The [Tc(phen)3] (PF6)3 complex has been synthesized by ligand substitution on [Tc(tu)6]3+. The reaction proceeds quickly in aqueous solution. A pure compound is obtained with 40% yield. It was characterized by Tc elemental analysis, cerimetric titration, conductometry and electrophoresis. The corresponding spectroscopic properties (UV, Vis, IR and NMR) are also reported and discussed.
A99Tc-ADP complex was prepared when KTcO4 was reduced in aquous medium by SnCl2, Na2S2O4, NaBH4 or Zn in the presence of ADP in excess. The resulting solution was studied by chromatography and spectrophotometry. Electrochemical reduction and substitution on [TcIII(tu)6]3+ were investigated as alternative synthetic routes. The anionic Tc-ADP complex was isolated as a solid. Cerimetric titrations confirmed the oxidation state +3 for the central atom. IR and1H-NMR data showed that the purine base is bonded to the Tc central atom but not the ribose moiety. No oxo groups seemed to be directly bonded to the Tc atom. The complex is rather stable in neutral solutions. However, it decomposes to pertechnetate and TcO2 at extreme pH values.
All complexes of the series [MO2L2]+ (M=Tc, Re; L=ethylenediamine (en), 1,3-diaminopropane (1,3-dap)) have been synthesized and their chemical reactivities investigated. The following properties were studied: stability of the aqueous solutions at different pH values, substitution kinetics, lipophilicity and protein binding. The complexes show very similar reactivity in aqueous solution. From a radiopharmaceutical point of view, no significant difference in their in vivo behavior is expected.
Authors:D. Gambino, C. Kremer, E. Savio, A. León, and E. Kremer
A series of Tc/V/ cationic complexes was synthesized by electrochemical reduction of TcO
. The electrolysis was performed in aqueous media containing amines as ligands: en, dien, trien and 1,3-dap*. The combination of different techniques allows to propose the general formula [TcO2/amine/2]+ for these compounds. Electrodeposition of TcO2 was a competitive reaction. The UV spectra were compared with those for other Tc/V/ amine complexes. The presence of two peaks, one in the range 303–312 nm and the other in 230–240 nm, could be verified. The latter was markedly sensitive to pH changes. Preliminary studies showed that kinetic stability decreases in the sequence en, 1,3-dap, trien, dien. The decomposition rate increased when the pH was lowered.
Authors:C. Kremer, D. Gambino, A. León, and E. Kremer
Electrolytic pertechnetate reduction at inert electrodes was studied as an alternative procedure for synthesizing Tc complexes. Pertechnetate reduction was carried out in aqueous media using different aminated ligands /en, dien, trien and 1,3-dap/ forming [TcO2/amine/2]+ type complexes. Simultaneously with synthesis of the desired Tc complex, TcO2 was electrodeposited onto the cathode. Conversion of TcO
to Tc complex and TcO2 was studied as a function of several variables /kind and concentration of supporting electrolyte, ligand concentration, pH, current and electrolysis time/.
Authors:D. Gambino, C. Kremer, S. Cartesio, A. León, and E. Kremer
The strong chemical resemblance between Tc and Re is applied to design and evaluate experiments with99mTc complexes. A combination of spectrophotometric and electrophoretic techniques allows to propose the formula [TcO2/amine/2]+ for compounds prepared by reduction of99mTcO
with Zn /solid phase/ in presence of several /bidentate/ amines.
Authors:F. Cerdá, C. Kremer, D. Gambino, and E. Kremer
Electrolytic reduction of pertechnetate was performed in aqueous solution containing -acceptor ligands. Cyanide and 1,10-phenanthroline were the selected ligands. In both cases, electrolyses produced a cathodic TcO2 deposit and soluble Tc complexes. When cyanide was the ligand, the complexes formed were [Tc (CN)6]5– and [TcO2 (CN)4]3–. When working with the amine, [Tc (phen)3]2+ and another positively charged species were found after reaction. Results are compared with previous studies with amines, and the usefulness of the electrolytic route to obtain Tc complexes is evaluated.
Authors:C. Kremer, S. Domínguez, M. Pérez-Sánchez, A. Mederos, and E. Kremer
The heavy use of99mTc in nuclear medicine and the recent development of188Re radiopharmaceuticals have encouraged the comparative study of Tc and Re coordination compounds. In this work, the electrochemistry of [MVO2 (amine)2]+ (M=Tc, Re; amine = ethylenediamine, 1,3-diaminopropane, diethylenetriamine, triethylenetetramine) complexes is studied by cyclic voltammetry and the results are compared. The voltammograms of these compounds, obtained at different pH values, show that [ReO2(amine)2]+ cations are thermodynamically stable even when protonated. On the other hand, analogous Tc compounds are not so stable and easily decompose if existing as [TcO(OH) (amine)2]2+.
Authors:A. Rey, M. Terán, C. Kremer, S. Molina, D. Gambino, E. Kremer, and A. León
Ligand exchange is one of the possible synthetic routes to obtain99mTc coordination compounds. However, the success of this route depends on the availability of good precursors. The objective of this work is the preparation of the complex [99mTc(tu)6]3+ (tu = thiourea), as a potential precursor for99mTc(III) coordination compounds. The preparation was successfully performed in acidic conditions, the excess of tu serving as reducing agent. At pH values higher than 3, the compound becomes unstable and on addition of polydentate ligands new Tc(III) complexes are formed. With edta, the complex99mTc(III)-edta was obtained in high yield.