Category Archives: Chemistry

LAWRENCE The University of Kansas senior class has honored a chemist with the 2023 HOPE Award to Honor an Outstanding Progressive Educator.

Shuai Sun, assistant teaching professor of chemistry, was presented with the award Nov. 18 during the Sunflower Showdown football game between KU and Kansas State.

The HOPE Award was established by the Class of 1959 and is given to a faculty member who greatly affects students lives and exemplifies Jayhawk values in the classroom through exceptional teaching strategies. Today, the award remains the only honor given to faculty by the senior class through the Student Alumni and Endowment Board.

Sun typically teaches between 300-600 students each year in introductory chemistry courses. The student who nominated Sun saidhe cares not just about students academic success, but also how they are doing mentally.

He helps students achieve their goals outside of the classroom, the student wrote. He has helped me through my tough medical times and has helped me with DEIB issues. He has been a very reliable and compassionate professor to me and many others.

Sun said he was deeply honored and humbled to receive the award.

This recognition holds a special place in my heart, as it reflects the meaningful connections and impactful learning experiences shared with my students, he said. I am grateful for their trust and the opportunity to contribute not only to their academic growth but also to their personal and professional development.

Sun earned a doctorate in physical chemistry (theoretical and computational chemistry) from the University of Alberta in Edmonton, Canada. Before that, he earned a master's degree in physical chemistry (colloid and interface chemistry) from Shandong University and a bachelor's degree in chemistry and chemical education from Shandong Normal University, both in China.

My journey in chemistry from my academic roots in China and Canada to teaching hundreds of students each year at KU has been driven by a passion for education and a commitment to the well-being and success of every student, Sun said. The joy and fulfillment I find in teaching are amplified by the engagement and curiosity of my students.

Sun, who also wonfirst place in Best of Lawrence for teacher five years in a row from 2019-2023, said the HOPE Award is a testament to the collective effort of the university community in fostering an environment where every student can thrive.

Together, we continue to uphold and advance the esteemed Jayhawk values in every aspect of our academic journey, Sun said.

Photo by Missy Minear, Kansas Althletics Inc.

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Class of 2024 honors chemistry professor Shuai Sun with HOPE ... - KU Today

If ever there was a time for chemists to show our mettle, this is it.

Projections indicate that if the chemical industry continues on its current trajectory, it will be responsible for 2438% of the total 202050 global carbon budget that would give us a fighting chance of limiting global warming to 1.5C. Or, to put it another more frightening way, business as usual is aligned with a 4C warming scenario.

The challenges are clearly unprecedented: predominantly fossil-based feedstocks, energy intensive production, inherent process emissions and complex but mostly linear value chains all work against the target low-carbon and more circular future state. Nothing short of a total rewire is required. But the flip side is equally true: the transition to a low-carbon, circular economy presents unparalleled opportunities for chemical innovation. So why do chemicals still sometimes feel like the elephant in the room?

As a chemist, I think we are well placed to rise to sustainability challenges by playing to our strengths. We have a head start when it comes to exploiting green skills and should capitalise on our existing toolkit. Our enquiring minds are primed to seek solutions to challenging problems, and we are steeped in navigating and managing risk. Even more fundamentally, we speak the language of carbon. While most of the population can claim they dont understand carbon emissions and footprints, we know exactly where the carbon is, long after it has left our labs and production facilities and flowed down the value chain.

Of course, we can cling to the barriers that frustrate our intentions. We know innovation is inherently difficult, especially when dealing with imperfect information. Many companies are finding plans to eliminate virgin fossil materials challenging to deliver, as recycled alternatives can still come with a hefty footprint of their own. But they cannot give up. Regulation can also be a double-edged sword. Few would decry progress towards a global UN Plastics Treaty, but the proposed EU Cross Border Adjustment Mechanism, which aims to level the playing field by taxing imports based on their associated emissions, is already meeting resistance over bureaucracy concerns.

There are increasingly positive signals, though. Regulators continue to internalise sustainability to align with an increasing stakeholder appetite for organisations to walk the walk on sustainability performance whether from end customers, buyers within supply chains or investors. Strengthening reporting and disclosure legislation is going further by linking to real climate transition plans rather than just laudable goals and the recent emergence of international sustainability standards clearly signpost what good looks like in this space.

This ever-strengthening link between organisations, their impact and how their stakeholders view their response will keep net zero and wider sustainability firmly on corporate agendas. Prevailing economic and political headwinds will only improve rather than erode the fundamental business case for sustainability and resilience. As customer-facing businesses look to their supply chains for help in meeting challenges, it will become increasingly uncomfortable for companies trying to hide upstream in the value chain.

So how do we, as chemists, maximise our role in realising positive sustainability outcomes in our organisations? I believe there are common themes we can draw on.

In my experience, few organisations have a firm foundation on which to build their response, and this keeps sustainability issues on the sidelines until someone comes asking. A pragmatic and beneficial approach is to map existing business or operating models against sustainability challenges, to properly understand what sustainability means in terms of risks, opportunities, impacts and dependencies and so frame this against other priorities. Introducing an internal carbon price can also be especially illuminating, helping to support business cases for targeted and prioritised interventions.

Beyond internal action we will also need wider engagements and collaborations if we are to fully match ambition with progress, especially those that bring us closer to end users and translate our chemistry into real world problem-solving. It is unlikely that any one business will solve its challenges wholly on its own and common solutions harbour advantages of lowering risk and increasing implementation efficiencies.

Most fundamentally though, I often find that organisations are failing to fully capitalise on the values and mindsets that already reside in their people, stifling productivity and what could be. When it comes to sustainability, most of us are already on the page. As individuals then, we need to champion our values and harness our skills. And as organisations, we need to create and live cultures where everyone contributes positively to the sustainability agenda so we can all play a fuller role in creating the future we need.

Roger Wareing is a former chemist turned business sustainability consultant

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Are chemicals the elephant in the sustainability room? | Opinion - Chemistry World

Elizabeths show Supper at Six was on the rocks in the penultimate episode of Lessons in Chemistry. What happened to the show within the show?

Considering the time period, it shouldnt be surprising that a lot of peoplemostly mendidnt like what Elizabeth Zott was doing with her series Supper at Six. It taught women more than just cooking, and she wasnt willing to lie about how great canned goods and processed foods were when she knew that wasnt the case.

That led to the series being on the rocks. Would Elizabeth make changes to protect herself and the staff, or would she end up walking? What would Elizabeth then do with her life?

In the end, Elizabeth decided she needed to stick to her values. As much as she loved cooking and loved teaching women they could be more than housewives, she needed to be true to herself. That meant leaving Supper at Six.

While at Mads science fair, Elizabeth realizes that she has truly missed chemistry. Thats what she wants to go back into, and thats what she ends up doing by the end of the series. As she realizes this, she decides to teach chemistry instead of teaching cooking.

Elizabeth doesnt leave everyone in the lurch, though. She secures a sponsor through Tampax and then announces that a new host will be selected from the audience. After all, many women have continued to show up to learn, and its their time to shine.

The final moments push us three years into the future, where Elizabeth is teaching menand women. However, she points out that they cant call her doctor yet. She hasnt finished her Ph.D just yet.

Lessons in Chemistry is available to stream on Apple TV+.

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What happened to Supper at Six in Lessons in Chemistry? - Claire and Jamie

The humble lines that link atoms and connote chemical connections in molecular structures are the simplest of chemistrys iconography. Yet those seemingly simple sticks belie our most complex and clouded concept: the chemical bond.

Bonds are chemistrys key intellectual property, but they are also a somewhat illusory idea. The chemical bond is a contingent and approximate concept, a chimeric heuristic that is moulded and adapted according to our need. Indeed, chemists still argue about what constitutes a bond, how it should be defined and whether they even really exist. Although if bonds are purely an invention, then it is one so supremely useful and utterly seductive that it is chemistrys greatest work of fiction. In our bonding collection, were celebrating the bond in all its fuzzy incarnations.

We might be approaching the point when the inadequate mental abstractions of the past start to hold us back

Despite a century of development in our increasingly sophisticated understanding of bonding, most chemists are content not to examine them too closely. The system first proposed by Gilbert Lewis in 1916 still endures as the cornerstone of chemistry education and practice and not because it is the most correct, but because it is so accessible and useful. Lewiss genius was intuiting his theory of electron pairing and sharing from observations made by other chemists and physicists regarding the structure of the atom, periodicity, and the properties and compositions of materials. When quantum physics came along a few years later, it promised to place bonding on a fundamental footing, and molecular orbital theory arguably could have superseded the Lewis model. Thanks largely to Linus Paulings valence bond theory, the Lewis model was instead adapted and incorporated, establishing its place as an ever-evolving idea.

More surprising than the Lewis models longevity, however, is that the phenomena it sought to explain are still being discussed and debated. What is a bond? What is going on in a bond? How and why do bonds form?We know that in covalent bond formation electron density accumulatesbetween the nuclei and energy is lowered, for example, but whether the basis for that energylowering effect is electrostatic or quantum mechanical is still debated.In this collection, Alistair Sterling and Martin Head-Gordon propose a theory that unifies the two sides of that debate. And Vanessa Seifert takes a nuanced look at how the way we think about bonds has helped chemistry progress.

Elsewhere in this issue, we look at the various ways bonds and bonding are still being explored and discovered. Mechanical bonds have gone from being a thought experiment to a new and entirely different type of connection that is essentially orthogonal to the outcomes of the Schrdinger equation. In the process, chemists have become expert at manipulating the delicate weak and non-bonding interactions that coax atoms into these unfamiliar arrangements. A veritable zoo of such weak bonds now exist for chemists to deploy in designing systems and engineering dynamic interactions. Finally, we look at the extremes of the chemical bonding spectrum and how the nature of the chemical bond changes as it is pushed into new realms by pressure and temperature.

Much has changed in the century since the Lewis model was proposed. In particular, the growth in computing power and computational techniques have overcome quantum chemistrys intital shortcoming of being too mathematically complicated to be of much use. Today, we have access to simulations at timescales and spatial scales relevant to understanding chemical phenomena. And the prospect of fully quantum calculations with quantum computers is on the horizon. As our understanding continues to develop we might approach the point when, in Lewiss words, the inadequate mental abstractions of the past start to hold us back. If that time is near, then bonds may yet come to divide us.

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Bonds are the ties that bind chemistry | Opinion - Chemistry World

ALBANY Sebastian Thomas had 10 assists in Wednesdays win against Boston University, a feat that tied a UAlbany mens basketball program record.

The scary part for UAlbany opponents?

Great Danes center Jonathan Beagle thinks Thomas, who transferred to UAlbany from Rhode Island, is just getting going. The talented big man, last seasons America East Rookie of the Year, actually thinks he somewhat got in the way of Thomas having an even better night in UAlbanys 86-72 win that opened Broadview Center.

"I think we're in a good flow, but, like we always talk about, we can do way better, Beagle said. I think I'm at the top of the floor too much, at the 3-point line, taking up his space. . . . I just need to get used to playing with these guys, and as we continue to do that, his 10 assists will probably go to 13.

It was probably too harsh a self-assessment, especially after a win that saw the Hudson Falls native contribute 14 points on 4 of 5 shooting from the floor, plus eight rebounds. But Beagles comments also showed how the sophomore is trying to learn the game of the programs new lead guard, who is doing the same with the Great Danes 6-foot-10 big man.

"He's the first center I've played with that's able to push the ball off a rebound, has play-making ability, can shoot it, finish, Thomas said of Beagle. He does it all. He's probably the first big man that I could say that I played with who kind of does it all.

While wing player Amare Marshall stole the show in the Great Danes Albany Cup win against Siena this past Sunday with a 33-point showing, Beagle and Thomas join Marshall in what UAlbany needs to be a high-scoring trio. Thats worked out so far this season, with Marshall averaging 17.4 points per game, Thomas scoring 16.6 and Beagle at 11.4 ahead of 4-3 UAlbanys 8 p.m. game Saturday against 1-4 Dartmouth at Broadview Center.

Each of those three players for UAlbany is capable of attacking in transition and in a 1-on-1 setting, but the Great Danes offense will be at its best when the 6-foot-1 Thomas and Beagle are able to add a potent pick-and-roll option to the menu for head coach Dwayne Killings team.

Once we figure out the pick-and-roll game, I think it will be something that a lot of teams will struggle with, said Thomas, who scored 16 points against Boston University.

But developing that on-court connection takes time.

"I think they really have a great respect for each other. They have a really good relationship; they spend a lot of time with each other, Killings said. I think what they can become is a really dynamic ball-screen tandem, if you will, a dribble-hand-off tandem. Some of that just takes time. Game reps, getting a feel for it.

Some of it, too, takes some re-programming.

For Thomas, that means being comfortable with heading up the floor without the ball in his hands on some possessions, so that Beagle can lead a fast break off his own rebound.

For Beagle, it means changing how he reacts after setting a screen.

In the past, Beagle set a pick, then usually popped to the perimeter to make himself an option for a pass on the perimeter. If Beagle got the pass, he was able to create his own shot or one for a teammate.

Now, its Thomas who can look for others, and UAlbany needs a rolling Beagle to create space for others and to be a threat to take a pass for a dunk.

So instead of constantly trying to be a facilitator, we want him to put pressure on the paint as much as he can, Killings said. And I think he's embracing it, it's just ... we all have habits that we do, [so] it's just [about] changing some of his habits.

I'm working on it, Beagle said. I've been watching film and I've been thinking about it more, but, give me a game or two, and I'll open the floor up more and I won't be in that habit.

UAlbany, though, already feels pretty good about its early season results. At 4-3, UAlbany is over .500 for the first time since February 2020 and is on its first three-game winning streak since February 2022.

When Beagle and Thomas fully get going as a duo?

Thats something that could make sure the Great Danes keep collecting wins.

I think they're coming along, Killings said. There's some possessions [already] that you're like, Wow, yeah, that's pretty impressive what those two guys can do not only for each other, but for other guys."

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UAlbany men's basketball: Beagle, Thomas developing on-court ... - The Daily Gazette

The newest bond in chemistry might not be a chemical bond at all.

The mechanical bond isnt something that you can really point to in space and say This is the bond, says David Leigh from the University of Manchester in the UK.

A mechanical bond is formed when one molecule is threaded through another, then cyclised or otherwise modified to trap the two components in a physically interlocked state like two rings in a chain link fence. Compared to the other bonds in the chemists lexicon such as the covalent bond, or even non-covalent linkages like the hydrogen bond, mechanical bonds are quite unusual.

Its a bond in that it holds two components together that would otherwise have independent degrees of freedom and fly apart, says Leigh, whose increasingly intricate interlocked molecules often incorporate multiple mechanical bonds in a single structure. But it differs from other kinds of bonds because you dont have intrinsic fixed limits to bond angles and bond lengths.

There is a lot thats different and special about the mechanical bond

Mechanical bonds are also unlike other chemical bonds in that they dont involve charge or the sharing of electrons, adds Steven Goldup, who makes mechanically bonded molecules with chemical function at the University of Birmingham, UK. The mechanical bond is literally just the inability of atoms and bonds to pass through one another, he says.

If you wanted to be really pedantic, and say that chemical bonds are about the sharing of charge between specify atoms, you probably would say it isnt a bond, Goldup adds. But the mechanical bond is a permanent interaction between two chemical entities that results in them not being able to separate which feels like a bond, Goldup says. It fulfills the macroscopic definitions of a bond.

The mechanical bonds unconventional nature including the large amplitude motions it permits between bonded parts is also its key appeal. Making mechanical bonds gives access to structures with properties that cannot easily be accessed any other way.

I think there is a lot thats different and special about the mechanical bond, says Fraser Stoddart from the University of Hong Kong, who shared the 2016 Nobel prize for his work on molecular machines enabled by mechanical bonding.

Mechanically bonded molecules typically fall into two broad categories. If a linear molecule is threaded through a macrocycle and then cyclised to form a pair of interlocked rings, the resulting structure is called a catenane. If the threaded molecule is fitted with bulky stoppers at each end which prevent it from unthreading, the result is a rotaxane.

The elaborate rotaxanes and catenanes made today can make it easy to forget that, until surprisingly recently, even the simplest interlocked structures seemed out of reach. In the 1980s and 1990s, threading molecules through each other just seemed virtually impossible, Leigh says. The structures produced in that period by Stoddart and [Jean Pierre] Sauvage were absolutely amazing.

The earliest reported example of a synthetic mechanical bond which Leigh recently revisited in his lab illustrates the challenge. The concept of the mechanically interlocked molecule had been floating around for a while when, in 1960, Edel Wasserman from Bell Telephone Laboratories, US, played the odds.

Wasserman mixed a 34-carbon macrocycle with a long chain molecule of similar size, which he then cyclised. If the long chain just happened to be threaded through the macrocycle at that moment, a mechanical bond would result. Wassermans idea was that maybe a molecule in a million will close with the thread through the ring, Stoddart says.

In a 1960 communication, Wasserman claimed he had detected traces of a mechanically interlocked pair of macrocycles made by this statistical method. But few were fully convinced by the experimental evidence Wasserman put forward.

In 2023, Leigh showed using modern spectroscopic methods that the catenane Wasserman claimed can indeed be formed by this reaction. It vindicates that Wassermans claims are justified, Stoddart says.

The milligram or so of material Wasserman made from 10 grams of starting material wasnt going to supply useful quantities of catenane, however. The next claim to catenane synthesis was even more remarkable, if no more practical. In 1964, Gottfried Schill from the University of Freiburg, Germany, published an approach called covalent templating. Using classical covalent bond chemistry he painstakingly constructed an interwoven polycyclic system, designed so that cleaving select covalent bonds in the last step of the synthesis would leave two rings held together only by a mechanical bond.

Once he had the bits and pieces linked by covalent bonds like acetyl bonds, he could hydrolyse them and he would have two interlocked rings, or a ring on a dumbbell, Stoddart says. Schill even went on to make molecular knots. It was remarkable chemistry I think he was worthy of a Nobel prize but it was 20-odd step synthesis, Stoddart says. So it was never really going to carry the day in terms of use.

The key step forward in philosophy and methodology came in 1983. Like Wasserman, Jean-Pierre Sauvage of the University of Strasbourg in France started with a mixture of a macrocyle and a linear molecule. Sauvages genius was to realize that you could use template effects to form threaded structures, says Leigh. Rather than rely upon chance association, Sauvage used metal ion templating to pre-associate the two starting materials, so that they were already in position when he cyclised the linear molecule to close the mechanical bond.

Following Sauvages advance, practical methods for making interlocked molecules, typically employing a templating or other associative interaction to hold the components in place, gradually began to appear.

The templating chemistry Sauvage adopted had its origins in macrocycle chemistry. In the 1960s, even macrocycles were extremely difficult to make, says Leigh. Being able to template things revolutionised that. This work was recognised by the 1987 chemistry Nobel, awarded to Donald Cram, Jean-Marie Lehn and Charles Pedersen.

It was an early Pedersen publication that set Stoddart on his own path toward a mechanical bonding breakthrough. In April 1967, just after starting his postdoc, Stoddart came upon Pedersens work in a brief communication. Petersen had reported the first crown ether, dibenzo-18-crown-6. I decided, being the sort of person I was, that if Peterson could make 18-membered rings, then maybe I could make even bigger and better ones, Stoddart says.

Stoddart made several macrocycles, up to 35 membered rings, from truncated cone-shaped carbohydrates called cyclodextrins. Then there was the disappointment, because they didnt do anything when we tested them, Stoddart says.

As Pedersen was already showing, however, there was plenty you could do with crown ethers. These cyclic structures could host all manner of guest ions and molecules, as Stoddart also began to explore.

It wasnt just the ether functionality of these macrocycles that could form non-covalent interactions with a guest molecule. One structure Stoddart made was a complex between dibenzo-30-crown-10 and a bipyridine platinum complex. The crystal structure revealed pipi stacking between an electron-rich benzene group on the crown ether and the electron-poor bipyridyl ligand of the platinum complex.

When the team subsequently assembled an all-organic hostguest complex between a crown ether and the linear organic molecule paraquat, the pieces clicked into place. When we saw the relationship between the ring and the paraquat, it didnt take much wit to see we were on the doorstep to the mechanical bond, Stoddart says. In 1989, the team exploited the pipi interaction between an electron-rich crown ether and the electron-deficient paraquat to assemble a catenane consisting of the crown ether mechanically interlocked with a macrocycle assembled from two paraquat p-phenylene units. The yield of that first reaction was 70%. And you can now make it literally in 97% yield, Stoddart says.

A key feature of Stoddarts structures, compared to Sauvages, was the strong pipi interaction between the component parts. When Sauvage washed the copper out, that stopped the crosstalk between the rings, whereas our rings had a lot of crosstalk and that meant that we could start thinking about making switches and ultimately machines, Stoddart says. In 1991, the team made a rotaxane version, which they called a molecular shuttle. That first shuttle was a degenerate system that just went back and forth, Stoddart says. But in 1994 we de-symmetrised it, to make the first rotaxane-based molecular switch. Myriad molecular machines followed.

Switches and machines were not the only way the motion afforded by interlocked molecules could be harnessed. In the early 2000s, Kohzo Ito at the University of Tokyo, Japan, invented a mechanically interlocked polymer which he called a slide ring gel. The material consisted of long polymer chains threaded onto cyclodextrins, forming mechanical crosslinks between neighbouring polymer chains rather than the usual covalent crosslinks. When you stretch a normal polymer network, stress builds up in the crosslinks, and thats where the polymer tends to break, Goldup says. The slide ring gels allow the strain to equalize across the network, and so the network effectively gets stronger.

Slide ring coatings featuring mechanical bonds have been explored as tough smart phone screens, and used in commercial products from golf ball coatings to sound absorption materials. They have even been investigated as stretchy binders for lithium-ion battery anodes.

Early in his independent academic career at the start of the 1990s, Leigh was looking to synthesise macrocycles that would absorb carbon dioxide from the atmosphere, when he accidentally made a catenane instead. At that time, making catenanes and rotaxanes was extremely rare, he says. Rather than Stoddarts aromatic stacking interactions or Sauvages metal ion templates, Leighs structures assembled due to hydrogen bonding. So we thought, lets see what we can do with those kinds of molecules.

From the mechanical bond assembly point of view, arguably one of Leighs key contributions is his 2006 active template approach. The active template turned mechanical bond formation from a supramolecular chemistry problem to a synthesis problem, Goldup says. The first active template systems took the idea of metal ion templates, and turned it into a catalytic process. The metal ion not only templated the association of the two components to be mechanically bonded, but catalysed the ring-closing step to form the catenane.

The latest iteration of this chemistry is the metal-free active template. Previously, most mechanically interlocked structures threaded themselves because they were designed to be the most thermodynamically stable structure, Leigh says. Those are relatively easy to make, he says. Much more interesting would be to form threaded structures that are not the most stable structure, Leigh adds. So how do you do that? Non-metal active template synthesis allows you to design molecules that will thread through each other, and the threading action causes them to react, he says. By stabilising the transition state, the threading action accelerates the cyclisation or stoppering group reaction. They just intrinsically form these higher energy mechanically interlocked structures on their own.

This chemistry is a world away from the original methods of Sauvage or Stoddart, which required many steps, were difficult to make, and required very specialist functional groups to be incorporated into the structures, Leigh adds. Now, with things like active template synthesis where the template interactions dont live on in the final product, you can make rotaxanes and catenanes out of almost anything, he says. Making catenanes and rotaxanes is now completely routine.

The intricately interwoven, multiply mechanically bonded molecules now being made illustrate how far the field has come. In the last 10 years, the level of complexity of mechanically interlocked molecules people are making, and the yields they are achieving, have gone up massively, Goldup says.

The research emphasis now is on application. A growing number of synthetic organic chemists, polymer chemists and beyond are beginning to introduce mechanical bonds into their molecules.

In the early days of mechanical bond exploration, the emphasis was on molecular machines. The mechanical bond is very mobile, and that caught peoples imagination, says Goldup, who spent several years as a postdoc in the Leigh lab making molecular machines. When Goldup started his own lab, he took a different approach. I was interested in how we can use the mechanical bond to solve chemical problems, he says.

Theres more to the mechanical bond than the motion it permits between bonded parts. A mechanical bond can be a very, very effective way of building up steric bulk, Goldup says. In a single step, making one mechanical bond results in a dramatic change in molecular shape that would take numerous covalent bond forming steps to reach. The resulting interlocked structure can be chiral even when assembled from two achiral starting structures. You can use that for sensing and catalysis, Goldup says. Were trying to solve the sort of chemical problems that everyone does in synthetic chemistry, just from a slightly different perspective.

One example is the enantioselective gold catalyst the team has developed. Gold catalysis is generally hard to render enantioselective because you have a linear coordination geometry at the gold, he says. That means the substrate binds on the opposite side of the metal to the chiral ligand. But with an interlocked molecule, the gold can be embedded within the flexible cavity created by the mechanical bond. We showed we got enantioselective catalysis, which was very exciting, Goldup says. Not because the catalyst was a world-beater, but because of the possibilities it suggests. These things are now relatively easy to build, and in theory we could use it to solve catalysis problems that cant easily be solved any other way.

How do you design and make a mechanically bonded molecule? Its essentially the same as for a complex natural product, Leigh says. The process starts with retrosynthesis with the one key difference that the molecule is being designed for function, not structure. If we do the retrosynthetic analysis and we realize that its much easier or cheaper to make the molecule if we include a methyl group, say, then well put that methyl group in, he says.

With natural product synthesis you dont have this structural flexibility. But once the molecule is made, the task is complete. With a mechanically bonded molecule, the finished product must do what it was designed for. A molecular walker that doesnt walk or a catenane that isnt threaded, those things dont tend to publish well, Leigh says.

Building a mechanically interlocked structure is now just another form of organic chemistry, Leigh adds. Once you design your molecule, you go away and build it using the same tools, skills and reactions that you would use doing natural product synthesis or a drug synthesis, he says.

The active template approach has turned mechanical bonding into a form of organic chemistry, Goldup agrees. Youre not thinking about binding constants, youre not doing titrations, you just mix three components and you get the interlocked structure you intended to get, Goldup says. The chemistry is now completely accessible.

But few organic chemists so far have really embraced the mechanical bond. If I was to go into an organic synthesis lab and say Do you want to make a rotaxane? I think most people would pull a face, Goldup says. Thats partly because the properties that mechanical bonds impart, and so the reasons for making one, are still being established, Goldup adds. Thats now our job, I think, to show people why they should make them.

One synthesis group starting to explore mechanical bonding is Ramesh Jasti and his team at the University of Oregon, US. Since his postdoc days in Carolyn Bertozzis team at the Molecular Foundry in Lawrence Berkeley National Lab, US, Jasti has focused on carbon nanomaterial synthesis. The one that really struck me was carbon nanotubes, which are very difficult to synthesise with control over the structure, Jasti says. He set out to assemble short sections of nanotube bond by bond, developing ways to make a carbon nanohoop, cyclioparaphenylene (CPP), with complete atomic precision.

The idea of linking pairs of these macrocycles with a mechanical bond had floated around the group for a while before the team had a go at making one. The mechanical bond gives you the opportunity to make things that move based on stimuli, Jasti says. If you bring that into the world of carbon nanostructures, which typically have more interesting electronic and optical properties but are more static structures, how might that manipulate the properties?

Jasti used the active template approach to produce mechanically interlocked CPP molecules. I think it was probably one of the most difficult things weve done, he says. It took two exceptional graduate students pretty much their whole careers they just devoured the literature to come up with a strategy and develop it to where it is now.

The challenge was not the mechanical bond forming reaction per se. If you make some of the structures that have been well explored, I think it can be very straightforward, Jasti says. But the combination of our molecules and the mechanical bond is tricky, he says.

The effort already looks like it might pay off, however. The team has just begun to explore the properties of their mechanically bonded nanohoops, but already there are hints of unusual behaviour. For example, we know that theres very efficient energy transfer from one interlocked ring to the next, Jasti says. The team shone light at a wavelength tuned to one ring, expecting to see some light emitted by that ring and some light emitted by the other after energy transfer. We only see an emission from the second ring, which must mean that the energy transfer is really fast, he says. You could imagine one day maybe programming a system to systematically move charge or something down a long chain of these things.

The team needs more material to test out some of the other properties they are interested in, but has already developed improved methods to make mechanically bonded CPPs at larger scale. Right now, I dont even think many people have even theoretically calculated the properties for these types of materials, Jasti says. Now that they see it, I think theoreticians will dream up a lot of possibilities- and then youll see a lot of papers come out.

James Mitchell Crow is a science writer based in Melbourne, Australia

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The mechanical side of bonding | Feature - Chemistry World