Click Chemistry

Contact: DI Dr. Astrid-Caroline Knall

Click chemistry has emerged as an established method to link functional moieties with each other. This concept is especially interesting for the preparation of functional materials such as block copolymers. To date, most publications deal with the well-explored azide-alkyne click chemistry.

The inverse electron-demand Diels-Alder reaction has only recently gained attention in the polymer science community although it represents an efficient way to combine different polymer chains to yield block copolymers with exciting new properties. Here, an electron deficient diene (for example, a tetrazine) reacts with an electron-rich dienophile to form a Diels-Alder adduct which is then (due to extrusion of nitrogen) converted into a pyridazine.

tetrazines_1.jpg

Due to its fast reactivity and bioorthogonal nature, this reaction has already been utilized for bioconjugation in various contexts (also in vivo) and, more recently, also been applied in polymer and materials science.

The electron-deficient nature of the targeted tetrazine structures, which is the leitmotif for enhanced reactivity in the ied-DA reaction, makes tetrazines also suitable electron-deficient monomers for conjugated donor-acceptor polymers. In combination with the right electron-rich partner, this could lead to alternative low-bandgap p-type donor polymers with interesting properties for photovoltaic applications.

Research Approach at ICTM

tetrazines_2.jpg

We investigate the scope of electron-deficient tetrazine monomers. These materials are expected to be highly interesting building blocks in polymer chemistry which will a) show high reactivity in inverse-electron demand Diels-Alder reactions and b) allow for low-bandgap conjugated polymers. Thus, novel copolymers with unique properties can be achieved.

Framework of the research

On this topic a research project is running:

  • TetraClick: Tetrazines as versatile building blocks in polymer chemistry (FWF, Hertha-Firnberg project No. T578)

For the part of the project dealing with electroactive polymers, ACK is currently working with Professor Iain McCulloch (Imperial College London) on this topic.

For further reading see:

chemcomm.jpg "Inverse electron demand Diels-Alder (iEDDA) functionalisation of macroporous poly(dicyclopentadiene) foams." Knall, A.-C.; Kovačič, S.; Hollauf, M.; Reishofer, D. P.; Saf, R.; Slugovc, C. Chem. Commun. 2013, 49, 7325-7327. DOI: 10.1039/C3CC42925C

CSR.jpg"Inverse-electron demand Diels Alder (iEDDA)-initiated conjugation: a (high) potential click chemistry scheme."
Knall, A.-C.; Slugovc, C. Chem. Soc. Rev. 2013, 42, 5131-5142.
DOI: 10.1039/C3CS60049A

thl.jpg"Kinetic studies of inverse electron demand Diels–Alder reactions (iEDDA) of norbornenes and 3,6-dipyridin-2-yl-1,2,4,5-tetrazine."
Knall, A.-C.; Hollauf, M.; Slugovc. C. Tetrahedron Lett. 2014, 55, 4763-4766. DOI: 10.1016/j.tetlet.2014.07.002