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- Metal Azolate/Carboxylate Frameworks as Catalysts in Oxidative and C-C Coupling ReactionsPublication . Tabacaru, Aurel; Xhaferaj, Nertil; Martins, Luisa; Alegria, Elisabete; Chay, Rogério; Giacobbe, Carlotta; Domasevitch, Konstantin V.; Pombeiro, Armando; GALLI, SIMONA; Pettinari, ClaudioThe five metal azolate/carboxylate (MAC) compounds [Cd(dmpzc)(DMF)(H2O)] (Cd-d.mpzc), [Pd-(H(2)dmpzc)(2)Cl-2] (Pd.dmpzc), [Cu(Hdmpzc)(2)] (Cu-dmpzc), [Zn4O(dmpzc)(3)]-Solv (Zn-dmpzcS), and [Co4O(dmpz(3)]-Solv (Co-dinpzcS) were isolated by coupling 3,5-dimethy1-1H-pyrazol-4-carboxylic acid (H(2)dmpzc) to cadmium(II), palladium(II), copper(II), zinc(II), and cobalt(II) salts. While Cd-clinpzc and Pd-dmpzc had never been prepared in the past, for Cu-dmpzc, Zndmpzc"S, and Co-dmpzc"S we optimized alternative synthetic paths that, in the case of the copper(II) and cobalt(11) derivatives, are faster and grant higher yields than the previously reported ones. The crystal structure details were determined ab initio (Cd-dmpzc and Pd-dmpzc) or refined (Cu-dmpzc, Zn-dmpzc"S, and Co-dmpzc-S) by means of powder X-ray diffraction (PXRD). While Cd-dmpzc is a nonporous 3D MAC framework, Pddmpzc shows a 3D hybrid coordination/hydrogen-bonded network, in which Pd(H(2)dmpzc)(2)Cl-2 monomers are present. The thermal behavior of the five MAC compounds was investigated by coupling thermal analysis to variable-temperature PXRD. Their catalytic activity was assessed in oxidative and C C coupling reactions, with the copper(II) and cadmium(II) derivatives being the first nonporous MAC frameworks to be tested as catalysts. Cu-dmpzc is the most active catalyst in the partial oxidation of cydohexane by tert-butyl hydropermdde in acetonitrile (yields up to 12% after 9 h) and is remarkably active in the solvent-free microwave-assisted oxidation of 1-phenylethanol to acetophenone (yields up to 99% at 120 degrees C in only 0.5 h). On the other hand, activated Zn-dmpzc"S (Zn-dmpzc) is the most active catalyst in the Henry C C coupling reaction of aromatic aldehydes with nitroethane, showing appreciable diastereoselectivity toward the syn-nitroalkanol isomer (syn:anti selectivity up to 79:21).
- Ruthenium(II) Arene Complexes Bearing Tris(pyrazolyl)methanesulfonate Capping Ligands.Electrochemistry, Spectroscopic, and X-ray Structural CharacterizationPublication . Marchetti, Fabio; Pettinari, Claudio; Pettinari, Riccardo; Cerquetella, Adele; Martins, Luisa; Guedes da Silva, M. Fátima C.; Silva, Telma F. S.; Pombeiro, ArmandoNovel [Ru(L)(Tpms)]Cl and [Ru(L)(Tpms(Ph))]Cl complexes (L = p-cymene, benzene, or hexamethylbenzene, Tpms = tris(pyrazolyl)-methanesulfonate, Tpms(Ph) = tris(3-phenylpyrazoly)methanesulfonate) have been prepared by reaction of [Ru(L)(mu-Cl)(2)](2) with Li[Tpms] and Li[Tpms(Ph)], respectively. [Ru(p-cymene)(Tpms)]BF4 has been synthesized through a metathetic reaction of [Ru(p-cymene)(Tpms)]Cl with AgBF4. [RuCl(cod)(Tpms)] (cod = 1,5-cyclooctadiene) and [RuCl(cod)(Tpms(Ph))] are also reported, being obtained by reaction of [RuCl2(cod)(MeCN)(2)] with Li[Tpms] and Li[Tpms(Ph)], respectively. The structures of the complexes and the coordination modes of the ligands have been established by IR, NMR, and single-crystal X-ray diffraction (for [RuL(Tpms)]X (L = p-cymene or HMB, X = Cl; L = p-cymene, X = BF4)) studies. Electrochemical studies showed that each complex undergoes a single-electron R-II -> R-III oxidation at a potential measured by cyclic voltammetry, allowing to compare the electron-donor characters of the tris(pyrazolyl)methanesulfonate and arene ligands, and to estimate, for the first time, the values of the Lever E-L ligand parameter for Tmps(Ph), HMB, and cod.
- Synthesis, Antimicrobial and Antiproliferative Activity of Novel Silver(I) Tris(pyrazolyl)methanesulfonateand 1,3,5-Triaza-7-phosphadamantane ComplexesPublication . Pettinari, Claudio; Marchetti, Fabio; Lupidi, Giulio; Quassinti, Luana; Bramucci, Massimo; Petrelli, Dezemona; Vitali, Luca A.; Guedes Da Silva, M. Fátima C.; Martins, Luisa; Smolenski, Piotr; Pombeiro, ArmandoFive new silver(I) complexes of formulas [Ag(Tpms)] (1), [Ag(Tpms)-(PPh3)] (2), [Ag(Tpms)(PCy3)] (3), [Ag(PTA)][BF4] (4), and [Ag(Tpms)(PTA)] (5) {Tpms = tris(pyrazol-1-yl)methanesulfonate, PPh3 = triphenylphosphane, PCy3 = tricyclohexylphosphane, PTA = 1,3,5-triaza-7-phosphaadamantane) have been synthesized and fully characterized by elemental analyses, H-1, C-13, and P-31 NMR, electrospray ionization mass spectrometry (ESI-MS), and IR spectroscopic techniques. The single crystal X-ray diffraction study of 3 shows the Tpms ligand acting in the N-3-facially coordinating mode, while in 2 and 5 a N2O-coordination is found, with the SO3 group bonded to silver and a pendant free pyrazolyl ring. Features of the tilting in the coordinated pyrazolyl rings in these cases suggest that this inequivalence is related with the cone angles of the phosphanes. A detailed study of antimycobacterial and antiproliferative properties of all compounds has been carried out. They were screened for their in vitro antimicrobial activities against the standard strains Enterococcus faecalis (ATCC 29922), Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae (ATCC 49619), Streptococcus pyogenes (SF37), Streptococcus sanguinis (SK36), Streptococcus mutans (UA1S9), Escherichia coli (ATCC 25922), and the fungus Candida albicans (ATCC 24443). Complexes 1-5 have been found to display effective antimicrobial activity against the series of bacteria and fungi, and some of them are potential candidates for antiseptic or disinfectant drugs. Interaction of Ag complexes with deoxyribonucleic acid (DNA) has been studied by fluorescence spectroscopic techniques, using ethidium bromide (EB) as a fluorescence probe of DNA. The decrease in the fluorescence of DNA EB system on addition of Ag complexes shows that the fluorescence quenching of DNA EB complex occurs and compound 3 is particularly active. Complexes 1-5 exhibit pronounced antiproliferative activity against human malignant melanoma (A375) with an activity often higher than that of AgNO3, which has been used as a control, following the same order of activity inhibition on DNA, i.e., 3 > 2 > 1 > 5 > AgNO3 >> 4.
- Cooperative metal–ligand Assisted E/Z isomerization and cyano activation at CuII and CoII complexes of arylhydrazones of active methylene nitrilesPublication . Mahmudov, Kamran; Kopylovich, Maximilian N.; SABBATINI, Alessandra; Drew, Michael G. B.; Martins, Luisa; Pettinari, Claudio; Pombeiro, ArmandoNew (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzoic acid (H2L4) and known sodium 2-(2-(dicyanomethylene)hydrazinyl)benzenesulfonate (NaHL1), 2-(2-(dicyano-methylene)hydrazinyl)benzoic acid (H2L2), and sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene)hydrazinyl)benzenesulfonate (NaHL3) were used in the template synthesis of a series of CuII and CoII complexes [Cu(H2O)2L1a]·H2O (1), [Cu(H2O)(3-pyon)L1b]·H2O (2), [Cu(H2O)(4-pyon)L1b] (3), [Co(H2O)-((CH3)2NCHO)(μ-L2a)]2·(CH3)2NCHO (4), [Cu3(μ3-OH)-(NO3)(CH3OH)(μ2-X)3(μ2-HL3)] (5), [Cu(H2O)(py)L3]·H2O (6), [Cu(H2O)2(μ-L4)]6 ·6H2O (7), [Cu(2-cnpyb)2(L1b)2]·2H2O (8), [Cu(2-cnpya)2(L1a)2]·2H2O (9), and [Cu(H2O)(4-cnpy)(L1a)2] (10), where 3-pyon = 1-(pyridin-3-yl)ethanone, 4-pyon = 1-(pyridin-4-yl)ethanone, py = pyridine, HX = syn-2-pyridinealdoxime, 4-cnpy = 4-cyanopyridine; 2-cnpya, 2-cnpyb, L1a, L1b, L2a are the ligands derived from nucleophilic attack of methanol (a) or water (b) on a cyano group of 2-cyanopyridine (2-cnpy), L1 or L2, respectively, giving the corresponding iminoesters (2-cnpya, L1a or L2a) or carboxamides (2-cnpyb or L1b). An auxiliary ligand, namely syn-2-pyridinealdoxime or pyridine, acting cooperatively with the metal ion (CuII in this case), induced an E/Z isomerization of the H2L4 ligand; the E- and Z-isomers were isolated separately and fully characterized (compounds 9 and 10, respectively). A one-pot activation of nitrile groups in different molecules was achieved in the syntheses of 8 and 9. Complexes 1−10 are catalyst precursors for the solvent-free microwave (MW)-assisted selective oxidation of secondary alcohols to the corresponding ketones, with typical yields in the 29−99% range (TOFs up to 4.94 × 103 h−1) after 30 min of MW irradiation.
- Novel coordination polymers with (Pyrazolato)-based tectons: catalytic activity in the peroxidative oxidation of alcohols and cyclohexanePublication . Timokhin, Ivan; Pettinari, Claudio; Marchetti, Fabio; Pettinari, Riccardo; CONDELLO, Francesca; GALLI, SIMONA; Alegria, Elisabete; Martins, Luisa; Pombeiro, ArmandoCoupling five rigid or flexible bis(pyrazolato)based tectons with late transition metal ions allowed us to isolate 18 coordination polymers (CPs). As assessed by thermal analysis, all of them possess a remarkable thermal stability, their decomposition temperatures lying in the range of 340-500 degrees C. As demonstrated by N-2 adsorption measurements at 77 K, their Langmuir specific surface areas span the rather vast range of 135-1758 m(2)/g, in agreement with the porous or dense polymeric architectures retrieved by powder X-ray diffraction structure solution methods. Two representative families of CPs, built up with either rigid or flexible spacers, were tested as catalysts in (0 the microwave-assisted solvent-free peroxidative oxidation of alcohols by t-BuOOH, and (ii) the peroxidative oxidation of cydohexane to cydohexanol and cydohexanone by H2O2 in acetonitrile. Those CPs bearing the rigid spacer, concurrently possessing higher specific surface areas, are more active than the corresponding ones with the flexible spacer. Moreover, the two copper(I)-containing CPs investigated exhibit the highest efficiency in both reactions, leading selectively to a maximum product yield of 92% (and TON up to 1.5 x 10(3)) in the oxidation of 1-phenylethanol and of 11% in the oxidation of cydohexane, the latter value being higher than that granted by the current industrial process.
- Coordination Chemistry of the (eta(6)-p-Cymene)ruthenium(II) Fragment with Bis-, Tris-, andTetrakis(pyrazol-1-yl)borate Ligands: Synthesis, Structural, Electrochemical, and CatalyticDiastereoselective Nitroaldol Reaction StudiesPublication . Pettinari, Claudio; Marchetti, Fabio; Cerquetella, Adele; Pettinari, Riccardo; MONARI, MAGDA; Mac Leod, Tatiana C. O.; Martins, Luisa; Pombeiro, ArmandoNovel [Ru(eta(6)-p-cymene)(kappa(2)-L)X] and [Ru(eta(6)-p-cymene)(kappa(3)-L)]X center dot nH(2)O complexes (L = bis-, tris-, or tetrakis-pyrazolylborate; X = Cl, N-3, PF6, or CF3SO3) are prepared by treatment of [Ru(eta(6)-p-cymene)Cl-2](2) with poly-(pyrazolyl)borate derivatives [M(L)] (L in general; in detail L = Ph(2)Bp = diphenylbis-(pyrazol-1-yl)borate; L = Tp = hydrotris(pyrazol-1-yl)borate; L = pzTp = tetrakis(pyrazol-1-yl)borate; L = Tp(4Bo) = hydrotris(indazol-1-yl)borate, L = T-p4Bo,T-5Me = (5-methylindazol-1-yl)borate; L = Tp(Bn,4Ph) = hydrotris(3-benzyl-4-phenylpyrazol-1-yl)borate; M = Na, K, or TI) and characterized by analytical and spectral data (IR, ESIMS, H-1 and C-13 NMR). The structures of [Ru(eta(6)-p-cymene)(Ph(2)Bp)Cl] (1) and [Ru(eta(6)-p-cymene)(Tp)Cl] (3) have been established by single-crystal X-ray diffraction analysis. Electrochemical studies allowed comparing the electron-donor characters of Tp and related ligands and estimating the corresponding values of the Lever E-L ligand parameter. The complexes [Ru(eta(6)-p-cymene)-(kappa(2)-L)X] and [Ru(eta(6)-p-cymene)(kappa(3)-L)]X center dot nH(2)O act as catalyst precursors for the diastereoselective nitroaldol reaction of benzaldehyde and nitroethane to the corresponding beta-nitroalkanol (up to 82% yield, at room temperature) with diastereoselectivity toward the formation of the threo isomer.
- Electrochemical properties of (H5-C5Me5)-rhodium and – iridium complexes Bis(pyrazolyl)alkane ligandsPublication . Martins, Luisa; Pettinari, Claudio; Marchetti, Fábio; Alegria, Elisabete; Pombeiro, ArmandoThe electrochemical properties of rhodium(III) 1-3 and iridium(III) 4-6 complexes containing bis(pyrazolyl)alkane ligands [MCp*Cl(R2C(3,5-R'2pz)2)]X (M = Rh (1) or Ir (4), R = R' = H, X = Cl; M = Rh (2) or Ir (5), R=H,R'=Me,X=Cl;M=Rh(3) or Ir (6), R=Me,R'=H,X=OTf;pz=pyrazolyl;Cp*=η5-C5Me5) were investigated by cyclic voltammetry and controlled potential electrolysis. They exhibit two sequential irreversible reductions assigned to the MIII → MII and MII → MI reductions, which are dependent on the methylation of the bis(pyrazolyl)alkane ligands.
- Arylhydrazones of barbituric acid: synthesis, coordination ability and catalytic activity of their Co-II, Co-II/III and Cu-II complexes toward peroxidative oxidation of alkanesPublication . Palmucci, Jessica; Mahmudov, Kamran; Guedes da Silva, Maria deFátima C.; Martins, Luisa; Marchetti, Fabio; Pettinari, Claudio; Pombeiro, ArmandoNew ortho-substituted arylhydrazones of barbituric acid, 5-(2-(2-hydroxyphenyl)hydrazono) pyrimidine-2,4,6(1H,3H,5H)-trione (H4L1) and the sodium salt of 2-(2-(2,4,6-trioxotetra-hydropyrimidin-5(2H)-ylidene)hydrazinyl) benzenesulfonic acid (H4L2), [Na(H3L2)(mu-H2O)(H2O)(2)](2) (1), were used in the synthesis of Cu-II, Co-II and Co-II/III complexes, [Cu(H2L1)(H2O)(im)]center dot 3H(2)O (im = imidazole) (2), [Co(H2O)(6)] [Co(H2L1)(2)](2)center dot 8H(2)O (3), [Co(H2L2)(im)(3)] (4), [Cu(H2L2)(im)(2)]center dot H2O (5) and [Co(H2O)(6)][H3L2](2)center dot 8H(2)O (6). The complexes are water soluble and the mono-or di-deprotonated ligands display different coordination modes, depending on the synthetic conditions. The electrochemical behaviour of all the compounds was investigated by cyclic voltammetry and controlled potential electrolysis, revealing that the ligands are also redox active. All the compounds were evaluated as catalysts for the peroxidative (with H2O2) oxidation of cyclohexane at room temperature. The compounds 2 and 3 are the most active ones (yields up to 21% and TON up to 213 are achieved, in the presence of 3).
- Synthesis and Coordination Chemistry of a New N-4-Polydentate Class of Pyridyl-Functionalized Scorpionate Ligands: Complexes of Fe-II, Zn-II, V-IV, Pd-II and Use for Heterobimetallic SystemsPublication . Wanke, Riccardo; Guedes Da Silva, M. Fátima C.; Lancianesi, Stefano; Silva, Telma F. S.; Martins, Luisa; Pettinari, Claudio; Pombeiro, ArmandoThe new potentially N-4-multidentate pyridyl-functionalized scorpionates 4-((tris-2,2,2-(pyrazol-1-ypethoxy)methyl)pyridine (TpmPy, (1)) and 4-((tris-2,2,2-(3-phenylpyrazol-1-yl)ethoxy)methyl)pyridine (TpmPy(Ph), (2)) have been synthesized and their coordination behavior toward Fe-II, Ni-II, Zn-II, Cu-II, Pd-II, and V-III centers has been studied. Reaction of (1) with Fe(BF4)(2)center dot 6H(2)O yields [Fe(TpmPy)(2)](BF4)(2) (3), that, in the solid state, shows the sandwich structure with trihapto ligand coordination via the pyrazolyl arms, and is completely low spin (LS) until 400 K. Reactions of 2 equiv of (1) or (2) with Zn-II or Ni-II chlorides give the corresponding metal complexes with general formula [MCl2(TpmPy*)(2)] (M = Zn, Ni; TpmPy* = TpmPy, TpmPy(Ph)) (4-7) where the ligand is able to coordinate through either the pyrazolyl rings (in case of [Ni(TpmPy)(2)Cl-2 (5)) or the pyridyl-side (for [ZnCl2(TpmPy)(2)] (4), [ZnCl2(TpmPy(Ph))(2)] (6) and [NiCl2(TpmPy(Ph))(2)] (7)). The reaction of (1) with VCl3 gives [VOCl2(TpmPy)] (8) that shows the N-3-pyrazolyl coordination-mode. Moreover, (1) and react with cis-[PdCl2(CH3CN)(2)] to give the disubstituted complexes [PdCl2(TprnPy)(2)] (9) and [PdCl2(TpmPy(Ph))(2)] (10), respectively, bearing the scorpionate coordinated via the pyridyl group. Compounds (9) and (10) react with Fe(BF4)(2) to give the heterobimetallic Pd/Fe systems [PdCl2(mu-TpmPy)(2)-Fe](BF4)(2) (11) and [PdCl2(mu-TpmPy(Ph))(2)Fe-2(H2O)(6)]BF4)(4) (13), respectively. Compound (11) can also be formed from reaction of (3) with cis-[PdCl2(CH3CN)(2)], while reaction of (3) with Cu(NO3)(2).2.5H(2)O generates [Fe(mu-TpmPy)(2)-Cu(NO3)(2)](BF4)(2) (12), confirming the multidentate ability of the new chelating ligands. The X-ray diffraction analyses of compounds (1), (3), (4), (5), and (9) are also reported.