Photocytotoxic organometallic compounds

Organometallic compounds have recently found applications in medicinal chemistry and as diagnostic tools in chemical biology. Naturally occurring biomolecules, viz., cobalamine, NiFe hydrogenase, Acetyl-CoA synthase, etc., also contain metal-carbon bonds. Among organometallic compounds having medicinal importance, (arene)ruthenium complexes, radioactive technetium complexes and ferrocene conjugates are notable ones. Applications of photoactive organometallic complexes or metal complexes conjugated with an organometallic moiety are of recent origin. Photodynamic therapy (PDT) is a promising method to treat cancer cells in presence of light. This review primarily focuses on different aspects of the chemistry of organometallic complexes showing photocytotoxic activities. Half-sandwich tungsten, iron or ruthenium complexes are known to show photonuclease and/or photo-crosslinking activity. Photoinduced organometallic CO releasing molecules also exert photocytotoxic activity. Attempts have been made in this review to highlight the photocytotoxic behavior of various metal complexes when conjugated with a photoactive organometallic moiety, viz., ferrocene.

Bioactivity and mechanical properties of nickel-incorporated hydrogenated carbon nanocomposite thin films

In this paper, the influence of nickel incorporation on the mechanical properties and the in vitro bioactivity of hydrogenated carbon thin films were investigated in detail. Amorphous hydrogenated carbon (a-C : H) and nickel-incorporated hydrogenated carbon (Ni/a-C : H) thin films were deposited onto the Si substrates by using reactive biased target ion beam deposition technique. The films' chemical composition, surface roughness, microstructure and mechanical properties were investigated by using XPS, AFM, TEM, nanoindentation and nanoscratch test, respectively. XPS results have shown that the film surface is mainly composed of nickel, nickel oxide and nickel hydroxide, whereas at the core is nickel carbide (Ni3C) only. The presence of Ni3C has increased the sp(2) carbon content and as a result, the mechanical hardness of the film was decreased. However, Ni/a-C : H films shows very low friction coefficient with higher scratch-resistance behavior than that of pure a-C : H film. In addition, in vitro bioactivity study has confirmed that it is possible to grow dense bone-like apatite layer on Ni/a-C : H films. Thus, the results have indicated the suitability of the films for bone-related implant coating applications. Copyright (C) 2011 John Wiley & Sons, Ltd.

Synthesis and characterization of cobalt(II), nickel(II), copper(II) and zinc(II) complexes of 2-nitrobenzoic acid with methyl carbazate as ancillary ligand. Crystal structure of the copper(II) complex

Divalent metal complexes of general formula M(2-nb)(2)(mc)(2)].2(2-nbH), where M = Co(II), Ni(II), Cu(II) or Zn(II), 2-nbH = 2-nitrobenzoic acid and mc = methyl carbazate (NH2NHCOOCH3), have been prepared and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray study of the Cu(II) complex revealed that the molecule is centrosymmetric, with two N,O-chelating mc ligands in equatorial positions and a pair of monodentate 2-nb anions in the axial positions. The lattice 2-nbH molecules help to establish the packing of monomers through hydrogen-bonding interactions. Thermal stability and reactivity of the complexes were studied by TG-DTA. Emission studies show that these complexes are fluorescent.

Estimation of vapour pressure and partial pressure of subliming compounds by low-pressure thermogravimetry

A method for the estimation of vapour pressure and partial pressure of subliming compounds under reduced pressure, using rising temperature thermogravimetry, is described in this paper. The method is based on our recently developed procedure to estimate the vapour pressure from ambient pressure thermogravimetric data using Langmuir equation. Using benzoic acid as the calibration standard, vapour pressure temperature curves are calculated at 80, 160 and 1000 mbar for salicylic acid and vanadyl bis-2,4-pentanedionate, a precursor used for chemical vapour deposition of vanadium oxides. Using a modification of the Langmuir equation, the partial pressure of these materials at different total pressures is also determined as a function of temperature. Such data can be useful for the deposition of multi-metal oxide thin films or doped thin films by chemical vapour deposition (CVD).

Reduction of aromatic nitro compounds to amines using zinc and aqueous chelating ethers: Mild and efficient method for zinc activation

A mild, environmentally friendly method for reduction of aromatic nitro group to amine is reported, using zinc powder in aqueous solutions of chelating ethers. The donor ether acts as a ligand and also serves as a co-solvent. Water is the proton source. This procedure is also a new method for the activation of zinc for electron transfer reduction of aromatic nitro compounds. The reduction is accomplished in a neutral medium and other reducing groups remained unaffected. The ethers used are dioxolane, 1,4-dioxane, ethoxymethoxyethane, dimethoxymethane, 1,2-dimethoxyethane, and diglyme.

Deformation-induced thermally activated grain growth in nanocrystalline nickel

Grain growth during indentation at low temperatures has been taken to imply that grain growth is largely stress induced and athermal in nanometals. Indentation experiments on electrodeposited nano-Ni indicate clearly that the load required for grain growth decreases with an increase in temperature, suggesting strongly that concurrent grain growth is thermally activated. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Deformation and Recrystallization texture evolution in Nano-crystalline Nickel

Deformation and recrystallization textures in nano-crystalline nickel with average grain size of 20 nm were investigated using X-ray diffraction, electron microscopy and differential scanning calorimetry. The deformation behaviour of nano-crystalline nickel is quite complicated due to intervention of other deformation mechanisms like grain boundary sliding and restoration mechanisms like grain growth and grain rotation to dislocation mediated slip. Recrystallization studies carried out on the deformed nano-crystalline nickel showed that the deformation texture was retained during low temperature annealing (300 degrees C), while at higher temperature (1000 degrees C), the texture got randomised. The exact mechanism of texture formation during deformation and recrystallization has been discussed.

Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of O-1(2) generation and its promising role in anti-tumor activity

In the present investigation, a Schiff base N'(1),N'(3)-bis(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-d icarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant K-b of 2.6 x 10(4) M-1, 5.7 x 10(4) M-1 and 4.5 x 10(4) M-1, respectively and they exhibited potent photo-damage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions. (C) 2012 Elsevier B.V. All rights reserved.

Synthesis and characterization of nickel/barium hexa-aluminate composite coatings

Electrodeposition of nickel/barium hexa-aluminate (Ni/BHA) composite coatings has been carried out from a Watt's bath on mild steel substrate. BHA powders with plate habit were synthesized by solution combustion synthesis followed by heat treatment to ensure complete conversion to the hexa-aluminate phase. Heat treated material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with X-ray analysis. The dispersion behaviour and stability of BHA suspensions with cationic and anionic surfactants at room temperature were studied by dynamic light scattering under different pH. The influence of BHA concentration in the electrolytic bath, deposition temperature, pH, current density and duty cycle on particle incorporation in the coatings were studied and conditions for maximum particle incorporation were established. Coatings with a roughness of about 0 center dot 4 mu m were produced by using this technique. Effect of BHA content on microhardness was also investigated. A reasonably good thickness of the coatings was achieved in a given set of conditions.

Mixed-ligand nickel(II) thiosemicarbazone complexes: Synthesis, characterization and biological evaluation

The syntheses and characterization of some new mixed-ligand nickel(II) complexes {Ni(L-1)(PPh3)] (1), Ni(L-1)(Py)] (2), Ni(L-2)(PPh3)]center dot DMSO (3), Ni(L-2)(Imz)] (4), Ni(L-3)(4-pic)] (5) and RNi(L-3))(2)(mu-4,4'-byp)]center dot 2DMSO (6)1 of three selected thiosemicarbazones the 4-(p-X-phenyl)thiosemicarbazones of salicylaldehyde) (H2L1-3) (A, Scheme 1) are described in the present study, differing in the inductive effect of the substituent X (X = F, Br and OCH3), in order to observe its influence, if any, on the redox potentials and biological activity of the complexes. All the synthesized ligands and the metal complexes were successfully characterized by elemental analysis, IR, UV-Vis, NMR spectroscopy and cyclic voltammetry. The molecular structures of four mononuclear (1-3 and 5) and one dinuclear (6) Ni(II) complex have been determined by X-ray crystallography. The complexes have been screened for their antibacterial activity against Escherichia coli and Bacillus. The minimum inhibitory concentrations of these complexes and their antibacterial activities indicate that compound 4 is the potential lead molecule for drug designing. (C) 2012 Elsevier Ltd. All rights reserved.

Photophysical behavior of poly(propyl ether imine) dendrimer in the presence of nitroaromatic compounds

This paper deals with a study of the photophysical property of poly(ether imine) (PETIM) dendritic macromolecule in the presence of aromatic compounds. The inherent photoluminescence property of the dendrimer undergoes quenching in the presence of guest aromatic nitro-compounds. From life-time measurements study, it is inferred that the lifetimes of luminescent species of the dendrimer are not affected with nitrophenols as guest molecules, whereas nitrobenzenes show a marginal change in the lifetimes of the species. Raman spectral characteristic of the macromolecular host-guest complex is conducted in order to identify conformational change of the dendrimer and a significant change in the stretching frequencies of methylene moieties of the dendrimer is observed for the complex with 1,3,5-trinitrobenzene, when compared to other complexes, free host and guest molecules. The photophysical behavior of electron-rich, aliphatic, neutral dendritic macromolecule in the presence of electron-deficient aromatic molecules is illustrated in the present study. (C) 2012 Elsevier B.V. All rights reserved.