Alzir A. Batista

Electronic structure, growth mechanism and photoluminescence of CaWO4 crystals

In this paper, aggregated CaWO4 micro- and nanocrystals were synthesized by the co-precipitation method and processed under microwave-assisted hydrothermal/solvothermal conditions (160 °C for 30 min). According to the X-ray patterns, all crystals exhibited only the scheelite-type tetragonal structure. The data obtained by the Rietveld refinements revealed that the oxygen atoms occupy different positions in the [WO4] clusters, suggesting the presence of lattice distortions. The crystal shapes as well as its crystallographic orientations were identified by field-emission scanning electron microscopy and high-resolution transmission electron microcopy. Electronic structures of these crystals were evaluated by the first-principles quantum mechanical calculations based on the density functional theory in the B3LYP level. A good correlation was found between the experimental and theoretical Raman and infrared-active modes. A crystal growth mechanism was proposed to explain the morphological evolution. The ultraviolet-visible absorption spectra indicated the existence of intermediary energy levels within the band gap. The highest blue photoluminescence emission, lifetime and quantum yield were observed for the nanocrystals processed in the microwave-assisted solvothermal method.

The reactivity of five-coordinate Ru(II) (1,4-bis(diphenylphosphino)butane) complexes with the N-donor ligands: ammonia, pyridine, 4-substituted pyridines, 2,2′-bipyridine, bis(o-pyridyl)amine, 1,10-phenanthroline, 4,7-diphenylphenanthroline and ethylenediamine

Abstract A series of Ru(II)(1,4-bis(diphenylphosphino)butane)(L)2 complexes was synthesized from [RuCl2(dppb) l2 (μ-dppb) or RuCl2 (dppb)- (PPh3); dppb = Ph2P(CH2)4PPH2, L = NH3, pyridine (py), 4-aminopyridine (4-NH2py), 4-cyanopyridine (4-CNpy), 4-dimethylaminopyridine (4-Me2Npy), 4-methylpyridine (4-Mepy), 4-phenylpyridine (4-Phpy), 4-vinylpyridine (4-Phy) and N-methylimidazole (Melm) and L2 = 2,2′-bipyridine (bipy), bis(o-pyridyl)amine (bpa), 1,10-phenanthroline (phen), 4,7-diphenylphenanthroline (or bathophenanthroline, batho) and ethylenediamine (en). The complexes were characterized by elemental analysis, cyclic voltametry, UV-Vis, NMR and IR spectroscopies. The structures of trans-RuCl2(dppb) (py)2 (3), cis-RuCl2(dppb)(bipy) (4) and cis-RuCl2(dppb) (phen) (5) were established by X-ray crystallographic analyses. Crystals of trans-3, cis-4-CH2Cl2 and cis-5-solvate are all monoclinic, space group P21/c, with Z=4; a = 12.946 (2), b = 14.204(3), c = 18.439(4) A , β = 90.08(2)° for trans-3; a=10.694(6), b=18.485(6), c=18.632(7) A , β = 90.26(3)° for cis-4·CH2Cl2; a = 17.094 (1), b = 9.923(2), c = 21.905(2) A , β = 98.883 (6)° for cis-5 solvate. The structures were solved by the heavy atom Patterson method and were refined by full-matrix least-squares procedures to R=0.069, 0.071 and 0.036 (Rw = 0.069, 0.076 and 0.039) for 1957, 4165 and 4824 reflections with l ≥ 3σ (l), respectively.

Electrochemical and spectroscopic studies on RuCl2(PPh3)2(N)2 and RuCl2(PPh3)2(N–N) complexes (N=pyridine derivatives and N–N=phenanthroline or bipyridine derivatives). X-ray structure of RuCl2(PPh3)2(phen)

Abstract A series of RuCl2(PPh3)2(N)2 and RuCl2(PPh3)2(N–N) complexes were synthesized from RuCl2(PPh3)3, (N)2=pyridine (py), 4-(N,N-dimethylamino)pyridine (4-dmNpy), 4-tert-butylpyridine (4-tBu-py), 4-methylpyridine (4-Mepy), 4-vinylpyridine (4-Vpy), 4-phenylpyridine (4-Phpy), isonicotinamide (4-CONH2py), 4-cyanopyridine (4-CNpy) N–N=1,10-phenanthroline (phen), 2,2′-bipyridine (bipy), 2,2′-bipyridine-4,4′-dimethoxy (MeO-bipy), 2,2′-bipyridine-4,4′-dimethyl (Me-bipy), 2,2′-bipyridine-4,4′-dithiomethyl (MeS-bipy), 2,2′-bipyridine-4,4′-dichloro (Cl-bipy) and 2,2′-bipyridine-4,4′-dinitro (NO2-bipy). The complexes were characterized by elemental analysis, cyclic voltammetry and UV–Vis, NMR and IR spectroscopies. The structure of the RuCl2(PPh3)2(phen) was established by single crystal X-ray crystallography.

Palladium(II) complexes with thiosemicarbazones: syntheses, characterization and cytotoxicity against breast cancer cells and Anti-Mycobacterium tuberculosis activity

Three PdII complexes were prepared from N(4)-substituted thiosemicarbazones: [Pd(aptsc)(PPh3)](NO3)•H2O, 1, [Pd(apmtsc)(PPh3)](NO3), 2, and [Pd(apptsc)(PPh3)](NO3)•H2O, 3, where PPh3 = triphenylphosphine; Haptsc = 2-acetylpyridine-thiosemicarbazone; Hapmtsc = 2-acetylpyridine-N(4)-methyl-thiosemicarbazone and Happtsc = 2-acetylpyridine-N(4)-phenyl-thiosemicarbazone. All complexes were characterized by elemental analysis, IR, UV-Vis, 1H and 31P{1H} NMR spectroscopies, and had their crystalline structures determined by X-ray diffractometry from single crystals. The monoanionic thiosemicarbazonate ligands act in a tridentate mode, binding to the metal through the pyridine nitrogen, the azomethine nitrogen and the sulfur atoms. The cytotoxic activity against the breast cancer cell line MDA-MB231 and the anti-Mycobacterium tuberculosis H37Rv ATCC 27294 activity were evaluated for the compounds. All PdII complexes were highly active against the studied cell line, presenting similar values of IC50, around 5 µmol L-1, while the clinically applied antitumor agent cisplatin was inactive. The compounds show remarkable anti-M. tuberculosis activities, presenting MIC values comparable or better than some commercial anti-M tuberculosis drugs.

Nitrosyl ruthenium complexes with general formula [RuCl3(NO)(PP)] (PP = {PPh2(CH2)nPPh2}, n = 1–3 and {PPh2-CHPPh2}). X-ray structure of [RuCl3(NO){PPh2(CH2)3PPh2}]

Abstract Ruthenium(II) complexes with general formula [RuCl3(NO)(PP)] were obtained in the solid state, where PP = PPh2(CH2)nPPh2 (n = 1) and PPh2-Ch = CH-PPh2. The 31P NMR spectra of these compounds measured in CH2Cl2 showed only singlets, consistent with a fac configuration containing two equivalent phosphorus atoms. However the X-ray diffraction data show that the [RuCl3(NO){PPh2(CH2)3PPh2}] complex crystallizes in a mer configuration, where one of the phosphorus atoms is trans to the NO group, in a slightly distorted octahedral geometry.

Copper(II) complexes with (2-hydroxybenzyl-2-pyridylmethyl)amine–Hbpa: syntheses, characterization and crystal structures of the ligand and [Cu(II)(Hbpa)2](ClO4)2·2H2O

Abstract Copper(II) complexes were synthesized and characterized by means of elemental analysis, IR and visible spectroscopies, EPR and electrochemistry, as well as X-ray structure crystallography. The group consists of discrete mononuclear units with the general formula [Cu(II)(Hbpa) 2 ](A) 2 · n H 2 O, where Hbpa=(2-hydroxybenzyl-2-pyridylmethyl)amine and A=ClO 4  − , n =2 ( 1 ), CH 3 COO − , n =3 ( 2 ), NO 3  − , n =2 ( 3 ) and SO 4  2− , n =3 ( 4 ). The structures of the ligand Hbpa and complex 1 have been determined by X-ray crystallography. Complexes 1 – 4 have had their UV–Vis spectra measured in both MeCN and DMF. It was observed that the compounds interact with basic solvents, such that molecules coordinate to the metal in axial positions in which phenol oxygen atoms are coordinated in the protonated forms. The e values were all less than 1000 M −1 cm −1 . EPR measurements on powdered samples of 1 – 3 gave g ∣∣ / A ∣∣ values between 105 and 135 cm −1 , typical for square planar coordination environments. Complex 4 ·3H 2 O exhibits a behaviour typical for tetrahedral coordination. The electrochemical behaviour for complexes 1 and 2 was studied showing irreversible redox waves for both compounds.

Cytoxicity and Apoptotic Mechanism of Ruthenium(II) Amino Acid Complexes in Sarcoma-180 Tumor Cells

Over the past several decades, much attention has been focused on ruthenium complexes in antitumor therapy. Ruthenium is a transition metal that possesses several advantages for rational antitumor drug design and biological applications. In the present study, five ruthenium complexes containing amino acids were studied in vitro to determine their biological activity against sarcoma-180 tumor cells. The cytotoxicity of the complexes was evaluated by an MTT assay, and their mechanism of action was investigated. The results demonstrated that the five complexes inhibited the growth of the S180 tumor cell line, with IC50 values ranging from 22.53 µM to 50.18 µM, and showed low cytotoxicity against normal L929 fibroblast cells. Flow cytometric analysis revealed that the [Ru(gly)(bipy)(dppb)]PF6 complex (2) inhibited the growth of the tumor cells by inducing apoptosis, as evidenced by an increased number of Annexin V-positive cells and G0/G1 phase cell cycle arrest. Further investigation showed that complex 2 caused a loss of mitochondrial membrane potential; activated caspases 3, caspase-8, and caspase-9 and caused a change in the mRNA expression levels of caspase 3, caspase-9 as well as the bax genes. The levels of the pro-apoptotic Bcl-2 family protein Bak were increased. Thus, we demonstrated that ruthenium amino acid complexes are promising drugs against S180 tumor cells, and we recommend further investigations of their role as chemotherapeutic agents for sarcomas.

A new nitrosyl ruthenium complex: synthesis, chemical characterization, in vitro and in vivo antitumor activities and probable mechanism of action.

This study describes the synthesis of a new ruthenium nitrosyl complex with the formula [RuCl(2)NO(BPA)] [BPA = (2-hydroxybenzyl)(2-methylpyridyl)amine ion], which was synthesized and characterized by spectroscopy, cyclic voltammetry, X-ray crystallography, and theoretical calculation data. The biological studies of this complex included in vitro cytotoxic assays, which revealed its activity against two different tumor cell lines (HeLa and Tm5), with efficacy comparable to that of cisplatin, a metal-based drug that is administered in clinical treatment. The in vivo studies showed that [RuCl(2)NO(BPA)]is effective in reducing tumor mass. Also, our results suggest that the mechanism of action of [RuCl(2)NO(BPA)] includes binding to DNA, causing fragmentation of this biological molecule, which leads to apoptosis.

RUTHENIUM COMPLEXES CONTAINING TERTIARY PHOSPHINES AND IMIDAZOLE OR 2,2'-BIPYRIDINE LIGANDS

Complexes RuCl3(PPh3)L2 (L = MeIm (1a, Im (1b)) and [RuCl2(PPh3)2(bipy)]Cl·4H2O (2) have been synthesized via the ruthenium(III) precursor RuCl3(PPh3)2 (DMA), and characterized, including an X-ray structural analysis for 1a (MeIm = N-methylimidazole, Im = imidazole, bipy = 2,2′-bipyridyl, and DMA = N, N′-dimethylacetamide). Crystals of 1a are monoclinic, space group P21/n, a = 10.5491(5), b = 20.4934(9), c = 12.8285(4) A, β = 90.166(4)°, Z = 4. The structure, which reveals a mer configuration for the chlorides, and cis-methylimidazoles, was solved by conventional heavy atom methods and was refined by full-matrix least-square procedures to R = 0.041 and Rw = 0.042 for 3328 reflections with I ⩾ 3σ(I). From the RuCl2(PPh3)3 precursor, the ruthenium(II) complexes RuCl2(PPh3)2L2 and [RuCl(PPh3)L4]Cl have been made (L = Im or MeIm), while [RuCl(dppb)Im3]Cl has been made from [RuCl2(dppb)]2(μ-dppb) (dppb = Ph2P(CH2)4PPh2).

Synthesis, characterization and cytotoxic activities of the [RuCl2(NO)(dppp)(L)]PF6 complexes

The synthesis and characterization of ruthenium compounds of the type [RuCl(2)(NO)(dppp)(L)]PF(6) [dppp=1,3-bis(diphenylphosphino)propane; L=pyridine, 4-methylpyridine, 4-phenylpyridine and dimethyl sulfoxide] are described. The complexes were characterized by elemental analysis, UV/Vis and infrared spectroscopy, cyclic voltammetry, and X-ray crystallography for the complexes with the pyridine and 4-methylpyridine ligands. In vitro evaluation of these nitrosyl complexes revealed cytotoxic activity from 7.1 to 19.0 microM against the MDA-MB-231 breast tumor cells and showed that, in this case, they are more active than the reference metallodrug cisplatin. The 1,3-bis(diphenylphosphino)propane and the N-heterocyclic ligands alone failed to show cytotoxic activities at the concentrations tested (maximum concentration utilized=200 microM).