lost in the fog of a cosmic storm floating on
whimsical wavelengths is the norm dancing through
the stars chasing spectrums of light The countdown
to the end of season two has begun. After this,
there'll be three more brand new episodes. You
don't want to miss them. They're going to be
awesome. I'm not sure what order they're going
to come out yet. I might end up actually making
the one I thought was going to be the last one
be the next one after this. I'm not entirely
sure. Juggling different things. During the rest
of the summer, there will be encores to fill
the gap and keep the podcast feed fresh for those
algorithms. It's also a chance to explore older
episodes if you haven't gone back in time into
the back catalog. There will also be more time
to reminisce on the season that was later. Today,
we're going to look at chemistry and material
science. Maybe another terrible, nerdy science
pickup line? I usually keep my 4F electrons buried
behind two layers of shielding, but you've got
the perfect sight symmetry to get through my
guard. Now, to make that make sense, hopefully,
anyway, Today we're going to be discussing lanthanide
elements and how we can design molecules to build
the technology for today and the future. In the
periodic table there are 15 lanthanide elements
ranging from atomic numbers 57 to 71. In my own
field of mineral exploration I would call them
rare earth elements. Perhaps you have heard about
them on the news over the last few years. They
are the linchpin of much of our modern technology.
This group is special because of their properties.
If you think back to grade school, we talked
about elements and their valence shells. Electrons
exist in regions away from the nucleus of the
atom. All elements or atoms want to have full
valence shells. Gases typically want to gain
electrons. Lithium and all the rest of the alkalis
have only one extra electron. They're so reactive
in part because the energy released by losing
that one electron. Lanthanide elements want to
lose three electrons and become three plus. So
far, no difference except the charge. But the
bonding is very different. Most of our everyday
substances, like water or carbon dioxide, they
conveyantly bond, meaning they share electrons.
The bonds themselves have shapes. Think of water
again. The two hydrogen atoms form bonds at 104
.5 degrees based on balancing electromagnetic
forces on the atom. Lanthanides don't share.
They exist. Once they are ionized, they will
surround themselves with as many other atoms
that have negative charge as they can. This makes
them useful and opens up different possibilities
to create novel molecules and structures. I think
this is as far as I can credibly take this. So
let's bring in today's guest. Today we have someone
who describes his research interest on LinkedIn
as looking at controlling the super molecule
assembly of inorganic building blocks to yield
materials with interesting properties. Kind of
like building things out of tiny Lego bricks.
He is a PhD candidate at Simon Fraser University
in the Department of Chemistry in the Lesnoff
Group. Please welcome Thomas Karpiak to the pod.
Hi, thanks for having me. I'm excited to be here.
And to be honest, I'm really happy that you came
on. And before we get you to help explain the
terrible pickup line that I used in the intro,
a little bit about you. So how did you end up
in a PhD project? Did it start with Legos as
a kid and just kind of, you know, let's do this
at the atomic scale? Yeah, I mean, I definitely
did like Legos as a kid, although I think exclusively
Star Wars Legos, so I don't know how that factored
in. But I think I'm mainly drawn to chemistry
because it's kind of like solving puzzles. Like
even when you're introduced to it in high school,
it's balancing equations, doing these sort of
things. And thankfully, that thread even continues
to like the highest levels of chemistry where
even now. You know, it's a lot of just using
extremely sophisticated instruments to really
just understand how molecules behave, and otherwise
you can't really, you know, it's a new area that
no one's ever looked at before, so you have to
sort of solve that puzzle. So I've been studying
as a grad student at SFU for four years, and
so I was first exposed to scientific research
in my last year in my undergrad degree, where
I did some summer research with... the Lesnov
lab. So we really do think in terms of Lego bricks
in our lab, our research is kind of like, instead
of some chemistry people think of, which is doing
synthetic work to stitch atoms together into
a new molecule. Instead, we think of taking individual
molecules and how are they going to assemble
together to give a certain structure. that this
material formed out of molecules will have properties
beyond even what the molecules normally have.
It sort of emerges from the structure. And so
this is what we call supramolecular chemistry.
And then my specific focus is on looking at lanthanides
and their supramolecular chemistry. Okay, one
follow -up question, because I'm sure I've walked
through the area for the Lesnov group, but is
there like... Any Lego statues of any sort of
like a mascot or anything like that for the lab?
I don't know if anybody's actually picked up
or grabbed any Legos to make anything, but we
probably should. It's a pretty good analogy for
the sort of work we do. I'll have to think what
we can do. Maybe we can make some molecules out
of Legos. I'll have to crack open some old bins
of toys. All right. So to the science, I guess
to begin with, let's start with your topic, which
is what are the lanthanides? Yeah, right. So
the lanthanides, it's a series of 15 elements.
It's tucked away at the bottom of the periodic
table. It's lanthanum through to lutetium. And
they differ from a lot of other elements that
people are... used to in that their electrons
are sitting in a different set of orbitals called
the f orbitals so this is different than what
organic chemists might play with stuff like carbon
nitrogen oxygen these have their electrons in
p orbitals maybe a bit simpler and then you know
an inorganic chemist might work with transition
metals something like zinc iron platinum these
have their electrons in d orbitals and they have
slightly more complicated behavior So the higher
or the further along the alphabet you go, it's
just further from the nucleus, right? Yeah, essentially.
And generally, I guess you could say the chemistry
gets a little bit more complicated or a little
bit more obscure. And because of that reason,
actually, comparatively, the lanthanides have
been fairly understudied. So, for example, I
have a quote here from... an introductory textbook
to chemistry from 1971, and it states about the
lanthanides, quote, lanthanum has only one important
oxidation state in aqueous solution, the 3 -plus
state. With few exceptions, this tells the whole
boring story about the other 14 lanthanides,
which is a little bit of... egg on their face
because uh nowadays in the present day the lanthanides
or or sometimes we refer them as the rare earth
elements they're actually extremely industrially
relevant um i pulled up some stats so so uh although
In 1994, that's the last I could go back to.
The global mining production of rare earth elements
was 65 ,000 metric tons. That's quadrupled to
the current day. And now the rare earth element
market is valid at about $4 billion and is expected
to raise to about $6 billion by 2030. So these
elements are actually now really important for
a lot of industries. The main one that people
might have heard of is they're used in permanent
magnets, which are now becoming really important
because they're essential to electric vehicles,
wind turbines. And then even so, like very small
amounts of these elements are still found in
almost all the technology you have, you know,
like your cell phone, your TVs, your computers,
your cars. And usually based on their magnetic
properties and based on their luminescent properties,
they're present in like... All of your LEDs,
your lasers, they're used medicinally for bioimaging
of cells. Even a funny one is that europium,
which will emit red light when you use UV light
to shine on it, it's actually used inside of
the uro for anti -counterfeiting. I don't know
if it was a coincidence that they used europium
for the uro, but there's a lot of different uses
for these elements. I think that just goes to
show like they're always in the news, too, right?
Like if we dive just sort of really adjacently
into politics, I mean, geopolitically, Canada
is being a place where we have a lot of them,
but we don't mind them. And there's other places
in the world like China, which has a stranglehold
on them as far as like. the ability to export
and use them, right? Yeah, you're 100 % correct.
There's definitely a lot of interest and a lot
of it stems politically about acquiring these
metals. So you could say, even without getting
into the details of the research yet, like this
really is already, you know, it's something that
could have a real effect on how we interact with
the chemistry moving forward, without even getting
into the research yet in the paper, right? Yeah,
I mean, any steps forward with fundamental understanding
of these elements can sort of trickle down to
all of that. And the nice thing for me is that
then I get to do the fundamental chemistry, which
I enjoy, and the sort of puzzle solving there.
And hopefully it can have some sort of ramifications
in some of these places. Right. So to kind of,
I think if there's one more step here, and I
was honestly a little confused when... trying
to brush up on my atomic chemistry for the understanding
of this episode. Lanthanides have, well, you've
already mentioned it, they become positively
charged when they lose their outer electrons.
And their outer electrons are not in, they're
in orbits beyond F, is that correct? Or they're
closer than F? This was the part that I was a
little confused by because it's, you know, it's
what also makes the pickup line joke work at
the beginning, right? Yeah, so depending on which
lanthanide you have, so they each will lose three
electrons to become three plus charge, and all
the remaining electrons will be residing in the
F orbitals. The three that get lost, they can
originate, well, two of them will originate from,
it would be called the 6s2 orbitals. So those
are like basically some orbitals that are beyond
the F orbitals. But because the electrons in
them, disappear in every case for all the lanthanides.
You don't really have to worry about them. They're
gone. You'd have to get to elements beyond the
lanthanides, like if I remember my periodic table
correctly, like up to lead. And then lead has
particular chemistry because the electrons in
the 6s2 orbital are then present and they're
imparting certain chemistry. But the neat thing
is that because they all lose three electrons
and the only ones remaining are in the F orbital,
they all have fairly similar chemistry from that
perspective. Right. And I guess the next thing
on my list is to figure out the difference between
bonding with a lanthanide and what people were
probably taught in high school of like, let's
just take a water molecule, for instance, and
you have that covalent bond. So what's the difference
there? Yeah, so covalent bonding is where your
atoms are sharing their electrons and forming
bonds that have a very set geometry based on
the electrons, which reside in orbitals that
are spatially defined. So when you are overlapping
those orbitals to share your electrons, you have
a very set geometry of what forms. So every carbon
is... you know gonna have either like a tetrahedral
shape and it's gonna lead to structures we all
know, like a diamond, or if they have a trigonal
planar shape, they lead to graphite. So it's
very well understood. To actually jump to understanding
lanthanide bonding, it's actually good to segue
through sort of the typical bonding in what we
call transition metals, which are the block of
metals in the middle of the periodic table, sort
of what we think of as metals, like iron, zinc,
stuff like that. Their bonding is sort of a middle
ground because now... The electrons forming the
bonds are in the d -orbitals. And d -orbitals
are similar but more complicated. They stick
out into different areas around the metal. They
stick out from the nucleus. And like a lanthanide,
the d - sorry, the transition metals are positively
charged. We have to call them cations. So they
form bonds with discrete anions that are going
to sort of approach around. So there's some sort
of like, you can imagine at the start, there's
some sort of coulomic attraction that's part
of that. Positive is attracted to negative, right?
Back to physics like that. So just two charges
is what you're saying? Yeah. Yeah, there's positive
attracted to negative, but then also it becomes
more nuanced because the electrons in the d -orbitals
actually have a repulsion to the electrons on
the anions. So you're overall attractive, but
you have certain geometry that will be better
to favor or to reduce repulsion between the orbitals
and the anions. So this leads to various... like
discrete geometries to reduce repulsion between
orbitals so for example a transition metal the
most common sort of picture you'll see is that
central positively charged metal and then surrounded
by six anions we call them ligands which the
six of them will be sort of situated like when
you have like a playing jack we call like an
octahedron So you can imagine they're all six
sticking out and sort of equally spaced around
that central metal. But in comparison to this
with the transition metal, when you get to a
lanthanide, you see far different behavior because
whereas a transition metal has its orbitals sticking
out and wanting to interact with those ligands,
the F orbitals are sucked in and buried. much
closer to the nucleus. So there's minimal interaction
with the environment. And this has to do with
the particular F orbitals. Like say if you take
like palladium, for example, in the transition
metals, palladium has 46 electrons, right? But
it's only 10 of those electrons we care about
that are in those sort of frontier d orbitals
and interacting with the ligands. The other 36
are... the core electrons they're closer to the
nucleus they're more tightly bound and they're
already not really doing anything they're just
the electrons you carry because you have all
of your protons and neutrons you know as you
go down the periodic table with a lanthanide
though the whole situation flips the f orbitals
actually lie closer to the nucleus and so all
the orbitals that hold the core electrons are
the ones that are farther out at the frontier
so if you're a ligand and you're approaching
this metal you're not actually seeing any orbitals
to interact with you're just seeing sort of like
you know it's like a core electron orbitals they
don't really do anything so i kind of think of
a lanthanide like like a big bowling ball of
positive charge. And so all of the anionic ligands
just want to sort of approach. And if you think
back to elementary chemistry, the bonds we're
going to form here are things like ionic bonds,
just like how sodium. And in sodium chloride,
you don't really have any electrons there guiding
the bonds. You just have positive, big ball of
positive, attracted to big ball of negative.
So it's the same sort of situation with the lanthanide.
So you can think of them a bit like you used
a bowling ball. I'd use like a point source.
It's just a positive charge that is going to
interact with other negative charges. It's not
doing anything. You're not changing the lanthanide
in any way. You're not interacting with it in
any way other than it's a charge. Yeah, well,
it's kind of like the electrons on a transition
metal have some sort of, they are driving a certain
geometry to form around that metal, but the electrons
in a lanthanide don't care that much. They're
not having an influence on the chemistry. They're
sort of tucked away inside. The reason that all
this is really important, though, is that, you
know, Well, the buried electrons don't care about
what geometry forms around them. The geometry
that forms actually ultimately decides how those
electrons end up behaving. So the analogy I came
up with is that it's kind of like how if you're
a musician in a room. based on the shape of that
room, the acoustics are going to change and you're
going to feel that change. So it's just like
these electrons sitting in a certain environment.
As it changes, the behavior of the electrons
is going to change. Us as chemists, we specifically
like to contextualize this using concepts of
symmetry. So like, for example, if you're this
musician, if you're in a, you could be in like
a triangular shaped room, a square shaped room,
a pentagonal shaped room. We would say that all
of those rooms have a sort of rotational symmetry.
If you close your eyes and you take the triangle
and rotate the room by 120 degrees and open your
eyes, it still looks the same to you. So there's
symmetry inside that room. There's other types
of symmetry. You could imagine a concert hall,
right? If you're standing at the stage of a concert
hall, then there's no rotational symmetry there,
but the left side of the room looks like a mirror
image of the right side of the room, right? So
that's a different type of symmetry. This is
mirror symmetry. And we use that language as
chemists a lot of the time to understand what's
happening. Because again, based on the symmetry
of the environment this lanthanide is put on,
then those electrons are going to behave differently.
And that's what informs the properties that they
end up having. Okay, so when I say, I usually
keep my 4F electrons buried behind two layers
of shielding, you've got the perfect site symmetry
to get through my guard. I guess that works because
you need symmetry to be able to interact at all
or to be connected to the 4F electrons. And under
normal circumstances, they are not going to impart
anything to the room. Yeah, exactly. And it's
a very flipped situation than any other element
where there's a really, you know, there's an
interplay between electrons. want a certain environment
and that environment changes how the electrons
behave but here the we have to use our chemistry
to force a certain environment to control how
the electrons behave and you know To reiterate,
the behavior of electrons is what causes all
properties in chemistry. So this is what's going
to cause these elements to show their unique
magnetic properties and unique luminescent properties
and allow us to have these fancy applications
for LEDs and magnets and stuff like that. You
know, what you just said there was something
that obviously rings true in my head, but I don't
think I've ever heard anyone say it that way,
at least not. in a very, very long time, that
the chemistry that we interact with on a daily
basis is really controlled by the electrons.
So I guess that should be a take -home for anyone
who's listening along. But more importantly,
also, do you know anyone that would use such
a terrible pickup line at a chemistry concert?
I'm not sure what your success rate would be.
They'd have to definitely know their lanthanide
chemistry. I think success is getting a laugh
and not actually picking anybody up. Or getting
that confused look is like, you're for cereal?
Yeah. All right. So to take this to from now,
we've understood that the electrons are what
make the chemistry and the interaction and the
properties of the chemistry that we interact
with. So I know this might be a tall ask. How
do we go from this group of... Lanthanides, this
group, has a wide variety of different properties
that we care about, from luminescence to magnetics
to superconductance. So how do those electrons
create these properties? Yeah, so there is 15
of these lanthanides, and each one has different
numbers of electrons. and then as you're putting
different numbers of electrons inside these orbitals
they're interacting differently the electrons
repel each other so we call it an electronic
structure which says that you know how happy
is this element as we arrange these electrons
in different ways um you know this has to do
with these orbitals which are sort of like a
you know not really a physical they don't really
physically exist but we sort of have to understand
them to the basis of like you know quantum mechanics
and stuff like this but ultimately it's just
how are these electrons moving around happily
inside that element so for example for luminescence
we can have light which is a form of energy be
absorbed by a lanthanide element this energy
needs to go somewhere so what happens is that
your electrons which are in a happy configuration
will then take on extra energy and this lets
them go into maybe some different configuration
that's more destabilized. Eventually these electrons
are going to want to relax back down to their
normal configuration and along the way they'll
lose some energy in the form of like vibrations
out of the molecule but eventually we need to
go from one configuration back to the the original
one and that's going to mean losing the rest
of our energy we've picked up from the light
and you know in order to conserve energy that
means the element then has to emits all the extra
energy in the form of another photon so we basically
absorb one photon it could be something like
ultraviolet light which has a lot of energy and
then after we lose a bit internally in some processes
of the the lanthanide then we eventually emit
another photon but it's going to be lower in
energy and if you think back to electromagnetism
in the spectrum of light, if we take less energy
from ultraviolet, we actually end up in the visible
spectrum. So this means that, for example, I
think I mentioned it, europium, if it accepts
UV photons, it will ultimately end up emitting
a very characteristic red light. Terbium is another
lanthanide. It will emit green light. And even
then, you know, beyond what we're familiar with
with the visible spectrum, you can have some
lanthanides like neodymium, erbium, ytterbium,
they actually emit in what we call the near IR,
so the infrared, near infrared light. And those
wavelengths are actually very important, for
example, for like... Surgeries and medicinal
applications, fiber optic and telecommunications,
both of those technologies hinge on the near
IR emission of neodymium in lasers and erbium
in fiber optic cables. And yeah, so every property
of these lanthanides sort of hinges on these
same sort of ideas. They have their magnetic
properties because they have so many unpaired
electrons that can behave in certain ways to
create magnetic moments. The superconducting
properties might be a bit beyond my pay grade,
but for sure, as far as I know, a lot of the
cutting -edge research there is finding some
success using lanthanides. For example, there's
some very funny compounds where their chemical
formula is lanthanum H10, I believe. Which, if
you're a chemist, is a very strange formula,
because normally you don't have 10 hydrogen atoms
alongside one other lanthanide. But again, like
I said, a bit beyond my pay grade. It just means
future work, right? Yeah, of course. Okay, well,
the paper at the center of the episode is Strategies
to Control the Geometry and Symmetry around Lanthanide
Centers for Tailored Luminescence and Magnetism.
Now that we know what lanthanides are, we know
a little bit about their properties, we can talk
about the paper more directly. We've kind of
already talked about symmetry, so let's, I guess,
start there with geometry. What does it really
mean? Like, that's the center of the paper, is
it not? Yeah, for sure. Yeah, we can definitely
dive into that. So in this paper, we did... Where
I sort of haven't mentioned one thing, it kind
of ties back to my bowling ball analogy. I consider
them like bowling balls because the other aspect
of these metals, you know, because they're all
the way at the bottom of the periodic table,
they also have a really large size. They're large,
they're big elements, they're big cations. So
whereas I mentioned a transition metal might
have six ligands around it, lanthanides can have,
you know, it could have six, but it could have
eight, nine, up to 12 different atoms or ligands
approaching around it. And this is another thing
that... complicates trying to control their geometry.
So in this specific project in this paper, we
did limit ourselves to an analysis of lanthanides
with eight ligands, which are the most common.
And so if you imagine taking a central point,
which is the lanthanide, and all the different
ways you could arrange eight other points around
that to give a sort of, you know, equal distance
between them all. It actually turns out there's
about five ways you can reasonably do this. One
of them is probably pretty obvious to people.
You can take your eight ligands and arrange it
as a cube around that lanthanide. So a lanthanide
could have eight of its ligands basically arranged
as a cube around it. As chemists, we would call
this actually a very high symmetry environment,
right? Because if you take a cube, you can keep
rotating it around and it always looks the same.
But actually a cubic arrangement is not actually
very common. It's not very favorable to, you
know, what we're trying to do is we're trying
to minimize repulsion between these ligands.
That's what's controlling the geometry because
each ligand is negatively charged. They repel
each other. And so if you take a cube, you can
actually do a better job of maximizing the distance
between each ligand by just taking the top face
and twisting it by 45 degrees. Then we get what's
called a square antiprism. And so this is the
most common geometry you encounter with a coordinate,
with lanthanides with eight ligands. And the
symmetry of this, we still consider this. a fairly
high symmetry you can now take that shape and
if you look down its axis you can rotate it by
90 degrees and it will then look the same as
it did so we say that this has four -fold rotational
symmetry you can rotate it by sequential four
-fold rotations or 90 degree rotations four times
to return back to where you were But we have
five total geometries we can have. Another one
that's the next most common is called dodecahedral.
It's a little bit harder to visualize. You can
imagine taking your hands as like C -shapes and
sort of cupping them like this. And then if you
sort of, you're encapsulating that middle space
with your cupped hands. If you arrange sort of
eight atoms around your two hands, this would
give you dodecahedral geometry. And this is sort
of a bit lower symmetry. Another one that's a
bit easier to visualize than that is hexagonal
bipyramidal. This is simply putting six of your
atoms as a hexagon, as sort of the equator around
your lanthanide, and then putting one and the
second one at the top and bottom to make this
sort of hexagonal bipyramid is where the name
comes from. This you would also consider to be
fairly high symmetry. We have sort of this six
-fold rotational symmetry. And lastly is bicapped
trigonal prismatic geometry. This is actually
the third most common geometry. It's a bit also
hard to visualize. I guess I would recommend
anyone to look up. The photos in the paper will
do a lot better job than me trying to explain
them. But this is kind of like taking six of
your atoms as triangles above and below the lanthanide,
and then the remaining two sort of go outward
in the equatorial plane to give this. It's the
lowest symmetry possible range. But what we were
interested to do in this paper is, you know,
take these five geometries. And what was interesting
to us is that Each of these geometries, we could
look through the literature and see that they
all have unique use cases where they're pivotal
to allowing certain properties or behaviors to
occur. We have examples in the literature. But
do people have the strategies to use our chemical
tools, our molecules that we want to put around
the lanthanide to specifically cause a certain
geometry to occur? And that was the goal of this
paper. If I understood that sentence correctly,
the goal of the paper was to predict, based on
an ion, what symmetry or what shape it was going
to take. Well, we wanted to use existing tools
that can take a molecular structure and tell
us what the geometry is. What we had came up
with is that if we can look at all the existing
data that exists to date of lanthanide molecules,
and the way we can do this is essentially as
chemists, we look at molecular structures by
determining their structures with x -rays and
determining crystal structures. And so there's
a database that to date has like, I think, 1
.5 million structures of different... So if we
could pull out every single one that has a lanthanide
and run these structures through some programs
that tell us what the geometry is and then also
tie it back to see what the exact structures
are, then we can know which sort of molecules
we can use to specifically get a certain geometry.
So you're taking... molecules that you potentially
have never, that are not in the literature, that
are not part of this, and suggesting what geometry
they would probably take. I think, yeah, ideally
that's what it would allow, is that we sort of
wanted to sort of distill the existing information,
the data that's out there, so we could sort of
have general guidelines, so that someone could
take new molecules they're looking at that they're
thinking of sort of wrapping around a lanthanide,
and they would have a better idea of what geometry
it might give, or what modification do I need
to make to my molecules to have a certain geometry
to maximize for this property I'm trying to target.
So to sort of be able to distill that information
to have some general guidelines. So you could
say, that this is almost like a seminal piece
of work. Like this is what's going to allow for
speedier discoveries of like the different properties
of different anions and being able to really
use those chemistries in ways that as of yet
are undiscovered, but this gives them the tool
to try to narrow down where they want to go.
Yeah, I mean, I hope that people will find it,
you know, useful. I mean, it's not that a lot
of these sort of concepts didn't already exist.
Of course, chemists have been trying to tune
their molecules to gain certain properties for
a long time. But we hoped that even just through
doing this work and putting it out there, maybe
it gives people sort of a different perspective
to think about it slightly differently. And,
you know, if we can see in one area of the literature
that people are using one certain strategy to
do something and Somebody else is doing something
else or they're missing something over in another
area. There's a lot of lanthanide chemistry going
on, but maybe to pull it all out of the data
autonomously and then have it to present to people,
maybe people can sort of see more holistically
what are the different strategies people can
use. Okay, so I guess that's a good thing to
segue into. So what did people use in the distant
past? I have this, let's put some stuff beside
it and guess and check. They weren't able to
predict what a particular symmetry was going
to be, so they had to go figure it out through
x -rays. Or was there a bit more of a predictive
tool? When did we make that switch? Yeah, I guess
historically, again, so for... As an example
of what this sort of chemistry would look like
in practice, when we talk about ligands and putting
atoms around lanthanides, what we really mean
is not just the atoms that make those eight points,
but those atoms are ultimately attached to something
on the outside. So, for example, you can take...
Or you could even imagine like a claw machine
game that goes and picks up a ball out of one
of those machines, right? That claw that comes
down and grabs it, you know, some people do chemistry
where they're trying to replicate that claw shape
with a molecule. So it grabs onto a lanthanide.
We call these chelates in general. Chelate, I
think, I could be wrong. I think it is Greek
for claw. Claw machine, claw is like three pronged,
I think. But you could imagine trying to make
molecules that are two pronged. That's very common.
Three pronged. You could have a molecule that's
four pronged. And so if you think about a eight
coordinate lanthanide, maybe you take two of
those four pronged molecules and you go from
top and bottom and encapsulate them. And so then,
you know, with these different... sort of classes
of molecules. There's ones that people have done
a lot of work because they found that they would
give a certain geometry and then they can go
deeper into that same system and see how to further
tune it. And it is essentially like sort of you
design a ligand, you attach it to your lanthanide,
and then it is sort of, well, now I have to go
get the crystal structure and see what happened.
So there is sort of that guess and check, unless
you're sort of working with an existing system
where you have some... predisposition that you
suspect already. So I think there's a missing
side of this, because at least up to this point,
and this only just occurred to me, I'm really
thinking about these on the molecule scale. And
then you just mentioned crystals again. So you
have to be dealing with more than just a single
molecule here if you're going to create a crystal
lattice and be able to look at this. So what
is that like in the lab? Like, do you have to
have it at a certain temperature? How do you
maintain purity? How do you do that? To grow
like a crystal of what you need to study? Yeah,
yeah. So, I mean, crystal growth is a really,
really interesting aspect because you kind of,
you need to do it. You need to be able to grow
a crystal of whatever. You could have a discrete
molecule that contains a lanthanide that you
need to study. You could have... You know, something
like what I would study, which is a super molecular
system that's assembling and contains lanthanides.
You could have a material like a mineral that
contains a lanthanide. But in every case, you
need to use X -ray diffraction of a crystal to
see its structure. And so, yeah, it really is
challenging to grow crystals. But sometimes there's
nothing more than what, you know, you can buy
like a kit from Walmart if you're a kid to do
crystal growth. I mean, you take like... copper
sulfate or you take sugar or salt and you leave
it in solution and as it slowly sits there and
the solution is evaporating it's becoming more
concentrated the the molecules eventually are
unhappy that it's too concentrated. It needs
to turn into a solid. So the trick is that if
that's slow enough, then the molecules kind of
have time to find their place. And instead of
sort of making some sort of powdery sort of substance,
they'll actually grow into an ordered crystal.
You don't need big crystals for X -ray diffraction.
I mean, we're not growing, you know, centimeter
-sized crystals. You can really use something
as small as... Fractions of a centimeter, millimeter
scale, but still they need to be nice quality
crystals and it's definitely... I'm sorry, I'm
going down all kinds of rabbit holes now. Are
you using water as the solvent or something else,
random? Yeah, I mean, as a chemist, I mean, obviously
the chemicals are your tools, but beyond that
also solvents are a massive aspect of how you
control what happens because your solvent...
Water is a solvent, but you could have things
people are familiar with. Ethanol, as chemists,
we still use that as a solvent. It has different
properties of how molecules dissolve into it,
how molecules bounce around inside that solvent.
So a lot of times to make sure you can grow the
right crystal, it's about choosing the right
solvents or mixtures of solvents. A lot of obscure
stuff, liquids that people have never heard of.
A whole range. So a big aspect of it is choosing
the right solvent. We've gone from electrons
determining chemistry to bowling balls of positive
charge to how we put together lanthanide molecules
as little Lego blocks to growing crystals all
in one episode. I guess, though, for this, the
paper, though, everything really does come back
to symmetry, right? Including, like, you'll see
that symmetry directly in the crystal lattice
and the way that that crystal is growing. And
that's the whole point of hitting it with the
x -rays. So you can see that lattice effect.
Yeah, yeah. No, you're 100 % correct. I mean,
the fact that x -rays diffract off of a crystal,
the understanding of that is, I mean, steeped
in symmetry and using symmetry to understand
that for sure. Again, we do a lot of our... We
use the language of symmetry to conceptualize
a lot of stuff in this realm of chemistry. Have
you ever, or I guess someone in the lab, because
you're dealing with lots of other people, all
of a sudden just something doesn't make much
sense and they have to go and figure out was
there contamination instead of like a change
in symmetry? Because the x -ray doesn't give
you chemistry itself. It's giving you the crystal
lattice, right? Yeah, I think me. In my day -to
-day lab, I think I've definitely had a vial
where I was trying to make some certain molecule,
saw a crystal in there, went down to our diffractometer
and determined its structure, and it was just
some other thing. It's very common for us to
accidentally run. Okay, I won't say very common,
but for example, I've definitely accidentally
mounted a crystal and determined its structure
and found out that it was actually just sodium
chloride. I've done that before because, you
know, salt's pretty pervasive. If you're combining
ionic species, then they have counter ions. And
if the counter ion crystallizes instead of what
you're trying to make, then... And that can happen.
So for sure, it happens. It can be disappointing.
Or sometimes it can be surprising if you were
trying to do one thing and instead some other
molecule came out and crystallized. And then,
you know, you have to spend six months trying
to reproduce that result, which has happened
to some people. That's kind of where I was going.
I was like, hmm, I have a feeling this could
derail a whole PhD for quite a while if something
weird came out of it. Yeah, in our group, we
have... We have one structure. So, I mean, it's
a, you know, it's a computer file that people
pass around, basically. I think it's existed
for maybe 10 years where, you know, my boss with
a new student will be like, hey, look at this
structure. Isn't this cool? But he won't tell
them that six people have already spent, you
know, 10 years trying to remake it. Sort of a,
what do you call that? Not a golden, I don't
remember the name. But yeah, we've been trying
to redo it for a long time. that's hilarious
um okay let's let's circle back to something
that i kind of skipped over because this is one
of the reasons you mentioned luminescence and
i think one of the reasons we this technology
or this paper really allows for is trying to
figure out what magnetization is going to work
best and um the way i'm going to try to explain
it and that you correct me and so we'll flip
it on its head and see see how good i did as
a prepping for this All materials, once it has
charge, can eventually kind of flip its direction.
They call it quantum tunneling or relax. So it
changes its magnetization vector over time. And
so part of the lanthanides being plus three,
if you get the right symmetry. you hopefully
are going to be able to create something that's
long lasting. So therefore, you can use it in
something like a hard drive. You can be able
to keep information around longer. Did I get
most of that correct? Yeah, no, you're on the
right track. So what you're talking about there
are what's called single molecule magnets or
SMMs. This is like... This is a pretty highly
active research area, at least in academics currently.
These are molecules, like you said, that have
a large magnetic moment that you can sort of
manipulate, but the magnetic moment will only...
sort of exist in a coherent state once you've
cooled it to a low enough temperature. And like
you said, it's sort of like this magnetic moment.
You can imagine it pointing either up or down.
And if you tie that back to like a one or a zero
in a computer, then the theory is that, you know,
if you could toggle to control switching between
up and down, then you could have each molecule
storing information. And, you know, then you're
shrinking. data storage down to the atomic level,
like maybe a 100 -fold increase in information
density. So people are really interested in this
area. But you're right. So actually, the quantum
tunneling of magnetization is the remaining drawback
in lanthanide SMMs that needs to be dealt with.
The analogy I could come up with to explain this
is An SMM is kind of like, you can imagine somebody,
some person who only likes to sleep on their
side, okay? So they are happy to be either facing
left or facing right, right? But in order to
swap between those two positions, they have to,
for a moment, be sleeping facing upright, and
they don't like that. That's unfavorable. So
in chemistry, we call this... this is like an
energy barrier in order to switch between the
two configurations so like either pointing up
or down it needs to pass through a configuration
that's not happy and there's a barrier to that
this is why once the temperature is high enough
there's enough energy to easily pass over the
barrier and you can't control it. So as people
have been designing lanthanide SMMs, I mean,
the main thing they can do is use ligands where
their electron density is placed such to make
that intermediate position really unhappy for
the electrons in the lanthanide to switch from
up to down. But quantum... tunneling of the magnetization
it's it's as the name suggests it's a quantum
mechanical phenomenon which is kind of like if
you're watching this this guy sleep and you blink
and all of a sudden he was facing left and now
he's just facing right and you you totally missed
it there was nothing you could do to control
it i when we talk about tunneling it's a in quantum
mechanics it means skipping right through an
energy barrier And you can't even control it.
So if you have quantum tunneling occurring with
your molecule to a high degree, then your ups
and downs are getting scrambled. And you can't
get store information unless you continue to
cool it lower and lower. And the goal right now
is to design molecules that can operate at high
enough temperatures where you don't have to...
It's a similar problem with superconducting.
If they only operate it at a very low temperature,
you need to use things like helium for cooling,
and that's a very expensive and dwindling resource.
Yeah, and the neat thing that sort of drew us
into this is that the quantum tunneling of magnetization,
to fix this problem, it's purely a problem of
symmetry. So what researchers have found is that
in your molecule, if you can keep the magnetic
moment aligned with a very high symmetry axis,
so like in the square antiprism I mentioned or
in a hexagonal bipyramidal, geometry, then as
it's aligned with this very high symmetry, that
sort of helps it know where it's supposed to
face and keep it from slipping out of its orientation
and then accidentally just like you blink and
it switches to the other orientation. If you
can have very high symmetry, it helps protect
against that. And so that's sort of what people
are looking into now. And that's why we thought
it would be in that. Very useful to provide some
tools to know how to better control symmetry.
Right. See, everything does come back to symmetry
with Lance and I. At least for me. I'm sure there's
some other aspects, but for me, I find this very
fascinating. So for sure, I'd like to hope that
a lot of it is based on symmetry. So just kind
of summing up before we get to a question where
this is going for future work, the paper... broadly
speaking, is a series of techniques that can
help predict what shape or symmetry or geometry
individual negatively charged molecules will
make with a lanthanide. And so that way you can
help predict its chemistry. That's a two sentence
sum up. Is that roughly correct? Yeah, yeah,
exactly. Yeah. Cool. So how is this going to
be used for the future? Does this mean eventually
this may lead to brighter screens, maybe finally
get quantum computing off the shelf and into
our rooms? Or where do you think this is going
to lead us to? Yeah, I mean, I hope that the
project exists as a useful tool for... sort of
making it a bit easier for this one aspect. You
know, for sure in all of these applications,
the point is that there is a lot of other considerations
when you're trying to make essentially the best
example of something, right? I mean, you have
so many other choices that you have to make or
that you're constrained by. You know, if you're
trying to make the best single molecule magnet,
then you also have to deal with constraints on
what do the ligands look like? How do their electrons
force that magnetic moment to behave. Even now,
sort of the cutting edge research is saying,
well, once that molecule is inside of a crystal,
how are you dealing with other things like vibrations?
Vibrations can cause, can help you pass over
that energy barrier as well, sort of like your
molecule gets bumped and its spin gets switched,
right? So how are we now going to design crystals
that best? hold these molecules, or how are we
going to figure out how to put these molecules
anchored onto surfaces, like as a material science
perspective. So I don't think that this project
in and of itself is like a silver bullet, but
obviously in any field as you move towards sort
of the best example, you need to be accounting
for so many things that it can help people better
understand at least this one aspect. So yeah,
maybe the future is quantum computing and this
data storage idea I'm talking about. For luminescence,
there's some really exciting stuff with, I mentioned,
bioimaging and anti -counterfeiting as well.
People are looking at, you can have the luminescence
change. As a function of external stimuli, so
you could have maybe toxic gas sensors, you could
have fancy thermometers that use luminescence
as their output. This is some of the things people
are looking at. Actually, one thing that I think
might be quite interesting that we were able
to pull out from our results, which I really
haven't touched to up to this point, but I mean,
there's 15 of these lanthanides, right? One factor
of them, which is why it hasn't really mattered
up to this point, is that all 15 of them, although
they have different physical properties, chemically
they behave very similarly. That's why they're
kind of treated as this monolith. But actually,
you know, it's funny. The reason why they're
called rare earths is not actually that they're
rare. They're actually quite abundant. They're
called rare because when you have an ore or a
mineral and you need to get, like, I need just
neodymium. out of this ore to sell it. Well,
they're so chemically similar that it's extremely
difficult to separate them. And in fact, the
separation procedures are quite nasty environmentally.
So with that... that perspective of mining and
as they're becoming these critical minerals,
a lot of people are actually interested in being
able to selectively recycle certain lanthanides
from magnet waste or electronic waste. So in
our paper, we were actually able to say that
the preference for a certain geometry actually
slightly changes as you go across this series
of lanthanides. So there's a little bit of a...
There's a little bit of a trend of the chemical
similarity is it actually does have a slight
nuance to it for what geometry is preferred.
So if you could use those slight difference in
preferences for a certain geometry, maybe you
could design a molecule that can selectively
grab onto and extract a certain lanthanide, just
like a claw machine, right? And if you can pull
out... the lanthanides from a waste mixture and
be able to selectively recycle it, then this
is also something people are very, very interested
in. Cool. Okay. Well, I've had you here for almost
an hour. I do have one more question, actually.
I was debating whether or not to ask it because
you brought it up. Vibrations and crystals and
symmetry, some of these symmetry geometries are
not the same in all directions. And isotropic,
they're not, you know, they're different in different
directions. I assume that has a lot to do with
the properties of that material as well. Yeah,
for sure. So like a cube is perfectly isotropic.
It's the same on all directions. Yeah, every
other geometry will have some amount of... anisotropicness.
It looks different along different directions.
So that is directly what causes some of these
properties. So when you think of like a single
molecule magnet, by definition, actually, they
need to have an anisotropic environment, because
that anisotropic environment is what means that
it's Easier for the magnetic moment. Yeah, exactly.
And it's anisotropic where on one direction it's
unfavored. That's why if you have a cubic geometry,
you can't use that for a single molecule magnet
because it's isotropic. So for sure, this is
very important for all of these properties. I
wish I had asked that earlier. Okay, so now to
wrap it up, call outs. This is your chance to
call out future work. A funny thing you guys
have as a tradition in the lab. I don't know.
Whatever tickles your fancy. Well, I guess I
can shout out that. So this project itself, it
was sort of like my primary research in the lab
is more sort of hands -on, whereas this project
was really only on a computer. It was writing
code. It was analyzing data. But the fun thing
is where we're going next with this is that I
personally am kind of taking the ideas that And
from a lot of reading and going through the literature,
I kind of have now sort of gained maybe a bit
better understanding and then my own results
from this analysis. So the fun part now is going
back into the lab and seeing if I can sort of
prove myself right. Can I use my own ideas of
guiding symmetry? And can I make some molecule
that has improved? luminescence. Day to day in
our lab we don't really do the magnetism stuff
too much but we do look at the luminescence and
so I am working on a project right now that we
think we can directly tie in our case actually
the super molecular structure inside of a crystal
and how we're using that. to in turn control
geometry, control symmetry, and cause improved
luminescence. So this is something I'm really
excited about and we're kind of looking into
now. So that's where this is kind of going next.
That's a perfect way of just describing science.
It's not just one paper. It's always like, okay,
what does that give me? How can I use this? How
can I test it? And that's how it all moves on.
You ready for the infamous last question? I think
so. You think so? All right. Hit us with your
favorite science joke. All right. I had to go
with the chemistry joke. I mean, that seemed
the correct thing to do. So here's my joke. Two
atoms are walking down the street. One says to
the other, I think I lost my electron. And the
other says, are you sure? First one says, yeah,
I'm positive. Very, very nice. Very nice. I think
a lot of chemistry jokes are. Or not the ones
that get a laugh, but get a little bit of a...
A groan. I know, I know. But those are the best
ones. Like, I'm a big fan of dad humor. Well,
thank you very much for coming on to the show,
sir. Thank you for having me. That brings another
episode to a close. Remember, if you haven't
done so already, leave a rating, a review for
the show. It really helps the show get out to
new people. And we've only got three more episodes
left in season two. I'll see you in two weeks.
Always seeking.