R. Karvembu

Synthesis, characterization and catalytic activities of ruthenium complexes containing triphenylphosphine/triphenylarsine and tetradentate Schiff bases

Abstract Ruthenium(II) complexes of the type [Ru(CO)(B)(L)] (B=AsPh3, pyridine, piperidine or morpholine; L=dianion of tetradentate Schiff bases) have been synthesized and characterized by physico-chemical methods. These complexes are found to be effective catalysts in the oxidation of primary and secondary alcohols using N-methylmorpholine-N-oxide as oxidant. The catalytic activity of these triphenylarsine complexes have been compared with that of triphenylphosphine complexes and with similar ruthenium(III) complexes. The formation of high valent Run+2O species as catalytic intermediate is proposed for the catalytic processes.

Abatement of mixture of volatile organic compounds (VOCs) in a catalytic non-thermal plasma reactor

Total oxidation of mixture of dilute volatile organic compounds was carried out in a dielectric barrier discharge reactor with various transition metal oxide catalysts integrated in-plasma. The experimental results indicated the best removal efficiencies in the presence of metal oxide catalysts, especially MnO(x), whose activity was further improved with AgO(x) deposition. It was confirmed water vapor improves the efficiency of the plasma reactor, probably due to the formation of hydroxyl species, whereas, in situ decomposition of ozone on the catalyst surface may lead to nascent oxygen. It may be concluded that non-thermal plasma approach is beneficial for the removal of mixture of volatile organic compounds than individual VOCs, probably due to the formation of reactive intermediates like aldehydes, peroxides, etc.

Synthesis and spectral studies of binuclear ruthenium(II) carbonyl complexes containing bis(β-diketone) and their applications

Abstract A series of new binuclear ruthenium(II) complexes of the type {[RuX(CO)(AsPh 3 ) 2 ] 2 L} (X=H or Cl; L=bis-β-diketone) have been synthesised by reacting [RuHX(CO)(AsPh 3 ) 3 ] (X=H or Cl) with various bis(β-diketones) of the general formula [(RCO)(R′CO)CHCH(R″)CH(COR)(COR′)] (R=CH 3 or C 6 H 5 ; R′=CH 3 or C 6 H 5 ; R″=H, C 6 H 5 , 4-(CH 3 )C 6 H 4 , 4-(OCH 3 )C 6 H 4 or 4-N(CH 3 ) 2 C 6 H 4 ) in 2:1 molar ratio in benzene. An octahedral structure has been tentatively proposed for all the new ligand bridged binuclear complexes. The new complexes have been subjected to the antibacterial and catalytic activity studies.

Synthetic, catalytic and biological studies of new binuclear ruthenium(II) complexes containing thiobis(β-diketones) and triphenylphosphine

Abstract A convenient synthesis of binuclear ruthenium(II) complexes of the type {[RuCl(CO)(PPh3)(B)]2(bis-β-dk)} (where B=PPh3, py, pip or mor; bis-β-dk=thiobis(β-diketonato ion) was accomplished by reacting [RuHCl(CO)(PPh3)2(B)] (where B=PPh3, py, pip or mor) with thiobis-β-diketones in benzene. The new compounds have been characterised by elemental analysis, IR, electronic, 1H and 31P NMR spectral data. The ruthenium(II) complexes were found to be efficient catalysts for the oxidation of primary alcohol to aldehyde in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant. The ligands and its ruthenium(II) complexes show growth inhibitory activity against the bacteria Escherichia coli, Bacillus sp. and Pseudomonas sp.

Monodentate coordination of N-[di(phenyl/ethyl)carbamothioyl]benzamide ligands: synthesis, crystal structure and catalytic oxidation property of Cu(I) complexes

New four-coordinated tetrahedral copper(I) complexes have been synthesized from the reactions between [CuCl(2)(PPh(3))(2)] and N-(diphenylcarbamothioyl)benzamide (HL1) or N-(diethylcarbamothioyl)benzamide (HL2) in benzene. These complexes have been characterized by elemental analyses, IR, UV/Vis, (1)H, (13)C and (31)P NMR spectroscopy. The molecular structure of both the complexes, [CuCl(HL1)(2)(PPh(3))] (1) and [CuCl(HL2)(PPh(3))(2)] (2) were determined by single-crystal X-ray diffraction, which reveals distorted tetrahedral geometry around each Cu(I) ion. The combination of 2 (0.005 mmol) with hydrogen peroxide (2.5 mmol) in acetonitrile is found to be an active catalyst for the oxidation of primary and secondary alcohols (0.5 mmol) to their corresponding acids and ketones, respectively, at room temperature.

Noble metal/functionalized cellulose nanofiber composites for catalytic applications.

In this study, cellulose acetate nanofibers (CANFs) with a mean diameter of 325 ± 2.0 nm were electrospun followed by deacetylation and functionalization to produce anionic cellulose nanofibers (f-CNFs). The noble metal nanoparticles (RuNPs and AgNPs) were successfully decorated on the f-CNFs by a simple wet reduction method using NaBH4 as a reducing agent. TEM and SEM images of the nanocomposites (RuNPs/CNFs and AgNPs/CNFs) confirmed that the very fine RuNPs or AgNPs were homogeneously dispersed on the surface of f-CNFs. The weight percentage of the Ru and Ag in the nanocomposites was found to be 13.29 wt% and 22.60 wt% respectively; as confirmed by SEM-EDS analysis. The metallic state of the Ru and Ag in the nanocomposites was confirmed by XPS and XRD analyses. The usefulness of these nanocomposites was realized from their superior catalytic activity. In the aerobic oxidation of benzyl alcohol to benzaldehyde, the RuNPs/CNFs system gave a better yield of 89% with 100% selectivity. Similarly, the AgNPs/CNFs produced an excellent yield of 99% (100% selectivity) in the aza-Michael reaction of 1-phenylpiperazine with acrylonitrile. Mechanism has been proposed for the catalytic systems.

Catalytic and antimicrobial activities of new ruthenium(II) unsymmetrical Schiff base complexes

Hexa-coordinated ruthenium(II) complexes of the type [Ru(CO)(PPh3)(Z)(L)] [Z = PPh3, pyridine (py) or piperidine (pip); L = anion of the Schiff base] have been prepared by reacting [RuHCl(CO)(PPh3)2(Z)] with tridentate Schiff bases derived by condensing anthranilic acid with acetylacetone, salicylaldehyde, o-vanillin and o-hydroxyacetophenone. The complexes were characterised by analytical and spectral (i.r., electronic, 1H- and 31P-n.m.r.) data, and were found to be effective catalysts for oxidising primary alcohols to aldehydes in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant. The Schiff bases and their ruthenium(II) complexes show growth inhibitory activity against pathogenic fungi Aspergillus flavus, Fusarium oxysporium and Rhizoctonia solani.

Synthesis, DNA/protein binding, molecular docking, DNA cleavage and in vitro anticancer activity of nickel(II) bis(thiosemicarbazone) complexes

A series of N-substituted isatin thiosemicarbazone ligands (L1–L5) and their nickel(II) complexes [Ni(L)2] (1–5) were synthesized and characterized by elemental analyses and UV-Visible, FT-IR, 1H & 13C NMR, and mass spectroscopic techniques. The molecular structure of the ligands (L1 and L2) and complex 1 was confirmed by single crystal X-ray crystallography. The single crystal X-ray structure of 1 showed distorted octahedral geometry. The interaction of calf thymus (CT) DNA and bovine serum albumin (BSA) with the nickel(II) complexes was explored using absorption and emission spectral methods. A DNA cleavage study showed that the complexes cleaved DNA without any external agents. The alterations in the secondary structure of the protein by the nickel(II) complexes (1–5) were confirmed by synchronous and three dimensional fluorescence spectroscopic studies. The interaction of the complexes with DNA/protein also has been supported by molecular docking studies. An in vitro cytotoxicity study of the complexes found significant activity against human breast (MCF7) and lung (A549) cancer cell lines, with the best results for complexes 4 and 2 respectively, where the IC50 value is less than 0.1 μM concentration.

Ruthenium(II) carbonyl complexes with N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives and triphenylphosphine as effective catalysts for oxidation of alcohols

Ruthenium(II) complexes, [RuCl(L)(CO)(PPh3)2] {where L = N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives}, are prepared from reaction between [RuHCl(CO)(PPh3)3] and N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives in toluene and characterized by elemental analysis and spectral data (electronic, infrared, 1H NMR, and 31P NMR). The combination of [RuCl(L)(CO)(PPh3)2] (0.01 mmol) and N-methylmorpholine-N-oxide (NMO) (3 mmol) is an active catalyst for the oxidation of primary, secondary, cyclic, allylic, aliphatic, and benzylic alcohols to their corresponding aldehydes and ketones at room temperature. The oxidation protocol is simple to operate and gives the corresponding carbonyl compounds good to excellent yields.

Thiobis(β-diketonato)-bridged binuclear ruthenium(III) complexes containing triphenylphosphine or triphenylarsine. Synthetic, spectral, catalytic and antimicrobial studies

Hexacoordinated binuclear ruthenium(III) complexes of the type {[RuX2(EPh3)2]2(bis-β-dk)} [X = Cl or Br; bis-β-dk = thiobis(β-diketone)] have been prepared by reacting [RuCl3(PPh3)3], [RuCl3(AsPh3)3], [RuBr3(AsPh3)3] or [RuBr3(PPh3)2(MeOH)] with thiobis(β-diketones) in a 2:1 molar ratio in benzene, and characterized by analytical, spectroscopic (i.r., electronic e.p.r.) and cyclic voltammetric data. An octahedral structure has been proposed. The complexes are effective catalysts for the oxidation of PhCH2OH and cyclohexanol to PhCHO and cyclohexanone respectively using N-methylmorpholine-N-oxide as co-oxidant. Some of the complexes have been subjected to antifungal activity studies.