DNA-binding and nuclease activity of 1,10-phenanthroline-based thiocyanato, acetato, azido and benzoato bridged dinuclear copper(II) complexes

The mononuclear Cu(II) complex [Cu(phen)(H2O)(NO3)(2)] (1), obtained by the reaction of 1,10-phenanthroline with Cu(NO3)(2)center dot 3H(2)O in methanol solution, reacts with anionic ligands SCN-, AcO-, N-3(-) and PhCO2- in MeOH solution to form the stable binuclear complexes [Cu-2(H2O)(2)(phen)(2)(mu-X)(2)](2) (NO3)(2), where X = SCN- (2), AcO- (3), N-3(-) (4) or PhCO2- (5). The molecular structure of complex 3 was determined by single-crystal X-ray diffraction studies. These complexes were characterized by electronic, IR, ESR, magnetic moments and conductivity measurements. The electrochemical behaviour of the complexes was investigated by cyclic voltammetry. The interactions of these complexes with calf thymus DNA have been investigated using absorption spectrophotometry. Their DNA cleavage activity was studied on double-stranded pBR322 plasmid DNA using gel electrophoresis experiments in the absence and presence of H2O2 as oxidant.

Synthesis, spectroscopic properties and biological evaluation of transition metal complexes of salicylhydrazone of anthranilhydrazide: X-ray crystal structure of copper complex

The transition metal complexes of salicylhydrazone of anthranilhydrazide (H2L) were synthesised. The structures of metal complexes were characterized by various spectroscopic [IR, NMR, UV-Vis, EPR], thermal and other physicochemical methods. The single-crystal X-ray diffraction study of [Cu(HL)Cl]center dot H2O reveal its orthorhombic system with space group P2(1)2(1)2 and Z=4. The copper center has a distorted square planar geometry with ONO and Cl as the donor atoms. The ligand and its metal chelates have been screened for their antimicrobial and anti-tubercular activities using serial dilution method. Metal complexes in general have exhibited better antibacterial and antifungal activity than the free ligand and in few cases better than the standard used. Among the bacterial strains used, the complexes are highly potent against Gram-positive strains compared to Gram-negative. Anti-tubercular activity exhibited by the Co(II) complex is comparable with the standard used. (C) 2011 Elsevier B. V. All rights reserved.

Novel tetranuclear distorted open-cubane copper complex containing oximate bridges: Synthesis, crystal structure, DNA binding and cleavage activity

The synthesis, molecular structure, DNA binding and nuclease activity of Cu4O4 open-cubane tetranuclear copper(II) complex with 3-2-(ethyl amino)ethyl]imino]-2-butanoneoxime (HL) are reported for the first time. The neutral tetranuclear Cu4L4(ClO4)(4)] complex crystallizes in tetragonal space group P (4) over bar2(1)c with the unit cell parameters; a = 13.798(4) angstrom, b = 13.798(4) angstrom, c = 14.119(6) angstrom, V = 2688(16) angstrom(3), Z = 8, R = 0.0636. Symmetrically equivalent copper atoms exhibit a CuN3O3 elongated distorted octahedral coordination environment, with three nitrogen atoms of the L ligand and one oxime-oxygen atom of second L ligand at equatorial positions, one oxime-oxygen atom of the third L ligand and perchlorate oxygen at axial positions. The complex shows quasireversible cyclic voltammetric response at 0.805 V (Delta E-p = 277 mV) at 100 mV s (1) in DMF for the Cu(II)/Cu(I) redox couple. The binding study of the complex with calf-thymus DNA has been investigated using absorption spectrophotometry. The complex shows strong nuclease activity on stranded pBR 322 plasmid DNA in the presence of hydrogen peroxide and marginal nuclease activity in the presence of reducing agent (dithiothreitol). (C) 2012 Elsevier B. V. All rights reserved.

Synthesis, characterization and phosphotriesterase mimetic activity of some Zn(II) and Cu(II) complexes

We report here the synthesis and characterization of a few phenolate-based ligands bearing tert- amino substituent and their Zn(II) and Cu(II) metal complexes. Three mono/binuclear Zn(II) and Cu(II) complexes Zn(L1)(H2O)].CH3OH.H2O (1) (H (2) L1 = 6,6(')-(((2-dimethylamino)ethylazanediyl)bis(methylene))bis(2, 4-dimethylphenol), Zn-2(L2)(2)] (2) (H (2) L2 = 2,2(')-(((2-dimethylamino)ethyl)azanediyl)bis(methylene)bis(4- methylphenol) and Cu-2(L3)(2).CH2 Cl-2] (3) (H (2) L3 = (6,6(')-(((2-(diethylamino)ethyl)azanediyl)bis(methylene)) bis(methylene))bis(2,4-dimethylphenol) were synthesized by using three symmetrical tetradendate ligands containing N2O2 donor sites. These complexes are characterized by a variety of techniques including; elemental analysis, mass spectrometry, H-1, C-13 NMR spectroscopic and single crystal X-ray analysis. The new complexes have been tested for the phosphotriesterase (PTE) activity with the help of P-31 NMR spectroscopy. The P-31 NMR studies show that mononuclear complex Zn(L1)(H2O)].CH3OH.H2O (1) can hydrolyse the phosphotriester i.e., p-nitrophenyl diphenylphosphate (PNPDPP), more efficiently than the binuclear complexes Zn-2(L2)(2)] (2) and Cu-2(L3)(2).CH2Cl2] (3). The mononuclear Zn(II) complex (1) having one coordinated water molecule exhibits significant PTE activity which may be due to the generation of a Zn(II)-bound hydroxide ion during the hydrolysis reactions in CHES buffer at pH 9.0.

Mixed-ligand nickel(II) thiosemicarbazone complexes: Synthesis, characterization and biological evaluation

The syntheses and characterization of some new mixed-ligand nickel(II) complexes {Ni(L-1)(PPh3)] (1), Ni(L-1)(Py)] (2), Ni(L-2)(PPh3)]center dot DMSO (3), Ni(L-2)(Imz)] (4), Ni(L-3)(4-pic)] (5) and RNi(L-3))(2)(mu-4,4'-byp)]center dot 2DMSO (6)1 of three selected thiosemicarbazones the 4-(p-X-phenyl)thiosemicarbazones of salicylaldehyde) (H2L1-3) (A, Scheme 1) are described in the present study, differing in the inductive effect of the substituent X (X = F, Br and OCH3), in order to observe its influence, if any, on the redox potentials and biological activity of the complexes. All the synthesized ligands and the metal complexes were successfully characterized by elemental analysis, IR, UV-Vis, NMR spectroscopy and cyclic voltammetry. The molecular structures of four mononuclear (1-3 and 5) and one dinuclear (6) Ni(II) complex have been determined by X-ray crystallography. The complexes have been screened for their antibacterial activity against Escherichia coli and Bacillus. The minimum inhibitory concentrations of these complexes and their antibacterial activities indicate that compound 4 is the potential lead molecule for drug designing. (C) 2012 Elsevier Ltd. All rights reserved.

Synthesis, antimicrobial, DNA-binding and photonuclease studies of Cobalt(III) and Nickel(II) Schiff base complexes

New metal complexes of the type M(nih)(L)](PF6)(n)center dot xAH(2)O and M(nih)(2)](PF6)center dot xH(2)O (where M = Co(III) or Ni(II), L = 1,10-phenanthroline (phen)/or 2,2' bipyridine (bpy), nih = 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone, n = 2 or 1 and x = 3 or 2) have been synthesized and characterized by elemental analysis, magnetic, IR and H-1 NMR spectral data. The electronic and magnetic moment 2.97-3.07 B.M. data infers octahedral geometry for all the complexes. The IR data reveals that Schiff base (nih) form coordination bond with the metal ion through azomethine-nitrogen, phenolic-oxygen and carbonyl-oxygen in a tridentate fashion. In addition, DNA-binding properties of these six metal complexes were investigated using absorption spectroscopy, viscosity measurements and thermal denaturation methods. The results indicated that the nickel(II) complex strongly bind with calf-thymus DNA with intrinsic DNA binding constant K-b value of 4.9 x 10(4) M-1 for (3), 4.2 x 10(4) M-1 for (4), presumably via an intercalation mechanism compared to cobalt(III) complex with K-b value of 4.6 x 10(4) M-1 (1) and 4.1 x 10(4) M-1 (2). The DNA Photoclevage experiment shows that, the complexes act as effective DNA cleavage agent. (C) 2012 Elsevier B.V. All rights reserved.

Naphthalene Carbohydrazone Based Dizinc(II) Chemosensor for a Pyrophosphate Ion and Its DNA Assessment Application in Polymerase Chain Reaction Products

A new naphthalene carbohydrazone based dizinc(II) complex has been synthesized and investigated to act as a highly selective fluorescence and visual sensor for a pyrophosphate ion with a quite low detection limit of 155 ppb; this has also been used to detect the pyrophosphate ion released from polymerase-chain-reaction.

Self-assembly of discrete metallamacrocycles employing half-sandwich octahedral diruthenium(II) building units and imidazole-based ligands

Equimolar combination of a series of binuclear half-sandwich p-cymene ruthenium(II) building units Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1a](OTf)(2), Ru-2(mu-eta(4)-N,N'-diphenyloxamidato)( MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1b](OTf)(2) and Ru-2(mu-eta(4)-C6H2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1c](OTf)(2) separately with imidazole-based ditopic ligands (L-1-L-2) in methanol yielded a series of tetranuclear metallamacrocycles 2-7](OTf)(4), respectively L-1 = 1,4-bis(imidazole-1-yl)benzene; L-2 = 4,4'-bis(imidazole-1-yl)biphenyl; OTf- = O3SCF3-]. Similarly, the reaction of Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)2](OTf)(2) 1a](OTf)(2) with a triazine-based tritopic ligand 1,3,5-tris(imidazole-1-yl) triazine (L3) in 3: 2 M ratio afforded an unexpected tetranuclear macrocycle 8](OTf)(4) instead of an expected trigonal prismatic cage 8a](OTf)(6). All the self-assembled macrocycles 2-8](OTf)(4) were isolated in moderate to high yields and were fully characterized by multinuclear H-1, F-19] NMR, IR and electrospray ionization mass spectrometry (ESI-MS). In addition, X-ray diffraction study on the single crystals of 3](OTf)(4) and 8](OTf)(4) also indicated the formation 2 + 2] self-assembled macrocycles. Despite the possibility of formation of different conformational isomeric macrocycles (syn-and anti) and polymeric product due to free rotation of ligand sites of imidazole linkers, the selective formation of single conformational isomer (anti) as the only product is quite interesting. Furthermore, the photo-and electrochemical properties of these assemblies have been studied using UV/Vis absorption and cyclic voltammetry analysis. (c) 2013 Elsevier B.V. All rights reserved.

Ligational behaviour of (E)-2-amino-N ` -1-(2-hydroxyphenyl) ethylidene]benzohydrazide towards later 3d metal ions: X-ray crystal structure of nickel(IV) complex

Ligational behaviour of (E)-2-amino-N'-1-(2-hydroxyphenyl)ethylidene]benzohydrazide (Aheb) towards later 3d metal ionscopper(II), cobalt(II), manganese(II), zinc(II), cadmium(II) and nickel(IV)] has been studied. Their structures have been elucidated on the basis of spectral (IR, H-1 NMR, UV-Vis, EPR and FAB-mass), elemental analyses, conductance measurements, magnetic moments, and thermal studies. During complexation Ni(II) ion has got oxidized to Ni(IV). The changes in the bond parameters of the ligand on complexation has been discussed by comparing the crystal structure of the ligand with that of its Ni(IV) complex. The X-ray single crystal analysis of Ni(aheb)(2)]Cl-2 center dot 4H(2)O has confirmed an octahedral geometry around the metal ion. EPR spectra of the Cu(II) complex in polycrystalline state at room (300 K) and liquid nitrogen temperature (77 K) were recorded and their salient features are reported. (C) 2014 Elsevier B.V. All rights reserved.

Contrasting reactivity behaviour of the RuHCl(CO)(PNP)] complex with electrophilic reagents XOTf (X = H, CH3, Me3Si)

A new ruthenium pincer complex RuHCl(CO)(PNP)] (PNP = PhCH2N(CH2CH2PPh2)(2)) (1) was synthesized and characterized. The reactivity of complex 1 with electrophilic reagents XOTf (X = H, CH3, and Me3Si; OTf = CF3SO3) was studied by variable temperature NMR spectroscopy with an aim to observe and characterize sigma complexes of type Ru(eta(2)-HX)Cl(CO)(PNP)]OTf] (X = H (2), CH3 (3), Me3Si (4)). Reaction of complex 1 with HOTf resulted in the formation of the dihydrogen complex, Ru(eta(2)-H-2)Cl(CO)(PNP)OTf] (2). On the other hand, the reaction between complex 1 and MeOTf and Me3SiOTf resulted in the direct elimination of MeCl and Me3SiCl via a S(N)2 type of reaction without the intermediacy of the respective sigma complexes 3 and 4. This contrasting reactivity behaviour has been rationalized taking into consideration the approach of the relatively bulky electrophites CH3+ and Me3Si+ onto the hydride moiety of the ruthenium fragment, which is sterically hindered.

Single-ion magnet behaviour of heptacoordinated Fe(II) complexes: on the importance of supramolecular organization

Supramolecular organization of a metal complex may significantly contribute to the magnetization dynamics of mononuclear SMMs. This is illustrated for a heptacoordinated Fe(II) complex with rather moderate Ising-type anisotropy for which a slow magnetization relaxation with significant energy barrier was reached when this complex was properly organized in the crystal lattice. Incidentally, it is the first example of single-ion magnet behaviour of Fe(II) in a pentagonal bipyramid surrounding.

New symmetrical dinucleating ligand based assembly of bridged dicopper(II) and dizinc(II) centers: Synthesis, structure, spectroscopy, magnetic properties and glycoside hydrolysis

Two dinuclear copper(II) complexes Li(H2O)(3)(CH3OH)](4)Cu2Br4]Cu-2(cpdp)(mu-O2CCH3)](4)(OH)(2) (1), Cu (H2O)(4)]Cu-2(cpdp)(mu-O2CC6H5)](2)Cl-2 center dot 5H(2)O (2), and a dinuclear zinc(II) complex Zn-2(cpdp)(mu-O2CCH3)] (3) have been synthesized using pyridine and benzoate functionality based new symmetrical dinucleating ligand, N, N'-Bis2-carboxybenzomethyl]-N, N'-Bis2-pyridylmethyl]-1,3-diaminopropan-2-ol (H(3)cpdp). Complexes 1, 2 and 3 have been synthesized by carrying out reaction of the ligand H3cpdp with stoichiometric amounts of Cu-2(O2CCH3)(4)(H2O)(2)], CuCl2 center dot 2H(2)O/C6H5COONa, and Zn(CH3COO)(2)center dot 2H(2)O, respectively, in methanol in the presence of NaOH at ambient temperature. Characterizations of the complexes have been done using various analytical techniques including single crystal X-ray structure determination. The X-ray crystal structure analyses reveal that the copper(II) ions in complexes 1 and 2 are in a distorted square pyramidal geometry with Cu-Cu separation of 3.455(8) angstrom and 3.492(1)angstrom, respectively. The DFT optimized structure of complex 3 indicates that two zinc(II) ions are in a distorted square pyramidal geometry with Zn-Zn separation of 3.492(8)angstrom. UV-Vis and mass spectrometric analyses of the complexes confirm their dimeric nature in solution. Furthermore, H-1 and C-13 NMR spectroscopic investigations authenticate the integrity of complex 3 in solution. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of antiferromagnetic interactions between the copper centers, with J = -26.0 cm(-1) and -23.9 cm(-1) ((H) over cap = -2JS(1)S(2)) in complexes 1 and 2, respectively. In addition, glycosidase-like activity of the complexes has been investigated in aqueous solution at pH similar to 10.5 by UV-Vis spectrophotometric technique using p-nitrophenyl-alpha-D-glucopyranoside (4) and p-nitrophenyl-beta-D-glucopyranoside (5) as model substrates. (C) 2015 Elsevier B.V. All rights reserved.

Template-free coordination-driven self-assembly of discrete hexanuclear prismatic cages employing half-sandwich octahedral Ru-2(II) acceptors and triimidazole donors

Coordination-driven self-assembly of dinuclear half-sandwich p-cymene ruthenium(II) complexes Ru-2(mu-eta(4)-C2O4)(CH3OH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1a) and Ru-2(mu-eta(4)-C6H2O4)(CH3OH)(2)(eta(6)-p-cymene)(2)](O3SCF3)(2) (1b) separately with imidazole-based tritopic donors (L-1-L-2) in methanol yielded a series of hexanuclear 3+2] trigonal prismatic cages (2-5), respectively L-1 = 1,3,5-tris(imidazole-1-yl) benzene; L-2 = 4,4',4 `'-tris(imidazole-1-yl) triphenylamine]. All the self-assembled cages 2-5 were characterized by various spectroscopic techniques (multinuclear NMR, Infra-red and ESI-MS) and their sizes, shapes were obtained through geometry optimization using molecular mechanics universal force field (MMUFF) computation. Despite the possibility due to the free rotation of donor sites of imidazole ligands, of two different atropoisomeric prismatic cages (C-3h or C-s) and polymeric product, the self-selection of single (C(3)h) conformational isomeric cages as the only product is a noteworthy observation. (C) 2015 Elsevier B.V. All rights reserved.

Photorelease of Pyridyl Esters in Organometallic Ru(II) Arene Complexes

New Ru(II) arene complexes of formula [((6)-p-cym)Ru(N-N)(X)](2+) (where p-cym = para-cymene, N-N = 2,2'-bipyrimidine (bpm) or 2,2'-bipyridine (bpy) and X = m/p-COOMe-Py, 1-4) were synthesised and characterized, including the molecular structure of complexes [((6)-p-cym)Ru(bpy)(m-COOMe-Py)](2+) (3) and [((6)-p-cym)Ru(bpy)(p-COOMe-Py)](2+) (4) by single-crystal X-ray diffraction. Complexes 1-4 are stable in the dark in aqueous solution over 48 h and photolysis studies indicate that they can photodissociate the monodentate m/p-COOMe-Py ligands selectively with yields lower than 1%. DFT and TD-DFT calculations (B3LYP/LanL2DZ/6-31G**) performed on singlet and triplet states pinpoint a low-energy triplet state as the reactive state responsible for the selective dissociation of the monodentate pyridyl ligands.

光系统II复合物的光仰制特征及其内源保护机理

本文以菠菜PSⅡ颗粒PSⅡ核心复合物和PSⅡ反应中心复合物为材料通过比较光抑制处理和单线态氧处理对上述制剂色素、蛋白和光谱特性的影响，．以及光抑制对细胞色素b559 (Cyt b559)和放氧的影响，研究了PSⅡ光抑制及其内源保护机理得到如下的结果: 1)光抑制处理和外源单线态氧处理对PSⅡ具有相似的破坏特性,同时，加入单线态氧的特异性清除剂组氨酸(His)可明显遏制光抑制处理对PSⅡ各组分的破坏这些结果说明单线态氧参与了PSⅡ的光破坏过程. 2) PSⅡ蛋白组分不仅受到强光的破坏，而且在照光后暗放置过程中还继续受到破坏 这种暗放置破坏过程具有温度敏感性因此推测在光照后暗放置过程中的PSⅡ蛋白降解是酶促反应这些结果证明，PSⅡ蛋白的光破坏具有活性氧损伤和酶促水解两种可能的破坏机理． 3)首次观察到PSⅡ中Cyt b559的高电势态(qt b559 HP)的百分含量在光抑制初期上升，随后下降的现象且这种变化受到外加强His的遏制。表明光抑制产生的单线态氧参与了Cytb559 HP百分含量的改变,同时还观察到这种变化的时间进程与PSⅡ蛋白二级结构在光抑制中变化的时间进程相似后者也表现出双相变化进程这说明光抑制产生的单线态氧引起了蛋白构象的变化后者导致了Cytb559 HP百分含量的改变. 4)在不同的处理条件下，PSⅡ放氧活性的变化与Cyt b559 HP百分含量的变化具有明显的相关性它们的变化可能具有相同的原因，即PSⅡ蛋白构象的改变． 5)无氧条件下照光时’PSⅡ反应中心复合物中的Cytb559的低电势态(Cytb559 LP)可从Pheo得到电子而被还原具有较高反应活性的Pheo被清除这体现了Cytb559 LP的一种光保护功能. 综合上述结果及参考已有的文献我们提出了一种以Cytb559为中心的PSⅡ光抑制快速内源保护机理的调控模型。光抑制通过影响PSⅡ蛋白构象而使Cytb559 HP和Cytb559 LP发生相互转换。Cytb559 HP具有清除活性氧的功能，而Cytb559 LP态则具有从Pheo或QA吸收电子的作甩因此它们可受PSⅡ不同状态的调节进行相互转换以淬灭活性自由基达到保护PSⅡ功能的目的。