Ruthenium(II) complexes of 2-(2′-pyridyl)naphthoimidazole: synthesis,characterization and DNA-binding studies

The perchlorate salts of two new ruthenium(II) complexes incorporating 2-(2′-pyridyl)naphthoimidazole are synthesized in good yield. Complexes [Ru(phen)₂(PYNI)]²⁺ (phen = 1,10-phenanthroline) 1 and [Ru(dmp)₂(PYNI)]²⁺ (dmp = 2,9-dimethyl-1,10-phenanthroline, PYNI = 2-(2′-pyridyl)naphthoimidazole) 2 are fully characterized by elemental analysis, FAB-MS, ES-MS, ¹H NMR and cyclic voltammetric methods. The DNA-binding behavior of the complexes have been studied by spectroscopic titration, viscosity measurements and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf-thymus DNA (CT-DNA), with their binding constants spanning the range (2.73–5.35) × 10⁴ M^?1. The experimental results show that 1 interacts with calf thymus DNA (CT-DNA) by intercalative mode, while 2 binds to CT-DNA by partial intercalation.     

Ruthenium(II) complexes: synthesis,cytotoxicity in vitro,apoptosis, DNA-binding,photocleavage, and antioxidant activity studies

Two new ruthenium(II) complexes, [Ru(dmp)₂(APIP)](ClO₄)₂ (1) (APIP?=?2-(2-aminophenylimidazo[4,5-f][1,10]phenanthroline), dmp?=?2,9-dimethyl-1,10-phenanthroline) and [Ru(dmp)₂(HAPIP)](ClO₄)₂ (2) (HAPIP?=?2-(2-hydroxyl-5-aminophenyl)imidazo[4,5-f][1,10]phenanthroline), were synthesized and characterized. The DNA-binding properties of these complexes were investigated by absorption titration, viscosity measurements, and photoactivated cleavage. The DNA-binding constants for 1 and 2 have been determined to be 2.3 (±?0.3)?×?10⁴ (mol?L^?1)^?1 and 3.3 (±?0.4)?×?10⁴ (mol?L^?1)^?1. The results indicate that 1 and 2 interact with DNA through intercalative mode. The cytotoxicities of 1 and 2 were assessed against BEL-7402, HepG-2 and MCF-7 cell lines using standard MTT assay. The apoptosis induced by these complexes was studied with the acridine orange/ethidium bromide staining method. The antioxidant activity on hydroxyl radical was also investigated.     

Heterometallic platinum(II) compounds with β-aminoethylferrocenes: synthesis, electrochemical behaviour and anticancer activity

A new family of heterometallic compounds 3-6 containing ferrocenyl and platinum(II) centers has been synthesized by reaction of 1-β-aminoethylferrocene (1) and 1,1'-bis(β-aminoethyl)ferrocene (2) with Pt(II) precursors. Using K(2)[PtCl(4)] as the Pt(II) source, the cis-square-planar neutral compounds [Fe{η(5)-C(5)H(4)(CH(2))(2)NH(2)}(2)PtCl(2)] (3) and [{Fe(η(5)-C(5)H(4)(CH(2))(2)NH(2))(η(5)-C(5)H(5))}(2)PtCl(2)] (5) were obtained. Reaction of cis-[PtCl(2)(dmso)(2)] with 1 and 2 resulted in the displacement of dmso and chloride ligands from the platinum coordination sphere, affording the cationic and neutral compounds [Fe{η(5)-C(5)H(4)(CH(2))(2)NH(2)}(2)Pt(dmso)Cl]Cl (4) and [Fe(η(5)-C(5)H(4)(CH(2))(2)NH(2))(η(5)-C(5)H(5))Pt(dmso)Cl(2)] (6). Compounds 3-6 were thoroughly characterized using multinuclear ((1)H, (13)C, (195)Pt) NMR, IR spectroscopy, ESI mass spectrometry and elemental analysis. Single-crystal X-ray analysis of heterometallic 6 confirmed the cis geometry of the molecule and revealed that the platinum atom is held in a perfect square-planar geometry. The electrochemical behaviour of the heterometallic compounds 3-6, which has been examined by cyclic (CV) and square wave (SWV) voltammetries in dichloromethane and dmso solution, is characterized by the reversible one-electron oxidation of the ferrocene moieties. The results of the biological activity studies revealed that the organometallic complex 5 is active against all cell lines with GI(50) values in the range 1.7-2.3 μM. When compared to the standard anticancer drug cisplatin, heterotrimetallic 5, possessing two aminoethylferrocenyl units coordinated to the Pt(II) center, showed a greater activity profile in the colon cancer cell line. Cell cycle studies revealed that the new mixed compound exhibits a mechanism of action different to cisplatin.     

Synthesis, characterization and cyclic voltammetric studies of β-ketooximato ruthenium(II) complexes

Summary -Ketooxime [RC(O)C(NOH)R] (R = Me or Ph) ligands (HL) react with [Ru(PPh₃)₃Cl₂] in refluxing EtOH to yield [Ru(PPh₃)₂(L)₂] complexes. For R = Me, one isomer was obtained, while two isomers were isolated when R = Ph, due to a bulk effect. The complexes are diamagnetic and absorb intensely in the vis. region due to MLCT transitions. In MeCN and CH₂Cl₂ solution, Ru^II-Ru^III oxidation occurs in the 0.69–0.92 V versus s.c.e. range. The oxidation potential depends on both the electronic nature of R and the stereochemistry of the complexes.     

Catecholato complexes of palladium(II)–naphthylazoimidazoles: synthesis,spectral characterization,electrochemistry and solvatochromic studies

[Pd(-NaiR)(O,O)] [-NaiR = 1-alkyl-2-(naphthyl--azo)imidazoles; R = Me (a), Et (b), CH₂Ph (c) and O,O = pyrocatecholato (cat) (3), 4-t-butylcatecholato (tbcat) (4), 3,5-di-t-butylcatecholato (dtbcat) (5), and tetracholorocatecholato (tccat) (6)] complexes were characterized by elemental analyses, i.r. and ¹H-n.m.r. spectral data. Studies by cyclic voltammetry suggest the existence of two redox couples, positive saturated calomel electrode (s.c.e.) that are due to catecholes to semiquinone, and semiquinone to quinone oxidations, respectively; two couples at negative to s.c.e. are associated with azo reductions. The complexes exhibit ligand-to-ligand charge-transfer transition in the near-i.r. region. The band position is largely dependent upon the substituent on the catechole frame and exhibits a negative solvatochromic effect. The transition is qualitatively assigned to the HOMO (cat) LUMO (-NaiR) transition.     

DNA-binding and photocleavage studies of metallofluorescein–porphyrin complexes of zinc(II) and copper(II)

The DNA-binding behaviors of the fluorescein?Cporphyrinatozinc(II) complex Zn(Fl-PPTPP) (Fl-PPTPP?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin) and fluorescein?Cporphyrinatocopper(II) complex Cu(Fl-PPTPP) with calf thymus DNA (CT-DNA) were investigated by UV?CVis absorption titrations, fluorescence spectra, viscosity measurements, thermal denaturation and circular dichroism. The results suggest that both complexes interact with CT-DNA by intercalation. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated. Both complexes exhibit significant DNA cleavage activity, and singlet oxygen may play an important role in these reactions.     

Heteropolymolybdate–amino acid complexes: synthesis,characterization and biological activity

Three Keggin-type polyoxometalates functionalized by amino acids, (C₅H₁₃N₂O₂)₂(H₃O)PMo₁₂O₄₀·8H₂O 1, (C₅H₁₄N₂O₂)₂SiMo₁₂O₄₀·12H₂O 2 and (C₅H₁₄N₂O₂)₂GeMo₁₂O₄₀·12H₂O 3, were synthesized and characterized by elemental analysis, IR and ¹H?NMR spectra and single-crystal X-ray diffraction. The X-ray crystallographic study showed that the structures of the three compounds involved N–H···O and O–H···O hydrogen bonds among the protonated ornithine cations, water molecules and the heteropolyanion cluster, and thus represent a model interaction between polyoxometalates and proteins. These complexes display inhibitory actions to the human cancer cells Hela and PC-3?m in vitro.     

Synthesis,characterization and DNA-binding properties of mixed porphyrin–polypyridyl ruthenium(II) complexes

Two mixed porphyrin–polypyridyl Ru^II complexes [Ru(bpy)₂(MPyTPP)Cl]Cl (1) and [Ru(phen)₂(MPyTPP)Cl]Cl ( 2 ) (bpy=2,2-bipyridine; phen=1,10-phenanthroline; MPyTPP=5-monopyridyl-10,15,20–triphenylporphyrin) have been synthesized and characterized by elementary analysis, e.s.–m.s., cyclic voltammetry and u.v.–vis. spectroscopy. The DNA-binding properties of these complexes were investigated by electronic spectra, c.d. spectra and viscosity experiments. The results suggested that both complexes (1) and (2) bind to DNA in an outside binding mode. At the same time, theoretical calculations applying the ab initio and the density functional theory (DFT) methods were also performed, and the results showed that there is no good planarity on the main ligand MPyTPP of these complexes, and there are rather great distortion angles (dihedral angles ca. 72°) between the porphrin ring and each of the 10-, 15-, 20-phenyl groups. This may be the reason why the complexes bind to DNA in an outside mode, instead of an intercalative mode.     

Nickel (II) complexes with β-enaminoketonato chelate ligands: Synthesis, solid-structure characterization and reactivity toward the addition polymerization of norbornene

Based on two β-enaminoketonato ligands [ArNC(CH₃)C(H)C(CF₃)OH] (L₁, Ar = 2,6-Me₂C₆H₃; L₂, Ar = 2,6-i-Pr₂C₆H₃), their mono(β-enaminoketonato)nickel (II) complexes [(ArNC(CH₃)C(H)C(CF₃)O)Ni(Ph)(PPh₃)] (1, Ar = 2,6-Me₂C₆H₃; 3, Ar = 2,6-i-Pr₂C₆H₃) and bis(β-enaminoketonato)nickel (II) complexes [(ArNC(CH₃)C(H)C(CF₃)O)₂Ni] (2, Ar = 2,6-Me₂C₆H₃; 4, Ar = 2,6-i-Pr₂C₆H₃) have been synthesized and characterized. The molecular structures of complex 1, 2 and 4 have been confirmed by single-crystal X-ray analyses. After being activated with methylaluminoxane (MAO) these catalytic precursors 1-4 could polymerize norbornene to afford addition-type polynorbornene (PNB). Interestingly, catalytic activities and PNB productivity were greatly enhanced due to the introduction of strong electron-withdrawing group - trifluoro methyl into the ligands. Catalytic activities, polymer yield, M_w and M_w/M_n of PNB have been investigated under various reaction conditions.     

Review: Synthesis,characterization, and DNA-binding properties of Ru(II) molecular “light switch” complexes

This article presents recent progress in our laboratory on the interactions of Ru(II) polypyridyl complexes with calf thymus DNA (CT-DNA). Mixed polypyridyl Ru(II) complexes [Ru(L)₄(AIP)]²⁺ and [Ru(L)₄PyIP]²⁺, where L is 4-amino pyridine and pyridine (AIP?=?2-(9-anthryl)-1H-imidazo[4,5-f][1,10]phenanthroline; PyIP?=?2-(1-pyrenyl)-1H-imidazo[4,5-f][1,10]phenanthroline), have been synthesized and characterized by elemental analysis, and physicochemical methods such as ESI-MS, UV-Vis, IR, and NMR spectroscopic techniques. Electronic absorption titrations, fluorescence spectroscopy, viscosity measurements, and salt-dependent studies of CT-DNA in the presence of incremental amounts of all four Ru(II) complexes clearly demonstrate that all four complexes bind to DNA by intercalation. The DNA-binding affinities of these complexes follow the order [Ru(4-APy)₄(PyIP)]^2+?>?[Ru(Py)₄PyIP]^2+?>?[Ru(4-APy)₄(AIP)]^2+?>?[Ru(Py)₄AIP]²⁺. Irradiation of pBR 322 DNA with these complexes results in nicking of the plasmid DNA. All four complexes were screened for antimicrobial activity. All complexes also exhibited DNA “light switch” properties. These results suggest that both ancillary ligand and intercalative ligand influence the binding of these complexes to DNA.     

Synthesis,characterization and antimicrobial activity studies of N - N ′-tetracarboxydiethyloxamide ligand and its metal(II) complexes

N-N′-tetracarboxydiethyloxamide (hereafter abbreviated as H₆L) was prepared by using L-aspartic acid and diethyl oxalate (DEO). A series of binuclear complexes of divalent metal chlorides viz. Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with H₆L have been prepared. Spectral studies (IR, UV and NMR) magnetic susceptibility, elemental analysis and molar conductance measurements confirm the formation of binuclear complexes, [M₂H₂L]/[M₂H₂L?·?4H₂O]. Electronic absorption spectra and magnetic susceptibilities suggest square-planar stereochemistry for Cu(II) and tetrahedral for Zn(II) complexes. Mn(II), Co(II), and Ni(II) coordinate two molecules of water and consequently show octahedral geometry. The in vitro antimicrobial activity of the synthesized compounds is discussed against bacterial strains such as S. aureus, S. epididermis, K. pneumonia, S. typhi, P. aerugenosa, and B. subtilis A. brasilense. The metal complexes show higher activity against all the microorganisms than the ligand.     

Synthesis,characterization and biological activity of copper(II) complexes with ligands derived from β-amino acids

Transition Metal Chemistry - Two copper(II) complexes with ligands derived from β-amino acids, 2-(1-aminocyclohexyl)acetic acid L1 and 2-(1-amino-4-(tert-butyl)cyclohexyl)acetic acid L2, were...     

New mononuclear copper(II) complexes from β-diketone and β-keto ester N-donor heterocyclic ligands: structure,bioactivity, and molecular simulation studies

Four new mononuclear copper(II) complexes with methyl acetoacetate and benzoylacetone in the presence of 1,10-phenanthroline and 2,2′-bipyridine were synthesized and characterized by elemental analyses, FT-IR, and UV–Vis spectroscopy. The molecular structures of complexes [Cu(MAA)(bpy)(ClO₄)] (1a), [Cu(bzac)(bpy)]ClO₄ (2a), [Cu(MAA)(phen)(ClO₄)] (1b) and [Cu(bzac)(phen)(ClO₄)] (2b) were determined by single crystal X-ray diffraction technique. 1a, 1b, and 2b are five coordinate with a distorted square pyramidal geometry and the structure of 2a consists of isolated [Cu(bzac)(bpy)]⁺ cations and perchlorate counter anions. The electrochemical studies of copper complexes in acetonitrile solution showed that Cu^II/Cu^I reduction processes are electrochemically irreversible. Cytotoxic activity of complexes was screened, including an MTT assay against gastric cancer cell line (MKN-45). The four Cu(II) complexes exhibited lethal effects against MKN-45 cell lines and the half maximal inhibitory concentration (IC₅₀) values obtained were much lower in comparison with 5-fluorouracil. In addition, MTT and migration studies revealed that benzoylacetone complexes are more active than complexes of methyl acetoacetate against the MKN-45 cancer cell lines. Docking simulations of Cu(II) complexes on DNA revealed that the most stable adducts with DNA bind in the minor groove. All complexes display a binding specificity to the A/T rich regions.     

Synthesis,characterization, and biological activity studies of copper(II)–metal(II) binuclear complexes of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone)

A new series of copper(II) mononuclear and copper(II)–metal(II) binuclear complexes [(H₂L)Cu] ? H₂O, [CuLM] ? nH₂O, and [Cu(H₂L)M(OAc)₂] ? nH₂O, n = 1–2, M = Co(II), Ni(II), Cu(II), or Zn(II), and L is the anion of dipyridylglyoxal bis(2-hydroxybenzoyl hydrazone), H₄L, were synthesized and characterized. Elemental analyses, molar conductivities, and FT-IR spectra support the formulation of these complexes. IR data suggest that H₄L is dibasic tetradentate in [(H₂L)Cu] ? H₂O and [Cu(H₂L)M(OAc)₂] ? nH₂O but tetrabasic hexadentate in [CuLM] ? nH₂O (n = 1–2). Thermal studies indicate that waters are of crystallization and the complexes are thermally stable to 347–402°C depending upon the nature of the complex. Magnetic moment values indicate magnetic exchange interaction between Cu(II) and M(II) centers in binuclear complexes. The electronic spectral data show that d–d transitions of CuN₂O₂ in the mononuclear complex are blue shifted in binuclear complexes in the sequences: Cu–Cu > Cu–Ni > Cu–Co > Cu–Zn, suggesting that the binuclear complexes [CuLM] ? nH₂O are more planar than the mononuclear complex. The structures of complexes were optimized through molecular mechanics applying MM ⁺force field coupled with molecular dynamics simulation. [(H₂L)Cu] ? nH₂O, [CuLM] ? nH₂O, and the free ligand were screened for antimicrobial activities on some Gram-positive and Gram-negative bacterial species. The free ligand is inactive against all studied bacteria. The screening data showed that [CuLCu] ? H₂O > [(H₂L)Cu] ? H₂O > [CuLZn] ? H₂O > [CuLNi] ? 2H₂O ≈ [CuLCo] ? H₂O in order of biological activity. The data are discussed in terms of their compositions and structures.     

Ruthenium(II) complexes containing 2,9-dimethyl-1,10-phenanthroline and 4,4′-dimethyl-2,2′-bipyridine as ancillary ligands: synthesis,characterization and DNA-binding

Two new Ruthenium (II) polypyridyl complexes [Ru(dmp)₂(ipbp)](ClO₄)₂ (1) (dmp = 2,9-dimethyl-1,10-phenanthroline, ipbp = 3-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-4H-1-banzopyran-2-one) and [Ru(dmb)₂(ipbp)](ClO₄)₂ (2) (dmb = 4,4′-dimethyl-2,2′-bipyridine) have been synthesized and characterized by elemental analysis, FAB-MS, ES-MS and ¹H NMR and cyclic voltammetric methods. The DNA-binding behaviors of these complexes were investigated by spectroscopic titration, viscosity measurements, and thermal denaturation. Absorption titration and thermal denaturation studies reveal that these complexes are moderately strong binders of calf thymus DNA (CT-DNA). Viscosity measurements show that the complexes 1 and 2 interact with CT-DNA by intercalative mode. The DNA-binding affinity of the complex 2 is larger than that of complex 1.     

Template synthesis and spectroscopic characterization of 16-membered [N4] Schiff-base macrocyclic complexes of Co(II), Ni(II), Cu(II), and Zn(II): in vitro DNA-binding studies

Template condensation between o-phthalaldehyde and 3,4-diaminotoluene resulted in mononuclear 16-membered tetraimine macrocyclic complexes, [MLCl₂] [M?=?Co(II), Ni(II), Cu(II), and Zn(II)]. The proposed stoichiometry and the nature of the complexes have been deduced from elemental analyses, mass spectra, and molar conductance data. The macrocyclic framework has been inferred from ν(C=N) and ν(M–N) bands in the IR spectra and the resonances observed in ¹H and ¹³C-NMR spectra. Octahedral geometry has been assigned for all these complexes on the basis of position of the bands in electronic spectra and magnetic moment data; distorted octahedral geometry has been assigned for the Cu(II) complex on the basis of EPR data. The low-conductivity data of all the complexes suggest their non-ionic nature. Interaction of these complexes with calf-thymus DNA (CT DNA) has been examined with fluorescence quenching experiments, which show that the complexes are avid binders of CT DNA.     

Interconversion of copper(II) to copper(I): synthesis,characterization of copper(II) and copper(I) 2,2′-biquinoline complexes and their microbiological activity

The complexes [Cu(biq)₂]Cl₂ and [Cu(biq)₂]BF₄·biq (biq?=?2,2′-biquinoline) have been prepared and characterized. The interconversion to copper(I) complex [Cu(biq)₂]BF₄·biq, from [Cu(biq)₂]Cl₂ has been established. The new complexes have been characterized by elemental analysis, conductivity and magnetic measurements, IR, UV-vis and ¹H- and ¹³C-NMR spectroscopy. The X-ray analysis of the complex [Cu(biq)₂]BF₄·biq supports the assumption of the interconversion of copper(II) to copper(I) in this case. The crystal structure shows that geometry around the metal is severely distorted from T_d, and displays many supramolecular motifs incorporating both hydrophobic (aryl···aryl) and hydrophilic (C–H···F) intermolecular interactions. The microbiological activity of the complexes against bacteria and fungi was found to be high against Candida albicans, and slight to moderate against bacteria. The antimicrobial activity of [Cu(biq)₂]BF₄·biq was slightly better than that observed for [Cu(biq)₂]Cl₂ against both bacteria and fungi.     

Design,synthesis,characterization,cytotoxic and structure activity relationships of novel Ru(Ⅱ) complexes

Platinum containing compounds have shown antineoplastic potential, but their clinical applications have been limited by high toxicity. Ruthenium containing complexes have long been known to be well suited for biological applications, and have long been utilized as replacements to popular platinum based-drugs. Here, we report a novel series of ruthenium(II) arene compounds bearing thiosemicarbazone and isonicotinylhydrazone ligands with potent anticancer activity their structure activity relationships and apoptosis was studied. The cytotoxic activity of the new ruthenium(II) arene compounds has been evaluated in several cell lines (Molt 4/C8, L1210, CEM, HL60 and BEL7402). Among them, ten complexes were found to be excellent in vitro growth inhibitory activity against various cell lines with IC50 in the sub-micromolar range.     

Synthesis and characterization of sterically encumbered β-ketoiminate complexes of iron(II) and zinc(II)

The synthesis, structure, and spectroscopic signatures of a series of four-coordinate iron(II) complexes of β-ketoiminates and their zinc(II) analogues are presented. An unusual five-coordinate iron(II) triflate with three oxygen bound protonated β-ketoimines is also synthesized and structurally characterized. Single-crystal X-ray crystallographic analysis reveals that the deprotonated bis(chelate)metal complexes are four-coordinate with various degrees of distortion depending on the degree of steric bulk and the electronics of the metal center. Each of the high-spin iron(II) centers exhibits multiple electronic transitions including ligand π to π*, metal-to-ligand charge transfer, and spin-forbidden d-d bands. The (1)H NMR spectra of the paramagnetic high-spin iron(II) centers are assigned on the basis of chemical shifts, longitudinal relaxation times (T(1)), relative integrations, and substitution of the ligands. The electrochemical studies support variations in the ligand strength. Parallel mode EPR measurements for the isopropyl substituted ligand complex of iron(II) show low-field resonances (g > 9.5) indicative of complex aggregation or crystallite formation. No suitable solvent system or glassing mixture was found to remedy this phenomenon. However, the bulkier diisopropylphenyl substituted ligand exhibits an integer spin signal consistent with an isolated iron(ii) center [S = 2; D = -7.1 ± 0.8 cm(-1); E/D = 0.1]. A tentative molecular orbital diagram is assembled.     

Cyanide-bridged manganese(II) and chloride-bridged copper(II) complexes with 2-pyridineethanol: synthesis,structural characterization and C-H⋯M interactions

[Mn(hepH)₂Ni(μ-CN)₂(CN)₂]_n (1) and [Cu₂(μ-Cl)₂(μ-hep)₂]_n (2) (2-pyridineethanol abbreviated to hepH) have been synthesized and characterized by FT-IR and Raman spectroscopies, elemental analyses, and single-crystal X-ray diffraction. X-ray single-crystal structure analysis reveals that the structures of 1 and 2 consist of 1-D infinite chains. The coordination environment of Mn(II) was identified as distorted octahedral, whereas Ni(II) has a square planar geometry in 1. Each Cu(II) in 2 adopts a distorted square pyramidal geometry in which the basal plane is constructed by oxygen and nitrogen atoms from hep and a bridging chloride ligand, respectively, and the apical position is occupied by the other chloride. The 1-D chains in 1 and 2 are extended into a 2-D supramolecular network by O?H?N and weak C?H?Cl hydrogen bonds, respectively. Adjacent 2-D layers are further connected by C?H?M interactions resulting in the formation of 3-D supramolecular networks. The most remarkable properties of complexes are the presence of close C–H?M interactions with distance values of 2.58 and 2.93 Å between H?Ni and H?Cu, respectively. The H?Ni interaction distance is shorter than the corresponding values of other tetracyanonickelate(II) complexes.