Technetium, chemistry

Technetium is an artificial element obtained by the radioactive decay of molybdenum. Element 43, named technetium in 1947, had been discovered in 1937 by Carlo Perrier and Emilio Segre in a sample obtained from the Berkely Radiation Laboratory (now Lawrence Berkeley National Laboratory) in California (Perrier and Segre 1937, 1947). By bombarding a molybdenum strip with 8-MeV deuterons in a 37-in. cyclotron, a radioactive molybdenum species (half-life, 65 h) had been obtained which decayed by yff-emission to a short-lived isotope (half-life, 6 h) with novel properties, identified as technetium-99m (Segre and Seaborg 1938). 

In 1965, Richards and his collaborators at Brookhaven National Laboratories (N.Y.) have introduced the Mo/ Tc generator for clinical application (Richards 1966). This radionuclide system made technetium-99m available for clinical research and has stimulated the development of the first labeled compounds, which had a considerable impact on radiochemistry and nuclear medicine (Andros et al. 1965 Harper et al. 1966 McAfee et al. 1964a, b Stern et al. 1965, 1966). In the years to follow, diagnostic nuclear medicine procedures based on Tc pharmaceuticals increased to approximately 85%. The reasons for this rapid growth were the ideal nuclear properties of techne-tium-99m, its availability worldwide as a radionuclide generator system, and the development of new labeling techniques. 

Labeling procedures have been greatly facilitated by kit preparations (Eckelman et al. 1971). Sterile kits for labeling contain the chemical ingredients in lyophilized form are commercially available and used to prepare Tc pharmaceuticals shortly before application to the patient. Manipulation is minimal, since all that needs to be done is adding the Tc activity to the kit. In some cases, heating of the reaction mixture is performed to increase the labeling yield. 

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Technetium chemistry and technetium radiopharmaceuticals. E. Deutsch, K. Libson, S. Jurisson and L. F. Lindoy, Prog. Inorg. Chem., 1983, 30, 75-139 (279). 

Recent advances in technetium chemistry bridging inorganic chemistry and nuclear medicine. E. Deutsch and K. Libson, Comments Inorg. Chem., 1984,3, 83-103 (30). 

Some recent interest in the technetium chemistry has been focused on complexes possessing a Tc=N3+ core. Tetrachloronitridotechnetate(VI) complexes can easily be synthesized by the reaction of pertechnetate with sodium azide in concentrated hydrochloric acid [34], Although its square-pyramidal structure resembles that of tetrachlorooxotechnetate(V) complexes, stable character of the nitrido complexes in aqueous solution shows a remarkable contrast to the oxo complexes. However, when a strong acid and a coordinating ligand are absent, the interconversion of di(p-oxo)nitridotechnetium(VI) complexes to the monomeric form occurs in the following complicated manner [35]... 

The utility of [TcOCU] in Tc chemistry is demonstrated by the first synthesis of 8-hydroxy-quinoline (8-Hox, (126)) complexes of technetium in 1984. Ligand (126) is usually one of the first choices to explore the coordination chemistry of an element, but it was as late as 1984 when the first complex with Tc was prepared. It was known that the reaction of [ Tc04] with 8-Hox leads to complexes with high brain uptake, and it was therefore important to define the structure of the active species. This sequence of events is very typical for technetium chemistry. Nuclear medicinal experiments indentify a Tc species with useful biological behavior, which prompts investigations into the basic coordination chemistry to identify the structure of the Tc... 

Deutsch, E. Libson, K. Jurisson, S. Lindoy, L. F., Ed., Technetium Chemistry and Technetium Radiopharmaceuticals 1983, iOWiley New York. 

Schwochau, K. Technetium Chemistry and Radiopharmaceutical Applications Wiley-VCH Weinheim, Germany,... 

Schwochau K (2000) Technetium, chemistry and radiopharmaceutical applications. Wiley-VCH, Weinheim... 

Rootwelt, K. (2005), Nuklecermedisin, 2nd ed. Gyldendal Norsk Forlag AS, Oslo, Norway. Schwochau, K. (2000), Technetium Chemistry and Radiopharmaceutical Applications, VCH Verlagsgesellschaft Mbh, Weinheim, Germany. 

The early technetium imaging agents have been reviewed in earlier versions of this Encyclopedia and in other references. This section is intended to be an overview highlighting developments in technetium chemistry. 

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