Publications by authors named "Victor M Deflon"

36 Publications

Gallium and indium complexes with new hexadentate bis(semicarbazone) and bis(thiosemicarbazone) chelators.

Dalton Trans 2021 Feb;50(5):1631-1640

Instituto de Química de São Carlos, Universidade de São Paulo, CEP 13566-590 São Carlos, SP, Brazil.

The synthesis of two new hexadentate potentially tetra-anionic acyclic chelators, an N2O4-donor bis(semicarbazone) (H4bsc) and an N2O2S2-donor bis(thiosemicarbazone) (H4btsc), is described. Coordination reactions of the ligands with gallium and indium precursors were investigated and yielded the complexes [Ga(Hbsc)] (1) and [In(Hbtsc)] (2), respectively. Ligands and complexes structures were confirmed by several techniques, including FTIR, NMR (1H, 13C, COSY, HSQC), ESI(+)-MS and single crystal X-ray diffraction analysis. The radioactive congeners [67Ga(Hbsc)] (1*) and [111In(Hbtsc)] (2*) were also synthesized and their radiolabeling yield and radiochemical purity were certified by HPLC and ITLC analyses. Biodistribution assays in groups of CD-1 mice showed a high uptake of both radiocomplexes in liver and intestine where 1* presented higher retention. In vitro and in vivo assays revealed higher stability of 1* compared with 2*, namely in the blood. The results suggest that radiocomplex 1* is a candidate for further investigation as it could be prepared in high yields (>95%), at low temperature (20-25 °C) and at fast reaction time (15 min), which are very desirable synthesis conditions for potential new radiopharmaceuticals.
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http://dx.doi.org/10.1039/d0dt04028bDOI Listing
February 2021

Fragmentation Study, Dual Anti-Bactericidal and Anti-Viral Effects and Molecular Docking of Cobalt(III) Complexes.

Int J Mol Sci 2020 Nov 7;21(21). Epub 2020 Nov 7.

Instituto de Química, Universidade Federal de Uberlândia, Uberlândia 38400-902, MG, Brazil.

Considering our previous findings on the remarkable activity exhibited by cobalt(III) with 2-acetylpyridine--R-thiosemicarbazone (Hatc-R) compounds against , the present study aimed to explored new structure features of the complexes of the type [Co(atc--R)]Cl, where R = methyl (Me, ) or phenyl (Ph, ) (C NMR, high-resolution mass spectrometry, LC-MS/MS, fragmentation study) together with its antibacterial and antiviral biological activities. The minimal inhibitory and minimal bactericidal concentrations (MIC and MBC) were determined, as well as the antiviral potential of the complexes on chikungunya virus (CHIKV) infection in vitro and cell viability. [Co(atc-Ph)]Cl revealed promising MIC and MBC values which ranged from 0.39 to 0.78 µg/mL in two strains tested and presented high potential against CHIKV by reducing viral replication by up to 80%. The results showed that the biological activity is strongly influenced by the peripheral substituent groups at the (4) position of the atc-R ligands. In addition, molecular docking analysis was performed. The relative binding energy of the docked compound with five bacteria strains was found in the range of -3.45 and -9.55 kcal/mol. Thus, this work highlights the good potential of cobalt(III) complexes and provide support for future studies on this molecule aiming at its antibacterial and antiviral therapeutic application.
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http://dx.doi.org/10.3390/ijms21218355DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664407PMC
November 2020

Novel tetranuclear Pd and Pt anticancer complexes derived from pyrene thiosemicarbazones.

Dalton Trans 2020 Jul;49(28):9595-9604

Department of Chemistry, University of Warwick, CV4 7AL, Coventry, UK.

Cyclometallated palladium(ii) and platinum(ii) pyrenyl-derived thiosemicarbazone (H2PrR) complexes of the type [M4(μ-S-PrR-κ3-C,N,S)4] (M = PdII, PtII; R = ethyl, cyclohexyl) have been synthesised in good yields and fully characterised. X-ray crystallography showed that the tetranuclear complex [Pt4(μ-S-PrCh-κ3-C,N,S)4](CH3)2COCHCl3 contains an eight-membered ring of alternating M-S atoms. The ethyl derivatives [M4(μ-S-PrEt-κ3-C,N,S)4] exhibit potent antiproliferative activity towards A2780 human ovarian cancer cells, with IC50 values of 1.27 μM (for M = PdII) and 0.37 μM (for M = PtII), the latter being an order of magnitude more potent than the anticancer drug cisplatin (IC50 1.20 μM). These promising complexes had low toxicity towards non-cancerous human MRC5 cells, which points towards an early indication of differential toxicity between cancer and normal cells. Experiments that investigated the effects of these tetranuclear complexes on the cell cycle, integrity of the cell membrane, and induction of apoptosis, suggested that their mechanism of action of does not involve DNA targeting, unlike cisplatin, and therefore could be promising for combatting cisplatin resistance.
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http://dx.doi.org/10.1039/d0dt01133aDOI Listing
July 2020

Intramolecular C(sp)-C (sp) bond formation between phenanthroline and β-diketone thiosemicarbazones in Pt complexes: crystal structures and computational studies.

Dalton Trans 2020 Jul 28;49(28):9564-9567. Epub 2020 May 28.

Núcleo de Desenvolvimento de Compostos Bioativos (NDCBio), Universidade Federal do Triângulo Mineiro, 38025-440, Uberaba, MG, Brazil.

[PtCl(phen)] reacts with thiosemicarbazones derived from β-diketones (HL) leading to an intramolecular C-C coupling between phen and the ketone upon formation of tetradentate N,N,N,S chelates [Pt(Lphen)]. The reactions proceed via bidentate coordination of the doubly deprotonated (L) followed by an intra-nucleophilic attack and consecutive C-C bond formation.
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http://dx.doi.org/10.1039/d0dt00367kDOI Listing
July 2020

Ru(II)-Naphthoquinone complexes with high selectivity for triple-negative breast cancer.

Dalton Trans 2020 Nov;49(45):16193-16203

Departamento de Química, Universidade Federal de São Carlos - UFSCar, Rodovia Washington Luiz, KM 235 CP 676, CEP 13561-901, São Carlos, SP, Brazil.

Six new ruthenium(ii) complexes with lapachol (Lap) and lawsone (Law) with the general formula [Ru(L)(P-P)(bipy)]PF6, where L = Lap or Law, P-P = 1,2'-bis(diphenylphosphino)ethane (dppe), 1,4'-bis(diphenylphosphino)butane (dppb), 1,1'-bis(diphenylphosphino)ferrocene (dppf) and bipy = 2,2'-bipyridine, were synthesized, fully characterized by elemental analysis, molar conductivity, NMR, cyclic voltammetry, UV-vis, IR spectroscopies and three of them by X-ray crystallography. All six complexes were active against breast (MCF-7 and MDA-MB-231) and prostate (DU-145) cancer cell lines with lower IC50 values than cisplatin. Complex [Ru(Lap)(dppe)(bipy)]PF6 (1a) showed significant selectivity for MDA-MB-231, a model of triple-negative breast cancer (TNBC), as compared to the "normal-like" human breast epithelial cell line, MCF-10A. Complex (1a) inhibited TNBC colony formation and induced loss of cellular adhesion. Furthermore, the complex (1a) induced mitochondrial dysfunction and generation of ROS, as is involved in the apoptotic cell death pathway. Preferential cellular uptake of complex (1a) was observed in MDA-MB-231 cells compared to MCF-10A cells, consistent with the observed selectivity for tumorigenic vs. non-tumorigenic cells. Taken together, these results indicate that ruthenium complexes containing lapachol and lawsone as ligands are promising candidates as chemotherapeutic agents.
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http://dx.doi.org/10.1039/d0dt01091jDOI Listing
November 2020

Cyclopalladated compounds containing 2,6-lutidine: Synthesis, spectral and biological studies.

J Inorg Biochem 2020 02 22;203:110944. Epub 2019 Nov 22.

UNESP - Univ Estadual Paulista, Institute of Chemistry, 14800-060 Araraquara, SP, Brazil. Electronic address:

Bridge splitting reactions between [Pd(C,N-dmba)(μ-X)] (dmba = N,N-dimethylbenzylamine; X = Cl, I, N, NCO) and 2,6-lutidine (lut) in the 1:2 molar ratio at room temperature afforded cyclopalladated compounds of general formulae [Pd(C,N-dmba)(X)(lut)] {X = Cl (1), I(2), NNN(3), NCO(4)}, which were characterized by elemental analyses and infrared (IR), H NMR spectroscopy. The molecular structures of all synthesized palladacycles have been solved by single-crystal X-ray crystallography. The cytotoxicity of the cyclopalladated compounds has been evaluated against a panel of murine {mammary carcinoma (4T1) and melanoma (B16F10-Nex2)} and human {melanoma (A2058, SK-MEL-110 and SK-MEL-5) tumor cell lines. All complexes were about 10 to 100-fold more active than cisplatin, depending on the tested tumor cell line. For comparison purposes, the cytotoxic effects of 1-4 towards human lung fibroblasts (MRC-5) have also been tested. The late apoptosis-inducing properties of 1-4 compounds in SK-MEL-5 cells were verified 24 h incubation using annexin V-Fluorescein isothiocyanate (FITC)/propidium iodide (PI). The binding properties of the model compound 1 on human serum albumin (HSA) and calf thymus DNA (ct-DNA) have been studied using circular dichroism and fluorescence spectroscopy. Docking simulations have been carried out to gain more information about the interaction of the palladacycle and HSA. The ability of compounds 1-4 to inhibit the activity of cathepsin B and L has also been investigated in this work.
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http://dx.doi.org/10.1016/j.jinorgbio.2019.110944DOI Listing
February 2020

Palladium(ii) complexes with thiosemicarbazones derived from pyrene as topoisomerase IB inhibitors.

Dalton Trans 2019 Nov;48(44):16509-16517

São Carlos Institute of Chemistry, University of São Paulo, 13560-970, São Carlos, Brazil.

New palladium complexes with thiosemicarbazonate ligands derived from pyrene exhibit potent antiproliferative activity against A2780 and cisplatin-resistant A2780Cis human ovarian cancer cells, which is dependent on substituent groups of the thiosemicarbazone ligands. Cellular accumulation and distribution studies confirmed that palladium enters the cell nucleus. DNA and topoisomerase IB studies show that one complex is a potent TopIB inhibitor, with selectivity for cancer versus normal cells.
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http://dx.doi.org/10.1039/c9dt02570gDOI Listing
November 2019

Non-mutagenic Ru(ii) complexes: cytotoxicity, topoisomerase IB inhibition, DNA and HSA binding.

Dalton Trans 2019 Oct;48(39):14885-14897

Dipartimentodi Biologia, UniversitàTorVergatadi Roma, 00133 Rome, Italy.

Herein we discuss five ruthenium(ii) complexes with good cytotoxicity against cancer cells. These complexes are named [Ru(tzdt)(bipy)(dppb)]PF6 (1), [Ru(mmi)(bipy)(dppb)]PF6 (2), [Ru(dmp)(bipy)(dppb)]PF6 (3), [Ru(mpca)(bipy)(dppb)]PF6 (4) and [Ru(2mq)(bipy)(dppb)]PF6 (5), where tzdt = 1,3-thiazolidine-2-thione, mmi = mercapto-1-methyl-imidazole, dmp = 4,6-diamino-2-mercaptopyrimidine, mpca = 6-mercaptopyridine-3-carboxylic acid, 2mq = 2-mercapto-4(3H)-quinazolinone, bipy = 2,2'-bipyridine and dppb = 1,4-bis(diphenylphosphino)butane. In vitro cell culture experiments revealed significant cytotoxic activity for 1-5 against MDA-MB-231, MCF-7, A549, DU-145 and HepG2 tumor cells, higher than that for the standard anticancer drug cisplatin. Compound/DNA interaction studies were carried out showing that 1-5 interact with DNA by electrostatic force of attraction or by hydrogen bonding. Moreover, the complexes interact, moderately and spontaneously, with human serum albumin (HSA) through the hydrophobic region. The five complexes are able to inhibit the DNA supercoiled relaxation mediated by human topoisomerase IB (TopIB), and complex 1 is found to be the most efficient TopIB inhibitor among the five compounds. The inhibitory effect and analysis of different steps of the TopIB catalytic cycle indicate that complex 1 inhibits the cleavage reaction impeding the binding of the enzyme to DNA and has no effect on the religation step. Complexes 1, 2 and 3 did not show mutagenic activity when they were evaluated by the cytokinesis-block micronucleus cytome assay in HepG2 cells and the Ames test in the presence and absence of mouse liver S9 metabolic activation. Therefore, it is necessary to perform further in-depth analysis of the therapeutic potential of these promising ruthenium complexes as anticancer drugs.
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http://dx.doi.org/10.1039/c9dt01905gDOI Listing
October 2019

Heterobimetallic nickel(II) and palladium(II) complexes derived from S-benzyl-N- (ferrocenyl)methylenedithiocarbazate: Trypanocidal activity and interaction with Trypanosoma cruzi Old Yellow Enzyme (TcOYE).

Eur J Med Chem 2019 Oct 5;180:213-223. Epub 2019 Jul 5.

Núcleo de Desenvolvimento de Compostos Bioativos (NDCBio), Universidade Federal do Triângulo Mineiro, Av. Dr. Randolfo Borges 1400, 38025-440, Uberaba, MG, Brazil. Electronic address:

Reactions of Ni(II) and Pd(II) precursors with S-benzyl-N-(ferrocenyl)methylenedithiocarbazate (HFedtc) led to the formation of heterobimetallic complexes of the type [M(Fedtc)] (M = Ni and Pd). The characterization of the compounds involved the determination of melting point, FTIR, UV-Vis, H NMR, elemental analysis and electrochemical experiments. Furthermore, the crystalline structures of HFedtc and [Ni(Fedtc)] were determined by single crystal X-ray diffraction. The compounds were evaluated against the intracellular form of Trypanosoma cruzi (Tulahuen Lac-Z strain) and the cytotoxicity assays were assessed using LLC-MK2 cells. The results showed that the coordination of HFedtc to Ni(II) or Pd(II) decreases the in vitro trypanocidal activity while the cytotoxicity against LLC-MK2 cells does not change significantly. [Pd(Fedtc)] showed the greater potential between the two complexes studied, showing an SI value of 8.9. However, this value is not better than that of the free ligand with an SI of 40, a similar value to that of the standard drug benznidazole (SI = 48). Additionally, molecular docking simulations were performed with Trypanosoma cruzi Old Yellow Enzyme (TcOYE), which predicted that HFedtc binds to the protein, almost parallel to the flavin mononucleotide (FMN) prosthetic group, while the [Ni(Fedtc)] complex was docked into the enzyme binding site in a significantly different manner. In order to confirm the hypothetical interaction, in vitro experiments of fluorescence quenching and enzymatic activity were performed which indicated that, although HFedtc was not processed by the enzyme, it was able to act as a competitive inhibitor, blocking the hydride transfer from the FMN prosthetic group of the enzyme to the menadione substrate.
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http://dx.doi.org/10.1016/j.ejmech.2019.07.014DOI Listing
October 2019

In vitro cytotoxicity and in vivo zebrafish toxicity evaluation of Ru(ii)/2-mercaptopyrimidine complexes.

Dalton Trans 2019 May;48(18):6026-6039

Laboratory of Molecular Genetics and Cytogenetics, Institute of Biological Sciences, Federal University of Goias-UFG, CEP 74690-900 Goiania, Goias, Brazil.

In this paper, four new ruthenium complexes, [Ru(N-S)(dppm)2]PF6 (1), [Ru(N-S)(dppe)2]PF6 (2), [Ru(N-S)2(dppp)] (3) and [Ru(N-S)2(PPh3)2] (4) [dppm = 1,1-bis(diphenylphosphino)methane, dppe = 1,2-bis(diphenylphosphino)ethane, dppp = 1,3-bis(diphenylphosphino)propane, PPh3 = triphenylphosphine and N-S = 2-mercaptopyrimidine anion] were synthesized and characterized using spectroscopy techniques, molar conductance, elemental analysis, electrochemical techniques and X-ray diffraction. The DNA binding studies were investigated using voltammetry and spectroscopy techniques. The results show that all complexes exhibit a weak interaction with DNA. HSA interaction with the complexes was studied using fluorescence emission spectroscopy, where the results indicate a spontaneous interaction between the species by a static quenching mechanism. The cytotoxicity of the complexes was evaluated against A549, MDA-MB-231 and HaCat cells by MTT assay. Complexes (1) and (2), which are very active against triple negative MDA-MB-231, were subjected to further biological tests with this cell line. The cytotoxic activity triggered by the complexes was confirmed by clonogenic assay. Cell cycle analyses demonstrated marked anti-proliferative effects, especially at the G0/G1 and S phases. The morphological detection of apoptosis and necrosis - HO/PI and Annexin V-FITC/PI assay, elucidated that the type of cell death triggered by these complexes was probably by apoptosis. The in vivo toxicological assessment performed on zebrafish embryos revealed that complexes (1) and (2) did not present embryotoxic or toxic effects during embryonic and larval development showing that they are promising new prototypes of safer and more effective drugs for triple negative breast cancer treatment.
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http://dx.doi.org/10.1039/c8dt03738hDOI Listing
May 2019

Isolation, synthesis and bioactivity studies of phomactin terpenoids.

Nat Chem 2018 09 30;10(9):938-945. Epub 2018 Jul 30.

Department of Chemistry, University of California, Berkeley, CA, USA.

Studies of secondary metabolites (natural products) that cover their isolation, chemical synthesis and bioactivity investigation present myriad opportunities for discovery. For example, the isolation of novel secondary metabolites can inspire advances in chemical synthesis strategies to achieve their practical preparation for biological evaluation. In the process, chemical synthesis can also provide unambiguous structural characterization of the natural products. Although the isolation, chemical synthesis and bioactivity studies of natural products are mutually beneficial, they are often conducted independently. Here, we demonstrate the benefits of a collaborative study of the phomactins, diterpenoid fungal metabolites that serve as antagonists of the platelet activating factor receptor. Our isolation of novel phomactins has spurred the development of a bioinspired, unified approach that achieves the total syntheses of six congeners. We also demonstrate in vitro the beneficial effects of several phomactins in suppressing the rate of repopulation of tumour cells following gamma radiation therapy.
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http://dx.doi.org/10.1038/s41557-018-0084-xDOI Listing
September 2018

Pt, Pd and Au complexes with a thiosemicarbazone derived from diacethylmonooxime: Structural analysis, trypanocidal activity, cytotoxicity and first insight into the antiparasitic mechanism of action.

Eur J Med Chem 2017 Dec 12;141:615-631. Epub 2017 Oct 12.

Núcleo de Desenvolvimento de Compostos Bioativos (NDCBio), Universidade Federal do Triângulo Mineiro, Av. Dr. Randolfo Borges 1400, 38025-440, Uberaba, MG, Brazil. Electronic address:

New complexes of composition [MX(HL1)] (M = Pt, Pd, X = Cl or I) and [MX(L1)] (M = Au, X = Cl; M = Pt, Pd, X = PPh) have been synthesized using a potentially tridentate thiosemicarbazone (HL1) containing an additional oxime binding site. Among other analytical methods, all the seven complexes have been structurally characterized by single crystal X-ray diffractometry. Interesting structural features such as the influence of the halide ligands on hydrogen bonds and the formation of supramolecular structures for the phosphine derivatives are discussed. The in vitro trypanocidal activity of the free ligand HL1 and its derivatives against both extracellular trypomastigote and intracellular amastigote (IC) forms of Trypanosoma cruzi (Tulahuen Lac-Z strain) and the cytotoxicity was assessed on LLC-MK2 cell line. The results showed that complexation of the thiosemicarbazone ligand HL1 to Pt, Pd and Au metal centers enhances the in vitro trypanocidal activity and that the cytotoxicity is dependent on both the metal center and coligands. Within the studied series, the Au complex showed the greatest potential, being not the most active but the most selective compound with a similar selectivity index to that of the standard drug benznidazole. In order to get a preliminary insight into the mechanism of action of these compounds, in vitro experiments of fluorescence quenching and enzymatic activity were performed using the Au complex and Trypanosoma cruzi Old Yellow Enzyme (TcOYE) which indicated that the gold derivative was capable of abstracting the hydride from the prosthetic FMN group of the enzyme. Additionally, molecular docking studies followed by semiempirical simulations showed that the [AuCl(L1)] binds to the binary complex TcOYE/FMN, almost parallel to the FMN prosthetic group, in a close distance that an electron/proton transfer might occur among them.
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http://dx.doi.org/10.1016/j.ejmech.2017.10.013DOI Listing
December 2017

Selective Ru(II)/lawsone complexes inhibiting tumor cell growth by apoptosis.

J Inorg Biochem 2017 11 26;176:66-76. Epub 2017 Aug 26.

Departamento de Química, Universidade Federal de São Carlos, CP 676, CEP 13565-905, São Carlos, SP, Brazil. Electronic address:

New Ru(II) complexes with lawsone (law) characterized as trans-[Ru(law)(PPh)(N-N)]PF, where PPh means triphenylphosphine and N-N is 2,2'-bipyridine (1), 4,4'-dimethyl-2,2'-bipyridine (2), 4,4'-dimethoxy-2,2'-bipyridine (3), 1,10-phenanthroline (4) or 4,7-diphenyl-1,10-phenanthroline (5), induce apoptosis in tumor cells. Cytotoxicity of the complexes against the tumor cell lines DU-145 (prostate cancer cells), MCF-7 (breast cancer cells), A549 (lung cancer cells) and lung non-tumor cell line MRC-5 demonstrated promising IC values, lower than those found for the cisplatin, a drug used as a reference. Due to the high cytotoxic activity and selectivity against A549 cells line, complex (5) was selected for detailed assays. The complex (5) inhibits cells migration in concentrations in a nanomolar range, inducing tumor cell death by apoptosis, as confirmed by flow cytometry experiments. Furthermore, the antiproliferative activity of complex (5) on A549 tumor cells is attributed to a cell cycle arrest at the Sub G1 phase, followed by a decrease in the number of cells at the S phase. In addition, the interaction of the complexes (1-5) with CT-DNA was evaluated by circular dichroism, in which no changes in the secondary structure of DNA were observed, suggesting a weak interaction of the complexes with the biomolecule. On the other hand, complexes (1-5) showed a higher interaction with human serum albumin (HSA) by non-covalent van der Waals forces and hydrogen bonding, resulting in static quenching.
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http://dx.doi.org/10.1016/j.jinorgbio.2017.08.019DOI Listing
November 2017

An extended π-system and enhanced electronic delocalization on symmetric [RuO(CHCOO)(L)] complexes combined with azanaphthalene ligands.

Dalton Trans 2017 Jun 12;46(24):7926-7938. Epub 2017 Jun 12.

Departamento de Química - Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto - Universidade de São Paulo - Av. Bandeirantes, 3900, Zip Code 14040-901, Ribeirão Preto, SP, Brazil.

We report on the investigation of a new series of symmetric trinuclear ruthenium complexes combined with azanaphthalene ligands: [RuO(CHCOO)(L)]PF where L = (1) quinazoline (qui), (2) 5-nitroisoquinoline (5-nitroiq), (3) 5-bromoisoquinoline (5-briq), (4) isoquinoline (iq), (5) 5-aminoisoquinoline (5-amiq), and (6) 5,6,7,8-tetrahydroisoquinoline (thiq). The crystal structure of complex 1, [RuO(CHCOO)(qui)]PF, was determined by X-ray diffraction analysis, showing a high degree of co-planarity between the [RuO] plane and the azanaphthalene ligands. Spectroscopic (UV-visible, NMR and infra-red) and electrochemical (cyclic voltammetry and spectroelectrochemistry) data showed correlation with the pK values of the azanaphthalene ligands and this dependence was rationalized in terms of the molecular orbital of the [RuO] unit and the structure of the ligands. By analysing the spectroscopic and electrochemical correlations, the ability of the azanaphthalene ligands to extend the electronic π-system of the [RuO] unit to the periphery of the compounds was demonstrated. This electronic effect accounts for the planarity of the structure of complex 1. It was also shown through molecular modeling results that, to explain the spectroscopic and electrochemical behaviour of these species, it is not possible to neglect the electronic mixing between the metallic and the acetate orbitals. Finally, this work revealed that electronic coupling is more pronounced in the azanaphthalene series of complexes than in pyridinic analogues and it is this coupling that determines the spectroscopic and electrochemical behaviour of the new species.
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http://dx.doi.org/10.1039/c7dt01152kDOI Listing
June 2017

Photoinduced Charge Shifts and Electron Transfer in Viologen-Tetraphenylborate Complexes: Push-Pull Character of the Exciplex.

J Am Chem Soc 2017 06 30;139(23):7681-7684. Epub 2017 May 30.

Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.

Viologen-tetraarylborate ion-pair complexes were prepared and investigated by steady-state and time-resolved spectroscopic techniques such as fluorescence and femtosecond transient absorption. The results highlight a charge transfer transition that leads to changes in the viologen structure in the excited singlet state. Femtosecond transient absorption reveals the formation of excited-state absorption and stimulated emission bands assigned to the planar (k < 10 s) and twisted (k ∼ 10 s) structures between two pyridinium groups in the viologen ion. An efficient photoinduced electron transfer from the tetraphenylborate anionic moiety to the viologen dication was observed less than 1 μs after excitation. This is a consequence of the push-pull character of the electron donor twisted viologen structure, which helps formation of the borate triplet state. The borate triplet state is deactivated further via a second electron transfer process, generating viologen cation radical (V).
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http://dx.doi.org/10.1021/jacs.7b01946DOI Listing
June 2017

Novel copper(II) complexes with hydrazides and heterocyclic bases: Synthesis, structure and biological studies.

J Inorg Biochem 2017 07 26;172:138-146. Epub 2017 Apr 26.

Instituto de Química, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil. Electronic address:

Five new copper(II) complexes of the type [Cu(NO)(NN)(ClO)], in which NO=4-fluorophenoxyacetic acid hydrazide (4-FH) or 4-nitrobenzoic hydrazide (4-NH) and NN=1,10-phenanthroline (phen), 4-4'-dimethoxy-2-2'-bipyridine (dmb) or 2,2-bipyridine (bipy) were synthesized and characterized using various spectroscopic methods. The X-ray structural analysis of one representative compound indicates that the geometry around the copper ion is distorted octahedron, in which the ion is coordinated to hydrazide via the terminal nitrogen and the carbonyl oxygen, and to heterocyclic bases via their two nitrogen atoms. Two perchlorate anions occupy the apical positions, completing the coordination sphere. The cytotoxic activity of compounds was investigated in three tumor cell lines (K562, MDA-MB-231 and MCF-7). Concerning K562 cell line, the complexes with 1,10-phenanthroline exhibit high cytotoxic activity and are more active than carboplatin, free ligands and [Cu(phen)]. Considering the cytotoxicity results, further investigations for the compounds [Cu(4-FH)(phen)(ClO)] I and [Cu(4-NH)(phen)(ClO)]∙HO III were performed. Flow cytometric analysis revealed that these complexes induce apoptotic cell death in MDA-MB-231 cell line and bind to DNA with K values of 4.38×10 and 2.62×10, respectively. These compounds were also evaluated against wild type Mycobacterium tuberculosis (ATCC 27294) and exhibited antimycobacterial activity, displayed MIC values lower than those of the corresponding free ligands.
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http://dx.doi.org/10.1016/j.jinorgbio.2017.04.024DOI Listing
July 2017

Uncommon and Emissive {[Au(CHNS)][Au(CHNS)](PF)} Mixed Au and Au Pseudotetranuclear Crystalline Compound: Synthesis, Structural Characterization, and Optical Properties.

J Phys Chem A 2016 Nov 9;120(46):9249-9256. Epub 2016 Nov 9.

Grupo de Espectroscopia Óptica e Fototérmica-GEOF, Centro de Estudos em Recursos Naturais-CERNA, Universidade Estadual de Mato Grosso do Sul - UEMS , CP 351, Dourados, Mato Grosso do Sul 79804-970, Brazil.

An uncommon emissive pseudotetranuclear compound, {[Au(CHNS)][Au(CHNS)](PF)}, was synthesized and characterized in terms of its structure and optical properties. The synthesis produced a crystalline compound composed of four gold atoms with two different oxidation states (Au and Au) in the same crystalline structure. The title complex belonged to a triclinic crystalline system involving the centrosymmetric P1̅ space group. X-ray diffractometry and vibrational spectroscopy (infrared, Raman, and SERS) were used for structural characterization of the new crystal. The vibrational spectroscopy techniques supported the X-ray diffraction results and confirmed the presence of bonds including Au-Au and Au-S. Optical characterization performed using UV-vis spectroscopy showed that under ultraviolet excitation, the emissive crystalline complex presented characteristic broad luminescent bands centered at 420 and 670 nm.
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http://dx.doi.org/10.1021/acs.jpca.6b08158DOI Listing
November 2016

Revisiting oxo-centered carbonyl-triruthenium clusters: investigating CO photorelease and some spectroscopic and electrochemical correlations.

Dalton Trans 2016 Oct;45(42):16799-16809

Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901, Ribeirão Preto-SP, Brazil.

We synthesized and characterized a series of oxo-centered carbonyl-triruthenium complexes with the general formula [RuO(CHCOO)(L)(CO)], where L = 2,6-dimethylpyrazine (dmpz) (1), isonicotinamide (adpy) (2), 4-acetylpyridine (acpy) (3), 3-methylpyridine (3-pic) (4), 4-methylpyridine (4-pic) (5), 4-tert-butylpyridine (4-tbpy) (6), 4-(dimethyl)aminopyridine (dmap) (7), or 4-aminopyridine (ampy) (8); we also investigated the photoreactivity of these complexes. Single-crystal X-ray diffraction helped to elucidate the structures of 1·HO, 7·CHCl, and 8. The unit cell of 8 is composed of four cluster units; the hydrogen bonds between the amino groups of the terminal ligand of a neighboring molecule and the oxygen atoms of CO or acetate bridging ligands hold these cluster units together. The spectroscopic (NMR, UV-visible, and IR) and the electrochemical properties (cyclic voltammetry) of these complexes correlated with the ancillary ligands in terms of their σ-donating and π-accepting characteristics. The molecular orbital and the electronic localized description of the [RuO]-CO unit helped to rationalize the correlations. The photoreactivity of compounds 1-8 was investigated by laser excitation at 377 nm. Given the CO photorelease quantum yields, σ-donor ligands and aqueous medium (more polar) stabilized the charge-transfer excited state that culminated in CO photosubstitution, leading to higher Φ values.
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http://dx.doi.org/10.1039/c6dt02511kDOI Listing
October 2016

Novel Zinc(II) Complexes [Zn(atc-Et)₂] and [Zn(atc-Ph)₂]: In Vitro and in Vivo Antiproliferative Studies.

Int J Mol Sci 2016 May 21;17(5). Epub 2016 May 21.

Faculdade de Ciencias Farmaceuticas, UNESP-Univ Estadual Paulista, Campus Araraquara, Araraquara, São Paulo 14800-903, Brazil.

Cisplatin and its derivatives are the main metallodrugs used in cancer therapy. However, low selectivity, toxicity and drug resistance are associated with their use. The zinc(II) (Zn(II)) thiosemicarbazone complexes [Zn(atc-Et)₂] (1) and [Zn(atc-Ph)₂] (2) (atc-R: monovalent anion of 2-acetylpyridine N4-R-thiosemicarbazone) were synthesized and fully characterized in the solid state and in solution via elemental analysis, Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis) and proton nuclear magnetic resonance (¹H NMR) spectroscopy, conductometry and single-crystal X-ray diffraction. The cytotoxicity of these complexes was evaluated in the HepG2, HeLa, MDA-MB-231, K-562, DU 145 and MRC-5 cancer cell lines. The strongest antiproliferative results were observed in MDA-MB-231 and HepG2 cells, in which these complexes displayed significant selective toxicity (3.1 and 3.6, respectively) compared with their effects on normal MRC-5 cells. In vivo studies were performed using an alternative model (Artemia salina L.) to assure the safety of these complexes, and the results were confirmed using a conventional model (BALB/c mice). Finally, tests of oral bioavailability showed maximum plasma concentrations of 3029.50 µg/L and 1191.95 µg/L for complexes 1 and 2, respectively. According to all obtained results, both compounds could be considered as prospective antiproliferative agents that warrant further research.
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http://dx.doi.org/10.3390/ijms17050781DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4881598PMC
May 2016

Gold(III) complexes with ONS-Tridentate thiosemicarbazones: Toward selective trypanocidal drugs.

Eur J Med Chem 2016 Sep 3;120:217-26. Epub 2016 May 3.

Departamento de Química, Universidade Federal do Triângulo Mineiro, Av. Dr. Randolfo Borges 1400, 38025-440, Uberaba, MG, Brazil. Electronic address:

Tridentate thiosemicarbazone ligands with an ONS donor set, H2L(R) (R = Me and Et) were prepared by reactions of 1-phenyl-1,3-butanedione with 4-R-3-thiosemicarbazides. H2L(R) reacts with Na[AuCl4]·2H2O in MeOH in a 1:1 M ratio under formation of green gold(III) complexes of composition [AuCl(L(R))]. These compounds represent the first examples of gold(III) complexes with ONS chelate-bonded thiosemicarbazones. The in vitro anti-Trypanosoma cruzi activity against both trypomastigote and amastigote forms (IC50try/ama) of CL Brener strains as well as the cytotoxicity against LLC-MK2 cells of the free ligands and complexes was evaluated. The complex [AuCl(L(Me))] was found to be more active and more selective than its precursor ligand and the standard drug benznidazole with a SItry/ama value higher than 200, being considered as a lead candidate for Chagas disease treatment. Moreover the in vitro activity against the replicative amastigote form (IC50ama) of T. cruzi was additionally investigated revealing that [AuCl(L(Me))] was also more potent than benznidazole still with a similar selectivity index. Finally, docking studies showed that free ligands and complexes interact with the same residues of the parasite protease cruzain but with different intensities, suggesting that this protease could be a possible target for the trypanocidal action of the obtained compounds.
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http://dx.doi.org/10.1016/j.ejmech.2016.05.003DOI Listing
September 2016

Inhibition of human DNA topoisomerase IB by nonmutagenic ruthenium(II)-based compounds with antitumoral activity.

Metallomics 2016 Feb;8(2):179-92

Departamento de Química, Universidade Federal de São Carlos, CP 676, CEP 13565-905, São Carlos, SP, Brazil.

Herein we synthesized two new ruthenium(II) compounds [Ru(pySH)(bipy)(dppb)]PF6 (1) and [Ru(HSpym)(bipy)(dppb)]PF6 (2) that are analogs to an antitumor agent recently described, [Ru(SpymMe2)(bipy)(dppb)]PF6 (3), where [(Spy) = 2-mercaptopyridine anion; (Spym) = 2-mercaptopyrimidine anion and (SpymMe2) = 4,6-dimethyl-2-mercaptopyrimidine anion]. In vitro cell culture experiments revealed significant anti-proliferative activity for 1-3 against HepG2 and MDA-MB-231 tumor cells, higher than the standard anti-cancer drugs doxorubicin and cisplatin. No mutagenicity is detected when compounds are evaluated by cytokinesis-blocked micronucleus cytome and Ames test in the presence and absence of S9 metabolic activation from rat liver. Interaction studies show that compounds 1-3 can bind to DNA through electrostatic interactions and to albumin through hydrophobic interactions. The three compounds are able to inhibit the DNA supercoiled relaxation mediated by human topoisomerase IB (Top1). Compound 3 is the most efficient Top1 inhibitor and the inhibitory effect is enhanced upon pre-incubation with the enzyme. Analysis of different steps of Top1 catalytic cycle indicates that 3 inhibits the cleavage reaction impeding the binding of the enzyme to DNA and slows down the religation reaction. Molecular docking shows that 3 preferentially binds closer to the residues of the active site when Top1 is free and lies on the DNA groove downstream of the cleavage site in the Top1-DNA complex. Thus, 3 can be considered in further studies for a possible use as an anticancer agent.
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http://dx.doi.org/10.1039/c5mt00227cDOI Listing
February 2016

Cytotoxicity of Ru(II) piano-stool complexes with chloroquine and chelating ligands against breast and lung tumor cells: Interactions with DNA and BSA.

J Inorg Biochem 2015 Dec 23;153:150-161. Epub 2015 Jul 23.

Departamento de Química, Universidade Federal de São Carlos - UFSCar, CEP 13565-905 São Carlos, SP, Brazil. Electronic address:

The synthesis and spectroscopic characterization of nine π-arene piano-stool ruthenium (II) complexes with aromatic dinitrogen chelating ligands or containing chloroquine (CQ), are described in this study: [Ru(η(6)-C10H14)(phen)Cl]PF6 (1), [Ru(η(6)-C10H14)(dphphen)Cl]PF6 (2), [Ru(η(6)-C10H14)(bipy)Cl]PF6 (3), [Ru(η(6)-C10H14)(dmebipy)Cl]PF6 (4) and [Ru(η(6)-C10H14)(bdutbipy)Cl]PF6 (5), [Ru(η(6)-C10H14)(phen)CQ](PF6)2 (6), [Ru(η(6)-C10H14)(dphphen)CQ](PF6)2 (7), [Ru(η(6)-C10H14)(bipy)CQ](PF6)2 (8), [Ru(η(6)-C10H14)(dmebipy)CQ](PF6)2 (9): [1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (dphphen), 2,2'-bipyridine (bipy), 5,5'-dimethyl-2,2'-bipyridine (dmebipy), and 4,4'-di-t-butyl-2,2'-bipyridine (dbutbipy)]. The solid state structures of five ruthenium complexes (1-5) were determined by X-ray crystallography. Electrochemical experiments were performed by cyclic voltammetry to estimate the redox potential of the Ru(II)/Ru(III) couple in each case. Their interactions with DNA and BSA, and activity against four cell lines (L929, A549, MDA-MB-231 and MCF-7) were evaluated. Compounds 2, 6 through 9, interact with DNA which was comparable to the one observed for free chloroquine. The results of fluorescence titration revealed that these complexes strongly quenched the intrinsic fluorescence of BSA following a static quenching procedure. Binding constants (Kb) and the number of binding sites (n~1) were calculated using modified Stern-Volmer equations. The thermodynamic parameters ΔG at different temperatures were calculated and subsequently the values of ΔH and ΔS were also calculated, which revealed that hydrophobic and electrostatic interactions play a major role in the BSA-complex association. The MTT assay results indicated that complexes 2, 5 and 7 showed cytostatic effects at appreciably lower concentrations than those needed for cisplatin, chloroquine and doxorubicin.
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http://dx.doi.org/10.1016/j.jinorgbio.2015.07.016DOI Listing
December 2015

Crystal structure of di-μ-methano-lato-bis-{[N'-(1-benzoyl-prop-1-en-2-yl)thio-phene-2-carbohydrazidato-κ(3) O,N',O']oxidovanadium(V)}.

Acta Crystallogr Sect E Struct Rep Online 2014 Oct 27;70(Pt 10):m353-4. Epub 2014 Sep 27.

Instituto de Química de São Carlos, Universidade de São Paulo, 13560-970, São Carlos, SP, Brazil.

The neutral binuclear mol-ecule of the title complex, [V2(C15H12N2O2S)2(CH3O)2O2], exhibits inversion symmetry and consists of two oxidovanadium(V) (VO)(3+) fragments, each coordinated by a dianionic and O,N',O'-chelating N'-(1-benzoyl-prop-1-en-2-yl)thio-phene-2-carbohydrazidate ligand. The V(5+) cations are bridged by two asymmetrically bonding methano-late ligands [V-O = 1.8155 (12) and 2.3950 (13) Å] originating from the deprotonation of the methanol solvent. The coordination sphere of the V(V) atom is distorted octa-hedral, with the equatorial plane defined by the three donor atoms of the thio-phene-2-carbohydrazidate ligand and the O atom of a methano-late unit. The axial positions are occupied by the oxide group and the remaining methano-late ligand. The axially bound methano-late ligand shows a longer V-O bond length due to the trans influence caused by the tightly bonded oxide group. The packing of the complex mol-ecules is dominated by dispersion forces.
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http://dx.doi.org/10.1107/S1600536814020327DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4257161PMC
October 2014

Gold(III) complexes in medicinal chemistry.

Future Med Chem 2014 Sep;6(13):1515-36

Universidade Federal do Triângulo Mineiro, Instituto de Ciências Exatas Naturais e Educação, Av. Dr. Randolfo Borges Júnior, 1400, Univerdecidade, 38064-200 Uberaba, MG, Brazil.

A number of gold(III) compounds has been designed with the objective of overcoming the disadvantages associated with the platinum-based drugs for cancer treatment. Compounds of a remarkable structural manifold show significant antiproliferative effects in vitro against a number of cancer cells, including cisplatin resistant ones. The target of most of them is, unlike that of cisplatin, not the DNA. Although the mechanisms of action displayed by the gold compounds in biological media are still under investigation, many studies show evidence that the cellular targets are mitochondria-based. Recent advances in gold(III) medicinal chemistry also recommend such compounds for other pharmacological applications such as the treatment of viral or parasitic diseases. The radioactive isotopes (198)Au and (199)Au present potential in radiotherapy.
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http://dx.doi.org/10.4155/fmc.14.87DOI Listing
September 2014

In vitro and in vivo trypanocidal activity of H2bdtc-loaded solid lipid nanoparticles.

PLoS Negl Trop Dis 2014 May 8;8(5):e2847. Epub 2014 May 8.

Instituto de Química de São Carlos, University of São Paulo, São Carlos, São Paulo, Brazil.

The parasite Trypanosoma cruzi causes Chagas disease, which remains a serious public health concern and continues to victimize thousands of people, primarily in the poorest regions of Latin America. In the search for new therapeutic drugs against T. cruzi, here we have evaluated both the in vitro and the in vivo activity of 5-hydroxy-3-methyl-5-phenyl-pyrazoline-1-(S-benzyl dithiocarbazate) (H2bdtc) as a free compound or encapsulated into solid lipid nanoparticles (SLN); we compared the results with those achieved by using the currently employed drug, benznidazole. H2bdtc encapsulated into solid lipid nanoparticles (a) effectively reduced parasitemia in mice at concentrations 100 times lower than that normally employed for benznidazole (clinically applied at a concentration of 400 µmol kg(-1) day(-1)); (b) diminished inflammation and lesions of the liver and heart; and (c) resulted in 100% survival of mice infected with T. cruzi. Therefore, H2bdtc is a potent trypanocidal agent.
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http://dx.doi.org/10.1371/journal.pntd.0002847DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4014426PMC
May 2014

Vanadium Complexes with Hydrazone or Thiosemicarbazone Ligands as Potential Anti-Mycobacterium tuberculosis Agents.

Curr Clin Pharmacol 2015 ;10(1):66-72

School of Pharmaceutical Sciences, Sao Paulo State University, 14801-902, Araraquara, SP, Brazil.

Tuberculosis (TB) is an infectious disease caused mainly by Mycobacterium tuberculosis (MTB) and still an important public health problem worldwide. Some factors like the emergence of multidrug resistant (MDR) and extensively drug-resistant (XDR) strains make urgent the research of new active compounds. Searching for new inorganic compounds against TB, three new dioxovanadium(V) complexes were obtained upon reaction of [VO(acac)2] with hydrazone and thiosemicarbazone ligands derived from di-2-pyridyl ketone. Spectroscopic studies and X-ray crystallography revealed asymmetrically oxo bridged binuclear complexes of the type [{VO(L(1,2))}2(μ-O)2], involving the hydrazone ligands, while a mononuclear square pyramidal complex of the type [VO2(L(3))] was formed with the thiosemicarbazone ligand. The compounds were tested against M. tuberculosis and three of them, with MICs values between 2.00 and 3.76 μM were considered promising for TB treatment. Such MIC values are comparable or better than those found for some drugs currently used in TB treatment.
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http://dx.doi.org/10.2174/1574884708666131229124748DOI Listing
February 2016

Manganese(II) complexes with thiosemicarbazones as potential anti-Mycobacterium tuberculosis agents.

J Inorg Biochem 2014 Mar 25;132:21-9. Epub 2013 Oct 25.

Instituto de Química de São Carlos, Universidade de São Paulo, 13566-590 São Carlos, SP, Brazil. Electronic address:

Through a systematic variation on the structure of a series of manganese complexes derived from 2-acetylpyridine-N(4)-R-thiosemicarbazones (Hatc-R), structural features have been investigated with the aim of obtaining complexes with potent anti-Mycobacterium tuberculosis activity. The analytical methods used for characterization included FTIR, EPR, UV-visible, elemental analysis, cyclic voltammetry, magnetic susceptibility measurement and single crystal X-ray diffractometry. Density functional theory (DFT) calculations were performed in order to evaluate the contribution of the thiosemicarbazonate ligands on the charge distribution of the complexes by changing the peripheral groups as well as to verify the Mn-donor atoms bond dissociation predisposition. The results obtained are consistent with the monoanionic N,N,S-tridentate coordination of the thiosemicarbazone ligands, resulting in octahedral complexes of the type [Mn(atc-R)2], paramagnetic in the extension of 5 unpaired electrons, whose EPR spectra are consistent for manganese(II). The electrochemical analyses show two nearly reversible processes, which are influenced by the peripheral substituent groups at the N4 position of the atc-R(1-) ligands. The minimal inhibitory concentration (MIC) of these compounds against M. tuberculosis as well as their in vitro cytotoxicity on VERO and J774A.1 cells (IC50) was determined in order to find their selectivity index (SI) (SI=IC50/MIC). The results evidenced that the compounds described here can be considered as promising anti-M. tuberculosis agents, with SI values comparable or better than some commercial drugs available for the tuberculosis treatment.
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http://dx.doi.org/10.1016/j.jinorgbio.2013.10.011DOI Listing
March 2014

Rhenium mixed-ligand complexes with S,N,S-tridentate thiosemicarbazone/thiosemicarbazide ligands.

Dalton Trans 2013 Apr;42(14):5111-21

Instituto de Química de São Carlos, Universidade de São Paulo, CP 780, São Carlos-SP, Brazil.

Rhenium(V) complexes containing tridentate thiosemicarbazones/thiosemicarbazides (H2L1) derived from N-[N′,N′-dialkylamino(thiocarbonyl)]benzimidoyl chlorides with 4,4-dialkylthiosemicarbazides have been synthesized by ligand-exchange reactions starting from [ReOCl(L1)]. The chlorido ligand of [ReOCl(L1)] (4) is readily replaced and reactions with ammonium thiocyanate or potassium cyanide give [ReO(NCS)(L1)] (6) and [ReO(CN)(L1)] (7), respectively. The reaction of (NBu4)[ReOCl4] with H2L1 and two equivalents of ammonium thiocyanate, however, gives in a one-pot reaction [ReO(NCS)2(HL1)] (8), in which the pro-ligand H2L1 is only singly deprotonated. An oxo-bridged, dimeric nitridorhenium(V) compound of the composition [{ReN(HL1)}2O] (11) is obtained from a reaction of (NBu4)[ReOCl4], H2L1 and sodium azide. The six-coordinate complexes [ReO(L1)(Ph2btu)] (12), where HPh2btu is N,N-diphenyl-N′-benzoylthiourea, can be obtained by treatment of [ReOCl(L1)] with HPh2btu in the presence of NEt3. Studies of the antiproliferative effects of the [ReOX(L1)] system (X = Cl−, NCS− or CN−) on breast cancer cells show that the lability of a monodentate ligand seems to play a key role in the cytotoxic activity of the metal complexes, while the substitution of this ligand by the chelating ligand Ph2btu− completely terminates the cytotoxicity.
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http://dx.doi.org/10.1039/c3dt32950jDOI Listing
April 2013

Neutral gold complexes with tridentate SNS thiosemicarbazide ligands.

Inorg Chem 2012 Feb 10;51(3):1604-13. Epub 2012 Jan 10.

Instituto de Química de São Carlos, Universidade de São Paulo, CP 780, São Carlos-São Paulo, Brazil.

Na[AuCl(4)]·2H(2)O reacts with tridentate thiosemicarbazide ligands, H(2)L1, derived from N-[N',N'-dialkylamino(thiocarbonyl)]benzimidoyl chloride and thiosemicarbazides under formation of air-stable, green [AuCl(L1)] complexes. The organic ligands coordinate in a planar SNS coordination mode. Small amounts of gold(I) complexes of the composition [AuCl(L3)] are formed as side-products, where L3 is an S-bonded 5-diethylamino-3-phenyl-1-thiocarbamoyl-1,2,4-triazole. The formation of the triazole L3 can be explained by the oxidation of H(2)L1 to an intermediate thiatriazine L2 by Au(3+), followed by a desulfurization reaction with ring contraction. The chloro ligands in the [AuCl(L1)] complexes can readily be replaced by other monoanionic ligands such as SCN(-) or CN(-) giving [Au(SCN)(L1)] or [Au(CN)(L1)] complexes. The complexes described in this paper represent the first examples of fully characterized neutral Gold(III) thiosemicarbazone complexes. All the [AuCl(L1)] compounds present a remarkable cell growth inhibition against human MCF-7 breast cancer cells. However, systematic variation of the alkyl groups in the N(4)-position of the thiosemicarbazone building blocks as well as the replacement of the chloride by thiocyanate ligands do not considerably influence the biological activity. On the other hand, the reduction of Au(III) to Au(I) leads to a considerable decrease of the cytotoxicity.
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http://dx.doi.org/10.1021/ic201905tDOI Listing
February 2012

Dithiocarbazate complexes with the [M(PPh3)]2+ (M = Pd or Pt) moiety: synthesis, characterization and anti-Trypanosoma cruzi activity.

J Inorg Biochem 2010 Dec 21;104(12):1276-82. Epub 2010 Aug 21.

Instituto de Química de São Carlos, Universidade de São Paulo, 13566-590 São Carlos, SP, Brazil.

New neutral Pd(II) and Pt(II) complexes of the type [M(L)(PPh(3))] (M = Pd or Pt) were prepared in crystalline form in high-yield synthesis with the S-benzyldithiocarbazates and S-4-nitrobenzyldithiocarbazates derivatives from 2-hydroxyacetophenone, H(2)L(1a) and H(2)L(1b), and benzoylacetone, H(2)L(2a) and H(2)L(2b). The new complexes [Pt(L(1a))(PPh(3))] (1), [Pd(L(1a))(PPh(3))] (2), [Pt(L(1b))(PPh(3))] (3), [Pd(L(1b))(PPh(3))] (4), [Pt(L(2a))(PPh(3))] (5), [Pd(L(2a))(PPh(3))] (6), [Pt(L(2b))(PPh(3))] (7) and [Pd(L(2b))(PPh(3))] (8) were characterized on the basis of elemental analysis, conductivity measurements, UV-visible, IR, electrospray ionization mass spectrometry (ESI-MS), NMR ((1)H and (31)P) and by X-ray diffraction studies. The studies showed that differently from what was observed for the H(2)L(1a) and H(2)L(1b) ligands, H(2)L(2a) and H(2)L(2b) assume cyclic forms as 5-hydroxypyrazolinic. Upon coordination, H(2)L(2a) and H(2)L(2b) suffer ring-opening reaction, coordinating in the same manner as H(2)L(1a) and H(2)L(1b), deprotonated and in O,N,S-tridentate mode to the (MPPh(3))(2+) moiety. All complexes show a quite similar planar fourfold environment around the M(II) center. Furthermore, these complexes exhibited biological activity on extra and intracellular forms of Trypanosoma cruzi in a time- and concentration-dependent manner with IC(50) values ranging from 7.8 to 18.7 μM, while the ligand H(2)L(2a) presented a trypanocidal activity on trypomastigote form better than the standard drug benznidazole.
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http://dx.doi.org/10.1016/j.jinorgbio.2010.08.009DOI Listing
December 2010