Ruthenium(II) Complexes of O,N-donor Schiff base ligands and their use as catalytic organic oxidants

Synthesis, Characterization, Computational and Biological Activity of Some Schiff Bases and Their Fe, Cu and Zn Complexes

Four new symmetrical Schiff bases derived from 2,2′-diamino-6,6′-dibromo-4,4′-dimethyl-1,1′-biphenyl or 2,2′-diamino-4,4′-dimethyl-1,1′-biphenyl, and 3,5-dichloro- or 5-nitro-salicylaldehyde, were synthesized and reacted with copper-, iron- and zinc-acetate, producing the corresponding complexes. The Schiff bases and their metal complexes were characterized by 1H-, 13C-NMR, IR and UV-Vis spectroscopy and elemental analysis. The structures of one Schiff base and the two zinc complexes were resolved by X-ray structure determination. Density functional theory (DFT) calculations at the B3LYP/6-31G(d) level of the latter compounds were carried out to optimize and examine their molecular geometries. The biomedical applications of the Schiff bases and their complexes were investigated as anticancer or antimicrobial agents.

Ruthenium(II) complexes containing quinone based ligands: synthesis, characterization, catalytic applications and DNA interaction

1,2-Naphthaquinone reacts with amines such as semicarbazide, isonicotinylhydrazide and thiosemicarbazide in high yield procedure with the formation of tridentate ligands HL(n) (n=1-3). By reaction of ruthenium(II) starting complexes and quinone based ligands HL(n) (n=1-3), a series of ruthenium complexes were synthesized and characterized by elemental and spectroscopic methods (FT-IR, electronic, (1)H, (13)C, (31)P NMR and ESI-MS). The ligands were coordinated to ruthenium through quinone oxygen, imine nitrogen and enolate oxygen/thiolato sulfur. On the basis of spectral studies an octahedral geometry may be assigned for all the complexes. Further, the catalytic oxidation of primary, secondary alcohol and transfer hydrogenation of ketone was carried out. The DNA cleavage efficiency of new complexes has also been tested.

Ruthenium(II) hydrazone Schiff base complexes: synthesis, spectral study and catalytic applications

Ruthenium(II) hydrazone Schiff base complexes of the type [RuCl(CO)(B)(L)] (were B=PPh(3), AsPh(3) or Py; L=hydrazone Schiff base ligands) were synthesized from the reactions of hydrazone Schiff base ligand (obtained from isonicotinoylhydrazide and different hydroxy aldehydes) with [RuHCl(CO)(EPh(3))(2)(B)] (where E=P or As; B=PPh(3), AsPh(3) or Py) in 1:1 molar ratio. All the new complexes have been characterized by analytical and spectral (FT-IR, electronic, (1)H, (13)C and (31)P NMR) data. They have been tentatively assigned an octahedral structure. The synthesized complexes have exhibited catalytic activity for oxidation of benzyl alcohol to benzaldehyde and cyclohexanol to cyclohexanone in the presence of N-methyl morpholine N-oxide (NMO) as co-oxidant. They were also found to catalyze the transfer hydrogenation of aliphatic and aromatic ketones to alcohols in KOH/Isopropanol.

Phenoxide bridged tetranuclear Co(II), Ni(II), Cu(II) and Zn(II) complexes: electrochemical, magnetic and antimicrobial studies

Phenoxide bridged later first row transition metal(II) complexes have been prepared by the interaction of later 3d transition metal(II) chlorides with tetranucleating compartmental Schiff base ligand system derived from 2,6-diformyl-4-methylphenol, p-phenylenediamine and 2-hydrazinobenzothiazole. Ligand and complexes were characterized by analytical, spectral (IR, UV-visible, ESR, FAB-mass and fluorescence), magnetic and thermal studies. All complexes are found to have octahedral geometry. The mutual influence of metal centres in terms of cooperative effect on the electronic, magnetic, electrochemical and structural properties was investigated. The Schiff base and its complexes have been screened for their antibacterial (against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa) and antifungal activities (against Aspergillus niger, and Candida albicans).

Synthesis, Characterization, and Electrochemical Study of Tetradentate Ruthenium-Schiff Base Complexes: Dioxygen Activation with a Cytochrome P450 Model Using 1- or 2-Methylimidazole as Axial Bases

Salicylaldehyde, 2-hydroxyacetophenone, and 3,5-dichlorosalicylaldehyde react with 1,2-diaminoethane to give three symmetrical Schiff bases H2L1, H2L2, and H2L3, respectively. With Ru(III) ions, these ligands lead to three complexes: Ru(III)ClL1 (1), Ru(III)ClL2 (2), and Ru(III)ClL3 (3). The purity of these compounds was estimated by TLC technique and microanalysis while their structures were supported by the usual spectroscopic methods such as NMR, infrared, and electronic spectra. The cyclic voltammetry in acetonitrile showed irreversible waves for all three ligands. Under the same experimental conditions, it was proved that the ruthenium is coordinated in the three complexes 1, 2, and 3 showing quasireversible redox systems. The behavior of these complexes and their comparison with cytochrome P450 are investigated using them as catalysts in the presence of molecular oxygen with an apical nitrogen base: 1- or 2-methylimidazole.

Synthesis, spectral characterization and catalytic studies of new ruthenium(II) chalcone thiosemicarbazone complexes

A series of new hexa-coordinated ruthenium(II) complexes of the type [Ru(CO)(EPh3)(B)(L)] (E = P or As; B = PPh3, AsPh3 or Py; L = chalcone thiosemicarbazone) have been prepared by reacting [RuHCl(CO)(EPh3)2(B)] (E = P or As; B = PPh3, AsPh3 or Py) with chalcone thiosemicarbazones in benzene under reflux. The new complexes have been characterized by analytical and spectroscopic (IR, UV-vis, 1H, 31P and 13C NMR) methods. On the basis of data obtained, an octahedral structure was assigned for all of the complexes. The chalcone thiosemicarbazones behave as dianionic tridentate O, N, S donors and coordinate to ruthenium via the phenolic oxygen of chalcone, the imine nitrogen of thiosemicarbazone and thienol sulfur. The new complexes exhibit catalytic activity for the oxidation of primary and secondary alcohols to their corresponding aldehydes and ketones and they were also found to be efficient catalysts for the transfer hydrogenation of carbonyl compounds.

Ruthenium(II) chalconate complexes: Synthesis, characterization, catalytic, and biological studies

A series of new hexa-coordinated ruthenium(II) carbonyl complexes of the type [RuCl(CO)(EPh(3))(B)(L)] (E = P or As; B = PPh(3), AsPh(3) or Py; L = 2'-hydroxychalcones) have been prepared by reacting [RuHCl(CO)(EPh(3))(2)(B)] (E = P or As; B = PPh(3), AsPh(3) or Py) with 2'-hydroxychalcones in benzene under reflux. The new complexes have been characterized by analytical and spectral (IR, electronic, (1)H, (31)P and (13)C NMR) data. Based on the above data, an octahedral structure has been assigned for all the complexes. The new complexes exhibit catalytic activity for the oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N-methylmorpholine-N-oxide (NMO) as co-oxidant and also found efficient catalyst in the transfer hydrogenation of ketones. The antifungal properties of the complexes have also been examined and compared with standard Bavistin.

Binuclear ruthenium(III) Schiff base complexes bearing N(4)O(4) donors and their catalytic oxidation of alcohols

An interesting series of binuclear ruthenium(III) Schiff base complexes bearing bis-salophen/bis-naphophen units of the general composition [(EPh(3))(X)Ru-L-Ru(X)(EPh(3))] (where E=P or As; X=Cl or Br; L=binucleating dianionic tetradentate ligands) have been synthesized and characterized by analytical (elemental analysis, magnetic susceptibility measurements), spectral (FT-IR, UV-vis and EPR) and electrochemical methods. These ruthenium(III) complexes have two N(2)O(2) metal binding sites, which are linked to each other with a biphenyl bridge and acts as potential catalyst for oxidation of wide range of primary and secondary alcohols to corresponding aldehydes or ketones with moderate to high conversion in the presence of N-methylmorpholine-N-oxide (NMO). The formation of high-valent Ru(V)=O species as a catalytic active intermediate is proposed for the catalytic processes.

Luminescent property and catalytic activity of Ru(II) carbonyl complexes containing N, O donor of 2-hydroxy-1-naphthylideneimines

The reaction of the chelating ligands (obtained by the condensation of 2-hydroxy-1-naphthaldehyde with various primary amines) with [RuHCl(CO)(EPh(3))(2)(B)] (where E=P; B=PPh(3), py or pip: E=As; B=AsPh(3)) in benzene afforded new stable ruthenium(II) carbonyl complexes of the general formula [Ru(Cl)(CO)(EPh(3))(B)(L)] (L=anion of bidentate Schiff bases). The structure of the new complexes was investigated using elemental analyses, spectral (FT-IR, UV-vis and (1)H NMR) and electrochemical studies and is found to be octahedral. All the metal complexes exhibit characteristic MLCT absorption and luminescence bands in the visible region. The luminescence efficiency of the ruthenium(II) complexes was explained based on the ligand environment around the metal ion. These complexes catalyze oxidation of primary and secondary alcohols into their corresponding carbonyl compounds in the presence of N-methylmorpholine-N-oxide (NMO) as the source of oxygen. The formation of high valent Ru(IV)=O species as a catalytic intermediate is proposed for the catalytic process.

Luminescent property and catalytic activity of Ru(II) carbonyl complexes containing N, O donor of 2-hydroxy-1-naphthylideneimines

The reaction of the chelating ligands (obtained by the condensation of 2-hydroxy-1-naphthaldehyde with various primary amines) with [RuHCl(CO)(EPh3)2(B)] (where E=P; B=PPh3, py or pip: E=As; B=AsPh3) in benzene afforded new stable ruthenium(II) carbonyl complexes of the general formula [Ru(Cl)(CO)(EPh3)(B)(L)] (L=anion of bidentate Schiff bases). The structure of the new complexes was investigated using elemental analyses, spectral (FT-IR, UV-vis and 1H NMR) and electrochemical studies and is found to be octahedral. All the metal complexes exhibit characteristic MLCT absorption and luminescence bands in the visible region. The luminescence efficiency of the ruthenium(II) complexes was explained based on the ligand environment around the metal ion. These complexes catalyze oxidation of primary and secondary alcohols into their corresponding carbonyl compounds in the presence of N-methylmorpholine-N-oxide (NMO) as the source of oxygen. The formation of high valent Ru(IV)=O species as a catalytic intermediate is proposed for the catalytic process.

Catalytic and biological activities of Ru(III) mixed ligand complexes containing N,O donor of 2-hydroxy-1-naphthylideneimines

A series of stable low spin Ru(III) complexes of the type [RuX2(EPh3)2(L)] (where E = P or As; X = Cl or Br; L = mono basic bidentate Schiff bases) have been synthesized and were characterized by analytical, spectral and electrochemical data. A distorted octahedral geometry has been proposed for all the complexes. These complexes catalyze oxidation of primary alcohols and secondary alcohol with high yields in the presence of N-methylmorpholine-N-oxide (NMO). The ruthenium(III) Schiff base complexes show growth inhibitory activity against the bacteria Staphylococcus aureus (209p) and E. coli ESS (2231).