonium bifluoride solution or a 0.1 to 0.5 M NaOH solution at 40-60 &#176;C. While the silica shells are dissolving, a high surface area support, such as carbon black, can be added to these solutions to obtain supported early transition metal carbide or nitride nanoparticles. If no high surface area support is added, then the nanoparticles can be stored as a nanodispersion or centrifuged to obtain a nanopowder.

A &#8220;removable ceramic coating method&#8221; is presented in visual format for the synthesis of non-sintered and metal-terminated monometallic and bimetallic early transition metal carbide and nitride nanoparticles with tunable sizes and crystal structures.

A reverse microemulsion is used to encapsulate monometallic or bimetallic early transition metal oxide nanoparticles in microporous silica shells. The ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

Synthesis of a Water-soluble Metal&amp;#8211;Organic Complex Array

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. The complexes were tested for catalytic activity in arylation and Suzuki-Miyaura reactions. For each reaction investigated, at least one of the four complexes successfully catalyzed the reaction.

Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from ...

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity in aqueous CO2 reduction. Different from traditional metal nanocrystals, the synthesis of metal single atoms involves a matrix material that can confine those single atoms and prevent them from aggregation. We report an electrospinning and thermal annealing method to prepare Ni single atoms dispersed and coordinated in a graphene shell, as active centers for CO2 reduction to CO. During the synthesis, N dopants play a critical role in generating graphene vacancies to trap Ni atoms. Aberration-corrected scanning transmission electron microscopy and three-dimensional atom probe tomography were employed to identify the single Ni atomic sites in graphene vacancies. Detailed setup of electrochemical CO2 reduction apparatus coupled with an on-line gas chromatography is also demonstrated. Compared to metallic Ni, Ni single atom catalyst exhibit dramatically improved CO2 reduction and suppressed H2 evolution side reaction.

Synthesis and Performance Characterizations of Transition Metal Single Atom Catalyst for Electrochemical CO2 Reduction

Here, we present a protocol for the synthesis and electrochemical testing of transition metal single atoms coordinated in graphene vacancies as active centers for selective carbon dioxide reduction to carbon monoxide in aqueous solutions.

This protocol presents both the synthesis method of the Ni single atom catalyst, and the electrochemical testing of its catalytic activity and selectivity ...

Synthesis of a Thiol Building Block for the Crystallization of a Semiconducting Gyroidal Metal-sulfur Framework

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and porous metal-dithiolene network in the highly ordered single crystalline state. Unlike the highly reactive free-standing thiols, which tend to decompose and complicate the crystallization of metal-thiolate open frameworks, the thioester reacts in situ to provide the thiol species, serving to mitigate the reaction between the mercaptan units and the metal centers, and to improve crystallization consequently. Specifically, the thioester was synthesized in a one-pot procedure: an aromatic bromide (hexabromotriphenylene) reacted with excess sodium thiomethoxide under vigorous conditions to first form the thioether intermediate product. The thioether was then demethylated by the excess thiomethoxide to provide the thiolate anion that was acylated to form the thioester product. The thioester was conveniently purified by standard column chromatography, and then used directly in the framework synthesis, wherein NaOH and ethylenediamine serve to revert in situ the thioester to the thiol linker for assembling the single-crystalline Pb(II)-dithiolene network. Compared with other methods for thiol synthesis (e.g., by cleaving alkyl thioether using sodium metal and liquid ammonia), the thioester synthesis here uses simple conditions and economical reagents. Moreover, the thioester product is stable and can be conveniently handled and stored. More importantly, in contrast to the generic difficulty in accessing crystalline metal-thiolate open frameworks, we demonstrate that using the thioester for in situ formation of the thiol linker greatly improves the crystallinity of the solid-state product. We intend to encourage broader research efforts on the technologically important metal-sulfur frameworks by disclosing the synthetic protocol for the thioester as well as the crystalline framework solid.

Here, we present a one-pot, transition-metal-free synthesis of thiols and thioesters from aromatic halides and sodium thiomethoxide, followed by the preparation of single crystals of a metal-dithiolene network using thiol species generated in situ from the more stable and tractable thioester.

We present a method for preparing thioester molecules as the masked form of the thiol linkers and their utilization for accessing a semiconducting and ...