Rajendran Manikandan

Synthesis, characterization and crystal structure of cobalt(III) complexes containing 2-acetylpyridine thiosemicarbazones: DNA/protein interaction, radical scavenging and cytotoxic activities

The synthesis, structure and biological studies of cobalt(III) complexes supported by NNS-tridentate ligands are reported. Reactions of 2-acetylpyridine N-substituted thiosemicarbazone (HL(1-3)) with [CoCl2(PPh3)2] resulted [Co(L(1-3))2]Cl (1-3) which were characterized by elemental analysis and various spectral studies. The molecular structure of the complex 1 has been determined by single crystal X-ray diffraction studies. In vitro DNA binding studies of complexes 1-3 carried out by fluorescence studies and the results revealed the binding of complexes to DNA via intercalation. The binding constant (Kb) values of complexes 1-3 from fluorescence experiments showed that the complex 3 has greater binding propensity for DNA. The DNA cleavage activity of the complexes 1 and 3 were ascertained by gel electrophoresis assay which revealed that the complexes are good DNA cleavage agents. Further, the interactions of the complexes with bovine serum albumin (BSA) were also investigated using fluorescence spectroscopic method, which showed that the complexes 1-3 could bind strongly with BSA. The antioxidant property of the complexes was evaluated to test their free-radical scavenging ability. Furthermore, in vitro cytotoxicity of the complexes against MCF-7 and A431 cell lines was assayed which showed higher activity and efficiently vanished the cancer cells even at low concentrations.

Ruthenium(III) S-methylisothiosemicarbazone Schiff base complexes bearing PPh3/AsPh3 coligand: Synthesis, structure and biological investigations, including antioxidant, DNA and protein interaction, and in vitro anticancer activities

New Ru(III) isothiosemicarbazone complexes [RuCl(EPh3)L(1-4)] (E=P or As) were obtained from the reactions between [RuCl3(EPh3)3] and bis(salicylaldehyde)-S-methylisothiosemicarbazone (H2L(1-3))/bis(2-hydroxy-naphthaldehyde)-S-methylisothiosemicarbazone (H2L(4)) ligands. The new complexes were characterized by using elemental analyses and various spectral (UV-Vis, IR, (1)H NMR, FAB-Mass and EPR) methods. The redox properties of the complexes were studied by using cyclic voltammetric method. The new complexes were subjected to various biological investigations such as antioxidant assays involving DPPH radical, hydroxyl radical, nitric oxide radical and hydrogen peroxide, DNA/protein interaction studies and in vitro cytotoxic studies against human breast cancer cell line (MCF-7). New complexes showed excellent free radicals scavenging ability and could bind with DNA via intercalation. Protein binding studies using fluorescence spectroscopy showed that the new complexes could bind strongly with bovine serum albumin (BSA). Photo cleavage experiments using DNA of E-coli bacterium exhibited the DNA cleavage ability of the complexes. Further, the in vitro anticancer activity studies on the new complexes against MCF-7 cell line exhibited the ability of Ru(III) isothiosemicarbazone complexes to suppress the development of malignant neoplastic disease cells.

Evaluation of DNA-binding, radical scavenging and cytotoxic activity of five coordinated Cd(II) complexes containing 2-acetylpyridine-N4-substituted thiosemicarbazone

A series of new five coordinated Cd(II) complexes of the type [Cd(Ln)Cl2] (n = 1–3) have been isolated and characterized using analytical, spectral and structural methods. The single crystal X-ray structure of one of the complexes [Cd(L2)Cl2] (2) has been determined and a distorted square pyramidal geometry has been found, in which Cd(II) is coordinated with two nitrogens, one sulfur and two chlorine atoms. The interactions of the complexes with calf thymus DNA (CT-DNA) have been explored by absorption, competitive, thermal denaturation and viscometric methods, which revealed that the compounds could interact with CT-DNA through groove binding. Investigation of the antioxidant properties showed that the Cd(II) complexes have a strong radical scavenging tendency against DPPH˙, OH˙ and NO˙ radicals. Further, the cytotoxic effect of the compounds examined on a human breast cancer cell line (MCF-7) showed that the complexes exhibited substantial cytotoxic activity.

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.

Ruthenium(II) carbonyl complexes bearing quinoline-based NNO tridentate ligands as catalyst for one-pot conversion of aldehydes to amides and o-allylation of phenols

Six new octahedral ruthenium(II) carbonyl complexes having the general molecular formula [RuCl(CO)(B)L(1-2)] (B = PPh3, AsPh3 or py; L(1-2) = quinoline based NNO ligand) were synthesized. The quinoline based ligands behave as monoanionic tridentate donor and coordinated to ruthenium via ketoenolate oxygen, azomethine nitrogen and quinoline nitrogen. The composition of the complexes has been established by elemental analysis and spectral methods (FT-IR, electronic, (1)H NMR, (13)C NMR, (31)P NMR and ESI-Mass). The complexes were used as efficient catalysts for one-pot conversion of various aldehydes to their corresponding primary amides in presence of NH2OH · HCl and NaHCO3. The effect of catalyst loading and reaction temperature on catalytic activity of the ruthenium(II) carbonyl complexes were also investigated. The synthesized complexes also possess good catalytic activity for the o-allylation of phenols in the presence of K2CO3 under mild conditions. The complexes afforded branched allyl aryl ethers according to a regioselective reaction.

Coordination behavior of ligand based on NNS and NNO donors with ruthenium(III) complexes and their catalytic and DNA interaction studies

Reactions of 2-acetylpyridine-thiosemicarbazone HL(1), 2-acetylpyridine-4-methyl-thiosemicarbazone HL(2), 2-acetylpyridine-4-phenyl-thiosemicarbazone HL(3) and 2-acetylpyridine-semicarbazone HL(4) with ruthenium(III) precursor complexes were studied and the products were characterized by analytical and spectral (FT-IR, electronic, EPR and EI-MS) methods. The ligands coordinated with the ruthenium(III) ion via pyridine nitrogen, azomethine nitrogen and thiolate sulfur/enolate oxygen. An octahedral geometry has been proposed for all the complexes based on the studies. All the complexes are redox active and display an irreversible and quasireversible metal centered redox processes. Further, the catalytic activity of the new complexes has been investigated for the transfer hydrogenation of ketones in the presence of isopropanol/KOH and the Kumada-Corriu coupling of aryl halides with aryl Grignard reagents. The DNA cleavage efficiency of new complexes has also been tested.

Palladium(II) 9,10-phenanthrenequinone N-substituted thiosemicarbazone/semicarbazone complexes as efficient catalysts for N-arylation of imidazole

A series of palladium complexes, [PdCl(L1–4)] (1–4) (L1 = 9,10-phenanthrenequinone thiosemicarbazone, L2 = 9,10-phenanthrenequinone methylthiosemicarbazone, L3 = 9,10-phenanthrenequinone phenylthiosemicarbazone, and L4 = 9,10-phenanthrenequinone semicarbazone), have been synthesized and characterized by elemental analyses, UV–vis, FT-IR, 1H and 13C NMR, and ESI-Mass spectroscopic methods. The catalytic efficiency of the synthesized complexes was examined against N-arylation of imidazole. The system works well with the electron-rich, -neutral, and -deficient aryl halides to afford the products in good to excellent yields. Sterically congested aryl halides and heteroaryl halides have also been used as substrates to provide N-arylated heterocycles. In addition, this methodology can be applicable to other substrates with N-containing heterocycles. Graphical abstract Palladium(II) 9,10-phenanthrenequinone N-substituted thiosemicarbazone/semicarbazone complexes as efficient catalysts for N-arylation of imidazole

Nickel(II) complexes containing ONS donor ligands: Synthesis, characterization, crystal structure and catalytic application towards C-C cross-coupling reactions

AbstractNickel(II) complexes containing thiosemicarbazone ligands [Ni(L)2] (1-3) (L = 9,10-phenanthrenequinonethiosemicarbazone (HL1), 9,10-phenanthrenequinone-N-methylthio semicarbazone (HL2) and 9, 10-phenanthrenequinone-N-phenylthiosemicarbazone (HL3)) have been synthesized and characterized by elemental analysis and spectroscopic (IR, UV-Vis, 1H, 13C-NMR and ESI mass) methods. The molecular structures of complexes 1 and 2 were identified by means of single-crystal X-ray diffraction analysis. The analysis revealed that the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate ONS fashion. The catalytic activity of complexes towards some C–C coupling reactions (viz., Kumada-Corriu, Suzuki-Miyaura and Sonogashira) has been examined. The complexes behave as efficient catalysts in the Kumada-Corriu and Sonogashira coupling reactions rather than Suzuki-Miyaura coupling. Graphical AbstractNickel(II) complexes bearing 9,10-phenanthrenequinone N-substituted thiosemicarbazone ligands were synthesized and characterized. The X-ray crystal structure of the complexes revealed a distorted octahedral geometry around the metal centre. These nickel complexes exhibited better catalytic activity in Kumada-Corriu and Sonogashira cross-coupling reactions than in Suzuki-Miyaura reaction.

Efficient and versatile catalysis for β-alkylation of secondary alcohols through hydrogen auto transfer process with newly designed ruthenium(II) complexes containing ON donor aldazine ligands

Abstract A new series of ruthenium(II) carbonyl complexes, [RuCl(CO)(EPh3)2(L1-2)] (1–4) (E = P or As; H2L1 = salicylaldazine, H2L2 = 2-hydroxynaphthaldazine), have been assembled from ruthenium(II) precursors [RuHCl(CO)(EPh3)3] and bidentate ON donor Schiff base ligands (H2L1-2). Both ligands and their new ruthenium(II) complexes have been characterized by elemental analyses, spectroscopic methods (UV, IR, NMR (1H, 13C, 31P) as well as ESI mass spectrometry. The molecular structures of H2L1 and 1 have been confirmed by single crystal X-ray diffraction. Based on the above studies, an octahedral coordination geometry around the metal center has been proposed for 1–4. To investigate the catalytic effectiveness of 1–4, the complexes have been used as catalysts in β-alkylation of secondary alcohols with primary alcohols and synthesis of quinolines. The effect of solvent, time, base, catalyst loading, and substituent of the ligand moiety on the reaction was studied. Notably, 1 was a more efficient catalyst toward alkylation of a wide range of alcohols and quinolines synthesis. The reusability of the catalyst was checked and the results showed up to six catalytic runs without significant loss of activity.