Towards Insulated Molecular Wires to Order: The Active Template Approach to Conjugated Rotaxanes

Lead Research Organisation: Queen Mary, University of London
Department Name: Sch of Biological and Chemical Sciences


Plastic electronics, electronic materials that are based on polymers, hold the promise of light weight, low power, cheap, versatile and mechanically flexible electronic devices, applications of which include flexible displays and wearable electronics based on circuits which can be printed using bubblejet printer technology. However, electrically conducting polymers (sometimes called molecular wires, MWs) are often unstable when operated the presence of air or moisture and can deteriorate due to interactions between the polymer chains. These drawbacks currently hinder the development of new commercial plastic electronic devices.

One approach which has been developed to help overcome these problems is to wrap the conjugated polymer in an insulating sheath, much as macroscopic wires are insulated using a rubber or plastic coating to prevent degradation and short circuits. These insulated molecular wires (IMWs) can be made by threading the conjugated polymer through the cavity of ring shaped molecules, to create a threaded structure, reminiscent of a bead on a thread, known as a poly-rotaxane (from rota, meaning wheel, and axel). This method has been shown to be extremely beneficial, dramatically improving the stability and properties of the conjugated polymer.

However, the existing methods for the synthesis of such poly-rotaxanes are currently extremely limited, hindering the development of these exciting materials. Our proposed research will greatly increase the availability of poly-rotaxane IMWs and will in the long term allow any polymer to be insulated with any macrocycle quickly and efficiently.

Ultimately, as a result of the proposed work we will be able to create designer insulated molecular wires to order, potentially revolutionising the use of these novel materials for plastic electronic devices.

Planned Impact

We propose to develop new methods for the synthesis of organic semiconductors that are insulated at the molecular level. These materials have been shown to have significantly enhanced properties, compared to their non-insulated equivalents, and the proposed work has the potential to generate a number of types of impact.

1) Academic Impact

The proposed research will have wide academic impact in areas which are typically considered fundamental and applied. At the fundamental level, by providing new methods for the synthesis of complex mechanically interlocked molecules we are developing tools for application not only in the synthesis of insulated molecular wires but also in the realisation of other novel mechanically interlocked materials with application as sensors, prodrugs and molecular machines. At the applied level, our proposed research will lead to increased availability and a deeper understanding of IMWs as materials for applications in display devices, photovoltaic devices and plastic electronics in general.

For more details see the "academic beneficiaries" section.

2) Technological/Commercial Impact

Rotaxane insulated molecular wires have been demonstrated to behave as semiconductors with enhanced photo- and electro-luminescence efficiencies and increased environmental stability as compared to their non-insulated counterparts. These properties make them ideal materials for application in robust plastic electronic devices suggesting they have potential to make a significant technological impact as components in commercial devices such as flexible displays, lighting systems, solar cells and sensors for biological molecules. Rotaxane insulated molecular wires also display improved stimulated emission compared with their non-insulated analogues amplified suggesting they may find application in cost effective, polymer-based continuous wave solid state lasers. These devices are key components of next generation fibre optic devices.

3) Societal Impact

The immediate societal impact of the proposed research will be the training by SMG of a highly skilled researcher (the PDRA) capable of carrying out research at the interface of organic, synthetic supramolecular, materials and plastic electronics. At the end of the project they will be capable of generating new ideas across a broad range of scientific areas and carrying out innovative research in academic or industrial environments. They will also have gained collaborative skills through interaction with researchers in other groups and other areas in order to design, test and evaluate new materials. This individual will be well positioned with the unique skill set gained during the project to make a significant contribution both within the UK and internationally.

In the longer term, the proposed research will accelerate the application of IMWs in real world plastic electronic devices with enhanced properties such as brighter low-energy lighting systems, flexible displays and wearable electronics. This has the potential to enhance UK living standards directly both through the creation of whole new types of devices and through lowering the cost, improving the performance and increasing the energy efficiency of existing products. The UK is also well positioned to take advantage of progress in the field of plastic electronics in terms of job and growth creation given the position of the UK as an acknowledged leader in the field both academically and industrially. Given the relatively low cost of plastic electronic manufacturing facilities (compared to silicon semiconductor technology) this includes the potential to assist in increasing the relative size of the manufacturing sector in the UK.

Finally, the production of cheap and flexible photovoltaic devices, along with the low power consumption of plastic electronic devices, both in the manufacturing phase and in use, means that replacing silicon based-devices, will contribute to combat climate change.


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Lewis JE (2017) Stepwise, Protecting Group Free Synthesis of [4]Rotaxanes. in Molecules (Basel, Switzerland)

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Lewis JE (2016) Iterative Synthesis of Oligo[n]rotaxanes in Excellent Yield. in Journal of the American Chemical Society

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Winn J (2013) Synthesis of a rotaxane Cu(I) triazolide under aqueous conditions. in Journal of the American Chemical Society

Description We developed an iterative, high yielding synthesis of triazole linked [n]rotaxanes. This work is currently being written up for publication. The method is extremely flexible and my group are now using it for the synthesis of functionalised conjugated molecules for a range of applications.

We also discovered a new class of mechanically protected Cu organometallic that are stable in water. These species are of potential interest in radoopharmaceuticals and display technologies. This discovery was published (JACS 2013) and has led to new collaborative projects on rotaxane-based OLEDS and radio-metal complexes.

A final scientific impact was that, as a side effect of developing our new iterative synthesis, Joby massively improved the general methodology for rotaxane synthesis in the group which has supercharged other areas of our research and led to significant new results and collaborations.
Exploitation Route The iterative AT-CuAAC methodology developed is now being applied by our collaborators in Bordeaux to study through space energy transfer in interlocked but non-bonded fluorophores. These studies are important as they will lead to a greater understanding of how to harness electronic energy for artificial photosynthesis.

Collaborators in Japan are now using the chemistry we developed in the synthesis of multiporphyrin arrays in excellent yields. The mechanical bond can stabilise demetallated heterocycles as well as preventing chromophore aggregation in solution.
Sectors Energy

Description Consolidator Grant
Amount € 2,000,000 (EUR)
Funding ID 724987 
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 05/2017 
End 05/2022
Description Marie Curie International Fellowships
Amount € 183,000 (EUR)
Organisation European Commission 
Sector Public
Country European Union (EU)
Start 10/2015 
End 09/2017
Description Collaboration with NIMS on rotaxane porphyrin conjugates 
Organisation National Institute for Materials Sciences
Country Japan 
Sector Academic/University 
PI Contribution Collaboration with Dr Thien Ngo on the synthesis of triazole linked porphyrin conjugates. This work began in response to our publications on the synthesis of rotaxanes and rotaxane triazolides
Collaborator Contribution The group in Japan uses materials provided by us to make new interlocked porphyrin species and characterise their behaviour.
Impact Two publications to date (Chem Eur J 2016; Chem Sci 2017)
Start Year 2013
Description Invitation to join a JSPS Network with University of Kanazawa, Japan 
Organisation Kanazawa University
Country Japan 
Sector Academic/University 
PI Contribution As a result of our recent publications Tomoki Ogoshi and I began a conversation about combining our respective chemistries to deliver new functional molecules. This culminated in being invited to join an international consortium, which includes significant travel funds, to facilitate further collaboration.
Collaborator Contribution So far contributions have been in the form of discussions and travel.
Impact No outputs as yet
Start Year 2015