Listen: Chemist Christopher Graves on Constructing Through Chemistry
Associate Professor of Synthetic Inorganic Chemistry & Environmental Studies Christopher Graves borrowed a metaphor or two from the world of construction for his Second Tuesday Social Sciences Cafe talk this spring. The series, which is sponsored by the Aydelotte Foundation and held in Kohlberg Hall's Scheuer Room, deals with failure in research and the important lessons learned by confronting these setbacks.
Listen: Christopher Graves Second Tuesday Aydelotte Cafe
Graves, who received a research grant from the National Science Foundation in July 2017, likened synthetic chemistry to construction and compared the research process to a bridge leading to a fog-covered area: The terrain is uncertain, and multiple bridges may need to be traversed before the desired destination is reached.
"You sort of know where maybe the bridge is going, but you really don't know," Graves says. "You have a vague outline of a tree that you hope to find, and we're going to walk along this crooked path and, hopefully, it's going to lead us to where we want to go."
Graves and his lab group explore the intersections of inorganic, organic, and green chemistries, and their work focuses on the development of novel aluminum complexes for application as catalysts.
Audio Transcript
Jamie Thomas: I'd like to welcome you to our second to last Tuesday Café sponsored by the Aydelotte Foundation, and today we're doing a presentation from one of our resident chemists, Christopher Graves. I'm Jamie Thomas, I'm from the linguistics department, and it's been a real pleasure to bring together different faculty over these two semesters to delight us and surprise us and regale us in their tales about research failure.
What's been really interesting over the course of this year working with my partners on the series, Rachel Buurma and Tim Burke, is to consider all the many ways that the research process flows throughout the faculty life cycle. What we've learned from faculty across rank, across department, across program, and even an interdisciplinary and transdisciplinary research, is that research is a process of discovery and it has it's ups and downs. Next time we're together we will get a chance to have some lunch and also learn from one of our economists, [inaudible 00:01:21], but today is all about chemistry.
The last thing I want to share with you is that today also happens to be Equal Pay Day. All right. Today you might see, I'm wearing my red, in celebration of Equal Pay Day around the world, and I just want to share something with all of you. That Equal Pay Day is about raising awareness about the gender wage gap that continues to persist throughout the United States and in countries around the world. The most recent figures show that women earn 80 cents on the dollar of their male colleagues, and this is according to the Institute of Women's Policy Research, and that gap is more pronounced for black and Hispanic women, who earn 63 cents and 54 cents respectively, on the dollar of their white male colleagues.
I share that with you. I'm not exactly sure about our situation here at Swarthmore, but it certainly bears talking about, that we would be good to be in solidarity with Equal Pay Day celebrators around the world.
All right, with that being said, I welcome Christopher Graves.
Christopher Graves: Thank you Jamie. Thank you all for coming, and Amy thank you for reminding me why I became a chemist and not a biologist. I'm going to talk today a little bit about how I think about research and how I run my research program and sort of a little bit of philosophy to start with.
I really enjoyed how Nat started her talk by showing us these beautiful pictures of poets gazing into space, and so I wanted to ask some of you today, when you hear the word chemist, what do you think of?
Audience: Beakers.
Graves: Beakers. I mean more people. People who are chemists. Who do you think of when you think of chemists.
Audience: People who are beakers.
Graves: People who are beakers. There is Beaker. Very well done. I'll start here with some caricatures of scientists, chemists, engineers, mad people, crazy lunatics, people who took us back in the future. Then, from popular culture, other mad men who use chemistry to do no good, and sort of my most offensive person on this slide in my mind is someone who can do magic with chemistry. If you've ever watched CSI, forensic scientists who shoot things into instruments and get answers that are just unbelievable, and that's because they are unbelievable.
They did not do their research. I think that sort of this together from popular culture has led to sort of a view point of what we do in a chemistry building is haphazardly throwing things together, hoping things succeed, not wearing goggles while we do so. That really has left sort of a vague sense of what a chemist is. This is my most philosophical slide. When I think of a chemist I think of a certain two people who are sort of luminaries obviously in the field. Madame Curie and Linus Pauling, both whom won two Nobel Prizes.
They changed the way we think about things. They discovered processes, they pushed the boundaries of science, they gave us models for thinking about molecules and thinking about the way that molecules react and behave in nature. How many of you have taken organic chemistry? Where are all of the organic people?
Not a lot, but if you remember [inaudible 00:05:03] carbon, you can thank Linus Pauling for giving you that model. Of course, chemists aren't all white people, which all of these slides have shown us. Chemistry is a very diverse field, so here's a picture Marie Daly, who was the first African American woman to earn her Ph.D in chemistry from Columbia in 1947. Chemists are also trailblazers and mentors and inspirational people.
Here are two of my inspirations. Greg Hillhouse. When I was done going through grad school and was thinking about becoming a professor as sort of the gay chemist, Greg was really the person who was at that time to my knowledge the only person who was very out and very who he was in conducting his research. He sort of pushed the boundaries of in my mind what I was able to do from that view point. Then, my good friend, Madeleine M. Joullié who on Equal Pay Day, this is a great sort of tribute thing to put her up. She is a 91-year-old chemist who is still active at Penn, was the first woman in a tenure track R1 position in organic chemistry and really is a trailblazer. These are my personal trailblazers or personal role models.
Okay so this still leaves us with questions, what do chemists do and what are we interested in? What do we do when we go into a lab and we think about problems? I have another throw back to John Bisset who talked about building in Paris and specifically the machines who went in to make these buildings. I'm going to start my analogy with the Paris Opera House, which is a beautiful building that serves either a beautiful or a boring purpose depending on where you sit on opera. To make that building we have a variety of building materials that go into turning it into something beautiful to make that be accomplished, we had a variety of machines to help us take those building materials and turn them into something like this.
You of course can make different types of buildings. You can make buildings with totally different functions. You can [inaudible 00:07:19]. You can make buildings that house people where people live. Then we can think about having buildings that have to act together and function in that sort of more macro sense, pulling all of their different functions together so people can live in cities.
I'm a chemist, so I'm not building buildings, but we can sort of use that analogy in the same way. As a chemist we have a variety of building blocks and building materials. We have things like sugar, so this is glucose. We have a variety of elements in their elemental form from the periodic table. Carbon dioxide. These are alkenes, so specific types of compounds that have functional groups or bonding between atoms that allow for different distributions of electrons. That's as [chemicy 00:08:08] as it gets. [inaudible 00:08:10] my dream gas.
As chemists we take these building blocks and we transform them, so we can also make beautiful structural motifs that have a very specific purpose. Here's vancomycin. We can take simple molecules and we can convert them into functional molecules, and so these are types of plastics, so a polymer industry. We can take our building blocks of life and turn them into enzymes and other biomolecules. We can convert simple molecules into fertilizers which really have sustained that human population on earth, and then we can take elements and turn them into specific types of materials. This is the magnetic material that's in wind turbines, and is responsible for allowing you to harvest energy.
Just like in building buildings, we also have machines that help us do this type of chemistry. You'll have to forgive me, I'm a molecular chemist, so my interest is in molecules, and so all of my machines are molecules. I have these machines here that we can use that can take these starting materials and turn them into these useful types of materials. This is really what I'm interested in. I'm interested in making new [inaudible 00:09:26] that make new types of materials and accomplish different types of reactions. I will highlight that every one of these machines I've put up there has won a Nobel prize at some point in history.
Okay, so my research program really has focused on making catalysts. That's sort of the more chemical term for the machine and the context that I put things. Who's heard the word catalyst before? What do you think of when you think of a catalyst? What does a catalyst do?
Audience: [inaudible 00:09:57]
Graves: It gets something going. What else?
Audience: Causes a reaction.
Graves: Causes a reaction.
Audience: [inaudible 00:10:07] not directly altered by the reaction.
Graves: Yeah. Very good, you can pass the Chem 10 quiz. A catalyst as they said is something that accomplishes a reaction. If we start here as our green cartoony catalyst, this is our starting point. You'll notice that throughout this reaction every time we cycle through here, we get the catalyst back, so the catalyst isn't used. The catalyst accomplishes the reaction, spits out product at the end.
To think about what a catalyst actually does in a chemical sense, it accomplishes two broad, fundamental things. It pulls reacting species, in this case, A and B, together, and when it does that it changes the way those molecules, the sort of ground states of those molecules. When it puts them in close proximity it can also perform bond making and bond breaking on those species to make the bonds in products. Break bonds in starting materials, make bonds in products.
One of the ways it does that is by taking electrons, which are some atomic particle and either putting them into a bond or taking them out of a bond. Okay. Good. So I'm interested in developing catalysts. Some of the more successful catalysts, like your catalytic converter on your car, sort of most of the pictures of the machines that I put on the previous slide, come from metals that are down here, and they're [inaudible 00:11:37] called scarce elements or precious metals. They're things we don't have a lot of, and because we don't have a lot of them, they're very, very expensive. So I have the red equals this beautiful BMW.
There's a big push in chemistry and certainly my research program is focused on ways of using these more abundant elements. Elements that we have a lot of that are more readily available, that therefore don't cost nearly as much money and you could argue are more sustainable. Here we have a price point difference of this nice toy car, which is blue. These, I actually picked these cars based on their actual prices, so I'm an aluminum chemist. Aluminum costs about two dollars a kilogram. Aluminum is up here in the blue. Platinum, which is one of the more successful catalytic materials in red, costs about $40000 a kilogram, and so we're talking about four to five times more expensive, or as a magnitude more expensive.
Aluminum also has the benefit is that it's actually less toxic than some of the more heavy metals, and so that also accomplishes an important goal. I'm interested in developing aluminum complexes that can do these types of catalytic reactions. Let's just talk very briefly about what it is we might want aluminum to be able to do. We have aluminum metal here. This is the hydrogen molecule. There is a bond between these two H atoms, and that bond has two electrons in it. We might want the aluminum to interact with that hydrogen and break that bond. To do that, that aluminum gives electrons. It puts two electrons, takes two electrons from itself and gives it to the hydrogen molecule. Then we can transfer that hydrogen away from aluminum. It can, in this case, we're making alcohol, we have a compound that can take those hydrogens off, and in this reaction you actually dump the electrons back into aluminum.
What we're seeing here is we break bonds by moving electrons, we make bonds by moving electrons. The problem with that is that aluminum doesn't move electrons. It is plus three. Almost, [inaudible 00:13:52] plus three. This is a big problem that my entire research program focuses on overcoming this issue. Again, inspired by Matt Anderson, I wrote a poem to put this in context. My poem is Roses are red, violets are blue, aluminum won't give me electrons, what do I do? You can argue that it is also probably good I didn't become a poet instead of a chemist, because it's not a very good poem, but I do strike the poet pose much better than I write poetry.
What do we do to overcome this? I've been very malfocused so far in my talk, right? I'm talking about aluminum and what aluminum can do, but in, I'm a coordination chemist, and what coordination chemistry means is you take a metal, and then you have a lot of organicy things around for the ride that coordinates that metal and that changes the way that metal behaves. Well, if we think about using a ligand or organic molecule that has the ability to give up electrons and take up electrons, you can generate a complex that overcomes this problem. I put this [pacmany 00:15:00] type thing in here, so we break the hydrogen bond. That ligand gives up the electrons. The metal is intimately involved. It bonds the hydrogens, and then when we transfer off that hydrogen, the ligand accepts those electrons again. This is really the crux of my research program. To put it in more of this stance, we keep a stable oxidation state of the ligand. Electrons don't change out the metal, they do change out the ligand and use those things together.
Okay, so I went to a talk once where a professor started by giving a picture of a bridge covered in fog, and I'm going to use the same analogy they used when they described what it's like doing research in the chemistry lab. That is, you think you have a plan. You sort of know where maybe the bridge is going, but you really don't know. You have a vague outline of a tree that you hope is the tree you want to find, and we're going to walk this [crookedy 00:15:59] path along and hopefully we're going to figure out where this leads and it's going to lead us to where we want to go.
I know not the majority of you aren't scientists and so in the science fields it's very common to work with students, and these are the students, [inaudible 00:16:21] who are in my group who all of the chemistry that I really am not going to talk to you about today they've done. I very rarely actually go in and mix chemicals together anymore, except in some rare circumstances when I make starting materials. You can thank them for my success.
I found this Tweet that was on Twitter, sort of the perfect time for when I'm planning this talk of how science works and it's a series of failures followed by minimal successes spaced out in between. I'm going to push back a little bit on this, and so Sara and one of the first ones of these I went to really put it the way I like it is research fail is misleading, right? I think I like research evolution more in that we learn from our mistakes and our project evolves around those mistakes and those learning opportunities that we have, and that's really what I'm going to share with you today, and talk about.
Okay, so how do we do that? For me, my research process really starts by scribbling down ideas, so this is a picture of my bulletin board in my office of random things I've thought about throughout my day. If I go to meetings, when I should be preparing course notes, things of that nature. These are ideas I have from reading, from talking to my husband, who's also a chemistry professor. It's good times at home. And thinking about the science that I want to do. Thinking about overcoming this fundamental problem of the aluminum.
Then, I give my students some ideas. I give them specific reactions to go in. To do, we come up with a plan. This is actually a picture from a notebook I kept when I was post-doc. I don't know why I have pictures of this on my computer but I do, so here they are. We come up with a research plan, so this is sort of the outline of the reaction that I want it to do. I write out the chemical reaction, and then I actually go into lab, my students go into lab, and we actually carry this plan out, and we take notes about what happened and keep track of things.
These are pictures from my research group of actual synthetic [inaudible 00:18:39] we use, and so everything I do is actually sensitive to water and sensitive to oxygen, and so we use some pretty fun pieces of equipment that get rid of those things, and so this is my glove box which as the name suggests has big gloves on it. You put your hands in and you do chemistry these vessels, and this is my Schlenk line where we can pump all of the oxygen out of our reacting vessels.
My students then they mix some chemicals together, and the plan that we have, and we make something, which is this brown gunk, so maybe that isn't what we want. We go back to the drawing board. We rethink our synthetic strategy. We go back into lab and we make some new things and so now we have beautiful yellow material which is what I want, that was great in this case.
This is really iterative, so you go back and forth, back and forth, back and forth figuring out what you've made at each stage and if you've gotten closer to what your goals are. Then another important part of this is grant writing, so we write a lot of grants in the physical sciences because chemistry is expensive. They don't give glove boxes away on the side of the street, and so sort of taking our ideas and our results then cumulates both in publications and grant proposals [inaudible 00:19:58].
Okay, so what is this yellow solid? We made something. We have an idea, have a vague idea of what this compound is because we've written down some notes and we've put certain chemicals in, so we aren't going about this totally blind, but some of the fun in doing synthetic chemistry is figuring out what you've made. Right, so my favorite detective Angela Lansbury, but no, this is Jessica Fletcher, can figure out how. We act as a detective to figure what our compounds are. We have a lot of analytical tools that we use, and it's sort of like a puzzle when you put all the pieces together. We can do nuclear magnetic resonance which gives us a variety of information. We can do x-ray defraction which gives us other pieces of information. Elemental analysis, [inaudible 00:20:50] electrochemistry. This for me is the most important one. We'll see a few of these as we go forward, which tells us if electrons are going into, which are up, and or out of our compounds, and so we have a direct measure of how the electrons are actually moving, which is important for us.
Then, computer. We also do a lot of modeling of our complexes. When you pull all this together, that yellow powder turns into this figure which tells us we have an aluminum that has these organic molecules bound to it.
Okay, and so I'm going to go through in very little detail, sort of an arc of project that I started when I started my independent career, but to do that I sort of have to tell you a specific type of organic molecule we're looking at for it's [inaudible 00:21:43] properties, which is called a dimine. This is an imine and there's two them so that's where the name comes from. Then the important electronic states are here where you can have no electrons added, one electron added, two electrons added. In theory, if you put an aluminum here, you have the ability to add two electrons and ultimately take two electrons away.
Okay, so when I started, this is the first thing we did, is we tried to make aluminum compounds of all three oxidation states, and so here is a picture of the first student who worked in my group. A picture of all of his notebooks and all of his spectral that came with it, and we published a paper on the synthesis and characterization of these, of our multiple oxidation states. This literally had three compounds in it, so that's going to become important.
Basically, a good success is permeable. I guess there was a lot of fail, fail, fail, fail, fail, succeed, fail, fail, fail, fail, succeed. We do things multiple times, so I'm making it seem worse than it really was. He made both a compound with one electron added and a compound with two electrons added. Somebody, and I forget who, in the February series, asked why don't we publish results when they don't work. My answer to that is, well, we do, we just do it very strategically, and so here's a line from this paper. It says, "Attempts to prepare aluminum complexes with neutral ligands were unsuccessful," and then I spout out all the things I tried and all the ways they failed. I do try when I write papers to highlight some of what I view the more important failures, in that if we're really trying to make three different things and we've only made two of them, I think you have to talk about why you don't have the other one there, and what you tried to do to do that.
The reviews of this paper are actually really good in that the reviewers really appreciate that I spelled out all the ways we were unable to make something. All right, so with this system, I used to be a uranium chemist, I made uranium compounds, and something you needed to worry about with uranium was access to metal and so you used these compounds that put a lot of material in the way of the metal to protect it, and so I'm sort of thinking the same way about aluminum which turns out is not correct. What we thought is well, let's just chop all of this stuff off of the ligands, let's just get rid of it all together. When you do that, you can make the neutral ligands complex.
This is the third piece of our goal, and so we have now, no electrons added in this system, just by taking those groups off of the [inaudible 00:24:40]. Things we've learned here, sort of our failures led to our successful synthesis of this complex. Now, Connor, my second student who worked on this project, this paper also had three structures in it, but a lot more reactivity than he did [inaudible 00:24:57]. Things are getting a little bit better.
All right, and then, sort of the final piece of this arc is something we're very much interested in, is not just can we add and remove electrons from our complex, but can we add them and remove them at energies we want to be able to add them and remove them for. Can we tune our compounds to be able to put electrons in or take electrons out. Most recently, Henry has worked on derivatives of the compounds that Connor made where he put a variety of different arguments in this position of [inaudible 00:25:40] organic part of the complex, and we recently published this, and so this is the most recent publication from the group, where now he has one and a half notebooks which have 11 compounds in this paper and it's 14 pages long, so things have gotten better and we've figured some things out with this. We did accomplish our goal, and so here we have a black line, which shows sort of a parent compound. If we add specific groups, we can shift to the red. If we add other specific groups we can shift in the other direction [inaudible 00:26:15].
The conclusion then was that we can indeed tune electrons. Okay, so that was the story arc. We started by walking over a bridge that's very cloudy, foggy, we don't know where we're going, and this is the bridge we're on now. We still don't actually know where we're going, but at least the bridge looks clearer and safer and there's some pretty trees in the direction.
What if we're on the wrong damn bridge. If I picked a bridge, and I'm walking on this bridge, and it could actually lead no where to where I want the bridge to go. In my group, and I think in most groups, we don't just take one bridge. We take multiple bridges simultaneously, so another project that I work on that I'll not go in much detail about, looks at a different type of ligand base. Instead of looking at dimines, in this case we're looking at, in all groups here where that all bond also exists in the three oxidation states, can we make these complexes that have this ability to accept the [inaudible 00:27:13] electrons.
A quick story out here, we started by making these complexes which each ligand has one point of contact, and so this is bad electrochemical data, and so we go down. We can take electrons out, that's great, but you'll notice when we go back that the up and the down do not equal one another and that is not good. Yes, we can take electrons out, no we cannot put those electrons back in. We did a ligand redesign, we got much more beautiful electrochemistry. Now we have more arms that are bound to that aluminum ion, more in all groups, and now we have, we take electron out, we take another electron out, and we put both electrons back in, so the up and down are about the same. Success.
But, we made a compound that has a lot of points of contact around the middle ion, and so what we find is we actually can't do multielectron chemistry with these complexes because we've taken all the space around the metal ion out. One of my students this summer is going to go with I hope what will be the [inaudible 00:28:18] on this case where we hit it just right and we have the right number of points of contact that leaves some space for the reaction to occur.
Okay, so that was my research program, and I'm going to end with pictures of my kid because [inaudible 00:28:33]. The question is what does a future chemist look like, and here's Freddy when I brought him to campus the other day, and if you look closely at his shirt it has brown bottles and flasks, and chemistry [inaudible 00:28:44] written on it, but if I'm being perfectly honest he's probably more interested in building buildings because that crane really was the highlight of his trip to campus.
Great, thanks [inaudible 00:28:56]
