Tc Complexes Research Articles

Synthesis of a new class of Tc chelating agents: N 2S 2 monoaminemonoamide (mama) ligands

A novel N 2S 2-monoamine amide (MAMA) bifunctional chelate was designed and synthesized for labeling of antibodies with Tc-99m. The chelate forms Tc complexes at a range of pH's and shows faster kinetics of complexation than N 2S 2-diamidedithiol (DADS) ligands. The MAMA chelate contains a carboxyl group for covalent attachment to amino groups on proteins.

Technetium(II) complexes of potentially heptadentate Schiff base ligands: synthesis and characterization. X-ray crystal structure of [Tc(tren-py 3)](PF 6) 2

The synthesis and characterization of structural isomers of tris[4-(2-pyridyl)-3-aza-3-butenyl] aminetechnetium(II) tetraphenylborate are described. Two other structural isomers, tris[4-(2-(6-methyl- pyridyl))-3-aza-3-butenyl]aminetechnetium(II) tetraphenylborate and tris[4-(2-pyridyl)3-aza-3-pentenyl]aminetechnetium(II) tetraphenylborate, are also reported. Fast atom bombardment mass spectra, electron spin resonance spectra, cyclic voltammetry and conductivity studies of the new, Tc(II) complexes of potentially heptadentate ligands are discussed. The X-ray crystallographic structure of the PF 6 − salt of the major isomer of tris[4-(2-pyridyl)-3-aza-3-butenyl]aminetechnetium(II) shows a pseudo seven coordinate capped octahedral geometry. The mean Tc-imine nitrogen distance is 2.071 Å, and the mean Tc-pyridine nitrogen distance is 2.109 Å. The Tc-tertiary amine nitrogen distance is 2.933(7) Å, but this nitrogen's lone pair is directed toward the Tc atom (the average Tc-NC angle is 102°). Crystal data for C 24H 27F 12N 7P 2Tc: monoclinic space group P2 1/ c, a=15.082(1), b=10.7455(8), c=19.777(1) Å, β=110.29(1)°, V=3006.2(8) Å 3 to give Z=4 and R=0.061.

Investigations of the technetium-hydrazido core. Synthesis and structural characterization of [(n-C4H9)4N][Tc2(NNPh2)2(C6Cl4O2)4].cntdot.CH2Cl2.cntdot.2CH3OH, a Tc(V)/Tc(VI) catecholate complex with the hydrazido ligands adopting the unusual *1 bridging mode

Reaction of the oxo-bis(tetrachlorocatecholate) Tc(V) complex [(n-C 4 H 9 ) 4 N] [TcO(C 6 Cl 4 O 2 ) 2 ] with N,N-diphenylhydrazine in CH 2 Cl 2 yields the binuclear paramagnetic Tc(V)/Tc(VI) mixed-valence complex [(n-C 4 H 9 ) 4 N] [Tc 2 (NNPh 2 ) 2 (C 6 Cl 4 O 2 ) 4 ]•CH 2 Cl 2 •2CH 3 OH (2). The structure of the molecular anion of 2 consists of two distorted octahedral Tc centers bridged by two hydrazido(2-) groups bonding in the η 1 mode, an unusual bonding motif for this ligand, having been previously described only for cyclopentadienyl-metal species

Technetium electrochemistry. 7. Electrochemical and spectroelectrochemical studies on technetium(III) and -(II) complexes containing polypyridyl ligands

The redox properties of a series of technetium(III/II) complexes of the general formula cis(X), trans(P)-(Tc{sup III/II}X{sub 2}(PR{sub w}R{prime}){sub 2}L){sup 10+}, where X = Cl or Br, PR{sub 2}R{prime} = dimethylphenylphosphine or ethyldiphenylphosphine, and L = 2,2{prime}-bipyridine (bpy), 4,4{prime}-dimethyl-2,2{prime}-bipyridine (Me{sub 2}bpy), or 1,10-phenanthroline (phen), were investigated in 0.1 M TEAP/acetonitrile by cyclic voltammetry at a platinum-disk electrode. These complexes exhibit diffusion-controlled, 1-equiv Tc(IV)/Tc(III) redox couples and also Tc(III)/Tc(II) redox couples. Spectropotentiostatic experiments on three complexes of this class in 0.5 M TEAP/DMF confirm the 1-equiv character of the Tc(III)/Tc(II) couple. The electrochemical behavior of Tc(II) complexes of the general formula trans(P)-(TcX(PR{sub 2}R{prime}){sub 2}terpy){sup +}, terpy = 2,2{prime}:6{prime},2{double prime}-terpyridine, was also investigated under the same conditions as above. These complexes exhibit diffusion-controlled, 1-equiv Tc(III)/Tc(II) redox couples and Tc(II)/Tc(I) redox couples. Spectropotentiostatic experiments on trans(P)-(TcCl(PMe{sub 2}Ph){sub 2}terpy){sup +} confirm the 1-equiv character of the Tc(III)/Tc(II) couple but show that the Tc(II)/Tc(I) couple is not reversible on the spectropotentiostatic time scale.

ChemInform Abstract: Technetium(V) and Rhenium(V) Complexes of 2,3‐Bis(mercaptoacetamido)propanoate. Chelate Ring Stereochemistry and Influence on Chemical and Biological Properties.

AbstractThe Tc complexes are prepared by reduction of TcO4‐ in the presence of the ligand, whereas the Re complexes are obtained by exchange reactions of (V) with the ligand.

Electrolytic99TcO 4 − reduction at inert electrodes: An alternative synthetic route to Tc complexes

Abstract 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 4 – 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/.

ChemInform Abstract: Multiple Bonds Between Main‐Group Elements and Transition‐Metals. Part 75. Alkyltechnetium Oxides: First Examples and Reactions.

AbstractTreatment of Tc2O7 with SnMe4 gives, besides (III) and (IV), on heating reduced products, especially the paramagnetic Tc(VI) complex (V) (Pn, Z=2).

Technetium nitrido complexes with amine and thiolate ligands: structural characterizations of nitridobis(1,1,2,2-tetramethylguanidine)bis(2,3,5,6-tetramethylbenzenethiolato)technetium, a complex with coordinatively bound 1,1,2,2-tetramethylguanidine

A methanol solution of the Tc(VI) complex (Ph 4 As)[TcNCl 4 ] is reduced in the presence of pyridine to give the orange Tc(V) complex [TcN(OH)(py) 4 ](Ph 4 B) (1); the pyridine ligands are labile and undergo exchange with free pyridine in solution. The TcO 2 + and TcN(OH) + cores also appear to be similar electronically, since the 99 Tc NMR chemical shifts for these two compounds are not significantly different. Compound 1 reacts with 2,3,5,6-tetramethylbenzenethiolate (tmbt) to give quantitative yields of the robust compound trans-TcN(tmbt) 2 (py) 2

Mixed-ligand complexes of technetium IX. Oxidative ligand exchange reactions on tetraphenylarsonium-bis(dithiooxalato)nitridotechnetate(V), (Ph 4As) 2[TcN(dto) 2]. X-ray crystal structure of a further modification of (Ph 4As) 2[TcN(dto) 2

(Ph 4As) 2[TcN(dto) 2] can be prepared starting from TcNCl 4 − or TcNCl 2(Ph 3P) 2. The compound crystallizes in at least two modifications: as well as a triclinic form (S. F. Colmanet and M. F. Mackay, Inorg. Chim. Acta, 147 (1988) 173) a monoclinic one has been found (space group C2/ c, Z = 4, a = 19.424(3), b = 11.254(2), c = 24.958(3) Å, β = 107.68(1)°; R = 0.048). Distances and angles in the complex anions in both modifications are almost identical within experimental error. Oxidation of [TcN(dto) 2] 2− by Cl 2 produces the Tc(VI) complex TcNCl 4 − exclusively, whereas during the Br 2 oxidation technetium(VI) intermediates are generated containing mixed Br/dto coordination spheres which can be monitored easily by EPR spectroscopy.

Synthesis and characterization of technetium(III) and technetium(II) complexes with mixed phosphine, chloride, and nitrogen-donor ligands. X-ray crystal structure of (2,2'-bipyridine)trichloro(triphenylphosphine)technetium

The synthesis and characterization of Tc(III) complexes of the types TcCl 3 (PMe 2 Ph)(LL) and TcCl 2 (PMe 2 Ph) 2 (LL) + , the neutral Tc(II) series TcCl 2 (PMe 2 Ph) 2 (LL), and the Tc(II) complex TcCl(PMe 2 Ph) 3 (bpy) + are reported (LL=2,2'-bipyridine (bpy), 1,10-phenanthroline (phen), 2,2'-bipyrimidine (bpm)). The electrochemistry of these complexes is discussed. An X-ray structure determination of TcCl 3 (PPh 3 )(bpy) was performed. Crystal data monoclinic, space group=P2 1 /n

ChemInform Abstract: Synthesis and Characterization of Mixed‐Ligand Technetium(II) Complexes Containing Halides, Phosphines, and Either 2,2′‐Bipyridine, 1,10‐Phenanthroline, or 2,2′:6′,2′′‐Terpyridine. X‐Ray Crystal Structures of cis(Cl),trans(P)‐(TcCl2(P(CH3)2C6H5)2(phen)) and trans(P)‐(TcBr(P(CH3)2C6H5)2(terpy))SO3CF3.

AbstractThe neutral Tc(II) complexes (III) are prepared by replacement of one halide and one phosphine ligand in mer‐Tc(III) complexes, as demonstrated with (I), followed by base‐induced reduction.

Lipophilic technetium complexes—VII. Neutral oxotechnetium(V) complexes of tridentate Schiff-bases containing monothioles as co-ligands

Five-coordinate oxotechnetium(V) complexes TcOL(SR), where H 2L = Schiff-bases N-salicylidene-2-aminothiophenole (H 2salabt), N-acetylacetone-2-aminothiophenole (H 2acacabt) or N-salicylidene-2-aminophenole (H 2sap) and RSH = thiophenoles, mercaptanes or 2-mercaptoacetic acid ethylester, are prepared by the reaction of tetrachlorooxotechnetate(V) or Tc(V) gluconate with a 1:1 mixture of the appropriate tridentate/monodentate ligands. The products are characterized by elemental analysis, u.v.—vis, i.r. and 1H-NMR spectroscopy. The compounds represent the first Schiff-base complexes of Tc(V) which contain monodentate thioles as co-ligands.

Single laser flow cytometric detection of lymphocytes binding three antibodies labelled with fluorescein, phycoerythrin and a novel tandem fluorochrome conjugate

In order to implement three-color surface immunofluorescence on a single laser flow cytometer, we combined a new fluorescent tandem conjugate (TC, R-phycoerythrin plus Texas red, available as DuoCHROME) with fluorescein (FITC)- and phycoerythrin (PE)-labelled monoclonal antibodies for the simultaneous detection of three antigens on individual lymphoid cells. Considerable amounts of fluorescence leaked from the PE component of the TC complex into the PE detector, which necessitated compensation of the PE signal. Single and double stainings of peripheral lymphocytes with FITC-, PE-and/or TC-labelled antibodies revealed that the individual labels all identified populations of similar size, and that subsets of T cells could be properly and accurately detected with TC as one label. Triple staining was used to study phenotypically activated HLA-DR + cells within functionally important subsets of CD4 + T cells, i.e., CD45R + CD4 + (naive, ‘suppressor inducer’ T) and UCHL1 + CD4 + (memory, ‘helper’ T) cells. In the blood of healthy subjects as well as patients with primary biliary cirrhosis, CD4 + UCHL1 + (i.e., memory) T cells were significantly more activated than CD4 + UCHL1 − cells. The reciprocal CD45R + CD4 + (naive) T subset expressed HLA-DR to a much lesser extent. In patient samples, this difference in CD4 + T subset activation was more pronounced than among normal lymphocytes. The described triple immunofluorescence staining technique facilitates true multicolor analysis of individual cells on a single laser flow cytometer. Such multiparameter investigations may prove to be important for the further understanding of the phenotypic and functional diversity of immunocompetent cells.

Quantitative study of the structure-stability relationship of Tc complexes

By studying structural parameters (van der Waals radius and bond length from x-ray crystallography) of more than 100 known Tc compounds and using the cone packing model, a stability indicator of the Tc compounds was derived. The indicator is based on the solid angle factor sum (SAS), which is calculated from van der Waals radii and bond lengths between all coordinating atoms and Tc. The average SAS value is 0.97 ± 0.13. The SAS value reflects the limits of the packing of ligand around Tc. The quantitative calculation of the SAS is useful for predicting stability and designing new Tc radiopharmaceuticals.

Lipophilic technetium complexes. VI. Neutral oxotechnetium(V) complexes with monothiole/tridentate dithiole coordination

Reaction of tridentate dithiole ligands HSCH 2CH 2XCH 2CH 2SH (HSXSH, X= O, S) and monothioles RSH (thiophenoles, aliphatic thioles, mercaptoacetic acid ethylester) with Tc(V) gluconate (or other starting materials containing the oxotechnetium(V) core such as tetrachlorooxotechnetate) leads to a series of mononuclear, neutral complexes of the general formula TcO(SXS)(SR). In the absence of the monodentate thioles, dinuclear complexes of the general formula (TcO) 2(SXS) 3 are formed. Infrared, NMR, and UV-Vis data of the resulting compounds are reported. A concept for designing smallsized, neutral Tc complexes, involving the principle of common reaction of both a tridentate and a monodentate ligand with an appropriate Tc precursor, is proposed.

Synthesis and properties of binuclear decakis (Trifluorophosphine) technetium(O) Complex

Decakis (trifluorophosphine) technetium (O) Tc2 (PF3)10 has been synthesized by means of cryochemical method. Compound Re2(PF3)10 described in literature previously [1] has been obtained by using the same technique. The synthesized trifluorophosphine complexes of Tc and Re which are close chemical analogues have similar physical - chemical properties. Both compounds have white colour. They are hydrolysed in the wet air. Vapour pressure of Tc2 (PF)10 is (6±3) .10-3 torr at 293K. When heated up to 550K Tc2 (PF3)10 decomposes with Tc and PF3 being liberated. The Tc2(PF3)10 bands 455 vw, (492 ms, 498 ms) (ν2PF3), 734 sh, 856 s (ν3PF3), 896 s (ν1PF3), 1016 w.br., 1122 w.br., 1237 w.br. and the Re2 (PF3)10 bands 460 vw, {492 ms, 508 ms} (ν2PF3), 744 sh, 859 s (ν3PF3), 893 s (ν1PF3), 1021 w.br., 1155 w.br., 1261 w.br., cm-1 were detected in infrared spectra of solid samples. The bands located above 1000 cm-1 were identified to be phosphide Tc and Re and phosphorus oxides impurities. The masses corresponding to M+2, M(PF3)+x, M2P(PF3)+y, MPF (PF3)+y, M2PF(PF3)+y ions, where M = Te, Re, X = 0+4, Y = 0+8 for Tc complex and X = 0+4, Y = 0+3 for Re complex were present in mass spectra of the compounds synthesized.

ChemInform Abstract: Mixed‐Ligand Complexes of Technetium. Part 4. Cationic, Hexacoordinated Tc(I) Complexes with Two Different Isocyanide Ligands in the Coordination Sphere, (Tc(R1NC)k(R2NC)6‐k)+ (k = 0‐6).

AbstractThe mixed‐ligand complexes (I) and (II) are obtained by refluxing hexakis‐thiourea technetium(III) chloride in methanol with a 100‐fold excess of mixtures of two isocyanides.

Reaction Mechanisms Responsible for Transformation of Pertechnetate in Photoautotrophic Organisms

Experimental data on the physiological effects of Tc on photoautotrophic and N2-fixing organisms all suggest a relation between their ability to generate strong reducing power and the incorporation of Tc. A series of biochemical experiments were undertaken to elucidate this problem. Isolated spinach chloroplasts, thylakoids and purified compounds of the photosynthetic electron transport chain were incubated with TcO4-. After illumination, the quantity of TcO4- transformed was measured with gel filtration chromatography. For part of the samples, the amount of extractable Tc(V) was determined. Isolated thylakoids showed reduction of TcO4- in the light, suggesting direct interference of TcO4- with the electron transport chain. Use of specific inhibitors and artificial electron carriers indicated that TcO4- withdraws electrons from ferredoxin. Competitive inhibition of TcO4- reduction by O2 and NADP+, as well as its capacity to function as a terminal acceptor in the diaphorase reaction with NADPH, indicates its interaction with the transport chain to be comparable to that of O2. In suspensions of thylakoids, TcO4- is mainly reduced into an extractable Tc(V) compound. Only part of the Tc fraction reduced by intact chloroplasts could, however, be extracted, whereas negligible quantities of unstable Tc(V) complexes were detected in intact plants. The stable complexes in vivo are supposed to originate through ligand exchange with strong complexing agents, such as thiol compounds. Disproportionation reactions of unstable Tc(V) compounds might result in complexes with Tc in lower oxidation states.

ChemInform Abstract: Synthesis and Characterization of Technetium(III) Complexes Containing 2,2′‐Bipyridine and 1,10‐Phenanthroline. X‐Ray Crystal Structures of cis(Cl),trans(P)‐(TcCl2(P(CH3)2C6H5)2(bpy))B(C6H5)4, cis(Cl),trans(P)‐(TcCl2(P(CH3)2C6H5)2(phen))B(C6H5)4, and cis(Cl),trans(P)‐(TcCl2(P(CH3CH2)(C6H5)2)2(bpy))SO3CF3.

AbstractThe Tc(III) complexes (III) are synthesized as shown in the scheme for the example (IIIa).

ChemInform Abstract: Reactivity of MOCl(L) (M: Tc or Re; L: N‐(2‐Oxidophenyl)salicylideneaminate or N‐(2‐Sulfidophenyl)salicylideneaminate) with Tertiary Phosphines. X‐Ray Molecular Structure of μ‐Oxo‐bis((N‐(2‐oxidophenyl)salicylideneaminato(2‐)NOO′)bis(dimethylphenylph# osphine)technetium(III)).

AbstractThe Tc(V) complex (Ia) is reduced by tertiary phosphines such as (II) (or PPh3) to give the dimeric Tc(III) complex (III) showing a very unusual Tc(III)‐O‐Tc(III) configuration.