Mixed-ligand oxovanadium complexes incorporating Schiff base ligands: synthesis, DNA interactions, and cytotoxicities

Three oxovanadium complexes, namely [VO(NOSAA)(bpy)] (1) (NOSAA = 2-hydroxy-5-nitrosalicylidene anthranilic acid, bpy = 2,2′-bipyridyl), [VO(NOSAA)(4,4′-dimebpy)] (2) (4,4′-dimebpy = 4,4′-dimethyl-2,2′- bipyridyl), and [VO(NOSAA)(phen)] (3) (phen = 1,10-phenanthroline), have been prepared and characterized. The binding modes and strengths of these complexes with calf thymus DNA (CT-DNA) were studied using various techniques. The chemical nuclease activities and photocleavage reactions of the complexes were also tested. All three complexes interact with CT-DNA through intercalative modes, and complex 3 possesses the largest binding affinity. All three complexes can efficiently cleave pBR322 DNA upon irradiation or under physiological conditions in the presence of H₂O₂, and complex 3 has the best cleaving ability. In vitro experimental results showed that the three complexes are cytotoxic against myeloma (Ag8.653) and gliomas (U251) cell lines and complex 3 again showed the highest efficacy.     

Penta- and hexacoordinate antimony(V) compounds with the tridentate O,N,O-donor ligand: Electrochemical transformations and antiradical activity

The electrochemical transformations and antiradical activity of penta- and hexacoordinate antimony(V) complexes I–V containing the tridentate O,N,O-donor ligand, N,N-bis(di-3,5-tert-butyl-2-hydroxyphenyl)amine, are studied. The oxidation of hexacoordinate triarylantimony(V) compounds R₃Sb(Cat-NH-Cat) (I–III) leads to the formation of neutral paramagnetic intermediates Ia–IIIa. Two anodic reversible one-electron stages are observed for pentacoordinate complexes R′₂Sb(Cat-N-Cat) (IV, V). The possibility of the formation of stable paramagnetic species in electrochemical oxidation is a reason for the antiradical activity of the complexes. The study of the reactions of compounds I–V with the electrogenerated superoxide radical anion, diphenylpicrylhydrazyl radical, peroxy radicals, and hydroperoxides formed by the autooxidation of unsaturated fatty acids (oleic, linoleic) shows that all complexes exhibit a pronounced antiradical activity. The highest effect is observed for compounds I, IV, and V characterized by the prolonged action.     

Crystal structures and electrochemical properties of two Mn(II) 2-sulfoterephthalate complexes with N-donor ligands

Two Mn(II) sulfoterephthalate complexes, [Mn(HStp)(o-Phen)₂] (I) and [Mn(HStp)(2,2′-Bipy)₂] (II) (H₃Stp = 2-sulfoterephthalic acid, o-Phen = 1,10-phenanthroline, 2,2′-Bipy = 2,2′-bipyridine), were synthesized under hydrothermal condition. Single crystal X-ray diffraction analyses reveal that complexes I and II possess similar structure, in which the center Mn²⁺ ions are hexa-coordinated with one Hstpanion and two N-donor ligands. For both of them, the formation of 3D supramolecular structures are based on both H-bonds and π...π/C-H...π stacking interactions. Electrochemical properties of complexes I and II have been investigated by means of cyclic voltmetry, which shows that electron transfer between Mn(III) and Mn(II) in electrolysis is quasi-reversible process.     

First MnIII complexes with tetradentate (N2O2) Schiff bases and tricyanomethanide: synthesis,crystal structure,and magnetic properties

The first Mn^III complexes with Schiff bases and tricyanomethanide-anion were synthesized: [Mn(salen)C(CN)₃(H₂O)] (1), [Mn(5-Brsalen)C(CN)₃(H₂O)] (2), [Mn(salpn)C(CN)₃(H₂O)] (3), [Mn(3-MeOsalen)C(CN)₃(H₂O)] (4), [Mn(5-Brsalen)(MeOH)(H₂O)][C(CN)₃] (5), and [Mn(3-MeOsalpn)(H₂O)₂][C(CN)₃] (6), where SalenH₂ is N,N′-bis(salicylidene)ethylenediamine, 5-BrsalenH₂ is N,N′-bis(5-bromosalicylidene)ethylenediamine, SalpnH₂ is N,N′-bis-(salicylidene)-1,3-diaminopropane, 3-MeOsalenH₂ is N,N′-bis(3-methoxysalicylidene)-ethylenediamine, 3-MeOsalpnH₂ — N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane. The tricyanomethanide anion in complexes 1–4 acts as a the terminal ligand, whereas in complexes 5 and 6 tricyanomethanide is not coordinated by Mn^III and acts as an out-of-sphere counterion. The structures of complexes 1–4 are characterized by the formation of dimers due to hydrogen bonds between the water molecules and oxygen atoms of the Schiff bases. The Mn...Mn distances inside the dimers are 4.69–5.41 Å. Complex 6 has a zigzag chain structure consisting of the [Mn(3-MeOsalpn)(H₂O)₂]⁺ cations bound by double bridging aqua ligands. The study of the magnetic properties of complexes 1, 3, 4, and 6 showed the existence of antiferromagnetic interactions between the Mn^III ions through the system of hydrogen bonds.     

Synthesis and crystal structures of the Zn(II) and Co(II) complexes containing the reduced derivative nitronyl nitroxide

Two complexes of formulas [Zn(Hfac)₂(IM-IMH-Bph)] (I) and [Co(Hfac)₃](IM-Bph) (II), where IM-Bph = 2,2′-bis(1′-oxyl-4′,4′,5′,5′-tetramethylimidazoline-2′-yl)-bis(2-formylphenyl) ether; Hfac = hexafluoroacetylacetonate, have been synthesized and characterized by single-crystal X-ray diffraction. The X-ray analysis demonstrates that both I and II are mononuclear complexes. In I, each zinc ion is five-coordinated with four oxygen atoms from two Hfac ligands and one oxygen atom from nitroxide. Complex II contains one Co(III) atom with six oxygen atoms from three Hfac ligands and uncoordinated IM-Bph diradical, in which the Co²⁺ ion and NIT-Bph biradical can undergo the redox reaction.     

Novel oxovanadium(iv) heterochelate complexes: synthesis, structure, ESR spectra, and photoluminescence properties

The reactions of oxovanadium(iv) salts with dimethylmalonate anions (H₂Dmm — C₃H₆(COOH)₂) and chelating N-donor ligands (2,2′:6′,2″-terpyridine (terpy), 2,2′-bipyridine (bpy)) led to the formation of new mononuclear heterochelate complexes [VO(Dmm)(terpy)]·4H₂O (1) and [VO(Dmm)(bpy)(H₂O)] (2). The structures of the synthesized compounds were determined by X-ray diffraction. The ESR spectra of the compounds at 293 and 100 K were analyzed and simulated. The photoluminescence properties were investigated.     

Manganese(III) complexes with tetradentate (N2O2) Schiff bases and dicyanamide

New Mn(III) complexes with Schiff bases and dicyanamide are synthesized: [Mn(Salpn)N(CN)₂] _n (two polymorphous modifications, Ia and Ib), {[Mn(5-BrSalen)N(CN)₂] · CH₃OH} _n (II), and [Mn(3-MeOSalen)N(CN)₂(H₂O)] (III), where SalpnH₂ = N,N′-bis(salicylidene)-1,3-diaminopropane, 5-BrSalenH₂ = N,N′-bis(5-bromosalicylidene)-1,2-diaminoethane, and 3-MeOSalenH₂ = N,N′-bis(3-methoxysalicylidene)-1,2-diaminoethane. Complexes Ia, Ib, and II have the polymer structure in which the dicyanamide anion binds the paramagnetic Mn(III) complexes with the Schiff bases into one-dimensional chains. Unlike them, in complex III the monomer units containing water and the dicyanamide anion as terminal ligands form dimers due to hydrogen bonds. The study of the magnetic properties of complexes Ia and II shows a weak antiferromagnetic interaction between the Mn³⁺ ions through the dicyanamide bridges in these complexes.     

Syntheses, spectroscopic characterization and metal ion binding properties of benzo-15-crown-5 derivatives and their sodium and nickel(II) complexes

New benzo-15-crown-5 derivatives containing nitro, amine and imine groups were prepared. Nitro compound (1) was prepared after the reaction?4′,5′-bis(bromethyl)benzo-15-crown-5 and o-nitrophenol in the presence of NaOH. After reduction process by using hydrazine hydrate and Pd/C amine compound (2) was formed. New crown ether imine compounds (3–5) were synthesized by the condensation of corresponding crown ether diamine (2) with salicylaldehyde derivatives. Sodium complexes of the crown compounds (1a–5a) form crystalline 1:1 (Na⁺: ligand) complexes with sodium perchlorate. Nickel(II) complexes (3b–5b) with 1:1 (Ni²⁺:ligand) stoichiometries were also been synthesized from the Schiff bases (3–5). The results indicated that the Schiff base ligands coordinated through the azomethine nitrogen and phenolic oxygen. The extraction ability of compounds (1, 3, 4 and 5) were also evaluated in chloroform by using several alkali and transition metal picrates such as Li⁺, Na⁺, K⁺, Cr³⁺, Mn²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Pb²⁺.     

Synthesis, characterization, DNA-binding, photocleavage, cytotoxicity and docking studies of Co(III) mixed ligand complexes

A new ligand, (2-ethoxy-6-(1H imadazo[4,5-f][1,10]phenanthroline-2-yl)phenol) (HEPIP) and its three Co(III) complexes [Co(phen)₂(HEPIP)](ClO₄)₃ (1), [Co(bpy)₂(HEPIP)](ClO₄)₃ (2) and [Co(dmb)₂(HEPIP)](ClO₄)₃ (3) have been synthesized and characterized. All three Co(III) complexes exhibited antitumor activity against four human tumor cell lines. The interaction of these complexes with calf thymus DNA was studied by absorption and emission spectroscopy, viscosity measurements and DNA cleavage assays. The DNA-binding constants of complexes 1, 2 and 3 were determined as 6.13 × 10⁵, 4.46 × 10⁵ and 3.72 × 10⁵ M^?1, respectively. The complexes appear to interact with DNA through intercalation. Studies on the mechanism of photocleavage indicated that both superoxide anion radical and singlet oxygen may play an important role.     

Synthetic aspects, crystal structures and antibacterial activities of manganese(III) and cobalt(III) complexes containing a tetradentate Schiff base

Three new Schiff base complexes, namely [Mn(L)Cl] · H₂O (1), [Co(L)Cl]₂ · 2CH₃COCH₃ (2) and [Co(L)NCS]₂ (3), where H₂L = 2,2′-[propane-1,2-diylbis(nitriloeth-1-yl-1-ylidene)]diphenol, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by reacting equimolar amounts of the respective metal chloride and the tetradentate Schiff base ligand (H₂L). While the mononuclear Mn(III) complex 1 was obtained with MnCl₂ in acetone medium, the same synthetic system yielded the binuclear Co(III) complex 2 in the presence of CoCl₂. Dissolution of 1 and 2 followed by crystallization with ammonium thiocyanate in methanol yielded two isostructural phenoxo-bridged binuclear complexes, namely [Mn(L)NCS]₂ (previously reported by us) and a new complex [Co(L)NCS]₂ (3), respectively. All the complexes 1–3 have been characterized by microanalytical, spectroscopic, single crystal X-ray diffraction and other physicochemical studies. Structural studies reveal that 1 adopts a distorted tetragonal pyramidal geometry while 2 and 3 comprise dimeric Co(III) units with bridging phenolate oxygen atoms. All the complex units in 1–3 and the respective solvent molecules are held together by weak intermolecular H-bonding to constitute a supramolecular network in the solid state. The antibacterial activity of the complexes has been tested against some Gram(+) and Gram(?) bacteria.     

Syntheses and spectroscopic characterization of double-armed benzo-15-crown-5 derivatives and their sodium and potassium complexes

A series of new benzo-15-crown-5 derivatives (1–6) containing formyl and imine groups were prepared. New formyl crown ethers (1 and 2) were prepared by reaction of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 2-hydroxy-5-methoxybenzaldehyde in the presence of NaOH. New Schiff bases (3–6) were synthesized by the condensation of corresponding aldehydes with 1,3-diaminopropane and 1,4-diaminobutane. Sodium and potassium complexes (1a–6a and 1b–6b) of the crown compounds forming crystalline complexes of 1:1 (Na⁺:ligand) and 1:2 (K⁺:ligand) stoichiometries were also synthesized. The structures of the aldehydes 1 and 2, imines 3–6 and complexes (1a–3a and 1b–3b) were confirmed on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, and mass spectroscopy.     

Synthesis, characterization, structures, and catalytic property of oxovanadium(V) complexes with hydrazone ligands

The reaction of [VO(Acac)₂] with 4-methyl-N′-[(2-hydroxy-1-naphthyl)methylidene]benzohydrazide (H₂L¹) and 4-methyl-N′-[1-(2-hydroxynaphthyl)ethyiidene]benzohydrazide (H₂L²), respectively, in methanol, affords two new oxovanadium(V) complexes [VO(OMe)L¹]₂ (I) and [VO(OMe)L²] (II). Both complexes have been characterized by elemental analysis, IR, and single crystal X-ray diffraction methods. Complex I is a methoxide-bridged dinuclear oxovanadium(V) compound, while complex II is a mononuclear oxovanadium(V) compound. The dinegative hydrazone ligands coordinate to the metal atoms through phenolate, imine, and deprotonated amide donor atoms. The geometry around vanadium atom in I is a distorted VNO₅ octahedron, while that in II is a VNO₄ square pyramid. Both complexes have effective catalytic property for the sulfoxidation reaction.     

Supramolecular assembly of three d10 metal coordination polymers based on the naphthalene-1,8-dicarboxylate ligand: Syntheses, structures and luminescent properties

Three d¹⁰ tetranuclear complexes, [Cd₄(1,8-nap)4(2,2′-bipy)₄(H₂O)8]·6H₂O (1,8-nap = naphthalene-1,8-dicarboxylate and 2,2′-bipy = 2,2′-bipyridine) (1), [Cd₄(1,8-nap)4(2,2′-bipy)₄(H₂O)8]·6H₂O (2) and [Zn₄(1,8-nap)₄(2,2′-bipy)₄(H₂O)4]·2H₂O (3), have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR and X-ray diffraction techniques. Complexes 1 and 2 are isomers showing one-dimensional ribbon-like structures connected by O-H…O hydrogen bonds, and the one-dimensional ribbons are further linked into the three-dimensional network by π-π stacking. In complex 3, the intramolecular O-H…O hydrogen bonds just exist in the inner of the single molecule ring to consolidate its structure, and the single molecules are further linked into a two-dimensional layer structure by the π-π stacking interactions. The luminescent properties reveal that all the complexes display luminescent properties in the violet region.     

Reaktion der Tautomeren 4-Hydroxy-2H-thiopyran-2-thion und 2-Mercapto-4H-thiopyran-4-on mit aliphatischen Aldehyden

5,6-Dihydro-4-hydroxy-6,6-dimethyl-2H-thiopyrane-2-thione (1 I) and its tautomer 2-mercapto-4H-thiopyrane-4-one (1 II) react with aliphatic aldehydes under different reaction conditions to yield mainly 5R-7,8-dihydro-2H,5H,6H-thiopyrano[2,3—b:6,5—b′]-bisthiopyran-4,6(3H)-diones2 and 2′R,4′R-5,6,6′,7′-tetrahydro-2-thioxo-spiro(4H-thiopyran-3(2H), 3′(4′H)-2′H,5′H-thiopyrano-[2,3—b]-thiopyran)-4,5′-diones3. The mechanisms of formation of the condensates2 and3 and their stereochemistry are discussed. The reaction yielding2 is analogous to the condensation of dimedone with subsequent anhydride formation.3 might be generated byDiels-Adler reaction of intermediately formed 2-thioxo-3-alkylidenethiopyranones4. An X-ray crystal structure analysis was carried out on3 b to establish its configuration and conformation.     

Substrate recognition by norovirus polymerase: microsecond molecular dynamics study

Molecular dynamics simulations of complexes between Norwalk virus RNA dependent RNA polymerase and its natural CTP and 2dCTP (both containing the O5′–C5′–C4′–O4′ sequence of atoms bridging the triphosphate and sugar moiety) or modified coCTP (C5′–O5′–C4′–O4′), cocCTP (C5′–O5′–C4′–C4′′) substrates were produced by means of CUDA programmable graphical processing units and the ACEMD software package. It enabled us to gain microsecond MD trajectories clearly showing that similar nucleoside triphosphates can bind surprisingly differently into the active site of the Norwalk virus RNA dependent RNA polymerase. It corresponds to their different modes of action (CTP—substrate, 2dCTP—poor substrate, coCTP—chain terminator, cocCTP—inhibitor). Moreover, extremely rare events—as repetitive pervasion of Arg182 into a potentially reaction promoting arrangement—were captured.     

Über substituierte 1,6-Dihydro-1,3,5-triazin-2,4-diamine, 1′,5′,6′,7′-Tetrahydrospiro[cyclopentan-1,4′-cyclopentapyrimidin]-2′(3′ H)-imine und das 6-Phenyl-2,4-pyrimidindiamin

Guanidine reacts with cyclohexanone, cycloheptanone, acetone and 3-pentanone, resp., in a molar ratio 2∶1 to give the 1,3,5-triazaspiro[5.5]undeca-and [5.6]dodeca-1,3-dien-2,4-diamines3 a and3 b resp. and the 6,6-dimethylresp. diethyl-1,6-dihydro-1,3,5-triazin-2,4-diamines3 d and3 e resp. On the contrary, action of guanidine on cyclopentanone yields not3 c, but the 1′,5′,7′-tetrahydrospiro[cyclopentane-1,4′-cyclopentapyrimidine]-2′(3′H)-imines2 c, 5 c and6 c resp., which are 1∶2- and 1∶3-condensates. Phenylacetone is transformed by guanidine (1∶2) to give 6-phenyl-2,4-pyrimidindiamine (8 f). The structure of the compounds cited is proved by NMR-, IR-, and (partially) mass spectra. The different courses of the formation of3 a, b, d, e, 2 c, 5 c and6 c resp. and8 f are also discussed. The structural formulae of some additional bases, which were synthesized from guanidine and cyclopentanone, 3-pentanone and phenylacetone resp. could not be established.     

Synthesis,structure, and properties of new spirooxindolodibenzodiazepine derivatives

An acid-catalyzed reaction of 3-(2-aminophenylamino)-5,5-dimethylcyclohexen-1-one with isatines leads to the formation of the earlier undescribed 3,3-dimethyl-2,3,4,5,10,11-hexahydrospiro[1H-dibenzo[b,e][1,4]diazepine-11,3′-2H-indole]-1,2′-dione derivatives (6). Spiranes 6 upon heating undergo auto-redox rearrangement with disintegration to 3,3-dimethyl-1,2,3,4-tetrahydrophenazine and the corresponding oxindole. Crystals of four derivatives of compound 6 were studied by X-ray diffraction method.     

Cytotoxicity, antioxidant, and antimicrobial activities of novel 2-quinolone derivatives derived from coumarin

Coumarins are important and useful compounds with diverse pharmacological properties. New coumarin derivatives namely N-aminoquinoline-2-one 1, 1-((4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)methyleneamino)quinolin-2(1H)-one 2 and 1,1′-(1E,1′E)-(1,4-phenylenebis(methan-1-yl-1-ylidene))bis(azan-1-yl-1-ylidene)diquinolin-2(1H)-one 3, were synthesized and characterized by UV–Vis, FT-IR, and NMR spectra in addition of elemental analysis. The synthesized compounds (2 and 3) show considerable anticancer activity against HEp-2 cell line. Synthesized compounds (2 and 3) were tested against selected types of microbial organisms and showed significant activities. The free-radical scavenging activity of synthesized compounds (2 and 3) have been determined by their interaction with the stable free-radical 1,1-diphenyl-2-picrilhydrazyl (DPPH) and all the compounds have shown encouraging antioxidant activities.