Welcome, Sigma Xi Showcase Visitors!

My name is Michael Yanagisawa, a senior at Brown University majoring in chemistry and biology. I have been conducting research in chemistry for the past two years and would love to share the progress I have made with you. Be sure to check out:

  • The personal video, a friendly, jargon-free video of my work,
  • The abstract, a more technical description of my research, and
  • The slide presentation, a more in-depth look at the research.

If you have any questions or comments, be sure to leave a comment in the Discussion section of the website. Also, to learn a little more about me, check out the About Me tab.

Personal Video

 

Abstract

Reaction of a Biomimetic Molybdenum-Centered Complex with Carbon Dioxide.
The global warming scare has prompted scientists of all disciplines to look into effective ways of dealing with carbon dioxide. Carbon dioxide’s ubiquity and stability in our atmosphere makes the carbon dioxide problem particularly daunting. Many processes in nature, however, have already found ways to convert carbon dioxide into fuel precursors; for example, the enzyme formate dehydrogenase (FDH) can reversibly convert carbon dioxide into formate. Our hope is that by copying the reactive part (i.e. the active site) of FDH, we can induce a similar reaction with a chemical complex made in the lab. We synthesized and characterized the biomimetic complex MoO(C2S2Ph2)22-, then reacted it with carbon dioxide. We aim to identify the product of the reaction using various spectral techniques (IR, UV-Vis, NMR, ESI, GC-MS, EPR) with hopes that the carbon dioxide molecule bind onto the metal center. Our findings give evidence for the formation of a molybdenum (V) dimer.

Slide Presentation

Advertisements
This entry was posted in Uncategorized. Bookmark the permalink.

23 Responses to Welcome, Sigma Xi Showcase Visitors!

  1. myanagis says:

    Hey, this is Mike. Welcome to my research site! Leave comments, feedback, questions, etc. below.

  2. Kasia says:

    Hi Mike! Fellow Brunonian here. I’m currently taking Chem0400 so your presentation really puts things in perspective for me (whoa! someone actually does what we learn about IRL!). As I’m someone who’s more of a biologist than a chemist, can you explain why your reaction yielded Mo(V) instead of Mo(IV)? Is one oxidation state preferable over the other?

    • myanagis says:

      If the carbon dioxide is reduced, then the Mo(IV) must be oxidized, to Mo(V) or Mo(VI). I’m not really sure if one is preferable — both are oxidation states are required for the catalytic cycle to work.

  3. Bhavik Nathwani says:

    Hello, Mike. Great presentation! I was wondering, in case the crystallization step is a bottleneck, would there be alternative approaches to identify the final product?

    • myanagis says:

      That’s what we’re working on now. The product seems to be an oil, refusing to crystallize. We’ve been trying to get reliable ESI data to nail down a molecular weight of the compound. We’re also running a labelled-CO2 reaction to see where the labelled carbon ends up. Hopefully the combination of these two results can lead us to a stronger predicted product. It still seems that the most sure-fire way to identify the final product is with crystallography, though.

  4. Yan Liu says:

    Hi Mike,

    A very nice presentation. There are many greenhouse gases that cause global warming. I am just curious why carbon dioxide is so special to you.

    Thanks

    • myanagis says:

      I think what makes carbon dioxide particularly interesting is that everybody knows about it. Even non-science people understand carbon dioxide — it spews from factories and out of our mouths — so it is easy for people to care about the research, to be immediately interested. It is this link between science research and real life that makes carbon dioxide so special to study.

  5. Vishal Patil says:

    Hi Mike,

    Interesting research! I was curious regarding reaction of CO2 with Mo center. Have you tried reduced temperature and time for this reaction? Sometimes heating for high temperature for longer period can lead to unwanted side reactions. Also, does your NMR data matches up with product you proposed?

    • myanagis says:

      We initially tried the reaction at room temperature and around 40-50 C for 1-4 days, but we didn’t observe anything. We did do a heated Mo center without CO2 under the same conditions, and it didn’t decompose … we do observe a distinct color change within 30 minutes, but run it for 2 days to allow the reaction to run to completion. The colors between the 30 minute period and the 2 day period are the same.

      The H-NMR data only show the dithiolene ligands (on the phenyl groups), and the C-NMR has been difficult to get conclusive data on. If a new carbon is bound to the metal it should show up on the CNMR, but this potential peak gets drowned out in the C-NMR noise and other carbon peaks.

  6. Rick Palmer says:

    Hi Mike. Very good presentation. I have a question. If you observe 2 peaks in the mass spectrum why do you need to average them?

    • myanagis says:

      There’s no need to average them … I just found it interesting (perhaps just a coincidence, too) that the two masses average out to the mass of the starting material. I was thinking (again, conjecture) that the two centers may undergo some sort of interaction to yield a larger and smaller product.

  7. SLM says:

    Mike: Good Presentation.

    I have a few general questions:

    1. Have you tried reacting the [MoO(pet)2]2- and MeCN alone without CO2 and looking at the reaction products?
    2. What did the NMR’s of your products indicate?
    3. What type of detector did you have on your GC-MS?
    4. Have you tried any general chromatography techniques besides GC-MS to isolate and purify your products?
    5. What is your general career goal?

    • myanagis says:

      1. Yup. We ran an identical reaction ( [MoO(pdt)2]2- in acetonitrile at 90 C for 2 days) without CO2, and the starting material did not change. This served as our temperature/time control.
      2. The H-NMR shows the relationship between the dithiolene phenyl groups and countercation ( [Et4N]+ ). The starting material showed the ratio we’d expect, but the ratios for the product weren’t very clear. The C-NMR potentially can show us if the CO2 binds onto the metal, but we haven’t seen a new carbonyl-esque CNMR peak in the product.
      3. I’m not sure I really understand the question … the model is Hewlett-Packard GCD 1800C GC-MS spectrometer, equipped with a mass spec detector. Hope this helps.
      4. We haven’t tried other purification techniques aside from crystallization because based off IR we believe the impurity is a minor product.
      5. I’m still not certain on my career path. I’ve been entertaining the ideas ranging from medicine to business; my plan right now is to take a year or two off (from school) to get a better feel on what I want to do. Suggestions/ conversation are appreciated.

  8. taupshaw says:

    Interesting work, Mike. If formate is successfully generated by this or related chemistry, what is done with it downstream, i.e., in what final form would it be used as a fuel or chemical feedstock. Another question is what are the conditions for the final step shown in the reaction Scheme on slide 10.

    • myanagis says:

      If formate is successfully generated by this chemistry, formate itself can be used as a source of fuel, which I find to be pretty cool by itself (Ref 2 in slideshow). The ideal final product would be methane, though; methane is already used as a source of fuel in natural gas. The reduction to methane would be a multi-step reaction — carbon dioxide to formate/formic acid to formaldehyde to ethanol to methane.

      Another group, though, has used a remodeled enzyme to convert carbon dioxide directly to methane, cutting out all these middle steps. This is pretty fascinating, and useful — CO2 the harmful gas becomes a substrate for energy production. A press release goes so far as to call this reaction the “holy grail of science.” (Ref: http://www.usu.edu/science/htm/one-step-closer-usu-biochemists-convert-greenhouse-gas-to-fuel/)

      The reaction conditions: I’m sorry they’re not attached on the slide show; somehow they didn’t copy over. To Mo(CO)2(pdt)2 in THF we add tetraethylammonium hydroxide (Et4N OH) in slight excess. The reaction is run for a day at room temperature in air-sensitive conditions.

      Hope this helps.

      • taupshaw says:

        Thanks Mike, interesting. How would you get the Et4N OH back out so you can re-cycle the catalyst, out of curiosity?

  9. myanagis says:

    The OH- displaces the two carbonyl groups on the metal center and the Et4N+ is required to counterbalance the metal anionic species. I’m not sure you could really retrieve the Et4NOH from the product. There’s evidence that the oxo ligand is retained when carbon dioxide is reduced.

  10. GLS says:

    Hi MiKe,

    Very nice and complete presentation. I will be judging your work.
    Below you will find questions, suggestions and comments.

    Following the discussion in your site I got some of my questions answered. I have some additional questions, though.
    Slide 3: you state that “CO2 reduction gets rid of favorable linear structure”, why is a linear structure favorable?
    Slide 7: your experiments are done at 2 atm, did you try experiments at normal pressure?
    Slide 9: I suggest that you call your colleague “Seo” (last name) rather than “Jun”
    Slide 10: do you prepare the reagent Mo(CO)3(CH3CN)?
    Slide 13: (comment) because you listed here 1H and 13C-NMR I expected to find the results even if they were non conclusive. Remember to always address the experiments you list.
    Slide 16: (comment) your units for the fragment masses are missing.
    Slide 17: I am not sure what you mean by “complementary metal center”, could you explain?
    Slide 21: (comment) citation 6 should include the name of the authors and affiliation.
    Question: did you visually inspect the color of your reaction of did you use UV-vis?
    Suggestion: increasing the capillary voltage of the ESI may lead to the dissociation of (non covalently bound) clusters, perhaps you could try that with your ion m/z 757.
    Question: I am a little confused with the dimer reported by Seo, what happened to the CO2? Was it shown that CO2 was reduced?
    Question: Is the final product colored? Did you try to separate it by HPLC?

    I realize that there are several questions to address, just do it in a short manner.

    Thanks!

    GLS

    • myanagis says:

      Thanks for the input.
      Background:
      -The literature often refers to CO2 as a linear molecule being more stable than the more complex and energetic non-linear structures. There is a big reorganization energy to go from linear to bent/non-linear.
      -Where did the CO2 go in Seo’s complex? I think this is one of the questions the group has. The CO2 is unaccounted for in the final dimer; the CO2 almost seems to activate the W centers, making them couple and dimerize. In a control trial, the starting material did not decompose in identical conditions without CO2.

      Synthesis:
      We synthesized Mo(CO)3(MeCN)3 by refluxing Mo(CO)6 in acetonitrile.

      Experiment:
      -We didn’t try the CO2 bulb at normal pressure, mainly because of our process of purifying and obtaining the CO2 in the bulb.

      Results:
      -By complementary metal center, I meant to suggest that perhaps two starting material compounds couple e.g. one donates a ligand to the other, hence “complementary”. It is a coincidence I wanted to remark on.
      -I visually inspected the color of the starting material and product, but we also took UV-Vis for identification purposes. The final color is a light yellow-green (starting material is a vibrant red-orange). We did not try HPLC yet.

  11. Rick Palmer says:

    Mike, in slide 19, how R1+R2 will be chosen to fit the MW 757 of the whole molecule with CO2 (MW 44) or S+O (MW 48)? There are 4 mass units difference. Thank you.

    • myanagis says:

      The ESI results we have are still preliminary (we are going to check the values once the ESI machine is working again). Once I retake the ESI I’ll have a better idea — both CO2 and S+O are in the ballpark.

  12. DrArnett says:

    Slide 12: This slide is unclear as to what was done and what was collected. The crude product was rinsed with ether. . . and collected? The crude product was then collected and called the “ether layer”? The “metal layer” was then redried. The next slide then describes tests on the “reaction” and on the “product” Which fraction was used for these tests, the “ether layer” or the “metal layer”?

  13. GLS says:

    Thanks for your answer Mike. Wonderful and interesting work. Good luck!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s