Technetium Chemistry

High-Valent Technetium Complexes

Recently, the {99(m)TcO3}+ core came in the focus of our research, due to our general interest in novel metal cores for the synthesis of radiopharmaceuticals.
With routine clinical applications in mind, we develop synthetic pathways to generate {99(m)TcO3}+ complexes to assess the potential of this metal core for nuclear medical applications.

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Novel Labeling Strategies for Radiopharmaceutical Applications

The site-specific conjugation of a metalloradionuclide such as 99mTc to a targeting vector, whilst retaining the affinity of the parent, is challenging. To address this issue, advantage can be taken of the rich coordination chemistry of technetium.
In this context, the TcVII core, fac-{TcO3}+, gained much interest. This metal core is compact and can be coordinated to different tripodal ligands. Besides its small size, complexes with the fac-{TcO3}+ core display a unique reactivity, particularly in water, that can be used as a creative route to prepare novel molecular imaging probes. With alkenes, complexes of the fac-{TcO3}+ core undergo metalmediated, vicinal cis-dihydroxylation reactions (alkene–glycol interconversion) through (3+2) cycloaddition. cis-Dihydroxylation reactions with osmium tetroxide [OsO4] have been known for a long time. With fac-{TcO3}+ complexes this reaction type enables a ligand-centered labeling strategy to be followed.

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Development of 99mTc Labels for Nanomedical Applications

Nanomedicine is a new area of medical research, which could revolutionize medical treatments and therapies in fields such as imaging, fast diagnostics, drug delivery and tissue regeneration in the next years. Therefore we are aiming at the development of a labeling procedure, which leads to a defined and characterized binding of a 99mTc-label to nanoparticles. Such a binding is essential for reproducibility and it is a keystone for the development of new nanomaterials for radiopharmaceutical applications. In this project we are using the mesoporous silica MCM-41 as a model to establish the (3+2) cycloaddition of fac-{99mTcO3}+ complexes with alkenes as a labeling procedure for target-specific silica based nanoparticles.

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Novel Organometallic Technetium Complexes

N-Heterocyclic carbenes (NHCs) are versatile strong electron donors (s-donor) which are known to stabilize metal centers in low and high oxidation states. Therefore, NHCs are interesting ligand systems for the development of new organometallic techentium compounds. In this project the suitability of (tripodal) NHCs as stabilizing ligands for 99(m)Tc chemistry is studied. We are aiming at the development of synthetic pathways, which are suitable for clinical translation

Technetium in an Oxygen Rich Coordination Environment

99Tc-oxides play a crucial role in nuclear waste deposition. Today, 99Tc from spent fuels is immobilized by encapsulation in an oxide matrix in glass or other inorganic matrices. A fundamental knowledge about the chemical behavior of Tc-oxides or Tc-oxo complexes will support a rational design of such materials to keep Tc permanently away from redistribution into the environment. We use polyoxometalates (POMs) as model systems for an oxygen rich coordination environment of technetium. The molecular design of polyoxo-complexes of technetium and a fundamental understanding of their properties will be a substantial contribution to a rational selection of materials and procedures for the nuclear waste management of 99Tc. Furthermore, some POMs show very interesting biochemical profiles, which makes this class of ligands very interesting for imaging applications.

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