Square pyramidal copper(II) complexes with forth generation fluoroquinolone and neutral bidentate ligand: Structure,antibacterial, SOD mimic and DNA-interaction studies

Coordination of neutral bidentate ligand to copper ion in combination with gatifloxacin have been focused in this article. The effect of complexation reflects antibacterial activity, DNA interaction and SOD mimic activity of individual greatly. The geometry at the central metal ion provides a site for binding of superoxide anion responsible for better SOD mimic behaviour.     

Spectroelectrochemical studies of some ruthenium(II) complexes with polypyridyl bridging ligands

Ruthenium(II) bis(2,2″-pyridyl) complexes with bridging ligands: 6,7-dichloro-2,3-di(2-pyridyl)quinoxaline; 2,3-di(2-pyridyl)-quinoxaline; 5-methyl-2,3-di(2-pyridyl) quinoxaline; 6,7-dibenzo-2,3-di(2-pyridyl)quinoxaline have been prepared. The electrochemical and spectroscopic properties of these complexes are reported. The resonance Raman spectroelectrochemical results indicate the presence of oxidation state sensitive marker bands in the resonance Raman spectra of the oxidized complexes. The spectroscopic data for the reduced complexes is similar for all four species. The resonance Raman data for the reduced species are dominated by 2,2″-bipyridyl vibrations.     

DNA interactions of new mixed-ligand complexes of cobalt(III) and nickel(II) that incorporate modified phenanthroline ligands

Four new mixed-ligand complexes, namely [Co(phen)(2)(qdppz)](3+), [Ni(phen)(2)(qdppz)](2+), [Co(phen)(2)(dicnq)](3+) and [Ni(phen)(2)(dicnq)](2+) (phen=1,10-phenanthroline, qdppz=naptho[2,3-a]dipyrido[3,2-H:2',3'-f]phenazine-5,18-dione and dicnq=dicyanodipyrido quinoxaline), were synthesized and characterized by FAB-MS, UV/Vis, IR, 1H NMR, cyclic voltammetry and magnetic susceptibility methods. Absorption and viscometric titration as well as thermal denaturation studies revealed that each of these octahedral complexes is an avid binder of calf-thymus DNA. The apparent binding constants for the dicnq- and qdppz-bearing complexes are in the order of 10(4) and >10(6) M(-1), respectively. Based on the data obtained, an intercalative mode of DNA binding is suggested for these complexes. While both the investigated cobalt(III) complexes and also [Ni(phen)(2)(qdppz)](2+) affected the photocleavage of DNA (supercoiled pBR 322) upon irradiation by 360 nm light, the corresponding dicnq complex of nickel(II) was found to be ineffective under a similar set of experimental conditions. The physico-chemical properties as well as salient features involved in the DNA interactions of the cobalt(III) and nickel(II) complexes investigated here were compared with each other and also with the corresponding properties of the previously reported ruthenium(II) analogues.     

Synthesis and structural characterization of mixed-ligand silver(I) complexes containing diphosphazanes and bidentate N-donor ligands

The reactions of a self-assembled silver(I) coordination polymer, [Ag₂{μ-PrⁱN(PPh₂)₂}(μ-NO₃)₂]_n (1) with various bidentate N-donor ligands such as DABCO, 2,2′-bipyridyl and 1,10-phenanthroline yield 1-D helices or π-π stacked polymers, depending on the chelate vector of the N-donor ligand. The molecular structures of the resultant complexes, [Ag₂{μ-PrⁱN(PPh₂)₂}(DABCO)(NO₃)₂]_n (2), [Ag₂{μ-PrⁱN(PPh₂)₂}(2,2′-bipy)₂(NO₃)₂] (3) and [Ag₂{μ-PrⁱN(PPh₂)₂}(1,10-phen)₂](NO₃)₂ (4) have been confirmed by single-crystal X-ray diffraction. Complex 2 exists as an infinite helical polymer because of the exo-bidentate nature of DABCO. Complex 3 assumes a 2D grid motif as a result of intermolecular π-π stacking among adjacent bipyridine moieties. The phenanthroline complex 4 exhibits strong inter- and intramolecular π-π stacking interactions.     

DNA-binding studies of mixed-ligand (ethylenediamine)ruthenium(II) complexes

A series of mixed-ligand ruthenium(II) complexes of the type [Ru(en)(2)bpy](2+) (bpy=2,2-bipyridine; 1), [Ru(en)(2)phen](2+) (phen=1,10-phenantroline; 2), [Ru(en)(2)IP](2+) (IP=imidazo[4,5-f][1,10]phenanthroline; 3), and [Ru(en)(2)PIP](2+) (PIP=2-phenylimidazo[4,5-f][1,10]phenanthroline; 4) have been isolated and characterized by UV/VIS, IR, and (1)H-NMR spectral methods. The binding of the complexes with calf thymus DNA has been investigated by absorption, emission spectroscopy, viscosity measurements, DNA melting, and DNA photo-cleavage. The spectroscopic studies together with viscosity measurements and DNA melting studies support that complexes 1 and 2 bind to CT DNA (=calf thymus DNA) by groove mode. Complex 2 binds more avidly to CT DNA than complex 1, complexes 3 and 4 bind to CT DNA by intercalation mode, 4 binds more avidly to CT DNA than 3. Noticeably, the four complexes have been found to be efficient photosensitisers for strand scissions in plasmid DNA.     

Biomimetic zinc(II) and cobalt(II) complexes with tri-tert-butoxysilanethiolate and imidazole ligands - Structural and spectroscopic studies

New, heteroleptic zinc and cobalt complexes with tri-tert-butoxysilanethiolate and imidazole co-ligands are characterized by crystal structure studies. The ligands exhibit different coordination modes to Co(II) ions: NOS₂ (with methanol as O-donor ligand) in 2′, NO₂S₂ in 2′′, N₂S₂ in 1, and to Zn(II) ions: N₂S₂ in 3 and N₃S in 4. Complex 2′ is a structural analog of cobalt-substituted active site of alcohol dehydrogenase. All four-coordinate Co(II) and Zn(II) complexes have tetrahedral geometry. Solution and solid state electronic spectra of cobalt(II) complexes are discussed and compared to literature data available for the cobalt-substituted liver alcohol dehydrogenase and sorbitol dehydrogenase. The EPR spectra of all cobalt complexes exhibit at 77 K a characteristic broad signal with g ∼3.6 and 5.6, strongly indicating a high-spin state, S = 3/2, of Co(II) complexes.     

Pseudohalide-bridged five-coordinate Ni(II) or Co(II) complexes with bulky bidentate ligands: Magneto-structural correlationship

Bidentate ligands 2,2′-biquinoline (biq) and 6,6′-dimethyl-2,2′-bipyridine (dmbpy) with steric hindrance substituents cis to the nitrogen atoms have been used in the synthesis of transition metal complexes. Six new doubly end-on azido-bridged binuclear complexes [M₂(biq)₂(μ_1,1-N₃)₂(N₃)₂] (M = Ni (1), M = Co (2)), [M₂(biq)₂(μ_1,1-N₃)₂Cl₂] (M = Ni (3), M = Co (4)), [M₂(dmbpy)₂(μ_1,1-N₃)₂(N₃)₂] (M = Ni (5), M = Co (6)) and one end-to-end thiocyanato-bridged polymeric [Ni(dmbpy)(μ_1,3-SCN)(NCS)]_n (7) have been synthesized and characterized by single crystal X-ray diffraction analysis and magnetic studies. Complexes 1-6 comprise five-coordinate M(II) ions bridged by two end-on azide ligands. The bridging M-N-M bond angles are in the small range 104.1-105.2°. Complex 7 consists of a singly thiocyanate-bridged Ni(II) chain in which Ni(II) ions are five-coordinate. This research suggests that the bulky ligands play a key role in the formation of five-coordinate coordination structure. All complexes display intramolecular intermetallic ferromagnetic coupling with J_NiNi and J_CoCo of ca. 23 or 13 cm⁻¹ based on the Hamiltonian (S₁ = S₂ = 1 for Ni₂, or 3/2 for Co₂). The singly SCN⁻-bridged chainlike complex 7 shows intrachain ferromagnetic interaction with J = 3.96(2) cm⁻¹ and D = −4.55(8) cm⁻¹ (. Magneto-structural correlationship has been investigated.     

Synthesis, physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H2O)Cl], [M(pcbh)(H2O)Cl] and [M(Hpabh)(H2O)2 (SO4)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest d(x(2)-y(2) as the ground state. The ligand is bidentate bonding through > C = N--and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H2O)2(SO4)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H2O)Cl] and [Ni(Hpabh)(H2O)2(SO4)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

Synthesis,physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H₂O)Cl], [M(pcbh)(H₂O)Cl] and [M(Hpabh)(H₂O)₂ (SO₄)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest as the ground state. The ligand is bidentate bonding through >C = N ? and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H₂O)₂(SO₄)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H₂O)Cl] and [Ni(Hpabh)(H₂O)₂(SO₄)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

Octahedral nickel(II) hexamethyleneimine-dithiocarbamato complexes involving bidentate N,N-donor ligands

The nickel(II) complexes of the compositions [Ni(hmidtc)(bpy)₂]ClO₄ (I), [Ni(hmidtc)(phen)₂]ClO₄ (II), [Ni(hmidtc)(phen)₂]SCN (III), [Ni(hmidtc)(phen)₂]PF₆ (IV), [Ni(hmidtc)(phen)₂]BPh₄ (V), [Ni(hmidtc)(phen)₂]AcO·2H₂O (VI) and [Ni(hmidtc)(phen)₂]Br·H₂O (VII), involving a combination of one hexamethyleneimine-dithiocarbamate anion (hmidtc) and two bidentate N,N-donor ligands (2,2′-bipyridine (bpy) for I or 1,10-phenanthroline (phen) for II-VII), have been prepared. The compounds were characterized by elemental analysis, molar conductivity measurements, UV-Vis and IR spectroscopy, magnetochemical measurements and thermal analysis. A single-crystal X-ray analysis of the complex I revealed a distorted octahedral geometry with the nickel(II) ion coordinated by four nitrogen atoms (from two bidentate-coordinated bpy molecules) and two sulfur atoms (from one bidentate-coordinated hmidtc anion), together giving an NiN₄S₂ donor set.     

Nitrosyl complexes of cobalt with hybrid bidentate ligands containing phosphorus and sulfur donor atoms

Nitric oxide reacts with [Co(PSR)₂](BF₄)₂ (PSR  1-(thioalkyl)-2-(diphenylphosphino)ethane) to form five-coordinate mononitrosyl {CoNO}⁸ complexes. On the basis of infrared and NMR data the [Co(NO)(PSR)₂]²⁺ cations are believed to have a trigonal–bipyramidal geometry, with a linear Co–NO linkage. The mononitrosyl derivatives disproportionate in solution giving [Co(NO)₂(PSR)₂]⁺ species, and probably Co(III) compounds. The stoichiometry of this reaction was examined in different solvents and in the presence of added halide or pseudohalide ions by NMR and IR techniques. The cobalt(III) complex [Co(NCS)₂(PSEt)₂]BF₄ has been isolated and characterized.     

In vitro antibacterial, antifungal & cytotoxic activity of some isonicotinoylhydrazide Schiff's bases and their cobalt (II), copper (II), nickel (II) and zinc (II) complexes

Isonicotinoylhydrazide Schiff's bases formed by the reaction of substituted and unsubstituted furyl-2-carboxaldehyde and thiophene-2-carboxaldehyde with isoniazid and, their Co (II), Cu (II), Ni (II) and Zn (II) complexes have been synthesized, characterized and screened for their in vitro antibacterial activity against Mycobacterium tuberculosis, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae, Bacillus cereus, Corynebacterium diphtheriae, Staphylococcus aureus and Streptococcus pyogenes bacterial strains and for in vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glabrata. The results of these studies show the metal complexes to be more antibacterial and antifungal against one or more bacterial/fungal strains as compared to the uncomplexed compounds. The brine shrimp bioassay indicated Schiff's bases, L3 and L6 and, their Cu (II) and Ni (II) metal complexes to be cytotoxic against Artemia salina, while all other compounds were inactive (LD50 > 1000).     

Studies on biologically active complexes of cobalt(II) and nickel(II) with dithiooxamide-derived ligands.

A number of cobalt(II) and nickel(II) complexes with novel dithiooxamide ligands derived from precursors such as benzonitrile, benzosulfonamide, benzaldehyde, benzoic acid, and phenol have been synthesized and characterized on the basis of their elemental analysis molar conductance, magnetic moment, H NMR and electronic and IR spectral data. These ligands and their complexes have been screened for their antibacterial activities against bacterial species Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, and Tuberculi bacilli. The studies indicate that in comparison to the ligands their metal complexes are more potent and antibacterial.     

Synthesis and structural studies of mixed-ligand rhenium(V) complexes anchored by tridentate pyrazole-based ligands

The novel oxorhenium dichlorides mer-[ReO(L1)Cl₂] (1) and fac-[ReO(L2)Cl₂] (2) (L1 = 2-[2-(pyrazol-1-yl)ethyliminomethyl]phenolate; L2 = 2-[2-(pyrazol-1-yl)ethylaminomethyl]phenolate) were synthesized by reacting [NBu₄][ReOCl₄] with L1H and L2H, respectively. X-ray structural analysis of 1 and 2 has shown that L1 and L2 act as (N,N,O)-tridentate chelators coordinating to the Re(V) centre in a meridional and in a facial fashion, respectively. The reactivity of 2 towards potential bidentate/dianionic substrates is strongly dependent on the donor atom set, being observed that the presence of sulphur favours the displacement of the ancillary ligand (L2). By contrast, complex 2 reacted with (O,O)-bidentate substrates (1,2-ethanediol and oxalic acid) providing the mixed-ligand complexes fac-[ReO(L2)(OCH₂CH₂O)] (3) and fac-[ReO(L2)(C₂O₄)] (4). Complexes 3 and 4 are air and water-stable and have been characterized by the common spectroscopic techniques (IR, ¹H and ¹³C NMR) and by X-ray diffraction analysis.     

EPR studies of copper(II) and cobalt(II) complexes of adriamycin

Cu2+ and Co2+ complexes of adriamycin (ADM) in aqueous solutions have been examined using EPR spectroscopy. An appreciable amount of Cu2+ and Co2+ complexes formed in the solutions were found to be in the EPR silent associated form, where the metal ions are antiferromagnetically coupled. The associated form of the Cu2+ complex may be neither a simple dimer nor coordination polymer but aggregates of a stacked type. Formation of a complex having Cu2+-ADM stoichiometry of 1:2 was observed for the solutions containing excess of ADM as an EPR observable species. The complex having Cu2+-ADM stoichiometry of 1:1 was not observed directly by EPR, but the presence of the complex is undeniable, especially at low pH range so far as large excessive ADM is not present. The Co2+ complex of ADM observed by EPR is in the high-spin (S = 3/2) state and may have a coordination structure of tetragonal symmetry. The EPR spectra of these complexes apparently show that the Cu2+ and Co2+ ions are bound at the carbonyl and phenolate oxygen in the 1,4-dihydroxyanthraquinone moiety and the amino nitrogen in the sugar part does not seem to participate in the coordination to the metal ions.     

Metalloantibiotics: synthesis, characterization and in-vitro antibacterial studies on cobalt (II), copper (II), nickel (II) and zinc (II) complexes with cloxacillin

The synthesis and characterization of cloxacillin (clox) complexes with divalent metal ions [Co (II), Cu (II), Ni (II) and Zn (II)] is described. The nature of bonding of the chelated cloxacillin and the structures of the metal complexes have been elucidated on the basis of their physical and spectroscopic data. In all the complexes, the cloxacillin acts as a uninegatively charged bidentate ligand with coordination involving the carboxylate-O and endocyclic-N of the beta-lactam ring. The new compounds have been screened for in-vitro antibacterial activity against Escherichia coli (a), Klebsiella pneumonae (b), Proteus mirabilis (c), Pseudomonas aeruginosa (d), Salmonella typhi (e), Shigella dysentriae (f), Bacillus cereus (g), Corynebacterium diphtheriae (h), Staphylococcus aureus (j) and Streptococcus pyogenes (k) bacterial strains. The brine shrimp bioassay was also carried out to study their in-vitro cytotoxic properties. All compounds, respectively, showed a promising activity (90%) against five bacterial species at 10 microg/ml concentration and a significant activity (52%) against the same test bacteria at 25 microg/ml concentration.     

Synthesis,physico-chemical characterization and antimicrobial activity of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes with some acyldihydrazones

Complexes of the type [M(bssdh)]Cl and [M(dspdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); Hbssdh = benzil salicylaldehyde succinic acid dihydrazone, Hdspdh = diacetyl salicylaldehyde phthalic acid dihydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra and X–ray diffraction studies. Magnetic moment values and electronic spectral transitions indicate a spin free octahedral structure for Co(II), Ni(II) and Cu(II) complexes. IR spectral studies suggest that both the ligands behave as monobasic hexadentate ligands coordinating through three > C = O, two > C = N– and a phenolate group to the metal. ESR spectra of Cu(II) complexes are axial type and suggest as the ground state. X–ray powder diffraction parameters for [Co(bssdh)]Cl and [Co(dspdh)]Cl complexes correspond to an orthorhombic crystal lattice. The ligands as well as their metal complexes show a significant antifungal and antibacterial activity against various fungi and bacteria. The metal complexes are more active than the parent ligands.     

Synthesis, physico-chemical characterization and antimicrobial activity of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes with some acyldihydrazones

Complexes of the type [M(bssdh)]Cl and [M(dspdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); Hbssdh = benzil salicylaldehyde succinic acid dihydrazone, Hdspdh = diacetyl salicylaldehyde phthalic acid dihydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra and X-ray diffraction studies. Magnetic moment values and electronic spectral transitions indicate a spin free octahedral structure for Co(II), Ni(II) and Cu(II) complexes. IR spectral studies suggest that both the ligands behave as monobasic hexadentate ligands coordinating through three > C = O, two > C = N- and a phenolate group to the metal. ESR spectra of Cu(II) complexes are axial type and suggest d(x(2)-y(2)) as the ground state. X-ray powder diffraction parameters for [Co(bssdh)]Cl and [Co(dspdh)]Cl complexes correspond to an orthorhombic crystal lattice. The ligands as well as their metal complexes show a significant antifungal and antibacterial activity against various fungi and bacteria. The metal complexes are more active than the parent ligands.     

Neutral mixed-ligand complexes of 2,2′-bipyridinedichloroplatinum(II) with dianionic aromatic chelating ligands as potential photosensitizers

The electronic spectra of NCS^? and I^? adducts of cobalt(II) human carbonic anhydrase I are pH dependent at pH values below 7. The pK_a of such equilibrium is dependent on the anion concentration and varies between 4.6 and 6.6. The ¹H NMR spectra show that the three histidine residues are bound to the metal ion over the entire pH range investigated. It is supposed that a Glu residue triggers the change in stereochemistry around the metal ion. It is possible that such a Glu residue is Glu 106 present in the active cavity.