Synthesis and photophysical properties of dansyl-based polyamine ligands and their Zn(II) complexes

The synthesis, potentiometric studies and photophysical properties of two new polyamine ligands (L1 and L2) possessing the dansyl chromophore were studied in aqueous 0.15 M NaCl. The compounds show the absorption and emissions bands characteristic of the dansylamide fluorophore and both present intramolecular excited state proton transfer at intermediate pH ranges. One of the ligands (L2) strongly coordinates Zn(II) leading to fluorescence quenching. A model compound (L3) of the dansyl moiety was also investigated.     

Synthesis and properties of electrochemiluminescent dinuclear Ru(II) complexes assembled with ester-bridged bis(bipyridine) ligands

New bridging ligands, such as bpy-(COOCH₂)-bpy (BL1), mbpy-(CH₂)₃COOCH₂-bpy (BL2), bpy-COO(CH₂)₆OOC-bpy (BL3), and bpy-COOCH₂PhPhCH₂OOC-bpy (BL4), have been synthesized and coordinated to [RuL₂(acetone)₂](PF₆)₂ for various [Ru(L)₂(BL)Ru(L)₂](PF₆)₄-type dinuclear ruthenium complexes (where BL = BL1, BL2, BL3, BL4, and L = bpy, o-phen, DTDP). Their electrochemical redox potentials, spectroscopic properties and relative electrochemiluminescence were investigated in detail. All dinuclear Ru complexes exhibit MLCT (metal-to-ligand charge transfer) absorption and luminescence bands in the visible region. ECL intensities of dinuclear ruthenium(II) complexes were affected not only by the kind of the ligand, but also by the nature of the bridging ligand. Among the synthesized dinuclear Ru complexes, [(DTDP)₂Ru(mbpy)-(CH₂)₃COOCH₂-(bpy)Ru(DTDP)₂](PF₆)₄ exhibited enhanced ECL intensities as high as 2.9 times greater than that of the reference, [Ru(o-phen)₃](PF₆)₂.     

Synthesis,characterization and bioactivity of four novel trinuclear copper(II) and nickel(II) complexes with pentadentate ligands derived from N-acylsalicylhydrazide

Four novel trinuclear copper(II)/nickel(II) complexes with four trianionic pentadentate ligands, N-(3-t-butylbenzoyl)-5-nitrosalicylhydrazide (H₃3-t-bbznshz), N-(3,5-dimethylbenzoyl)salicylhydrazide (H₃3,5-dmbzshz), N-(phenylacetyl)-5-bromosalicylhydrazide (H₃pabshz) and N-(3-t-butylbenzoyl)salicylhydrazide (H₃3-t-bbzshz) have been synthesized and characterized by X-ray crystallography. These trinuclear compounds all have an M–N–N–M–N–N–M core formed by three metal ions and two ligands. The geometries of three Cu(II) ions in compound Cu₃(3-t-bbznshz)₂(H₂O)(DMF)(py)₂ · DMF (1) alternate between distorted square pyramidal and square planar, while in compound Cu₃(3,5-dmbzshz)₂(py)₂ (2), they are all square planar. Three Ni(II) ions in compound Ni₃(pabshz)₂(DMF)₂(py)₂ (3) and Ni₃(3-t-bbzshz)₂(py)₄ · 2H₂O (4) follow square-planar/octahedral/square-planar coordination geometry. Compounds 1, 2 and 4 are bent trinuclear, with the bend angles of 156.4°, 141.49° and 127.1°, respectively, while the three nickel ions in compound 3 are strictly linear, with an angle of 180°. Studies on the trinuclear Ni(II) complexes show that the β-branched N-acylsalicylhydrazide ligands with sterically flexible Cα methylene groups are easier to yield linear trinuclear Ni(II) complexes, while α-branched N-acylsalicylhydrazides ligands tend to form bent trinuclear Ni(II) complexes. Antibacterial screening data indicate that the trinuclear Cu(II) compound 2 is more active than 1 and mononuclear Cu(II) compound, bent trinuclear Ni(II) compound 4 is more active than linear compound 3 and less active than tetranuclear nickel compound in the previous study.     

Synthesis, characterization, and DNA-binding properties of Ln(III) complexes containing gatifloxacin

Four novel water-soluble complexes of Ln(III) with gatifloxacin (HGA), [La(HGA)3Cl3] x 2H2O, [Nd(HGA)3Cl3] x 2H2O, [Eu(HGA)3Cl3] x 2H2O, [Tb(HGA)3Cl3] x 2H2O, have been synthesized and characterized by elemental analyses, molar conductivities, IR spectra, fluorescence spectra, and thermogravimetry/differential thermal analysis (TG-DTA). In addition, the DNA-binding properties of the ligand and its complexes have been investigated by absorption, fluorescence spectra, and viscosity measurements. The experimental results indicated that the complexes and ligand bind to DNA via groove binding mode.     

Synthesis,structural characterization and antimicrobial activities of 12 zinc(II) complexes with four thiosemicarbazone and two semicarbazone ligands

Twelve zinc(II) complexes with thiosemicarbazone and semicarbazone ligands were prepared and characterized by elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FT-IR and 1H and 13C NMR spectroscopy. Seven three-dimensional structures of zinc(II) complexes were determined by single-crystal X-ray analysis. Their antimicrobial activities were evaluated by MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 5- and 6-coordinate zinc(II) complexes with a tridentate thiosemicarbazone ligand (Hatsc), ([Zn(atsc)(OAc)](n) 1, [Zn(Hatsc)(2)](NO(3))(2).0.3H(2)O 2, [ZnCl(2)(Hatsc)] 3 and [Zn(SO(4))(Hatsc)(H(2)O)].H(2)O 4 [Hatsc=2-acetylpyridine(thiosemicarbazone)]), showed antimicrobial activities against test organisms, which were different from those of free ligands or the starting zinc(II) compounds. Especially, complex 2 showed effective activities against P. aeruginosa, C. albicans and moderate activities against S. cerevisiae and two molds. These facts are in contrast to the results that the 5- or 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridine-4N-morpholinethiosemicarbazone, ([Zn(mtsc)(2)].0.2EtOH 5, the previously reported catena-poly [Zn(mtsc)-mu-(OAc-O,O')](n) and [Zn(NO(3))(2)(Hmtsc)] [Hmtsc=2-acetylpyridine (4N-morpholyl thiosemicarbazone)]), showed no activities against the test microorganisms. The 5- and 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridinesemicarbazone, ([Zn(OAc)(2)(Hasc)] 6 and [Zn(Hasc)(2)](NO(3))(2) 7 [Hasc=2-acetylpyridine(semicarbazone)]), showed no antimicrobial activities against bacteria, yeasts and molds. Complex [ZnCl(2)(Hasc)] 8, which was isostructural to complex 3, showed modest activity against Gram-positive bacterium, B. subtilis. The 1:1 complexes of zinc(II) with pentadentate thiosemicarbazone ligands, ([Zn(dmtsc)](n) 9 and [Zn(datsc)](n) 10 [H(2)dmtsc=2,6-diacetylpyridine bis(4N-morpholyl thiosemicarbazone) and H(2)datsc=2,6-diacetylpyridine bis(thiosemicarbazone)]), did not inhibit the growth of the test organisms. On the contrary, 7-coordinate zinc(II) complexes with one pentadentate semicarbazone ligand and two water molecules, ([Zn(H(2)dasc)(H(2)O)(2)](OAc)(2).5.3H(2)O 11 and [Zn(H(2)dasc)(H(2)O)(2)](NO(3))(2).H(2)O 12 [H(2)dasc=2,6-diacetylpyridine bis(semicarbazone)]), showed modest to moderate activities against bacteria. Based on the X-ray structures, the structure-activity correlation for the antimicrobial activities was elucidated. The zinc(II) complexes with 4N-substituted ligands showed no antimicrobial activities. In contrast to the previously reported nickel(II) complexes, properties of the ligands such as the ability to form hydrogen bonding with a counter anion or hydrated water molecules or the less bulkiness of the 4N moiety would be a more important factor for antimicrobial activities than the coordination number of the metal ion for the zinc(II) complexes.     

Synthesis and structural characterization of copper(II) bishexafluoroacetylacetonate complexes with N-donor ligands

The reactions of Cu(hfac)₂ with different N-donor ligands such as 2-ethynylpyridine and imidazole give copper complexes Cu(hfac)₂(ethynylpyridine) (1) and Cu(hfac)₂(ImH)₂ (2), respectively. The reaction of Cu(hfac)₂ · (ethynylpyridine) (1) and ethynylpyridine with oxygen in tmeda (tmeda = N,N,N′,N′-tetramethylethylenediamine) in the presence of copper(I) chloride gives Cu(hfac)₂(tmeda) (3). Finally, [Cu(hfac)₂(H₂O)]₂(μ-TCNE) (4) was prepared by reaction of Cu₂O on the free acid β-diketone in the presence of TCNE (TCNE = tetracyanoethylene) (ratio 1.5:1:1), under an atmosphere of oxygen-free Ar. The previously synthesized Cu(hfac)TCNE proceeded further reaction by disproportionation, yielding [Cu(hfac)₂(H₂O)]₂(μ-TCNE). All new compounds have been structurally characterized and their thermal properties were examined by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

Synthesis,characterization and structure of ruthenium(II) phosphine complexes with N-heterocyclic thiolate ligands

The [Ru(dppb)(mbt)₂], mbt = 2-mercaptobenzothiazole, complex, isolated from the reaction of the mer-[RuCl₃(dppb)(OH₂)] complex with the 2,2′-dithiobis(benzothiazole), mbts, was characterized by spectroscopic and electrochemical techniques (E_1/2 = 0.78 V versus NHE) and its structure was determined by crystal X-ray analysis. The structural analysis suggests that the S–S bond of the mbts ligand is cleaved, thus forming two four-membered chelate rings coordinated to the ruthenium through the N,S-donor atoms of the mbt reduced ligands, with an average bite angle of 67.295(11)°. The ¹H and ¹³C NMR signals observed for mbts ligand coordinated to the metal center, the changes in the vibrational spectra, and the appearance of a MLCT band in the electronic spectrum of the complex point for the reduced state of the ruthenium metal center, Ru^II. These reducing processes are suggested to be due to the methanol interference, which is observed to be strongly affected by N-methylmorpholine. The cytochrome c electrochemistry was analyzed by using the SAMs formed by the mbts and the [Ru(dppb)(mbt)₂] complex on gold, with only the former presenting electroactivity.     

Synthesis and characterization of thiolato-bridged cadmium(II) complexes with NNS-chelating thiolic ligands

Cadmium(II) complexes with 2-[(2-aminoethyl)amino]ethanethiol (HL¹), 2-[(3-aminopropyl)amino]ethanethiol (HL²), 2-[(2-pyridylmethyl)amino]ethanethiol (HL³), and 2-[[2-(2-pyridyl)ethyl]amino]ethanethiol (HL⁴), [Cd(L¹)](ClO₄) (1), [Cd(L²)](ClO₄)·1/2CH₃OH (2), [Cd{Cd(L²)₂}₂](ClO₄)₂·CH₃CON(CH₃)₂ (3a·CH₃CON(CH₃)₂), [Cd{Cd(L²)₂}₂]Cl₂·2CH₃OH (3b·2CH₃OH), [Cd{Cd(L³)₂}₂](ClO₄)₂ (4), [Cd(L⁴)](ClO₄) (5), have been synthesized and characterized by measurements of the infrared and electronic spectra. The X-ray crystal structures show that 3a and 3b have a thiolato-bridged trinuclear core with a linear arrangement of three metal atoms.     

Mononuclear metal complexes with ciprofloxacin: Synthesis, characterization and DNA-binding properties

Five novel metal complexes of the quinolone antibacterial agent ciprofloxacin with Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺ and have been prepared and characterized with physicochemical, spectroscopic and electrochemical techniques. In all these complexes, ciprofloxacin acts as a bidentate deprotonated ligand bound to the metal through the pyridone oxygen and one carboxylate oxygen. The central metal in each complex is six-coordinate and a slightly distorted octahedral geometry is proposed. The lowest energy model structures of the Mn²⁺, Fe³⁺ and complexes have been determined with molecular modeling calculations. The cyclic voltammograms of the complexes have been recorded in dmso solution and in 1/2 dmso/buffer (containing 150 mM NaCl and 15 mM trisodium citrate at pH 7.0) solution and the corresponding redox potentials have been estimated. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT DNA) with UV and fluorescence spectroscopies and cyclic voltammetry. UV studies of the interaction of the complexes with DNA have shown that these compounds can bind to CT DNA. The binding constants of the complexes with CT DNA have also been calculated. The cyclic voltammograms of the complexes in the presence of CT DNA have shown that the complexes can bind to CT DNA by both the intercalative and the electrostatic binding mode. Competitive studies with ethidium bromide (EB) have shown that the complexes exhibit the ability to displace the DNA-bound EB indicating that the complexes bind to DNA probably via intercalation in strong competition with EB for the intercalative binding site.     

Nickel(II) complexes bearing pyrazolylimine ligands: Synthesis, characterization, and catalytic properties for ethylene oligomerization

Four phenyl-substituted pyrazolylimine ligands 2-(C₃HN₂Me₂-3,5)(C(Ph)N(4-R₂C₆H₂(R₁)₂-2,6)) (L1: R₁ = ⁱPr, R₂ = H; L2: R₁ = H, R₂ = NO₂; L3: R₁ = R₂ = H; L4: R₁ = H, R₂ = OCH₃) were synthesized. The influences of steric bulk and electronic effect of pyrazolylimine ligands on the structures of their corresponding nickel complexes were investigated. Ligands with more bulky and electron withdrawing substituents on N-phenyl ring produced four-coordinate nickel complexes (2-(C₃HN₂Me₂-3,5))(C(Ph)(4-R₂C₆H₂(R₁)₂-2,6)NiBr₂ (1, R₁ = ⁱPr, R₂ = H; 2, R₁ = H, R₂ = NO₂)), whereas the ligands with less bulky and electron donating substituents on N-phenyl ring formed bis-pyrazolylimine dinickel tetrahalides (bis-2-(C₃HN₂Me₂-3,5))(C(Ph)N(4-R₂C₆H₂ (R₁)₂-2,6)Ni₂Br₄ (3, R₁ = R₂ = H; 4, R₁ = H, R₂ = OCH₃)) and six-coordinate nickel dihalides (bis-2-(C₃HN₂Me₂-3,5))(C(Ph)N(4-R₂C₆H₂(R₁)₂-2,6) NiBr₂ (5, R₁ = R₂ = H;6, R₁ = H, R₂ = OCH₃)). The solid-state structures of complexes 1, 4 and 5 have been confirmed by X-ray single-crystal analyses. Activated by methylaluminoxane (MAO), complexes 1, 2, 5 and 6 showed moderate to high activity for ethylene oligomerization, and complex 5 revealed the highest activity up to 8.96 × 10⁵ g oligomer/(mol Ni · h). The proportions of resultant oligomers were mainly C4-C8 and a little C10-C14 determined by gas chromatography/mass spectrometry.     

Synthesis and characterization of nickel(II) and copper(II) complexes with tetradentate Schiff base ligands

The 1:1 condensation of 1,2-diaminopropane and 1-phenylbutane-1,3-dione at high dilution gives a mixture of two positional isomers of terdentate mono-condensed Schiff bases 6-amino-3-methyl-1-phenyl-4-aza-2-hepten-1-one (HAMPAH) and 6-amino-3,5-dimethyl-1-phenyl-4-aza-2-hexen-1-one (HADPAH). The mixture of the terdentate ligands has been used for further condensation with pyridine-2-carboxaldehyde or 2-acetylpyridine to obtain the unsymmetrical tetradentate Schiff base ligands. The tetradentate Schiff bases are then allowed to react with the methanol solution of copper(II) and nickel(II) perchlorate separately. The X-ray diffraction confirms the structures of two of the complexes and shows that the condensation site of the diamine with 1-phenylbutane-1,3-dione is the same.     

Synthesis and characterization of the acetazolamide complexes of Co(II) and Zn(II)

The preparation and characterization of the complexes of Acetazolamide (Acm) with Co(II) and Zn(II) are described. The complexes are of the type M(Acm)₂(NH₃)₂. Monodentate or bidentate behaviour of Acm from the electronic properties and the IR spectral data is discussed. The probable structures of the complexes are proposed.     

Synthesis and characterization of ruthenium(II) complexes bearing the bis(2-pyridylmethyl)amine ligand

The reaction of [Ru(CO)₂Cl₂]_n with bis(2-pyridylmethyl)amine (bpma) in refluxing ethanol followed by anion exchange yields two products: cis,fac-[Ru(bpma)(CO)₂Cl]PF₆ (1a, 71%) and trans,fac-[Ru(bpma)(CO)₂Cl]PF₆ (1b, 29%). Reaction of 1a with AgBF₄ in acetone, followed by acetonitrile and then anion exchange gave cis,fac-[Ru(bpma)(CO)₂(CH₃CN)](PF₆)₂ (2a). In the same way, 1b afforded trans,fac-[Ru(bpma)(CO)₂(CH₃CN)](PF₆)₂ (2b). Reaction of depolymerized [Ru(CO)₂Cl₂]_n with bpma in ethanol at room temperature afforded cis,cis-[Ru(η²-bpma)(CO)₂Cl₂] (3). In refluxing ethanol, 3 was converted to cis,fac-[Ru(bpma)(CO)₂Cl]Cl (1a-Cl). Heating 3 in chlorobenzene afforded 1b-Cl, exclusively; heating 3 in ethylene glycol gave mainly 1a-Cl. Heating 1a-Cl in ethanol resulted in no isomerization, but heating in chlorobenzene gave a mixture of 3 and 1b-Cl. Anion exchange for PF₆ with 1a-Cl and 1b-Cl afforded 1a and 1b, respectively, whereas anion exchange for BPh₄ afforded 1a-BPh₄. Compounds 1a, 1b, 2a and 3 have been structurally characterized.     

Synthesis, characterization, structure, molecular modeling studies and biological activity of sterically crowded Pt(II) complexes containing bis(imidazole) ligands

The syntheses, structures and biological evaluation of a series of cisplatin-like complexes containing bis(imidazole) derivatives - the so-called Joseph ligands - are described. Their cytotoxicity is discussed in terms of their polar surface area, rate of aquation, and lipophilicity. The X-ray crystal structure of the platinum diiodido derivative of dimethyl 2-(di(1H-imidazol-2-yl)methyl)malonate) is reported and compared to those of related systems. Molecular modeling studies are focused on the hydrogen bonding properties of such systems, and their relevance to antitumor activity.     

Synthesis,characterization and DNA binding studies of platinum(II) complexes with benzimidazole derivative ligands

The aim of this study was to synthesize and evaluate plasmid DNA interaction of new platinum(II) complexes with some 2-substituted benzimidazole derivatives as carrier ligands which may have potent anticancer activity and low toxicity. Twelve benzimidazole derivatives carrying indole, 2-/or 3-/or 4-methoxyphenyl, 4-methylphenyl, 3,4-dimethoxyphenyl, 3,4,5-trimethoxyphenyl, 4-methoxybenzyl, 3,4,5-trimethoxybenzyl, 3,4,5-trimethoxystyryl, 3,4,5-trimethoxybenzylthio or dimethylamino ethyl groups in their position 2 and twelve platinum(II) complexes with these carrier ligands were synthesized. The chemical structure of the platinum complexes have been characterized by their elemental analysis and FIR, ¹H NMR and mass spectra and their ¹H NMR and FIR spectra were interpreted by comparison with those of the ligands. The interaction of all the ligands and their complexes with plasmid DNA and their restriction endonuclease reactions by BamHI and HindIII enzymes were studied by agarose gel electrophoresis. It was determined that complex 1 [dichloro-di(2-(1H-indole-3-yl)benzimidazole)platinum(II)·2H₂O] has stronger interaction than carboplatin and complex 10 [dichloro-di(2-(3,4,5-trimethoxystyryl)benzimidazole)platinum(II)·2H₂O] has stronger interaction than both carboplatin and cisplatin with plasmid DNA.     

Synthesis, characterization, and magnetic properties of new binuclear CuCu bis(oxamato) complexes

Two new neutral, binuclear Cu^IICu^II bis(oxamato) complexes with the formula [Cu₂(opba)(pmdta)(MeOH)] · 1/2MeOH · dmf (3) and [Cu₂(nabo)(pmdta)(MeOH)] (4), with opba = o-phenylene-bis(oxamato), nabo = 2,3-naphthalene-bis(oxamato), pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine and dmf = dimethylformamide have been synthesized and their crystal structures have been determined. The structure of 3 consists of dimeric [Cu₂(opba)(pmdta)(MeOH)] entities, joined together by mutual intermolecular Cu?O contacts of the Cu²⁺ ion of one [Cu(opba)]²⁻ complex fragment and one carboxylate atom of the oxamato group of a second [Cu(opba)]²⁻ complex fragment. The structure of 4 consists of neutral binuclear complexes joined together by hydrogen bonds and π-π interactions, giving rise to an unique supramolecular 1D-chain. The magnetic properties of 3 and 4 were studied by susceptibility measurements versus temperature. For the intramolecular J parameter, identical values of (−114 ± 2) cm⁻¹ (3) and (−112 ± 2) cm⁻¹ (4) were obtained.     

Synthesis,spectroscopic, and biological characterization of the palladium(II) oxalato complexes with heterocyclic ligands

Palladium(II) oxalato complexes with heterocyclic ligands have been prepared and characterized by spectroscopic and biological studies. The compounds are of the general formula Pd(ox)(L)_n where ox = oxalato For n = 1, the ligand is isoxazole, 3,5-dimethylisoxazole, 2-methyl-benzoxazole, 2,5-dimethylbenzoxazole, and ethylenediamine, for n = 2, the ligand is N methylimidazole, N-ethylimidazole, N-propylimidazole, 3-amino, 5-methylisoxazole, and 5-amino 3,4 dimethylisoxazole. The Pd(ox)(L)₂ soluble in water are monomeric square-planar; the Pd(ox)(L) that are little soluble in water are dimeric square-planar with the ligand bridging bidentate except to the chelate ethylenediamine. All the compounds exhibit a certain inhibitorial effect with the exception of the Pd(ox)(en) derivative.     

Synthesis, characterization and crystal structures of Cd(II) and Zn(II) complexes with 2,2′-biimidazole

The reactions of zinc and cadmium salts with 2,2′-biimidazole (H₂biim) yielded a series of compounds in which the ligand is coordinated in the chelating bidentate mode. ZnCl₂ and [Ag(H₂biim)](NO₃) in methanol in a 2:1 proportion produced Zn(H₂biim)Cl₂, in which the metal has a distorted tetrahedral coordination. A 1:2 ratio led to [Zn(H₂biim)₂(CH₃OH)₂](NO₃)₂, containing an octahedrally coordinated Zn(II) center with the O-bonded methanol ligands occupying trans positions. The corresponding [Cd(H₂biim)₂(CH₃OH)₂](NO₃)₂ compound was obtained from CdCl₂. By starting with Cd(NO₃)₂ and Cd(ClO₄)₂ in aqueous media, the related octahedral bis-chelate compounds [Cd(H₂biim)₂(NO₃)(H₂O)](NO₃) and Cd(H₂biim)₂(ClO₄)₂, respectively, were isolated, the apical positions being filled by perchlorate oxygens in the latter case. With Cd(BF₄)₂, the glass container participated in the reaction and a tris-chelate complex [Cd(H₂biim)₃]₂(SiF₆)(BF₄)₂ · 6EtOH was isolated. The [Cd(H₂biim)₃]²⁺ and ions define an extended hydrogen-bonded network, in which ions surrounded by disordered ethanol molecules occupy large cavities. The two free N-H groups provide H₂biim with a unique ability to form hydrogen bonds and their interactions with counter anions or other acceptors play a determining role in controlling molecular packing. The IR spectra of all compounds are discussed.     

Synthesis, structures and magnetic properties of nicotinato-copper(II) complexes with polybenzimidazole and polyamine ligands

Four novel nicotinato-copper(II) complexes containing polybenzimidazole and polyamine ligands were synthesized with formula [Cu₂(bbma)₂(nic)₂](ClO₄)₂·CH₃OH·0.5H₂O (1), [Cu₂(dien)₂(nic)₂](ClO₄)₂·2CH₃OH (2), [Cu(ntb)(nic)]ClO₄·H₂O (3) and [Cu(tren)(nic)]BPh₄·CH₃OH·H₂O (4), in which bbma is bis(benzimidazol-2-yl-methyl)amine, dien is diethylenetriamine, ntb is tris(2-benzimidazolylmethyl)amine, tren is tris(2-aminoethyl)amine and nic is nicotinate anion. All of the complexes were characterized by elemental analysis, IR and X-ray diffraction analysis. Complexes 1 and 2 contain centrosymmetric dinuclear entity with the two Cu(II) atoms bridged by two nicotinate anions in an anti-parallel mode. The Cu···Cu separation is 7.109 Å for 1 and 6.979 Å for 2. Complexes 3 and 4 are mononuclear with nicotinate coordinated to Cu(II) ion by the carboxylate O atom in 3 and the pyridine N atom in 4. All of the complexes exhibit abundant hydrogen bonds to form 1D chain for 1, 3, 4 and 2D network for 2. Magnetic susceptibility measurements over the 2-300 K range reveal very weak ferromagnetic interaction between the two Cu(II) ions in 1 and antiferromagnetic interaction in 2 mediated by nicotinate ligand, with J value to be 0.15 and −0.19 cm⁻¹, respectively.     

Synthesis, characterization and DNA-binding properties of a new cobalt(II) complex: Co(bbt)2Cl2

A new bis(N-benzyl-benzotriazole)dichloro Co(II) complex (Co(bbt)(2)Cl(2)) was synthesized and the structure was characterized by X-ray crystallography, IR spectrum and elemental analysis. The electrochemical characterization of Co(bbt)(2)Cl(2) was measured in detail, and the interaction of this Co(II) complex with fish sperm DNA was studied by electrochemical techniques and ultraviolet-visible (UV-Vis) spectrophotometry. The cyclic voltammetry (CV) showed that Co(bbt)(2)Cl(2) had two reduction peaks and one oxidation peak on gold electrode. It was found that the currents of both the reduction peaks and the oxidation peak decreased significantly in the presence of DNA compared with those in the absence of DNA, which indicated that Co(bbt)(2)Cl(2) could interact with DNA. The binding of DNA with the complex was not only electrostatic binding but also intercalation.