Chemotherapeutic Activities of New η6-p-Cymene Ruthenium(II) and Osmium(II) Complexes with Chelating SS and Tridentate SNS Ligands.

A series of new chelating bidentate (SS) alkylimidazole-2-thione-Ru(II)/Os(II) complexes (3ai, 3aii, 3aiii, 3bii/4aiii, 4bi, 4bii), and the tridentate (SNS) pyridine-2,6-diylimidazole-2-thione-Ru(II)/Os(II) complexes (5bi, 5civ/6bi, 6ci, 6civ) in the forms [MII(cym)(L)Cl]PF6 and [MII(cym)(L)]PF6 (M = Ru or Os, cym = η6-p-cymene, and L = heterocyclic derivatives of thiourea) respectively, were successfully synthesized. Spectroscopic and analytical methods were used to characterize the complexes and their ligands. Solid-state single-crystal X-ray diffraction analyses revealed a "piano-stool" geometry around the Ru(II) or Os(II) centers in the respective complexes. The complexes were investigated for in vitro chemotherapeutic activities against human cervical carcinoma (HeLa) and the non-cancerous cell line (Hek293) using the MTT assay. The compounds 3aii, 5civ, 5bi, 4aiii, 6ci, 6civ, and the reference drug, 5-fluorouracil were found to be selective toward the tumor cells; the compounds 3ai, 3aiii, 3bii, 4bi, 4bii, and 6bi, which were found not to be selective between normal and tumor cell lines. The IC50 value of the tridentate half-sandwich complex 5bi (86 ± 9 µM) showed comparable anti-proliferative activity with the referenced commercial anti-cancer drug, 5-fluorouracil (87 ± 15 µM). The pincer (SNS) osmium complexes 6ci (36 ± 10 µM) and 6civ (40 ± 4 µM) were twice as effective as the reference drug 5-fluorouracil at the respective dose concentrations. However, the analogous pincer (SNS) ruthenium complex 5civ was ineffective and did not show anti-proliferative activity, even at a higher concentration of 147 ± 1 µM. These findings imply that the higher stability of the chelating (SS) and the pincer (SNS) ligand architectures in the complexes improves the biological (anti-proliferative) activity of the complexes by reducing the chance of ligand dissociation under physiological conditions. In general, the pincer (SNS) osmium complexes were found to be more cytotoxic than their ruthenium analogues, suggesting that the anti-proliferative activity of the imidazole-2-thione-Ru/Os complexes depends on the ligand's spatial coordination, the nature of the metal center, and the charge of the metal complex ions.

Oxidation of Styrene to Benzaldehyde Catalyzed by Schiff Base Functionalized Triazolylidene Ni(II) Complexes.

Four new Schiff base functionalized 1,2,3-triazolylidene nickel complexes, [Ni-(L1NHC)2](PF6)2; 3, [Ni-(L2NHC)2](PF6)2; 4, [Ni-(L3NHC)](PF6)2; 7 and [Ni-(L4NHC)](PF6)2; 8, (where L1NHC = (E)-3-methyl-1-propyl-4-(2-(((2-(pyridin-2-yl)ethyl)imino)methyl)phenyl)-1H-1,2,3-triazol-3-ium hexafluorophosphate(V), 1, L2NHC = (E)-3-methyl-4-(2-((phenethylimino)methyl)phenyl)-1-propyl-1H-1,2,3-triazol-3-ium hexafluorophosphate(V), 2, L3NHC = 4,4'-(((1E)-(ethane-1,2-diylbis(azanylylidene))bis(methanylylidene))bis(2,1-phenylene))bis(3-methyl-1-propyl-1H-1,2,3-triazol-3-ium) hexafluorophosphate(V), 5, and L4NHC = 4,4'-(((1E)-(butane-1,4-diylbis(azanylylidene))bis(methanylylidene))bis(2,1-phenylene))bis(3-methyl-1-propyl-1H-1,2,3-triazol-3-ium) hexafluorophosphate(V), 6), were synthesised and characterised by a variety of spectroscopic methods. Square planar geometry was proposed for all the nickel complexes. The catalytic potential of the complexes was explored in the oxidation of styrene to benzaldehyde, using hydrogen peroxide as a green oxidant in the presence of acetonitrile at 80 °C. All complexes showed good catalytic activity with high selectivity to benzaldehyde. Complex 3 gave a conversion of 88% and a selectivity of 70% to benzaldehyde in 6 h. However, complexes 4 and 7-8 gave lower conversions of 48-74% but with higher (up to 90%) selectivity to benzaldehyde. Results from kinetics studies determined the activation energy for the catalytic oxidation reaction as 65 ± 3 kJ/mol, first order in catalyst and fractional order in the oxidant. Results from UV-visible and CV studies of the catalytic activity of the Ni-triazolylidene complexes on styrene oxidation did not indicate any clear possibility of generation of a Ni(II) to Ni(III) catalytic cycle.

Chemical composition and antimicrobial activity of hexane leaf extract of Anisopus mannii (Asclepiadaceae).

OBJECTIVE: The aim was to determine the chemical constituents and antimicrobial activity of the hexane leaf extract of Anisopus mannii against a wide range of human pathogenic microorganisms. METHODS: The chemical constituents of the hexane leaf extract was determined using gas chromatography-mass spectrometry (GC-MS) analysis; and the antimicrobial activity was evaluated on "standard strains", clinical susceptible and resistant bacterial and fungal isolates using the disc diffusion and broth microdilution methods. RESULTS: GC-MS analysis of the hexane leaf extract revealed 32 compounds, representing 73.8% of the identified components. The major compounds were hexadecanoic acid, ethyl ester (34%), oxirane, hexadecyl- (11%) and 9, 12, 15-octadecatrienoic acid, ethyl ester, (Z, Z, Z) (9.6%). Results from the antimicrobial activity demonstrated higher inhibition zones against Bacillus cereus (29 mm), followed by Streptococcus pyogenes (28 mm). Other notable inhibitions were observed with Enterococcus faecalis (27 mm), Proteus vulgaris (26 mm) and MRSA (25 mm). The MIC values ranged from 0.625 mg/mL to 1.25 mg/mL while the MBC/MFC values ranged from 2.5 mg/mL to 5.0 mg/mL. CONCLUSION: These results support the traditional use of the plant and demonstrate the huge potential of A. mannii as a source of antimicrobial compounds.

1-(4-Nitro-phen-yl)-1H-imidazol-3-ium chloride.

In the title salt, C9H8N3O2(+)·Cl(-), the least-squares planes of the imidazolium and benzene rings are almost coplanar, making a dihedral angle of 4.59 (1)°. In the crystal, the chloride anion links the organic mol-ecules through N-H⋯Cl hydrogen bonds, forming chains that run diagonally across the bc face, which compliment strong C-H⋯O hydrogen bonds between neighbouring mol-ecules. These chains are connected to adjacent chains through two weak C-H⋯Cl inter-actions, resulting in hydrogen-bonded sheets extending along the b and c axes. The absolute structure of the title compound was determined using a Flack x parameter of 0.00 (6) and a Hooft y parameter of 0.03 (2).

1-[4-(1H-imidazol-1-yl)phen-yl]ethanone monohydrate.

In the crystal structure of the title compound, C(11)H(10)N(2)O·H(2)O, the solvent water mol-ecule links the organic mol-ecules through O-H⋯O and O-H⋯N hydrogen bonds, forming chains that run diagonally across the bc face. These chains are connected to adjacent chains through weak C-H⋯O inter-actions, resulting in hydrogen-bonded sheets extending along the b and c axes. The sheets are connected along the a axis through π-π inter-actions, with centroid-centroid distances of 3.7571 (9) and 3.7231 (9) Å.