Stable and lipophilic technetium-99m dithiosemicarbazone complexes with 5-6-5 membered chelate ring structure

Modification of the chelate ring structure of technetium-99m (99mTc) dithiosemicarbazone (DTS) chelate was carried out in pursuit of a more stable and lipophilic compound. A new DTS chelating molecule, pentane-2,4-dione bis(N-methylthiosemicarbazone) (PETS), with a 5-6-5 membered chelate ring structure, was synthesized and labeled with 99mTc, PETS generated two 99mTc compounds as major products. Both had much higher stability and lipophilicity than a 5-5-5 membered 99mTc DTS compound, as well as great stability in plasma. Both 99mTc-PETS compounds were rapidly extracted by the brain and heart when injected into mice. Thus, the modified chelate ring structure afforded a preferable characteristics to DTS chelate as for the chelating site for technetium radiopharmaceuticals.     

Complexation of Co(II) Tetra-p-methoxyphenylporphine with molecular oxygen in the presence of unsaturated hydrocarbons

Conclusions It has been established that Co(II) porphyrins form five-coordinated complexes with olefins having a high level of donor capability, and six-coordinated complexes in the presence of oxygen. For these systems, we have found the equilibrium constants and the rate constant for the forward reaction of formation of the six-coordinated complex with oxygen in the example of 2-methyl-1-butene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 533–536, March, 1984.     

Synthesis and characterization of the complexes of pentane-2,4-dione with nickel(II) and cobalt(III): [Ni(acac)2].0.5CH3OH and [Co(acac)2NO3].2H2O (acac = pentane-2,4-dione)

Two mononuclear complexes, [Ni(acac)2].0.5CH3OH (1) and[Co(acac)2NO3].2H2O (2) (acac = pentane-2,4-dione), have been synthesized and characterized by single crystal X-ray analysis. Complex 1 crystallizes in the monoclinic space group P2(1)/c with a = 9.295(4), b = 11.450(5), c = 12.974(6) A, V = 1379.1(11) A(3),beta = 92.854(7), and Z = 4. Complex 2 crystallizes in the triclinic space group P(-1) with a= 8.153(9), b = 9.925(11), c = 10.355(12), V = 746.3(15) A(3), alpha = 70.530(16), beta =71.154(15), gamma = 80.698(16) and Z = 2. Complex 1 has a one-dimensional chain-like structure, which is extended by weak hydrogen contacts, while complex 2 shows a three-dimensional network structure.     

Synthesis and Crystal Structure of the Copper(Ⅱ) Complex with 1,10-Phenanthroline-5,6-dione

<正>The complex Cu(phon)(NO3)2(CH3CN) (phon = 1,10-phenanthroline-5,6-dione) has been synthesized and characterized by elemental analysis, infrared and UV-Vis spectra. X-ray diffraction analysis at room temperature indicates that the complex crystallizes in orthorhombic system, space group P212121 with a = 8.353(1), b = 11.299(2), c = 17.764(2) A, V= 1676.5(4) A3, Z = 4, C14H9CuN5O8, Mr = 438.8, Dc = 1.739 g/cm3, F(000) = 884 and μ(MoKα) = 1.361 mm-1. The final R and wR factors for the observed reflections with I > 2σ(I) are 0.0353 and 0.0855, respectively. R = 0.0432 and wR = 0.0899 for all data. The structure of the title complex consists of a neutral mononuclear entity. The central Cu (II) atom is five-coordinated by two nitrogen donors of one ligand, two unidentate NO3- ions and one CH3CN molecule. The coordination geometry of Cu (II) can be considered as a distorted trigonal bipyramidal configuration. The complex ability of the NO3-ion has more effect than that of the ClO4- ion on the structure of th     

Structural characterization and electronic properties determination by high-field and high-frequency EPR of a series of five-coordinated Mn(II) complexes

The isolation, structural characterization, and electronic properties of a series of high-spin mononuclear five-coordinated Mn(II) complexes, [Mn(terpy)(X)(2)] (terpy = 2, 2':6',2' '-terpyridine; X = I(-) (1), Br(-) (2), Cl(-) (3), or SCN(-) (4)), are reported. The X-ray structures of the complexes reveal that the manganese ion lies in the center of a distorted trigonal bipyramid for complexes 1, 2, and 4, while complex 3 is better described as a distorted square pyramid. The electronic properties of 1-4 were investigated by high-field and high-frequency EPR spectroscopy (HF-EPR) performed between 5 and 30 K. The powder HF-EPR spectra have been recorded in high-field-limit conditions (95-285 GHz) (D < gbetaB). The spectra are thus simplified, allowing an easy interpretation of the experimental data and an accurate determination of the spin Hamiltonian parameters. The magnitude of D varies between 0.26 and 1.00 cm(-)(1) with the nature of the anionic ligand. Thanks to low-temperature EPR experiments, the sign of D was unambiguously determined. D is positive for the iodo and bromo complexes and negative for the chloro and thiocyano ones. A structural correlation is proposed. Each complex is characterized by a significant rhombicity with E/D values between 0.17 and 0.29, reflecting the distorted geometry observed around the manganese. Finally, we compared the spin Hamiltonian parameters of our five-coordinated complexes and those previously reported for other analogous series of dihalo four- and six-coordinated complexes. The effect of the coordination number and of the geometry of the Mn(II) complexes on the spin Hamiltonian parameters is discussed.     

Synthesis, structure and properties of ruthenium(II) complexes with quinolinedione derivatives as chelate ligands: Crystal structure of [Ru(CO)2Cl2(6-methoxybenzo[g]quinoline-5,10-dione)]

The reaction of the dimer complex [{Ru(CO)₃Cl₂}₂] with the ligands 4,6-dichloroquinoline-5,8-dione and 6-methoxybenzo[g]quinoline-5,10-dione in ethanol solution led to the neutral mononuclear complexes of general formula [Ru(CO)₂Cl₂(κ²-quinolinedione-N,O)]. The complexes were characterized by elemental analysis, IR and RMN spectroscopy, and the molecular structure of [Ru(CO)₂Cl₂(6-methoxybenzo[g]quinoline-5,10-dione)] was determined by single-crystal X-ray diffraction. The redox chemistry of ligands and complexes was investigated by cyclic voltammetry, and their potential antitumor activity was also evaluated.     

Spectrophotometric studies and applications for the determination of yttrium in pure and in nickel base alloys

Yttrium reacts with 5-(4'-chlorophenylazo)-6-hydroxypyrimidine-2,4-dione (I), 5-(2'-bromophenylazo)-6-hydroxypyrimidine-2,4-dione (II), 5-(2',4'-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (III), 5-(4'-nitro-2',6'-dichlorophenylazo)-6-hydroxypyrimidine-2,4-dione (IV), 5-(2'-methyl-4'-hydroxyphenylazo)-6-hydroxypyrimidine-2,4-dione (V) to form a dark pink complexes, having an absorption maximum at 610, 577, 596, 567 and 585 nm, respectively. The complex formation was completed spontaneously in theil buffer solution and the resulting complex was stable for at least 3 h after dilution. Under the optimum conditions employed, the molar absorptivities were found to be 1.60 x 10(4), 1.29 x 10(4), 1.96 x 10(4), 1.45 x 10(4) and 1.21 x 10(4) l mol(-1) cm(-1) and the molar ratios were (1:1) and (1:2) (M:L). The linear ranges were found within 95 microg of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. Interfering species and their elimination have been studied. The precision and recovery are both satisfactory.     

Rhenium analogues of promising renal imaging agents with a [99mTc(CO)3]+ core bound to cysteine-derived dipeptides, including lanthionine

The coordination chemistry of lanthionine (LANH2) and cystathionine (CSTH2) dipeptides, which respectively consist of two cysteines and one cysteine and one homocysteine linked by a thioether bridge, is almost unstudied. Recently for fac-[99mTc(CO)3(LAN)]- isomers, the first small 99mTc(CO)3 agents evaluated in humans were found to give excellent renal images and to have a high specificity for renal excretion. Herein we report the synthesis and characterization of Re complexes useful for interpreting the nature of tracer 99mTc radiopharmaceuticals. Treatment of [Re(CO)3(H2O)3]OTf with commercially available LANH2 (a mixture of meso (d,l) and chiral (dd,ll) isomers) gave three HPLC peaks, 1A, 1B, and 1C, but treatment with CSTH2 (l,l isomer) gave one major product, Re(CO)3(CSTH) (2). Crystalline Re(CO)3(LANH) products were best obtained with synthetic LANH2, richer in meso or chiral isomers. X-ray crystallography showed that these dipeptides coordinate as tridentate N2S-bound ligands with two dangling carboxyls. The LANH ligand is meso in 1A and 1C and chiral in 1B. While 1A (kinetically favored) is stable at ambient temperature for days, it converted into 1C (thermodynamically favored) at 100 degrees C; after 6 h, equilibrium was reached at a 1A:1C ratio of 1:2 at pH 8. The structures provide a rationale for this behavior and for the fact that 1A and 1C have simple NMR spectra. This simplicity results from fluxional interchange between an enantiomer with both chelate rings having the same delta pucker and an enantiomer with both chelate rings having the same lambda pucker. Agents with the [99mTc(CO)3]+ core and N2S ligands show promise of becoming an important class of 99mTc radiopharmaceuticals. The chemistry of Re analogues with these ligands, such as the LAN2- complexes reported here, provides a useful background for designing new small agents and also tagged large agents because two uncoordinated carboxyl groups are available for conjugation with biological molecules such as proteins.     

Synthesis and crystal structure of an unusual mixed crystal containing an oxorhenium(V) and imidorhenium(V) complex

An unusual mixed crystal of a square-pyramidal oxorhenium(V), [ReOCl(Hdua)], and an octahedral imidorhenium(V) complex, [Re(dua)Cl₂(PPh₃)], was prepared from the reaction of trans-[ReOCl₃(PPh₃)₂]_and (6Z)-6-(2-aminobenzylideneamino)- 5-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione (H₃dua) in ethanol. Characterization was performed by single crystal X-ray structure determination and IR spectroscopy. The chelate Hdua is coordinated as a tridentate diamido-imine, and dua is chelated as an imido-imino-amide.     

Evaluation of 99mTc-HIDA complex as a cholescintigraphic agent (author's transl)

In the reaction labeling N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid (HIDA) with 99mTc, several complexes with different chemical characteristics were observed to occur with slight changes in the labeling conditions. Among these complexes, a complex detected in the bile of rats was limited to one complex, named as complex II. The preparation method of 99mTc-HIDA complex II and the exchange reaction between this complex and penicillamine indicate that 99mTc is coordinated with HIDA as low-hydrolyzed 99mTc in this complex. This complex is excreted rapidly through the bile and within 1 hr, about 65% of the total activity injected is recovered from bile in rats. The organ distribution of this complex was studied in mice by radioassay and in rabbits by scintillation camera and, in both cases, the radioactivity was accumulated in the gallbladder. These results suggest that the 99mTc chemical state, low-hydrolyzed state, relates to the bile excretion behavior of this complex, a potentially useful cholescintigraphic agent.     

Relationships between structure, retention and biological activity of some Schiff base ligands and their complexes

The lipophilicity of a series of Schiff base ligands and their complexes with nickel(II) and copper(II) has been determined by reversed-phase thin-layer chromatography using binary dioxane-water mobile phase. Chelate ligands were prepared by condensation of diamine and the corresponding beta-diketone. Copper(II) and nickel(II) complexes with chelate ligands containing ethane-1,2-diamine or propane-1,2-diamine as the amine part and pentane-2,4-dione and/or 1-phenylbutane-1,3-dione, pentane-2,4-dione and/or 1,1,1-trifluoropentane-2,4-dione, or 1,1,1-trifluoropentane-2,4-dione and/or 1-phenylbutane-1,3-dione as the beta-diketone part were synthesized. Some of investigated compounds were screened for their in vitro antifungal activity against Sacharomyces cerevisiae and antibacterial activity against Escherichia coli. Chromatographically obtained lipophilicity parameters were correlated both with calculated n-octanol-water partition coefficient C log P and antimicrobial activities. Satisfactory correlations were obtained. Chromatographic data proved to be reliable parameters for describing the lipophilic properties of the investigated compounds. Additionally, the principal components analysis was performed on the data chromatographically obtained. This statistical method was useful for distinguishing compounds and objective comparison of their lipophilicity parameters.     

Complexes of 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine: formation of mononuclear complexes, and self-assembly of double helical dinuclear and tetranuclear copper(II) and trinuclear nickel(II) complexes

The potentially pentadentate ligand 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine (H2L1), readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-aminomethylpyridine (ampy), shows limited tendency to form 1:1 M:L complexes with labile metal ions, although [CuL1] and [NiL1] were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Co(III) was characterized by a crystal structure as the neutral 1:2 complex [Co(L1)(HL1)] with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Fe(III) is known to form a symmetrical 1:2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Co(III) complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon. The most remarkable tendency of H2L1, however, is towards the formation of robust double helical complexes: a dinuclear Cu(II) complex [Cu2L1(2)] forms, as well as a trinuclear Ni(II) complex [Ni(3)(L1)2(OAc)2(MeOH)2]. Moreover, in the presence of added H2dipic, the tetranuclear complex [Cu4(L1)2(dipic)2(OH2)2] is obtained. All helical complexes have been characterized by X-ray crystal structure analyses, and all crystals feature a racemic mixture of left- and right-handed double helices stabilized by inter-ligand pi-stacking (inter-ring distances of 3.2-3.8 A) of ligands which each span several metal ions. Using the chelating ligand pentane-2,4-dione (acac), each of the two pairs of adjacent monodentate ligands in [Ni3(L1)2(OAc)2(OH2)2] have been shown to be available for substitution without destroying the helical structure, to form [Ni3(L1)2(acac)2], also characterized by a crystal structure.     

NMR investigation of the interaction of vanadate with carbasilatranes in aqueous solutions

Reaction of vanadate with carbasilatranes [methoxy{N,N',N' '-2,2',3-[bis(1-methylethanolato)(propyl)]amino}silane (1), methoxy{N,N',N' '-2,2',3-[bis(1-ethanolethanolato)(propyl)]amino}silane (2), and {N,N',N' '-2,2',2-[bis(ethanolato)(glycolpropyl ether)]amino}silane (3)] in aqueous solution results in the formation of vanadosilicates and five-coordinated chelate vanadium(V) complexes as evidenced by 51V, 1H, and 13C NMR spectroscopy. Chiral carbasilatrane S,S-1 was characterized in the solid state by X-ray diffraction, revealing a trigonal bipyramidal geometry around the metal ion, with one unidentate methoxy group and one atrane nitrogen atom at the axial positions and one carbon and two atrane oxygen atoms at the equatorial plane of the bipyramid. Crystal data (Mo Kalpha; 100(2) K) are as follows: orthorhombic space group P2(1)2(1)2(1); a = 8.8751(6), b = 9.7031(7), c = 14.2263(12) A; Z = 4. The complexation of vanadium either with 1 or 2 is stereoselective yielding approximately 94% of the complex containing ligand in the S,R-configuration. The lower ability of the S,S- and R,R-diastereoisomers of 1 and 2 to ligate vanadate was attributed to stereochemical factors, dictating a square pyramidal geometry for the chelated complexes. A dynamic process between the vanadium chelate complexes and the respective carbasilatranes was evaluated by 2D {1H} EXSY NMR spectroscopy. These spectra show that the vanadate complexes with the open carbasilatranes exchange more slowly with the free ligand compared to the respective alcohol aminate complexes.     

Novel 99mTc labeled σ receptor ligand as a potential tumor imaging agent

A novel 99mTc labeled complex, [N-[2-((2-oxo-2-(4-(3-phenylpropyl)piperazin-1-yl)ethyl) (2-mercaptoethyl)amino)acetyl]-2-aminoethanethiolato]Technetium(V) oxide (PPPE-MAMA′-99mTcO) ([99mTc]-2) has been designed and prepared based on the integrated approach. The corresponding rhenium complex (PPPE-MAMA′-ReO)(Re-2) has been prepared and characterized. In vitro competition binding assays show moderate affinity of Re-2 towards σ1 and σ2 receptors with Ki values of 8.67 ± 0.07 and 5.71 ± 1.88 μmol, respectively. Planar images obtained at 0.5 h, 4 h, 20 h after I.v. Injection indicate the accumulation of [99mTc]-2 in MCF-7 human breast tumor bearing mice at 20 h. Furthermore, the accumulation of [99mTc]-2 has been inhibited at 20 h after co-injection of [99mTc]-2 plus haloperidol (1 mg/kg). Biodistribution studies of [99mTc]-2 display an in vivo tumor uptake of 0.14% ± 0.01% ID/g at 24 h post I.v. Injection with a tumor/muscle ratio of 6.02 ± 0.87. The above results suggest that [99mTc]-2, derived from a previously published lead compound, retains certain tumor uptake and affinity for σ receptors. [99mTc]-2 may be used as a basis for further structural modifications to develop tumor imaging agents with high affinity for σ receptors.     

一种含[Ni(CN)4]2-和[Cu(pn)]2+构筑元组成的超分子配合物的合成、单晶结构和磁学性质

A cyano-bridged heterometallic supramolecular complex {[Cu(pn)]₃[Ni(CN)₄]₃}_n (1) has been synthesized and structurally characterized by single crystal X-ray diffraction. 1 displays an interesting 3D structure formed by μ₄, μ₃-[Ni(CN)₄]^2- tectons bridging five-coordinated and six-coordinated Cu(II) ions. The magnetic property shows that 1 behaves as weakly ferromagnetic interactions between the adjacent Cu(II) ions through the diamagnetic spacer NC-Ni-CN. CCDC: 624387.     

Synthesis, reactivity, and X-ray crystal structure of some mixed-ligand oxovanadium(V) complexes: first report of binuclear oxovanadium(V) complexes containing 4,4'-bipyridine type bridge

Reaction of the tridentate ONO Schiff-base ligand 2-hydroxybenzoylhydrazone of 2-hydroxybenzoylhydrazine (H2L) with VO(acac)2 in ethanol medium produces the oxoethoxovanadium(V) complex [VO(OEt)L] (A), which reacts with pyridine to form [VO(OEt)L.(py)] (1). Complex 1 is structurally characterized. It has a distorted octahedral O4N2 coordination environment around the V(V) acceptor center. Both complexes A and 1 in ethanol medium react with neutral monodentate Lewis bases 2-picoline, 3-picoline, 4- picoline, 4-amino pyridine, imidazole, and 4-methyl imidazole, all of which are stronger bases than pyridine, to produce dioxovanadium(V) complexes of general formula BH[VO2L]. Most of these dioxo complexes are structurally characterized, and the complex anion [VO2L]- is found to possess a distorted square pyramidal structure. When a solution/suspension of a BH[VO2L] complex in an alcohol (ROH) is treated with HCl in the same alcohol, it is converted into the corresponding monooxoalkoxo complex [VO(OR)L], where R comes from the alcohol used as the reaction medium. Both complexes A and 1 produce the 4,4'-bipyridine-bridged binuclear complex [VO(OEt)L]2(mu-4,4'-bipy) (2), which, to the best of our knowledge, represents the first report of a structurally characterized 4,4'-bipyridine-bridged oxovanadium(V) binuclear complex. Two similar binuclear oxovanadium(V) complexes 3 and 4 are also synthesized and characterized. All these binuclear complexes (2-4), on treatment with base B, produce the corresponding mononuclear dioxovanadium(V) complexes (5-10).     

Syntheses and characterization of dicarbonyl-nitrosyl complexes of technetium(I) and rhenium(I) in aqueous media: spectroscopic, structural, and DFT analyses

This work describes new synthetic routes to produce mixed carbonyl-nitrosyl complexes of technetium(I) and rhenium(I) in aqueous media. NaNO2, NOHSO4, and NO2(g) have been used to produce in situ nitrous acid as the primary source of NO+. Starting from the organometallic precursor fac-[MX3(CO)3]+, 1 (M = 99Tc, Re; X = Cl, Br), the formation of mixed dicarbonyl-mononitrosyl complexes was observed in aqueous hydrochloric and hydrobromic acid. Time-dependent analyses of the reactions by means of HATR-IR and 99Tc NMR spectroscopy in solution revealed the almost quantitative substitution of one CO ligand by NO+ and, thus, the formation of complexes with facial arrangement of the three pi-acceptor ligands. In the case of technetium, the monomeric complex (NEt4)[TcCl3(CO)2NO] (3a) and the dimeric, chloride-bridged, neutral complex [TcCl(mu-Cl)(CO)2NO]2 (4a) were produced. In the case of rhenium, the monomeric species (NEt4)[ReBr2X(CO)2NO] (X = Br (3b), NO3 (5)) was solely isolated. The X-ray structure of complexes 4a and 5 are discussed. The crystallographic analyses revealed the coordination of the NO+ group trans to the terminal chloride (4a) or the bromide (5), respectively. Crystal data: complex 4a (C4Cl4N2O(6)Tc2), monoclinic, Cc, a = 18.82(3) A, b = 6.103(6) A, c = 12.15(2) A, alpha = 90 degrees , beta = 105.8(2) degrees , gamma = 90 degrees , V = 1343(3) A(3), Z = 4; complex 5 (C10H20N3O(6)Br2Re), orthorhombic, P2(1)2(1)2(1), a = 10.2054(5) A, b = 12.5317(7) A, c = 13.9781(7) A, V = 1787.67(16) A(3), Z = 4. The isolated complexes and their potential facial isomers have been further investigated by density functional theory (DFT) calculations. The energy differences of the isomers are relatively small; however, the calculated energies are consistent with the formation of the observed and isolated compounds. The calculated bond lengths and angles of complex 5 are in good agreement with the data determined by X-ray diffraction. Experiments on the no-carrier-added level starting from fac-[99mTc(H2O)3(CO)3]+ revealed the formation of the complex fac-[99mTcCl(H2O)2(CO)2NO]+ in reasonable good yields. This aqueous-based, synthetic approach will enable the future evaluation of this novel, low-valent metal precursor for potential use in radiopharmacy.     

Structural features of some organotin(IV) complexes of semi- and thio-semicarbazones

Some five- and six-coordinated di and tri-n-butyl tin(IV) semi- and thio-semi carbazates have been synthesized. The characterization of these complexes, by IR, NMR (¹H, ¹³C, ¹¹⁹Sn), ¹¹⁹Sn), ¹¹⁹Sn Mössbauer and Mass spectroscopies along with X-ray diffraction, reveals that complexes of biionic ligands of the type Bu₂Sn L″ are five-coordinated having trigonal bipyramidal geometry. However, complexes of monoionic ligands of the type Bu₂SnL′₂ are six-coordinated in a distorted cis-octahedral geometry and Bu₃SnL′ are five-coordinated with a trigonal bipyramidal structure. X-ray structural studies on the compound Bu₂Sn(O.C₆H₄.CH:N.N.CS.NH₂), show that it crystallizes in a monoclinic lattice with a = 16.90 Å, b = 9.71 Å, c = 8.60 Å, and β = 103°45′.     

Studies of structural effects on the half-wave potentials of mononuclear and dinuclear nickel(II) diphosphine/dithiolate complexes

Two series of mononuclear Ni(II) complexes of the formula (PNP)Ni(dithiolate) where PNP = R2PCH2N(CH3)CH2PR2, R = Et and Ph, have been synthesized containing dithiolate ligands that vary from five- to seven-membered chelate rings. Two series of dinuclear Ni(II) complexes of the formula {[(diphosphine)Ni]2(dithiolate)}(X)2 (X = BF4 or PF6) have been synthesized in which the chelate ring size of the dithiolate and diphosphine ligands have been systematically varied. The structures of the alkylated mononuclear complex, [(PNPEt)Ni(SC2H4SMe)]OTf, and the dinuclear complex, [(dppeNi)2(SC3H6S)](BF4)2, have been determined by X-ray diffraction studies. The complexes have been studied by cyclic voltammetry to determine how the half-wave potentials of the Ni(II/I) couples vary with chelate ring size of the ligands. For the mononuclear complexes, this potential becomes more positive as the natural bite angle of the dithiolate ligand increases. However, the potentials of the Ni(II/I) couples of the dinuclear complexes do not show a dependence on the chelate ring size of the ligands. Other aspects of the reduction chemistry of these complexes have been explored.     

Derivatization of glucose and 2-deoxyglucose for transition metal complexation: substitution reactions with organometallic 99mTc and Re precursors and fundamental NMR investigations

Synthetic strategies for the bifunctionalization of glucose and 2-deoxyglucose at position C-1 for transition metal coordination are reported. In particular organometallic technetium and rhenium complexes for potential use in diagnostic nuclear medicine were synthesized and investigated. Specifically, a common iminodiacetic acid (IDA) moiety was O-glycosidically connected through an ethylene spacer group to produce the pure alpha- (in case of 2-deoxyglucose) and beta-anomer (in case of glucose). Reaction of the sugar derivatives with the organometallic precursor [M(H2O)3(CO)3]+ (M = 99mTc, Re) produced single products in high yield, which are water-soluble and water-stable. The displacement of the three water molecules of the metal precursor and thus the tridentate coordination of the metal-tricarbonyl core exclusively via the amine and the two carboxylic acid functionalities of the IDA chelate was verified by means of 1D and 2D 1H NMR spectroscopy, mass spectrometry, and IR spectroscopy. The radioactive-labeled products (99mTc) proved their excellent stability in vitro in physiological phosphate buffer (pH = 7.4) and human plasma over a period of 24 h at 37 degrees C.