New Oxorhenium(V) Complexes from the Widely Used Diaminedithiol (DADT) Ligand System

Synthesis of the 2,9-dimethyl-4,7-diaza-4-alkyl-2,9-decanedithiol (1, alkyl = morpholinylethyl in a, and alkyl = pyrrolidinylethyl in b), following a widely used synthetic scheme for diaminedithiol (DADT) ligands, led to the isolation of 1-alkyl-2-(1‘-methyl-1‘-sulfanylethyl)-3-(2‘ ‘-methyl-2‘ ‘-sulfanylpropyl)diazolidine (3) as the major product. Both ligands 1 and 2 gave complexes with the oxorhenium ReO(V) core. Ligand 1 gave the expected ReO[SNNS] complex (2) with the side chain on nitrogen in the syn configuration. Ligand 3 gave, in the presence of a monodentate aromatic thiol, complexes of the ReO[SNN][S][S] (4) and ReO[SNN][S] type (5), respectively, in which the diazolidine ring has rearranged to a thiazolidine ring. Crystallographic analysis showed that in 4 the coordination geometry about the metal is distorted octahedral where the equatorial plane is defined by the sulfur and one of the nitrogen atoms of the ligand and the two sulfurs of the aromatic thiols, while the axial positions are occupied by the oxygen of the ReO core and the second nitrogen of the ligand. Specifically, complex 4a crystallizes in space group P21/c, a = 15.63(1) Å, b = 15.28(2) Å, c = 16.07(1) Å, β = 113.78(2)°, V = 3512(5) Å3, Z = 4. Complex 4b crystallizes in space group P21/n, a = 14.560(9) Å, b = 14.804(9) Å, c = 19.85(1) Å, β = 90.94(2)°, V = 4278(1) Å3, Z = 4. In 5b, the coordination geometry is distorted square pyramidal with the SNN donor atom of the ligand and the aromatic thiol defining the equatorial plane and the doubly bonded oxygen occupying the apex of the pyramid. Complex 5b crystallizes in space group P1̄, a = 9.387(5) Å, b = 11.306(5) Å, c = 14.040(6) Å, α = 84.51(1)°, β = 84.45(2)°, γ = 87.17(1)°, V = 1475(1) Å3, Z = 2. All isolated complexes are neutral and lipophilic. Complete assignments of 1H and 13C NMR resonances are reported

Synthesis and Characterization of Novel Oxotechnetium (⁹⁹Tc and ^99mTc) and Oxorhenium Complexes from the 2,2‘-Bipyridine (NN)/Thiol (S) Mixed-Ligand System

The synthesis and characterization of oxotechnetium and oxorhenium mixed-ligand complexes of the general formula MO[NN][S]3 (M = 99Tc and Re), where NN represents the bidentate ligand 2,2‘-bipyridine and S represents a monodentate thiophenol, is reported. The complexes were prepared by ligand exchange reactions using 99Tc-gluconate and ReOCl3(PPh3)2 as precursors for the oxotechnetium and oxorhenium complexes, respectively. Compound 1 (M = 99Tc, S = 4-methylthiophenol) crystallizes in the monoclinic space group P21/a, a = 23.12(1) Å, b = 14.349(6) Å, c = 8.801(4) Å, β = 94.81(2)°, V = 2918(2) Å3, Z = 4. Compound 3 (M = Re, S = 4-methylthiophenol) crystallizes in the monoclinic space group P21/a, a = 23.018(9) Å, b = 14.421(5) Å, c = 8.775(3) Å, β = 94.78(1)°, V = 2903(2) Å3, Z = 4. Compound 4 (M = Re, S = 4-methoxythiophenol) crystallizes in the orthorhombic space group Pbca, a = 16.32(1) Å, b = 24.55(2) Å, c = 16.94(1) Å, V = 6788(9) Å3, Z = 8. In all cases, the coordination geometry around the metal is distorted octahedral with the equatorial plane being defined by the three sulfur atoms of the thiophenols and one nitrogen atom of 2,2‘-bipyridine, while the apical positions are occupied by the second nitrogen atom of 2,2‘-bipyridine and the oxygen of the MO core. The complexes are stable, neutral, and lipophilic. Complete 1H and 13C NMR assignments are reported for all complexes. The analogous oxotechnetium complexes have been also synthesized at tracer level (99mTc) by mixing the 2,2‘-bipyridine and the corresponding thiol with Na99mTcO4 generator eluate using NaBH4 as reducing agent. Their structure was established by chromatographic comparison with authentic oxotechnetium and oxorhenium complexes using high performance liquid chromatography techniques

Glutathione Interaction with SNS/S Mixed-Ligand Complexes of Oxorhenium(V): Kinetic Aspects and Characterization of the Products

A series of oxorhenium(V) SNS/S mixed-ligand complexes [ReO(Ln/L)] carrying different types of tridentate ligands (Ln) and the same monodentate coligand (L) [L = C6H5S, L1 = C2H5N(CH2CH2S)2 (1), L2 = (C2H5)2NCH2CH2N(CH2CH2S)2 (2), L3 = C2H5SCH2CH2N(CH2CH2S)2 (3), and L4 = 2,6-(SCH2)2NC5H3 (4)] have been synthesized and characterized by spectroscopic methods and elemental analyses. X-ray structure determination was performed for complexes 3 and 4. Complex 3 adopts the expected distorted trigonal bipyramidal geometry around the metal in a syn configuration, while complex 4, due to the aromatic character of the nitrogen of the SNS donor-atom set, exhibits a distorted square pyramidal geometry. The interaction of complexes 1−4 with glutathione (GSH) was studied by high-performance liquid chromatography, revealing the rapid formation of the respective daughter complexes 5−8, wherein the L coligand has been substituted by GS. The daughter complexes 5−8 have been characterized by ES-MS and 2D NMR spectroscopy. Kinetic aspects of the interaction of complexes 1−3 with GSH have been studied by isothermal titration microcalorimetry providing direct measurements of the interaction rate constants as well as of the total enthalpy change. The reaction of complex 1 exhibits the slowest rate and that of complex 2 the fastest. This is in agreement with previously reported trends for analogous 99mTc complexes

Glutathione Interaction with SNS/S Mixed-Ligand Complexes of Oxorhenium(V): Kinetic Aspects and Characterization of the Products

A series of oxorhenium(V) SNS/S mixed-ligand complexes [ReO(Ln/L)] carrying different types of tridentate ligands (Ln) and the same monodentate coligand (L) [L = C6H5S, L1 = C2H5N(CH2CH2S)2 (1), L2 = (C2H5)2NCH2CH2N(CH2CH2S)2 (2), L3 = C2H5SCH2CH2N(CH2CH2S)2 (3), and L4 = 2,6-(SCH2)2NC5H3 (4)] have been synthesized and characterized by spectroscopic methods and elemental analyses. X-ray structure determination was performed for complexes 3 and 4. Complex 3 adopts the expected distorted trigonal bipyramidal geometry around the metal in a syn configuration, while complex 4, due to the aromatic character of the nitrogen of the SNS donor-atom set, exhibits a distorted square pyramidal geometry. The interaction of complexes 1−4 with glutathione (GSH) was studied by high-performance liquid chromatography, revealing the rapid formation of the respective daughter complexes 5−8, wherein the L coligand has been substituted by GS. The daughter complexes 5−8 have been characterized by ES-MS and 2D NMR spectroscopy. Kinetic aspects of the interaction of complexes 1−3 with GSH have been studied by isothermal titration microcalorimetry providing direct measurements of the interaction rate constants as well as of the total enthalpy change. The reaction of complex 1 exhibits the slowest rate and that of complex 2 the fastest. This is in agreement with previously reported trends for analogous 99mTc complexes