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Aim: Obtain radioimages of amyloid-β fibers using 99mTc-complexes. Methodology: Tridentate thiosemicarbazone and thiocarbonohydrazone ligands containing fragments (stilbene, azobenzene, benzothiazole or benzoxazole) with affinity for amyloid-ß fibers and its Re(I) complexes have been prepared. The molecular structures of several ligands and complexes were determined by x-ray diffraction. Binding affinity studies toward Aß1-42 fibers were performed for the ligands and Re(I) complexes. The ability of formation of some 99mTc(I) complexes, their biodistribution and in vivo stability have been established. Results & conclusion: Complexes of stilbene and benzothiazole thiosemicarbazonates show similar affinity for amyloid-β fibers to the free ligand. These 99mTc complexes present a reasonable in vivo stability and a low capability to cross the blood–brain barrier although not sufficient to brain amyloid imaging.

Chagas disease remains a serious public health concern with unsatisfactory treatment outcomes due to strain-specific drug resistance and various side effects. To identify new therapeutic drugs agai...

Reactions of (NBu4)[MOCl4] complexes (M = Tc or Re) with an excess of hexafluoroacetylacetone (Hhfac) give products with a composition of (NBu4)[MOCl3(hfac)] as bright yellow (Tc) or red (Re) solids. The products are stable as solids but rapidly decompose in solution. A number of related phenylimidorhenium(V) complexes were synthesized starting from [Re(NPhF)Cl3(PPh3)2], where (NPhF)2– is a para-fluorinated phenylimido ligand. Products with compositions of [Re(NPhF)Cl2(PPh3)(acac)], [Re(NPhF)Cl2(PPh3)(hfac)], [Re(NPhF)Cl2(PPh3)(tfac)], [Re(NPhF)Cl2(PPh3)(naphtfac)], and [Re(NPhF)Cl2(PPh3)(tbutfac)] (Hacac = acetylacetone, Htfac = trifluoroacetylacetone, Hnaphtfac = naphthoyltrifluoroacetylmethane, and Htbutfac = tert-butyroyltrifluoroacetylmethane) were isolated from reactions of the quite soluble [Re(NPhF)Cl3(PPh3)2] with the corresponding β-diketones and studied spectroscopically and by X-ray diffraction. The β-diketonates are coordinated in a meridional arrangement with the phenylimide. The formation o...

Homoleptic eightfold coordinated methyl isocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu

Homoleptic eight-fold coordinated methylisocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu4]4[W(CN)8] with methyl triflate MeOTf gives [W(CNMe)8][OTf]4. The even stronger methylating mixture of methyl fluoride MeF and arsenic pentafluoride AsF5 in liquid sulfur dioxide SO2 is able to fully alkylate both [NBu4]4[W(CN)8] and [NBu4]3[W(CN)8]. The paramagnetic octakis(methylisocyanide)- tungsten(V) [W(CNMe)8][AsF6]5 is thermally highly unstable above −30 °C. All compounds have been characterized via single-crystal X-ray diffraction, IR and Raman, as well as NMR or EPR spectroscopy

Phenyltelluroxane clusters of the composition [{(PhTe)19O24}2I18(solv)] (1) are formed during the hydrolysis of [PhTeI3]2 or the oxidation of various phenyltellurium(II) compounds with iodine under hydrolytic conditions. The compounds consist of two half‐spheres with a {(PhTe)19O24}9+ network, which are connected by 18 iodine atoms. The spherical clusters can accommodate solvent molecules such as pyridine or methanol in the center of two rings formed by iodine atoms. The presence of other metal ions during the cluster formation results in a selective replacement of the central {PhTe}3+ units of each half‐sphere as has been demonstrated with the isolation of [{(PhTe)18({Ca(H2O)2}O24}2I16] (2) and [{(PhTe)18({Y(NO3)(H2O)}O24}2I16] (3). A crownether‐like coordination by six oxygen atoms of the telluroxane network is found for the {Ca(H2O}2}2+ and {Y(NO3)(H2O)}2+ building blocks. Mass spectrometric studies show that considerable amounts of the intact clusters are transferred to the gas phase without dissociation., Large telluroxane clusters are formed during the hydrolysis of [PhTeI3]2 or the oxidation of [PhTe]2 with iodine under hydrolytic conditions. They consist of two half‐spheres with {(PhTe)19O24}9+ networks, which are connected by 18 iodine atoms. The central {PhTe}3+ units of each half‐sphere can be replaced by other metal ions. Mass spectrometry shows that the intact clusters are transferred to the gas phase without dissociation.

Potentially tridentate, phosphine-containing Schiff bases with P,N,O and P,N,P donor sets have been prepared from 2-(diphenylphosphino)benzaldehyde, salicylaldehyde, 2-aminophenol and 2-((diphenylphosphino)phenyl)methylamine and reacted with (NEt4)(2)[Re(CO)(3)Br-3] in methanol. Deprotonation and the formation of neutral [Re(CO)(3)(L)] complexes with tridentate coordination of the Schiff bases has been obtained for the salicylidene derivatives, while the potential P,N,P ligand L-3 forms [Re(CO)(3)Br(L-3)] with the Schiff base in a bidentate bonding mode. The formation of a cationic [Re(CO)(3)(L-3)](+) complex with tripodal coordination of the organic ligand could be achieved by the addition of Ag(PF6) to the reaction mixture. The obtained rhenium(I) complexes were studied spectroscopically and by X-ray diffraction.

[PtCl

The mixed isocyanide/carbonyl complexes cis- and trans-[Re(CO)3Br(CNArDipp2)2] (ArDipp2 = 2,6-(2,6-(i-Pr)2C6H3)2C6H3) can be synthesized from reactions of [Re(CO)5Br] and CNArDipp2 depending on the conditions applied. Reduction of the neutral Re(I) species gives the monoanionic complex [Re(CO)3(CNArDipp2)2]− or the neutral [Re(CO)3(CNArDipp2)2], which contain rhenium in the formal oxidation states “−1” and “0”, respectively.

[PtCl2(phen)] reacts with thiosemicarbazones derived from β-diketones (H2LR) leading to an intramolecular C-C coupling between phen and the ketone upon formation of tetradentate N,N,N,S chelates [PtII(LRphen)]. The reactions proceed via bidentate coordination of the doubly deprotonated (LR)2- followed by an intra-nucleophilic attack and consecutive C-C bond formation.

The salicylidene Schiff bases of bis(2‐aminophenyl)diselenide and ‐ditelluride react with [MIICl2(PPh3)2] (M = Ni, Pt) or [PdII(OAc)2(PPh3)2] with formation of square‐planar complexes with the general formulae [MII(LY)(PPh3)] (M = Ni, Pd, Pt, Y = Se, Te). The ligands coordinate to the metals as tridentate {O,N,Se/Te} chelates. The reduction of the dichalcogenides and the formation of the chalcogenolato ligands occurs in situ by released PPh3 ligands. A mechanism for such reactions has been derived from the experimental data with the aid of DFT calculations. It suggests a higher polarization of the dichalcogenide bond with partial charge separation upon coordination to a metal centre, which therefore facilitates the cleavage of the dichalcogenide bond with PPh3. In accordance with the proposed mechanism, best yields are obtained with a strict exclusion of oxygen, but in the presence of water.

One‐pot reactions of the catechol‐scaffolding aroylbis(N,N‐diethylthiourea) H2Lcat with mixtures of alkaline earth nitrates M(NO3)2 (M2+ = Ca2+, Sr2+ or Ba2+) and (NEt4)[AuCl4] or [Au(tht)Cl] (tht = tetrahydrothiophene) in methanol in the presence of Et3N as supporting base give rise to neutral trinuclear gold(I) {2}‐metallacoronates with the composition of {M ⊂ [Au2(Lcat)2]} (1). Similar reactions with the pyridine‐centered aroylbis(N,N‐diethylthiourea) H2Lpy, however, produce complexes with the same metal‐to‐ligand ratio but with higher nuclearity {2M ⊂ [Au4(Lpy)4]} (2). In both 1 and 2, Au(I) ions are exclusively S‐bonded with the organic ligands and adopt a virtually linear coordination fashion. Such metal‐ligand binding is responsible for the formation of metallacoronands, which accommodate alkaline earth metal ions in their molecular voids, thereby resulting in host–guest coordination assemblies. The level of metal‐ligand aggregation in the resulting assemblies is dependent on the denticity, size and flexibility of the centered building block of the aroylbis(N,N‐diethylthiourea) ligands.

Three new neutral oxorhenium(V) complexes were prepared with a 5-hydroxy-3-methyl-5-phenyl-pyrazoline-1-(S-benzyldithiocarbazate) ligand (H2bdtc): ReOCl(bdtc)(triphenylphosphine) [1] , ReOBr(bdtc)(triphenylphosphine) [2] and ReO(bdtc)(cysteamine) [3] . These rhenium complexes were characterized based on elemental, ESI(+)-MS, IR, NMR (1H and 31P), and X-ray diffraction analysis. The bdtc ligand took on different coordination arrangements for the three rhenium complexes, a planar conformation for 1 and a facial conformation for complex 3. Complexes 1 and 3 crystallize with monoclinic space groups P21/n and P21/c, respectively. The conformational stability caused by the unimolecular arrangement of the ligands was evaluated by the Density Functional Theory (DFT) calculation with the purpose of determining the balance involving the equilibrium among the possible stereoisomers in isolated phase and solvent. Moreover, frontier molecular orbitals, Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM), bond order indices and molecular electrostatic potential analysis were performed to understand the electronic properties.

A series of thiosemicarbazones was obtained by condensation of halogenated N-(diethylaminothiocarbonyl)benzimidoyl chlorides (3b–3h) with 4,4-dimethyl-3-thiosemicarbazide. The activity of the halogenated compounds against the parasite Trypanosoma cruzi was evaluated and compared to the previously reported activity of the corresponding non-substituted thiosemicarbazone. It was found that the halogen-substitution enhances in most cases the anti-parasitic activity. The meta-fluorinated compound (4g) was identified as the most potent one (IC50= 9.0 μM, CC50 > 200 μM), having a selectivity index (SI = IC50/CC50), which is 4-times higher than that of the non-substituted compound. Slight modification of the reaction conditions employed for the synthesis of some of the benzoylthioureas 3a–3g led to the unexpected formation of novel halogenated 6-amino-1,3,5-thiadiazine-2-thiones.

The reaction of isophthaloylbis(N,N-diethylthiourea), H2L1, with UO2(CH3COO)2·2H2O and NEt3 as a supporting base gives a tetranuclear, anionic complex of the composition [{UO2(L1)}4(OAc)2]2–, in which the uranyl ions are S,O-chelate bonded. Each two of them are additionally linked by an acetato ligand. Similar reactions of various uranyl starting materials (uranyl acetate, uranyl nitrate, (NBu4)2[UO2Cl4]) with corresponding pyridine-centered ligands (pyridine-2,6-dicarbonylbis(N,N-dialkylthioureas), H2L2) yield mononuclear, neutral compounds, in which the thiourea derivatives are coordinated as S,N,N,N,S-five-dentate chelators. The equatorial coordination spheres of the formed hexagonal bipyramidal complexes [UO2(L2)(solv)] are completed by solvent ligands (H2O, MeOH, or DMF). Attempted reactions without a supporting base result in decomposition of the organic ligands and the formation of hexanuclear uranyl complexes with pyridine-2,6-dicarboxylato ligands, while the use of an excess of base results in co...

One-pot reactions of the catechol-scaffolding aroylbis(

One-pot reactions of 2,6-dipicolinoylbis(

Nine thiosemicarbazone ligands (H2Ln, n = 1–9) containing benzothiazole or benzoxazole groups at the C(2) atom of the thiosemicarbazone have been prepared and characterized. A crystal structure study was performed on six of these free ligands and the role of the π–π interactions in the molecular association was analyzed. The coordination behavior of the thiosemicarbazones towards the {Re(CO)3}+ fragment was investigated and three types of complexes were obtained: mononuclear fac-[ReX(H2Ln)(CO)3], X = Cl or Br, with bidentate ligands, dinuclear [Re2(HLn)2(CO)6] with monodeprotonated bridging thiosemicarbazonates yielding Re2S2 cores and tetranuclear [Re4(L2)2(CO)12(EtOH)2] with an unusual bideprotonated thiosemicarbazonate ligand. The intermolecular interactions before and after metal coordination were analyzed. In the dinuclear complexes, two different approximate symmetries were observed depending on the relative orientation of the thiosemicarbazonate ligands with respect to the Re2S2 diamond. The intramolecular interactions in the dimers and their relationship with the two possible symmetric dispositions were analyzed. The findings, in conjunction with theoretical calculations, allowed the main stabilizing factors for each type of symmetry to be elucidated.

The deep blue, paramagnetic Cs2[TcII(NO)F5] is formed during reactions of pertechnetate, acetohydroxamic acid, and CsF in aqueous HF. A reaction of Cs2[Tc(NO)F5] with BF3·MeOH in acetonitrile gives yellow blocks of the fluorido-bridged dimer [{TcI(NO)(CH3CN)4}2F](BF4)3. The compound is stable as solid and in acetonitrile solutions. The complex cation contains a bent μ-F– ligand and two linear nitrosyl groups.

Reactions of (NBu4)[TcOCl4] or [TcCl3(PPh3)2(CH3CN)] with in situ-prepared lithium arylselenolates and -tellurolates give (NBu4)[TcVO(ArE)4] (E = Se, Te; Ar = phenyl) and [TcIII(ArE)3(PPh3)(CH3CN)] (E = Se, Te; Ar = phenyl, 2,6-Me2phenyl, mesityl) complexes, respectively. The products contain square-pyramidal (TcV compounds) and trigonal bipyramidal (TcIII complexes) coordinated technetium atoms. Density functional theory calculations indicate that the Tc–chalcogen bonds in the TcIII compounds have a greater bond order than those in the TcV compounds.

Fluoridotetrakis(trifluoroacetato)nitrosyltechnetate(II) was prepared by the dissolution of Cs2[Tc(NO)F5] in trifluoroacetic acid and addition of (NBu4)F·3H2O. The compound crystallizes as a mixed Cs+/NBu4+ salt in the form of green crystals. Unlike the [Tc(NO)F5]2− salts, the product is soluble in organic solvents and can be used as a precursor for ongoing ligand exchange procedures with organic ligands. The corresponding reactions with triphenylphosphine (PPh3), 1,2-bis(diphenylphosphino)ethane (DPPE) or pyridyldiphenylphosphine (pyPPh2) give technetium(I) complexes of the compositions Cs[Tc(NO)(PPh3)2(CF3COO)2F], [Tc(NO)(DPPE)2(OOCCF3)](PF6) and [Tc(NO)(κN,P-pyPPh2)(κP-pyPPh2)(CF3COO)2]. The products were studied spectroscopically and by X-ray diffraction. The 99Tc NMR resonances of the novel Tc(I) nitrosyls appear between −627 and +952 ppm, which is at a remarkably high field and in the range where normally the signals of Tc(III) compounds are observed.

Chagas disease remains a serious public health concern with unsatisfactory treatment outcomes due to strain-specific drug resistance and various side effects. To identify new therapeutic drugs against

A series of 16 "3 + 2" mixed-ligand complexes of the general composition [ReO(L1)(L2)] (H

Tris(1-phenyl-1H-1,2,3-triazol-4-yl)phosphine oxide (OP(1,2,3Tz1-Ph)3) and tris(1-benzyl-1H-1,2,3-triazol-4-yl)phosphine oxide (OP(1,2,3Tz1-benz)3) react with (NBu4)[ReOCl4] under partial hydrolysi...

A series of 16 "3 + 2" mixed-ligand complexes of the general composition [ReO(L1)(L2)] (H2L1a-H2L1d = tridentate thiosemicarbazones having a phenyl group with 4-H, 4-F, 3,5-di-F, and 4-CF3 substituents; HL2a-HL2d = bidentate N,N-diethyl-N'-benzoylthioureas with 4-H, 4-F, 3,5-di-F, and 4-CF3 substituents at the benzoyl groups) have been synthesized and characterized by spectroscopic methods and X-ray diffraction. Irrespective of the individual fluorine substitution, the complexes are stable and possess the same general structure. Some systematic electronic effects of the fluorine-substitution patterns of the ligands have been found on the 13C NMR chemical shifts of the N-C═N carbon atoms of the {L1}2- and the C═O carbon atoms of the {L2}- ligands. Antiparasitic properties of the rhenium complexes have been tested against epimastigotes and trypomastigotes forms of two Trypanosoma cruzi strains and the amastigotes form of one of them. The results of this study indicate that the activity of the rhenium complexes can clearly be modulated by fluorine substitution of their ligands. Some of the fluorinated compounds show a high activity against epimastigotes and trypomastigotes forms of the parasites. Reactions between (NBu4)[TcOCl4] and two representatives of the fluorinated ligands (H2L1b, 4-F-substituted, and H2L1c, 4-CF3-substituted) form stable complexes of the composition [TcOCl(L1b)] and [TcOCl(L1c)]. Subsequent reactions of these products with HL2b (4-F-substituted) give the corresponding [TcO(L1)(L2)] mixed-ligand complexes. Also, the technetium compounds are stable as solids and in solutions and have structures corresponding to those of their rhenium analogues.

Chemical properties and biological activity of Au(III) compounds obtained from dichlorido[2‐(dimethylaminomethyl)phenyl‐C1,N]gold(III), [Au(damp‐C1,N)Cl2], and halogenated, potentially tridentate thiosemicarbazones have been studied. The results of this work show that the complexation of the halogenated thiosemicarbazones with Au(III) enhances their stability against hydrolysis and retains or enhances their anti‐parasitic activity. Fluorination in the periphery of the ligands has expectedly no influence on the structural chemistry of the obtained Au(III) complexes, but modulates their biological behaviour. Best results with a remarkably high selectivity index for the trypomastigote form of Trypanosoma cruzi were obtained with the complex containing the ligand, which presents a 3,5‐fluorine substitution in meta‐position of an aromatic ring, [Au(dampH)(L‐3,5‐F)]Cl.

Reactions of thiosemicarbazone ligands (H2L1) with [ReX3(NPh)(PPh3)2] (X = Cl or Br) led to the formation of stable rhenium(V) complexes of composition [ReX(NPh)(HL1)(PPh3)]X. The Re(V) complexes have been characterized by diverse techniques including FTIR, 1H and 31P NMR, elemental analysis, HRMS and single-crystal X-ray diffraction analysis. The crystal structures of the complexes rhenium complexes showed the formation a distorted octahedron environment around the Re(V) metal center, with the axial positions being occupied by the halogen atom and by the nitrogen atom from the phenylimido moiety, while the equatorial positions are occupied by the S,N,S-thiosemicarbazonate and the triphenylphosphane ligands. Furthermore, the “3 + 2” mixed ligand complex [Re(NPh)(L1b)(Et2btu)], where HEt2btu is N,N-diethyl-N’-benzoylthiourea, could be obtained from an equimolar reaction of [ReCl(NPh)(HL1)(PPh3)]Cl with the bidentate thiourea in the presence of NEt3. Finally, DFT calculations were applied in order to propose a complex suitable for biocouplings upon substitution of a NH2 group at the 4-position of the phenylimido ligand in [Re(NPh)(L1b)(Et2btu)]. The compounds studied here represent the first examples of phenilimidorhenium(V) complexes with thiosemicarbazones.

In this article we describe the synthesis and characterization of [PhTe(tu)2][PhTeI4] and [MesTe(tu)][PhTeX4] (tu = thiourea, X = Br, I), containing multivalent tellurium species. During the syntheses of the compounds, the formation of different species, such as [PhTe(tu)I] or [I(tu)2][PhTeI4] was found, which were isolated and characterized. Thiourea was used in order to explore the relevance of Te···S bonds in the solid state structures of the products compared to related compounds with Te···X and X···X bonds in their molecular structures. Different types of chalcogen-chalcogen, chalcogen-halogen and halogen-halogen interactions are described by the combination of crystallographic data and computational methods. The nature of these interactions was evaluated by the noncovalent interaction index (NCI), and quantum theory of atoms in molecules (QTAIM) analyses.

A novel propargyl-substituted thiocarbamoylbenzamidine has been synthesized. The compound acts as a tetradentate ligand and forms stable complexes with the {ReVO}3+ and {TcVO}3+ cores. 'Click' couplings of the resulting complexes with benzyl azide lead to prototype triazole derivatives, which were analyzed by NMR, IR, and mass spectrometry as well as by X-ray diffraction. A similar coupling procedure has been applied for an azido-modified angiotensin-II peptide, which gives the desired rhenium(V) bioconjucate with good yields. The ease of this coupling and the stability of the conjugate recommends such tetradentate thiocarbamoylbenzamidines also for clinically relevant bioconjugates with 99mTc.

2,6-Diacetylpyridine-bis(benzoylhydrazone), H2LPh, reacts with Pb(OAc)2·3H2O and NEt3 as a supporting base forming a polymeric solid of the composition [Pb(LPh)]n. A reaction with pyridine results in cleavage of the polymer and formation of the dimeric, crystalline compound [Pb(py)(LPh)]2. Similar reactions with PbX2 salts (X = Cl, Br, I) also give almost insoluble solids of the tentative composition [Pb(H2LPh)X2]n. After ongoing reactions with DMSO, single deprotonation of the organic ligand and the formation of pseudo-dimeric [Pb(HLPh)X]2 complexes was observed. Depending on the presence of solvent molecules they form different supramolecular aggregates by π–π interactions. The use of Pb(NO3)2 results in a dimeric structure with relatively short Pb–O bonds of 2.442(2) A between the monomeric sub-units. The formed dimers aggregate to a polymeric assembly by hydrogen bonds. The products were studied by spectroscopic methods and X-ray diffraction.

Reactions between [Tc(I)(NO)X2(PPh3)2(CH3CN)] complexes (X = Cl, Br) and KCp form the pseudotetrahedral organotechnetium compounds [Tc(I)(NO)(Cp)(PPh3)X]. The halide ligands can readily be replaced by other halides or organometallic ligands giving access to a novel family of technetium(i) compounds with the robust {Tc(NO)(Cp)(PPh3)}(+) core.

[PdI(TePy-2)(I2TePy-2)2] is obtained via a rare oxidation reaction of palladium powder by the in situ generated diiodine adduct of bis-2-pyridylditelluride at room temperature. An X-ray diffraction study reveals the molecular structure of [PdI(TePy-2)(I2TePy-2)2], where the palladium atom is surrounded by an iodide and three tellurium atoms (two [I2TePy-2] and one [TePy-2] groups). The oxidation states for the tellurium atoms were analysed using calculated atomic charges and electron localization function (ELF). The optical bang gap for [PdI(TePy-2)(I2TePy-2)2] was determined through theoretical (DFT) and experimental (diffuse reflectance UV–Visible) studies and the electrochemical behavior for the compound was examined by cyclic voltammetry.

The unprecedented use of 2,2,2-trifluoroethanol as reaction solvent provided a facile and convenient access to symmetrically 3,3-disubstitued quinoline-2,4-diones in moderate to excellent yields and high regioselectivity, by reaction of 4-hydroxy-2-quinolones with electrophiles like methyl iodide, as well as benzyl and allyl bromides in the presence of K2CO3. Silver (I) oxide is required to increase the yield of the methylations.

The compounds [Pd2I2{Te((2,6-OCH3)2C6H3)}2(PCy3)2] (1), [Pd2I2{Te((2,6-OCH3)2C6H3)}2(PR2R')2]∙2CH3CN (2), [Pd2{Te((2,6-OCH3)2C6H3)}2(phen)2][Hg2Br6(phen)2] (3), [Pd2Cl2(TePh2)2(TePh)2] ∙ DMF (4), [Pd2(SePh)2(2,2′-bipy)2][HgBr4]∙2DMF (5), [Pd2(SePh)2-(phen)2][HgI4]∙5DMF (6), [Pd2{Te((2,6-OCH3)2C6H3)}2(phen)2][Hg2I6]-[Hg((2,6-OCH3)2C6H3)2] (7) containing [Pd2(µ-ER)2] core (E = Se, Te; R = aryl) were synthesized and characterized by IR spectroscopy, elemental analysis and X-ray crystallography. Intermolecular metallophilic interactions were evaluated through crystallographic studies combined with Density Functional Theory calculations. The structural stability of 4–7 were investigated taking in account the interactions E⋯E, Pd⋯Pd and Pd⋯Hg between [Pd2(µ-ER)2] cores.

Chagas disease remains a serious public health concern with unsatisfactory treatment outcomes due to strain-specific drug resistance and various side effects. To identify new therapeutic drugs againstTrypanosoma cruzi, we evaluated both thein vitroandin vivoactivity of the organometallic gold(III) complex [Au(Hdamp)(L14)]Cl (L1 =SNS- donating thiosemicarbazone), which was denoted 4-Cl. Our results demonstrated that 4- Cl was more effective than benznidazole (Bz) in eliminating both the extracellular trypomastigote and the intracellular amastigote forms of the parasite without cytotoxic effects on mammalian cells. In very-low-dosein vivoassays, 4-Cl reduced parasitaemia and tissue parasitism in addition to protecting the liver and heart from tissue damage. All these changes resulted in the survival of 100% of the mice treated with 4-Cl during the acute phase. We hypothesised that 4-Cl can act directly on the parasite and may participate in the modulation of IFN-γ production at the acute stage of the disease. Molecular docking simulations showed that the compound may interact with cruzain, a thiol protease considered a possible antiparasitic drug target, primarily by hydrophobic interactions. These analyses predicted that the Cys25 residue in the cruzain binding site is approximately 3.0 Å away from the S and Au atoms of the gold compound, which could suggest formation of a possible covalent bond between cruzain and the inhibitor. Overall, we confirmed the potential of 4-Cl as a new candidate for Chagas disease treatment.

PhTe(CH2)3NH3Cl (1) is readily converted to [PhTeX2(CH2)3NH3]X (X = Cl: 2, X = Br: 3) either by reactions with X2 (X = Cl, Br) or by air oxidation after treatment with concentrated HX (X = Cl, Br). Similar reactions with HI or I2 resulted in the formation of unattractive viscous oils only. Solutions of compound 1 are stable on air under slightly acidic conditions, but undergo a reaction with CO2 from the air under formation of the corresponding carbamate, when aqueous ammonia or NEt3 are added. The reaction is more efficient when CO2 is bubbled through the solution. The ion pair [PhTe(CH2)3NH3]+[PhTe(CH2)3NHCO2]− is formed from such solutions in high yields. The products have been studied spectroscopically and by X-ray diffraction.

Reactions of (NEt4)2[Re(CO)3Br3] with N-heterocyclic thiols such as 2-mercaptobenzimidazole (H2Sbenzim), 2-mercaptothiazoline (HSthiaz), or 5-mercapto-1-methyltetrazole (HSmetetraz) give rhenium(I) complexes of various compositions: (NEt4)[Re(CO)3Br2(H2Sbenzim)], [Re(CO)3(HSthiaz)3]Br, and (NEt4)[Re2(CO)6(μ-S-Smetetraz-κS)(μ-N,S-Smetetraz-κS,N)2]. Corresponding reactions with 2-mercaptopyridine (HSpy) and bis(2-pyridine)diselenide [(Sepy)2] did not give defined products in reasonable yields, whereas [Re(CO)5Br] reacts with HSpy and (Sepy)2 with formation of [Re(CO)3(HSpy)3]Br and [Re2(CO)6(Sepy)2], respectively. All reactions were performed without the addition of a supporting base and the sulfur-containing organic ligands are coordinated in their thione forms with the exception of Smetetraz– in its μS-bridging coordination mode in (NEt4)[Re2(CO)6(μ-S-Smetetraz-κS)(μ-N,S-Smetetraz-κS,N)2], which can be regarded as thiolate. The bonding mode of the selenium containing ligands in the dimeric compound [Re2(CO)6(Sepy)2] (C–Se distance: 1.93 A) can also best be described as selenolate. The products are stable on air at an ambient temperature. They were studied spectroscopically and by X-ray diffraction.

Novel, potentially pentadentate ligands (H3L) for an optimal coordination of {MVO}3+ and {MV(NPh)}3+ cores (M = Re, Tc) have been tailored by a computer-aided procedure. They can be prepared by reactions of 2-aminobenzyliminodiacetic acid diethylester with N,N-[(dialkylamino)(thiocarbonyl)]benzimidoyl chlorides and subsequent hydrolysis. The ligands react with [ReOCl3(PPh3)2] or [Re(NPh)Cl3(PPh3)2] under triple deprotonation and form compounds of the general compositions [ReO(L)] and [Re(NPh)(L)], respectively. The organic ligands occupy the remaining five coordination positions of the {ReO}3+ and {Re(NPh)}3+ cores in all compounds studied. The phenylimido complexes hydrolyze in basic media under formation of their oxidorhenium(V) analogs.

Reactions of bis(2-pyridyl)diselenide, py 2 Se 2 (py = 2-C 5 H 4 N) with [(Ph 3 P)AuCl], [(Ph 3 P)CuCl] and CuCl 2 ·2H 2 O result in the formation of the complexes [Au(pyHSe) 2 ]Cl ( 1 ), [Cu 4 (pySe) 4 ] ( 2 ) and [Cu(py 2 Se 2 )Cl 2 ] ( 3 ) respectively. When the compounds 2 and 3 are exposed to air, they form the polymeric compound [Cu(pySeO 2 ) 2 ] n ( 4 ), which contains 2-pyridylseleninic species [pySeO 2 ] − . Compound 4 is also obtained by the reaction of py 2 Se 2 and CuBr followed by spontaneous oxidation in air. All compounds were characterized by single-crystal X-ray diffraction, elemental analysis, and infrared spectroscopy.

The potentially tetradentate benzamidine/thiosemicarbazone ligand, Et2N–(C S)–NH-C(Ph) = N–(o-C4H6)–C(Me) = N–NH–(C S)–NH–Me (H2L) readily reacts with Ni(CH3COO)2, [PdCl2(CH3CN)2], [PtCl2(PPh3)2] and (NBu4)[ReOCl4] under formation of complexes of the compositions [M(L)] (M = Ni (1), Pd (2), Pt (3)) and [ReO(L)(OMe)] (4). In all complexes, H2L is doubly deprotonated and bonded to the central metal ion via its N2S2 donor set. Complexes 1, 2 and 3 have distorted square-planar coordination spheres, while the rhenium compound 4 is an octahedral trans oxido/methoxido complex. The H2L proligand shows a medium cytotoxicity with an IC50 value of 21.1 μM. While the rhenium complex 4 exhibits a stronger antiproliferative effect (IC50 = 5.52 μM), the nickel, palladium and platinum complexes are almost inactive.

A series of lanthanide complexes with general formula [Ln(NTA)3X] were prapared [Ln = Y (a), Er (b), Eu (c), NTA = naphthoyltrifluoroacetone, X = H2O (1), phen = phenanthroline (2), bpyO1 = 2, 2′-bipyridine N-oxide (3), and bpyO2 = 2, 2′-bipyridine-N,N′-dioxide (4)]. The crystal structures of [Eu(NTA)3bpyO2] (4b), [Er(NTA)3bpyO1] (3c), and [Er(NTA)3phen] (2c) were determined. X-ray crystallographic analysis reveals that the complexes are of mononuclear structure with three NTA and one ancillary ligand. The photoluminescence spectra of 3c and 4b exhibit strong characteristic emissions arising from Eu3+ central ion due to the efficient sensitization of bpyO1 and bpyO2, respectively.

N-[3-(Phenyltellanyl)propyl]picolinamide (HL1) or N-[N″,N″-methyl(phenyl)aminothiocarbonyl]-N′-[3-(phenyltellanyl)propyl]benzamidine (HL2) react with equivalent amounts of PtCl2 or PdCl2 with formation of neutral [MCl(L1-κN,N′,Te)] or [MCl(L2-κS,N,Te)] chelates. A corresponding reaction of HL2 with HgCl2 results in the formation of [HgCl2(HL2-κS,Te)]. Treatment of [PtCl(L1-N,N′,Te)] with elemental iodine results in the exclusive oxidation of the metal ion and the platinum(IV) complex [PtI3(L1-κN,N′,Te)] could be isolated in reasonable amounts. A decomposition of the tellurium-containing ligand and the formation of [PdI2(PhTeI)2] was observed during a similar procedure with the corresponding palladium complex. The bonding situation inside the latter compound was analyzed through density functional theory calculations.

N-(Dialkylthiocarbamoyl)benzimidoyl chlorides react with o-(salicylidenimine)benzylamine with formation of a novel class of tetradentate benzamidine ligands (H2LEt and H2LMorph), which readily react with Ni(CH3COO)2, [PdCl2(CH3CN)2], and [PtCl2(PPh3)2] under formation of complexes of the composition [M(LR)] [M = Ni (4), Pd (5), Pt (6)]. In all complexes, H2LR is doubly deprotonated and bonded to the metal ion via its N2OS donor set and establishes a distorted square-planar coordination sphere. The antiproliferative effects of the compounds on MCF-7 and Hep-G2 cells were studied. The complexes of H2LMorph are generally more active than those of H2LEt. While H2LEt and its complexes exhibit stronger effects on the Hep-G2 line, the corresponding compounds of H2LMorph show almost equal effects on the two cell lines. In each series of compounds, the cytotoxicity increases in the order H2LR << 4 < 5 < 6.

One-pot reactions of 2, 6-bis(acetobenzoyl)pyridine (H2L) with a mixture of LnCl3 (Ln = Ce, Gd) and Ni(CH3COO)2 (ratio 2:1:2) in CH2Cl2/MeOH in the presence of a supporting base like Et3N give trinuclear complexes with the general composition [Ni2Ln(L)2(CH3COO)3(MeOH)2/3] (1) in high yields. Trinuclear [Ni2Ln(L)2(PhCOO)3(MeOH)2] (2) complexes are formed when similar reactions are performed starting from NiCl2, and benzoic acid (PhCOOH) is added subsequently. Under the same conditions, reactions with the corresponding cobalt(II) salts result in the formation of a neutral [Co8(μ3-O)2(L)6] complex, which has a bis(triple-helical) structure. The cobalt(II) analogues to compounds 1 and 2, however, can be synthesized by a pre-treatment of the lanthanide salts with H2L and subsequent addition of the cobalt salts, and benzoic acid (in the case of 2).

A novel aroylbisthiourea, H3pyr(Et2tu)2 (V), has been prepared from 2,5-pyrroledicarboxylic chloride, NH4SCN and diethylamine. The compound reacts with (NBu4)[ReOCl4] in MeOH under formation of the dimeric oxidorhenium(V) complex [{ReO(OMe)}2{Hpyr(Et2tu)2}2] (VI), which undergoes a condensation in wet acetonitrile and forms the μ-oxido-bridged tetramer [(Re2O3)2{Hpyr(Et2tu)2}4] (VII). The pyrrole rings remain protonated and do not contribute to the coordination of the transition metal. The tetrameric complex is able to accommodate a molecule of water in its molecular cavity.

The reaction of sodium phenylselenolate and copper(I) chloride generates in situ a “CuSePh” species, which can be stabilized by N, N′-donor ligands such as bpy (2, 2′-bipyridine) or phen (1, 10-phenanthroline) in order to generate compounds with μ2-SePh– or μ3-SePh– groups connecting the copper atoms. The intermediate stabilization of mononuclear “CuSePh” building blocks by the coordination N, N′-donor ligands prevents from the rapid formation of less soluble polymers and gives access to three new compounds, [{Cu2(bpy)2(μ3-SePh)}{CuCl2}2]2, [{Cu4(phen)3(μ2-SePh)(μ3-SePh)}2(μ2-Cl)2] (CuCl2)2·2(PhSe)2, and [Cu6(bpy)2(μ2-SePh)2(μ3-SePh)4]·(THF).