This episode centers on the work of Dr. Robert Gilliard, Jr. and his innovative exploration of the main-group elements. The discussion will convince you that innovation in synthetic chemistry is definitely not dead by highlighting Robert’s team’s work to leverage abundant, but non-traditional elements such as bismuth, beryllium and others to enable new chemistries and expand the toolset for tackling some of our biggest challenges as mankind. This is a must for anyone looking for proof that chemistry is alive and thriving!
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There is one thing Robert Gilliard, Jr. refutes categorically; that there is no innovation in chemistry. As an innovator, he has made a career on the risky proposition of finding value in a part of the periodic table that has been historically underappreciated, the main-group elements.
In his fearless exploration of the properties of bismuth, germanium, beryllium and boron, Robert is discovering new chemistries and inventing new applications. He believes in moving beyond the well of tried-and-true chemistry to explore less-traditional approaches and making them part of the standard chemistry toolset.
This is a classic Bringing Chemistry to Life episode; one that those genuinely passionate about chemistry will love. Paolo and Robert speak about new properties, reactivities and applications in synthetic chemistry and material science, all coming from the “forgotten,” abundant and cheap main-group elements. A wonderful story of relentless pursuit of knowledge that proposes a vision for a very different chemistry of tomorrow.
Dr. Robert J. Gilliard, Jr. 00:05
As you can already see with some of the chemistry we have done, there's potential to develop different types of chemistry that, you know, you might not even thought was possible.
Paolo 00:17
Robert Gilliard, Jr. is a chemistry innovator. What chemists have explored and leveraged for years; the reliable transformations enabled by the use of transition metals. Robert takes his research in a different, somewhat counterintuitive direction, main group elements. And he's discovered a lot by embracing the unexpected. In this season two episode of Bringing Chemistry to Life, we speak with another member of Chemical and Engineering News' 2020 Talented 12 about their work and trends in their field. I'm your host, Dr. Paolo Braiuca from Thermo Fisher Scientific. We began by asking Dr. Gilliard, about how his multidisciplinary work in chemistry began.
Dr. Robert J. Gilliard, Jr. 01:05
I pretty much started, you know, developing some of the things that I use now, you know, way back as an undergraduate. So even though as an undergraduate was working on organometallic chemistry, inorganic, organic, doing a lot of things with fluorescent molecules, and all of those things I still use in my research today.
Paolo 01:24
So, it all came organically together, somehow.
Dr. Robert J. Gilliard, Jr. 01:27
It did, it did. So, I have pulled, you know, things from my past in terms of different types of techniques and concepts that I learned to tackle different challenges and problems in my current program.
Paolo 01:41
When I was looking into your background and trying to get a sense for your scientific production, I was really, really impressed. I guess it's better if you try to describe it, rather than me trying to derive on a sort of logic behind it.
Dr. Robert J. Gilliard, Jr. 01:55
Yeah, so I am trained in inorganic chemistry. So that's, that's my basis. But we study the main group elements. And I would say that that's the central thing, across all of the different projects that we have. And you know, to most people, it does look like we do a lot of different, or research, a lot of different areas. And that is definitely true. But there are enough connecting things between them that we're able to have impact in a lot of areas without having to reinvent the wheel in every single field. So, for example, a lot of the ligands we use across all of those projects are very similar. So, there is that connection between the projects, but we utilize the main group elements to do the majority of what we do with a bit of transition metals sprinkled in there when we need them.
Paolo 02:48
I think it's fair to say that a lot of the chemistry you explore is rather unexplored, right, or underutilized potentially? Are you driven by this desire of understanding what is still unexplored or do you have a sort of list of challenges that you're trying to address and you believe that, you know, the main group elements could be the key to, you know, accessing your activities, for example, or new types of chemistry that are at the moment are not quite common or utilized?
Dr. Robert J. Gilliard, Jr. 03:16
It's a bit of both, actually. So, there's some things that we're targeting, particularly with regard to some of our materials related projects. But at the core of my program, I enjoy understanding fundamental reactivity, new chemical bonding, new reactivity that has not been observed before. And that actually is what has led to these more targeted projects where we look at specific applications. But it was a fundamental interest in understanding new reactivity trends that led to that.
Paolo 03:49
So, in a lot of your areas, there's still a relatively limited amount of literature. So, you're a pioneer in many ways. Do you think that as knowledge progresses, your work will become more and more application driven? Right, rather than more fundamental.
Dr. Robert J. Gilliard, Jr. 04:05
I think there's still an incredible amount of fundamental chemistry that still needs to be understood. But certainly, what we've already found just in the last three or four years is that a lot of these fundamental bonding concepts, and new types of molecules can be applied to a lot of problems that most people don't know about. But yeah, I think fundamental chemistry, in my opinion, is what drives application. People often forget about it, but there's very little you can do that's applied without the fundamental science to support it.
Paolo 04:41
The real leaps happen when there is real fundamental understanding. That's where you can actually make make the jump and have a real, a real progress. Would you agree with that?
Dr. Robert J. Gilliard, Jr. 04:52
Yeah, I agree. I don't think that is appreciated as much particularly here in the United States. So, you mentioned about my field being, you know, emerging. But in Europe, for example, there are a lot more people that do the type of chemistry that I do. So, it's kind of a massive effort there compared to the United States. And what we do, a typical person in main group chemistry needs to have very good synthetic skills. Because a lot of the molecules that we make, you can't necessarily just, you know, react everything in open air, you have to have training in air sensitive chemistry. And there's a lot of reactive molecules that not a lot of people either want to handle or can handle. So that's, that's part of our consideration as well.
Paolo 05:41
An interesting example where you probably meet, you know, the fundamental understanding with some sort of horizon of applicability might be the work you guys have done in material science. It seems to be a lot based on organoboron cations, right? Which is surprising to start with, Boron cations, you know, when I started, you know, they were just probably not a thing, right? It's a super electrophilic, not stable at all. I never thought that someone could could actually use them at all in something useful, yet you did. So can you tell us a bit more about this chemistry? And how does it work?
Dr. Robert J. Gilliard, Jr. 06:23
Sure. So, as you mentioned, that boron cations are not necessarily known for, or I should say it originated with totally being a laboratory curiosity. Something people are interested in making, charged boron species, these types of compounds have now emerged into really important intermediates in catalysis. And that's what the majority of the people use them for. But in those types of catalytic reactions, a lot of times when you form these cationic boron species, or boranium ions, they don't have to be isolated, meaning you generate them in solution and then they're immediately used for some other purpose. But we've found that if you electronically satisfy the boron center enough, using either pi conjugation, or ligand-based strategies that the boron center can remain cationic, but then also be stable enough to isolate. And we've made a number of those molecules. And that was our interest initially, being able to make stable boron-doped heterocycles that are charged. When we did that, we found that some of the solutions were changing colors on us. And we originally attributed that to them being so reactive that they were decomposing. And then we found that those types of molecules were not decomposing in the traditional sense. But they were responding to different stimuli. And so that is what started our efforts in developing boron cations for materials chemistry. Because we found that the strategies that we develop are generalizable and can be applied to many different types of boron heterocycles. And we can control that chemistry by either functionalizing the boron heterocycle, with different electron donating or withdrawing groups, or by changing the ligand. And that's something we're going to be following up on. And we have more to say about that topic later this year.
Paolo 08:18
It’s difficult in an audio format without the support of any slide, but can you describe what kind of heterocyclic structures and ligands you use to stabilize the boron cation?
Dr. Robert J. Gilliard, Jr. 08:28
Yeah, so we in my group have been focusing our efforts on stabilizing boron cations with electron-donating carbon-based ligands. And for the majority of the compounds we've made, those have been carbines, meaning these are carbon two centers that have a lone pair of electrons, they bind to boron kind of in a native type of coordinate covalent type bond. And that provides stability to the boron center. So that positive charge is kind of dampened or lessened. Such as, it's not extremely reactive anymore. It's it's stable enough to handle. And the other class of compounds that we're now exploring are these carbone ligands. So, these types of carbone ligands feature a carbon zero center, and instead of just being carbon, having a donating component, they're also pi donating. So, it's kind of like serving as a four electron donor instead of a two electron donor like carbines are.
Paolo 09:30
So how did you come to this type of structure? Would you started from trying to stabilize the boron cations and or to solve some sort of specific problem and then you notice the properties? Or is there any parallel with any other line of research that you're doing that led you to do this the sort of structures?
Dr. Robert J. Gilliard, Jr. 09:49
Yeah, so when I when I started, this position, one of the ideas that I had is that, you know, a lot of people in my field focus on traditional inorganic synthesis. Or they focus on traditional organic synthesis, or they focus on traditional main group chemistry. And one of the things that I wanted to do was see what happens when you combine the two. And that led me to develop a research project when I was going on the job market that took organic molecules, heterocycles, carbon-based systems that are conjugated and see what happens when you start to selectively dope them with boron or other types of main group elements in specific positions of the heterocycles. And so that was the original idea. At the time, we didn't know that we were exactly going to use boron. So, we started with elements like germanium, silicon, and so on, and so forth. And we found that boron really led us to these types of applications that we were interested in. And we've started to make more of those than anything else. But it was originally an interest in understanding main group doping, the effect main group elements have on conjugated molecules.
Paolo 10:59
I suppose that most of these molecules are solid and so you use some sort of solvents. Is there any effect that the type of solvent you use interaction between the solvent gives to the property of the material?
Dr. Robert J. Gilliard, Jr. 11:11
Oh, absolutely. For the majority of the boron systems we make, there are substantial solvatochromic effects. So, we have to consider that throughout all of our chemistry, because the coordinating solvents, for example, can provide stability, in some cases. The coordinating solvents like THF can provide also changes to the optical properties. So, we have to be conscious of that throughout all of the all of the types of reactions that we that we run.
Paolo 11:42
So, you mentioned optical and chromatic properties of this material. So, is this where the material science potential application comes in?
Dr. Robert J. Gilliard, Jr. 11:52
Yes. So we are now in the process, based on that original discovery on thermochromic materials. We're now in the process of trying to understand how we tune the critical temperature of these materials. So that means how do we pinpoint where these materials will change color based on temperature. That's a lot harder to do. So, what we can do now is we can say, yes, we can make a thermochromic material that will change color based on temperature. In the materials field has a lot harder time saying we want to make a thermal color material that changes color at minus 10. So, understanding the structure function relationships is what we are trying to do moving forward.
Paolo 12:34
What is the potential application on the horizon for these types of materials?
Dr. Robert J. Gilliard, Jr. 12:40
It's really substantial in terms of the potential of these types of thermochromic, or thermoluminescent materials. A lot of people that discussed, for example, military type applications in terms of the uniforms that soldiers wear. So, for example, soldiers have to carry a lot of equipment when they are out in the field. But you can imagine if you had a thermochromic material that was coated on their type of uniform, that if they were in the jungle, in temperatures that were cooler, that material, if you develop it in correct way could be green. That very same uniform, if you make it such that it changes color, when it warms up if you're in the desert, it can be tan to allow them to blend in with their surroundings without having to give them a completely different set of clothing or uniform. There are other different types of applications that that folks are interested in, in packaging science and different food safety. I often give the example of the Pfizer vaccine because that particular vaccine has to remain cold for it to be effective. So, you can imagine if that vial that the vaccine is in were coated with a thermochromic or thermoluminescent material, if during shipping, there was any type of problem, somebody left the cooling source off, the freezer got turned off, it broke, if it were coated in that type of thermochromic material and it warmed up. If that vial changes color that would notify somebody that is not a scientist, that this vial or vaccine has been compromised because it's now a different color than when it left, whatever the facility was.
Paolo 14:22
How much air stable are these things? So, to be using the application you were mentioning?
Dr. Robert J. Gilliard, Jr. 14:29
I think our next studies are going to surprise people. Because boron cations typically have been known as a reactive species. But now we're at the point where we can tune these boron cations and temper the reactivity using different types of structural effects on the molecule that leads to stable compounds that you can actually handle in air. And that's something that I think is going to be really important moving forward. So cationic boron systems that are air stable, or air tolerant, is going to be the next wave of results that come out of my lab.
Paolo 15:10
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Would you agree with the fact that chemistry has been over utilizing a relatively small number of tools, because they are very well understood, right? And, and and reliable, so chemists tend to just go back there all the time. And there's there's a little bit of a lack of innovation in the synthetic approach.
Dr. Robert J. Gilliard, Jr. 15:59
Absolutely true. You know, what has driven a lot of the, the science we there's a few elements that people use, because they know they work well. But there's a lot of undiscovered chemistry. As you can already see, with some of the chemistry we have done, there's potential to develop different types of chemistry that, you know, you might not even thought was possible, and even many cases, achieve or, you know, surpass the chemistry of some of the elements that are more traditional in many cases. So, I like being different. I like studying the different types of elements that not many people utilize, and then hopefully bring some over to my side. So, I think what normally happens is once you figured out the synthetic challenges, and once you figured out the technology, then everybody starts to use it. I think that is happening with our boron chemistry, you're for sure see more boron cations used in this regard moving forward.
Paolo 16:59
I was speaking about exactly this thing with Pep Cornella, from Max Planck Institute, so I'm sure you know him.
Dr. Robert J. Gilliard, Jr. 17:06
Yes. Absolutely.
Paolo 17:07
We interviewed him just few weeks ago, and, and he was describing his work on these new ideas using bismuth, you know, in in catalysis. Which is so much linked with what you also do, right?
Dr. Robert J. Gilliard, Jr. 17:20
Right.
Paolo 17:21
In many ways, and we were discussing about this, this desire to explore new reactivities, right, and introduce innovation in chemistry, but also going into the sort of risky areas. Because you really don't know if if you can get to a result at the end.
Dr. Robert J. Gilliard, Jr. 17:38
Right.
Paolo 17:39
I think this could be an interesting segue to, to kind of speak a little bit about some other line of research that you pursue. I mean, I mentioned bismuth, you know, your work on the group 15 elements. I mean, that's there's a lot, there's a lot of fascinating, you know, concepts in in there.
Dr. Robert J. Gilliard, Jr. 17:56
Pep and I've had many conversations about bismuth. And our approaches are different in that he's a catalysis expert and I'm a structure and bonding expert, but there's some overlap, and that the molecules that we make can absolutely be used for those types of applications. So, I spent the beginning part of my independent career trying to design and synthesize bismuth, different types of neutral molecules, low valent compounds, cations, that are in electronic states that are unusual. And you make the molecule so unusual, and so unhappy, in terms of the electronics at the bismuth center, that they typically react with other molecules, and that's what you're trying to get to, is a fine line between making something reactive, and then making it too reactive that you can't handle it. But right in the middle, it's a sweet spot, that it can be used to develop other type of chemistry. So actually, what we've done now, as we're thinking about the types of bismuth compounds that were made, and how they can be used in small molecule activation, and catalysis. So, one of the things Pep and I've talked about is, is sending molecules to them to for them to use in some of their different types of catalytic systems. So, we're very interested in that.
Paolo 19:14
And this is fascinating, right? Because you're, you're you're looking at some, you know, new, surprisingly, new areas of chemistry. And you're after some properties that don't belong to other elements, right? Or the more well-understood transition metals, and you can do new things, you know, in activating extremely unreactive molecules, like, you know, CO2, for example, as that's, that's quite that's something, right? If If you can achieve a level of efficiency, and people have traditionally tried the sort of old tools, right, for us, what's new for a new results. But it doesn't seem the correct way. It looks like you need to be braver here.
Dr. Robert J. Gilliard, Jr. 19:56
Yeah. So, I think you know, like you mentioned, people can do small molecule activation. A lot of people can. Well, there's a discussion about how much energy it takes to to activate the small molecule. But you can do small molecule activations with a lot of different transition metals.The reason people are interested in main group elements, particularly things like bismuth, and because a lot of folks forget that bismuth is one of the or is the only nontoxic group 15 element. So, it's almost completely nontoxic. Unless you add something else that is toxic to it, it alone is nontoxic, and in the properties are still not well understood. So, Pep's group have made some of the first redox active bismuth complexes. In my group, we've made some very rare examples of bismuth cations and low coordinate bismuthinidene molecules. And these types of compounds, that chemistry that small molecule activation chemistry, and different types of catalytic processes. This is very new; we're talking in the last one to two years that this is really been studied.
Paolo 21:04
What's the future for this area? What do you see what you see happening in the coming two to five years?
Dr. Robert J. Gilliard, Jr. 21:11
I think what will happen in general, with these types of complexes, is that main group redox active chemistry and catalysis will not be as uncommon as it is, right now. I think this will pretty rapidly emerge as folks like Alex Radosevich at MIT, folks like Pep at Max Planck and our group work together with synthetic folks and structure and bonding folks to really advance the field. And that brings up you know, kind of another topic on these types of collaborative effort. I think, if you want to solve these kinds of grand challenges in chemistry, is going to take people working together, I think the days of, you know, doing solo chemistry, you're really taking on the huge challenges are pretty much over.
Paolo 21:59
And and you're demonstrating in your approach to the work that the most exciting science is happening at the interface between sort of different different disciplines, right? It's, you know, having this sort of multidisciplinary and collaborative, as you're saying now, approach is really key to get real disruptive results for the for chemistry or any science really.
Dr. Robert J. Gilliard, Jr. 22:20
And I think this is what makes it exciting for me, being able to not be so restrictive in thought, you know, thinking, you know, there's one specific thing that we have to target. And this is the only thing is going to be useful for. Well, actually, sometimes the combination of traditional chemistry in one area and traditional chemistry and another one combine together yields a result that, you know, is more important than either the two alone in many cases. So, we have some of those scenarios that are developing in our group, whoever we've made molecules that are important. And we've looked at applications that are important, but when you put them together, you find really some unusual properties that you wouldn't have predicted before.
Paolo 23:09
Do you really think that synthetic chemistry is going to look different few years down the line?
Dr. Robert J. Gilliard, Jr. 23:13
I think there's always innovation, right. And synthetic chemistry is totally unpredictable in terms of how much you know, you know, fundamental science has been explored. And how much of that is is going to be applied. But I think there's absolutely no doubt that the applications of main group elements will rapidly emerge, we're seeing all different types of chemistry being developed across both the S and P blocks of the periodic table that just couldn't have been predicted. even five years ago, the field is developing so quickly at this point, that, you know, we have so many journals, and so many investigators it’s even difficult to keep up with, even for somebody like me, who this is what I eat and breathe, and you know, and read constantly. And still Is this a lot of information.
Paolo 24:04
Yeah, absolutely. And it is very interesting, what you're saying because very often chemistry is perceived as a discipline, which is not really progressing anymore, right? Particularly if you compare it to, you know, the booming life sciences, you know, think about genetics, right? Or all that sort of areas in life science. And this is absolutely not true, right. And perhaps we are at the verge of enriching the tools at the disposal by synthetic chemist and, you know, opening new horizons, which is quite exciting time.
Dr. Robert J. Gilliard, Jr. 24:38
Right? Absolutely. And there's this in the main group field, this this subset of main group chemists that are interested in transition-metal-like chemistry of the main group elements, meaning that you take a main group element complex, and it behaves in pretty much the same or a similar way that a transition metal complex was. That thought or idea had been out in the literature for quite some time, but you can see that there are intervening years where there's a lot of activity, and then it kind of slows down. But now we're in the middle of what I consider to be a huge upswing in terms of the number of investigators that are exploring that type of chemistry. So, I would absolutely reject the notion that chemistry is, is anyhow dead. There's a lot of innovation that that is taking place. And that will continue to take place.
Paolo 25:28
And I'm really glad you're going there. Because, you know, very often the driver is or has been, right, let's, let's try and take something that works now, I don't know the use of precious metals and replace it with something cheaper, right? Or more readily available. And, and that's, and that's like an obvious rather, if you wish, but I don't think that is the most interesting part. Because what is what is more interesting, what you find afterwards, is that yes, you can potentially replace, you know, these other materials in the same application. But the beauty of it is they actually open the door to different activities and different potential reactions. And that's a real progress.
Dr. Robert J. Gilliard, Jr. 26:06
I think you're absolutely right. I mean, a lot of times when we discuss different types of Earth-abundant chemistry, a lot of folks go to the narrative of you know, there's a lot of palladium catalyzed coupling chemistry. You know, if we could take bismuth instead of palladium and go from, you know, bismuth one to bismuth three, and do an oxidative addition and reductive eliminate to get back to the starting material. Well, that's ideal. And that's nice to say. But you're right. The reality is, what you observe with bismuth may be radically different than what you observed with palladium. But it can also be just as valuable in many cases. So, the potential for the new reactivity, I think, is equally important as being able to mimic transition metals, because we don't need to mimic them necessarily. Because there's, you know, a lot of transition metal compounds while they are expensive, the amount you need is quite small in many cases. So, I think the potential for new fundamental chemistry, different types of bond activation mechanisms for the main group elements is really the motivation, some developing new chemistry.
Paolo 27:15
Is there still space for studying further antimony or germanium? Or even, you know, some better understood elements like the alkaline Earth metals?
Dr. Robert J. Gilliard, Jr. 27:28
Yeah, I think there is huge potential for all of these types of elements that you mentioned, because you mentioned the key point that the thought, particularly by folks that are not in the main group field, is that there are a lot of, you know, we already know what they do. Well, that's actually not true. I think there's a perfect example of us not knowing everything about the elements that just came out a few weeks ago, I commented on it for C&E News. The discovery by Sjoerd Harder's group and the alkaline earth metal, calcium can activate dinitrogen. So, dinitrogen activation is typically a transition metal-based process. And that's where it comes into play that low coordinate S block elements, we've worked in this area folks like Cameron Jones, and Sjoerd Harder's worked in this area, Mike Hill have developed these types of systems where if you can manage to stabilize these low coordinate S block complexes or alkaline Earth, they are Earth abundant molecules, they are in many cases biocompatible. And then if you can do something like dinitrogen activation, which is typically mediated by a transition metal, then that that is a valuable process. And no one knew until a couple of weeks ago, that that type of system was possible. And that discovery is only possible, because of low coordinate, low oxidation, chemistry, innovation in that area, you will never get that application.
Paolo 28:58
And this is only possible if you look at it from the right perspective, right? With with the idea of getting the fundamental understanding
Dr. Robert J. Gilliard, Jr. 29:05
Right. Folks like like, in my area who study different ligand-based strategies, what happens when you coordinate a specific type of ligands, such as NAG-MAG, such as a carbine into an alkaline Earth metal, what happens when you reduce these molecules when you start to form cations. You have to understand that chemistry to be able to get to anything on the applied side.
Paolo 29:27
Robert, this has been you know, a fascinating conversation. But then I feel like we only scratched the surface and this, there's so much in your work and there's so much in your passion in describing you know your work, but in general, what's happening in the chemical field. It's refreshing really. So, so I just want to congratulate you for that. So, you know you're obviously you are in a in a growing field and there's certainly a bright future ahead for you. If you had to look back, what were a couple of key things for you as you were growing as a scientist, and that you will pass on as an advice for younger scientists just starting their career?
Dr. Robert J. Gilliard, Jr. 30:06
I think, in terms of what I found to be useful, is be somewhat fearless. And when I say that, I mean, fearless in terms of don't be afraid to tackle new challenges, to explore new areas to venture out and, you know, travel to different areas, because one of the things that was really important in the advancement of my career was going to Europe, meeting folks there. I did a postdoc in Europe, I spent time at ETH Zurich. And I met and I was able to collaborate with a different set of people that I would not have met if I stayed just here in the United States. And those types of taking those types of so-called risks and venturing out is really what helped me throughout my career. But that was the same thing going back to when I started, right. So, if I hadn't done that undergraduate research, if I didn't take the initiative to knock on a faculty members door and say, hey, I would like to, you know, explore research in your group, I wouldn't have even known about this field. So, being somewhat fearless and being taking the initiative to reach out and explore is something I think is very important throughout your career.
Paolo 31:26
That was Dr. Robert Gilliard, Jr., Assistant Professor of Chemistry at the University of Virginia, and one of the Chemical and Engineering News' Talented 12. Thanks for joining us for this season two episode of Bringing Chemistry to Life and keep an ear out for more. If you enjoyed this conversation, you're sure to enjoy Dr. Gilliard's book, video podcasts and other content recommendations. Visit thermofisher.com/BCTL to download them. This is where you can also request your free podcast T-shirt. Check your app for the Episode Notes. We added the URL there as well. This episode was produced by Matt Ferris, Matthew Stock, and Emma-Jean Weinstein