Sebastião S. Lemos

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

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.

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.

Comparison of EPR-Visible Cu2+ Sites in pMMO from Methylococcus capsulatus (Bath) and Methylomicrobium album BG8

X-band (9.1 GHz) and S-band (3.4 GHz) electron paramagnetic resonance (EPR) spectra for particulate methane monooxygenase (pMMO) in whole cells from Methylococcus capsulatus (Bath) grown on (63)Cu and (15)N were obtained and compared with previously reported spectra for pMMO from Methylomicrobium album BG8. For both M. capsulatus (Bath) and M. album BG8, two nearly identical Cu(2+) EPR signals with resolved hyperfine coupling to four nitrogens are observed. The EPR parameters for pMMO from M. capsulatus (Bath) (g( parallel) = 2.244, A( parallel) = 185 G, and A(N) = 19 G for signal one; g( parallel) = 2.246, A( parallel) = 180 G, and A(N) = 19 G for signal two) and for pMMO from M. album BG8 (g( parallel) = 2.243, A( parallel) = 180 G, and A(N) = 18 G for signal one; g( parallel) = 2. 251, A( parallel) = 180 G, and A(N) = 18 G for signal two) are very similar and are characteristic of type 2 Cu(2+) in a square planar or square pyramidal geometry. In three-pulse electron spin echo envelope modulation (ESEEM) data for natural-abundance samples, nitrogen quadrupolar frequencies due to the distant nitrogens of coordinated histidine imidazoles were observed. The intensities of the quadrupolar combination bands indicate that there are three or four coordinated imidazoles, which implies that most, if not all, of the coordinated nitrogens detected in the continuous wave spectra are from histidine imidazoles.

Copper(I) pseudohalide complexes with 4,6-dimethylpyrimidine-2(1H)-thione and triphenylphosphane as ligands. The X-ray crystal structures of [Cu(N3)(dmpymtH)(PPh3)2] and [Cu(NCS)(dmpymtH)(PPh3)2]

Abstract The preparation of mixed-ligand copper(I) coordination compounds containing pseudohalides (azide and thiocyanate), 4,6-dimethylpyrimidine-2(1H)-thione (dmpymtH), and triphenylphosphane is described. The crystalline and molecular structure of [Cu(N3)(dmpymtH)(PPh3)2] (2) and [Cu(NCS)(dmpymtH)(PPh3)2] (3) have been determined by X-ray diffraction methods. The copper atom has a tetra-coordinate CuNP2S chromophore with distorted tetrahedral coordination in both complexes. Vibrational and 1H, 13C, 31P NMR spectra of the complexes are discussed and related to the structures.

Novel zwitterionic oxorhenium(V) complexes: synthesis, characterization and crystal structure of [ReOX2(Hdhp)(PPh3)] (X = Cl, Br; H2dhp = 2,3-dihydroxypyridine)

Dois novos complexos zwitterionicos de oxorrenio(V), [ReOCl2(Hdhp)(PPh3)] (1) e [ReOBr2(Hdhp)(PPh3)] (2) (H2dhp = 2,3-dihidroxipiridina), foram sintetizados e caracterizados por espectroscopia de absorcao no infravermelho, ressonância magnetica nuclear de 1H e 31P, analise elementar e determinacao da estrutura cristalina e molecular por difracao de raios X em monocristais. Os complexos apresentam geometria de coordenacao octaedrica bastante distorcida, com os dois ligantes haletos arranjados em posicoes cis equatoriais, o ligante trifenilfosfina em posicao trans a um dos haletos e o ligante Hdhp- coordenado de forma bidentada atraves de seus atomos de oxigenio, sendo um em posicao trans ao ligante oxo e o outro em posicao trans com relacao ao outro haleto. Este ligante tem seu atomo de nitrogenio protonado. Os compostos 1 e 2 apresentam empacotamento cristalino bastante diferente, influenciado em ambos os casos por ligacoes de hidrogenio intermoleculares dos tipos N-H...X (X = Cl, Br) e N-H...O.

(4,6‐Di­methyl­pyrimidine‐2‐thiol­ato)(tri­phenyl­phosphine)­gold(I)

The title compound, [Au(4,6-Me2pymS)(PPh3)] or [Au(C6H7N2S)(C18H15P)], exhibits a linear Au atom S—Au—P geometry, with Au—P = 2.247 (2) A, Au—S = 2.289 (2) A and P—Au—S = 178.19 (11)°. There is an intramolecular interaction between one N atom of the 4,6-Me2pymS ligand and the Au atom, with an Au⋯N distance of 3.154 (8) A.

PREPARAÇÃO E CARACTERIZAÇÃO ESPECTROSCÓPICA DE COMPLEXOS DE BORO - UMA PROPOSTA PARA UMA PRÁTICA INTEGRADA DE QUÍMICA INORGÂNICA

As a proposal for an undergraduate second or third year inorganic laboratory course, the present paper describes the preparation of three representative boron complexes: potassium tetrafluoroborate, pyridoxin boron complex and potassium bis(oxalato)borate. The complexes are characterised by infrared and multinuclear magnetic resonance spectroscopy (1H, 11B and 19F) where isotopic effects are demonstrated.