Technetium coordination compound

TCO4 and have synthesized ligands that will form technetium coordination compounds that either absorb or fluoresce strongly to give high sensitivity. 

Exhibit optical transparency at die wavelength used for detection Be electrochemically inactive at the potentials used for reduction of Tc04 and for electrochemical modulation of the formed technetium coordination compound... 

Radiopharmaceutical imaging with technetium coordination compounds ... 

The electrochemical investigation of technetium coordination compounds has attracted considerable attention 1, 2 ] in light of the application of complexes with the isotope Tc-99m in diagnostic nuclear medicine and in view of the expected important role of the redox properties in their biological activity. 

Technetium-99m coordination compounds are used very widely as noniavasive imaging tools (35) (see Imaging technology Radioactive tracers). Different coordination species concentrate ia different organs. Several of the [Tc O(chelate)2] types have been used. In fact, the large majority of nuclear medicine scans ia the United States are of technetium-99m complexes. Moreover, chiral transition-metal complexes have been used to probe nucleic acid stmcture (see Nucleic acids). For example, the two chiral isomers of tris(1,10-phenanthroline)mthenium (IT) [24162-09-2] (14) iateract differentiy with DNA. These compounds are enantioselective and provide an addition tool for DNA stmctural iaterpretation (36). 

The chelating ligands that are present upon reduction of TCO4 with staimous ion determine the coordination complex that forms. Complexes of a variety of oxidation states, structures, and ligand composition can form. Certain stable motifs, often called technetium cores (Figure 1), form the basis of small coordination compounds and molecules that can be linked to biomolecules. 

A series of compounds MCTcOLj], where M = AsPh4 and L=—SCHjCHjS—, -NEt4 —SCH(COOMe)CH(COOMe)S— —SC(CN)=C(CN)S—, or (—S)C(Se-)=C(CN)2 has been prepared by reactions of technetium(V) gluconate with various dithiol ligands and their Tc content was determined by fast activation (the total time for a determination was about 6 min) with good analytical accuracy and reproducibility. New Tc coordination compounds, TcLj (L = monothiodibenzoylmethane), TCOOHL2 (L = 6-mercap-... 

As mentioned above, [M(OH2)3(CO)3] can be considered as a normal aqua ion with only three available coordination sites. Substitution of the water molecules with almost any type of chelator (classic/nonclassic) forms kinetically stable coordination compounds. This holds true for mono-, bi-, and tridentate ligands, regardless of their hardness or softness. This behavior also represents the distinct feature of [M(OH2)3(CO)3] as compared with other technetium and rhenium metal centers, and is one of its major advantages for the labeling of molecules for imaging and therapeutic purposes. 

The coordination chemistry involves the oxidation states from -i-7 to -1. Coordination numbers from 4 to 9 are known. Crystal field considerations and magnetic susceptibility measurements show that technetium forms low-spin compounds. Dinuclcar complexes frequently display metal to metal bond character. There is some evidence that technetium complexes are thermodynamically less stable and kinctically more reactive than the corresponding complexes of rhenium. A multitude of coordination compounds of technetium has been synthesized and unambiguously characterized. Investigations of the complex chemistry have been enormously stimulated by the development of Tc radiopharmaccuticals. 

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