Synthesis,crystal structure,DNA binding,and oxidative cleavage activity of copper(II)-bipyridyl complexes containing tetraalkylammonium groups

Two copper(II) complexes of disubstituted 2,2′-bipyridine (bpy = 2, 2′-bipyridine) with tetraalkylammonium groups, [Cu(L¹)₂Br](ClO₄)₅·2H₂O (1) and [Cu(L²)₂Br](ClO₄)₅·H₂O (2) (L¹ = [4, 4′-(Et₃NCH₂)₂-bpy]²⁺, L² = [4, 4′-((n-Bu)₃NCH₂)₂-bpy]²⁺), have been synthesized and characterized. X-ray crystallographic study of 1 indicates that Cu(II) is a distorted trigonal bipyramidal or square pyramid. DNA binding of both complexes was studied by UV spectroscopic titration. In the presence of reducing reagents, the cleavage of plasmid pBR322 DNA mediated by both complexes was investigated and efficient oxidative cleavage of DNA was observed. Mechanistic study with reactive oxygen scavengers indicates that hydrogen peroxide and singlet oxygen participate in DNA cleavage.     

Synthesis and characterization of bis(2,2′-bipyridine) ruthenium complexes containing thiosemicarbazide ligands: unique redox series

Two series of heterochelates of ruthenium(II) containing two bipyridyl molecules and a bidentate chelating sulfur---nitrogen donor ligand in the form of 4-aryl substituted thiosemicarbazides have been synthesized and characterized. The first series of complexes are dicationic in which the ring substituted 4-aryl thiosemicarbazides (N---S) are chelated in the keto form through the hydrazinic nitrogen and the thione sulfur atom. They are of the [Ru(bpy)₂NS]⁺² type. The second series have the general formula [Ru(bpy)₂NS]⁺¹ in which the thiosemicarbazide moiety remains chelated to the Ru^II centre through the hydrazinic nitrogen and the deprotonated thiolato S-atom. All the complexes have been characterized by elemental analysis, UV-vis, IR and EPR spectroscopy. The complexes were found to constitute a three membered redox series which were investigated by cyclic voltammetry.     

Solid state coordination chemistry of copper(II)/α-hydroxycarboxylato/2,2′-bipyridine systems

Four new two-ligand complexes of copper(II) with 2,2′-bipyridine and one of three different α-hydroxycarboxylic acids (lactic, H₂LACO; 2-methyllactic, H₂MLACO; and mandelic, H₂MANO) were prepared. Complexes 1–3 of general formula [Cu(HL)₂(bipy)]·nH₂O (HL=monodeprotonated acid), were characterized by elemental analysis, IR, electronic and EPR spectroscopy, magnetic measurements and thermogravimetric analysis. Complexes 1 (HL=HLACO, n=2), 2 (HL=HMLACO, n=1) and 3a (the result of attempted recrystallization of 3, of formula [Cu(HMANO)(bipy)₂](HMANO)·H₂MANO·CH₃CN were studied by X-ray diffractometry. The copper atom is in an elongated, tetragonally distorted octahedral environment in 1 and 2 and in 3a has a coordination polyhedron intermediate between a square pyramid and a trigonal bipyramid, as evaluated in terms of the parameter τ. In 1 and 2 the α-hydroxycarboxylato ligand is bidentate and monoanionic but in 3a there are three forms: a monodentate monoanion, a monoanionic counterion, and a neutral molecule.     

Structures of 3,3′-dicarbometoxy-2,2′-bipyridine complexes with silver(I) and copper(II) cations

The structures of 3,3′-dicarbometoxy-2,2′-bipyridine (dcmbpy) complexes with copper(II) and silver(I) cations have been determined using single crystal X-ray-diffraction. The crystals of Cu(dcmbpy)Cl₂ are monoclinic, C2/c, a = 16.966(3), b = 18.373(3), c = 13.154(2) Å, β = 126.543(3)°. The crystals of Ag(dcmbpy)NO₃ · H₂O are also monoclinic, C2/c, a = 16.7547(13), b = 11.0922(9), c = 18.7789(18) Å, β = 100.228(7)°. The results have been compared with the literature data on the complexes of dcmbpy and its precursors: 2,2′-bipyridine (bpy) and 3,3′-dicarboxy-2,2′-bipyridine (dcbpy). Two types of complexes of 3,3′-carboxy derivatives of bpy are distinguished: (1) with metal atom bonded to two N atoms of the same molecule and (2) with metal atom bonded to two N atoms of two different molecules. The Cu(dcmbpy)Cl₂ complex belongs to the first type, whereas Ag(dcmbpy)NO₃ · H₂O belongs to the second type.     

Synthesis, characterization and crystal structure determination of zinc (II) and mercury (II) complexes with 2,2′-dimethyl-4,4′-bithiazole

The 2,2′-dimethyl-4,4′-bithiazole ligand (1), (dm4bt), and its Zn and Hg complexes have been prepared. A conformational property calculation at the DFT level for the ligand shows the anti conformation is energetically more stable by about 22.83 kJ/mol and the rotational barrier is about 32.01 kJ/mol for the anti → syn conversion, a phenomena happening during complex formation. The complexes [Zn(dm4bt)Cl₂] (2) and [Hg(dm4bt)Cl₂] (3) have spectral properties typical for d¹⁰ metal diimine systems. The structures of the ligand and the two complexes have been determined by the single crystal diffraction method. The X-ray structure determinations show that both complexes are four coordinated by two chloride atoms and one bidentate dm4bt. In the Hg complex one of the two chlorides is set at a semi-bridging position.     

Synthesis,characterization, and metal complexes of polyacetylenes with pendant 2,2′‐bipyridyl groups

5‐Ethynyl‐2,2′‐bipyridine ( 1 ; bpyC≡CH) polymerized in the presence of catalytic amounts of [RhF(COD)(PPh₃)] or [Rh(μ‐OH)(COD)]₂ (COD = 1,5‐cyclooctadiene) in 74–91% yields. In contrast, [Rh(μ‐X)(NBD)]₂ (X = Cl or OMe; NBD = norbornadiene) did not catalyze the polymerization of 1 or gave low yields of the polymer. The obtained polymer, poly(5‐ethynyl‐2,2′‐bipyridine) [ 2 ; (bpyC?CH)_n], was highly stereoregular with a predominant cis–transoidal geometry. Random copolyacetylenes containing the 2,2′‐bipyridyl group with improved solubility in organic solvents were obtained by the treatment of a mixture of 1 and phenylacetylene ( 3 ) or 1‐ethynyl‐4‐n‐pentyl‐benzene with catalytic amounts of [RhF(COD)(PPh₃)]. A block copolymer of 1 and 3 was prepared by the addition of 1 to a poly(phenylacetylene) containing a living end. The reaction of 2 with [Mo(CO)₆] produced an insoluble polymer containing [Mo(CO)₄(bpy)] groups, whereas with [RuCl₂(bpy)₂] or [Ru(bpy)₂(CH₃COCH₃)₂](CF₃SO₃)₂, it gave soluble metal–polymer complexes containing [Ru(bpy)₃]²⁺ groups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3167–3177, 2005     

Cobalt complexes of terpyridine ligands: Crystal structure and nuclease activity

Cobalt(II) (1) and cobalt(III) (2) complexes of tridentate ligand, imidazole terpyridine (Itpy), have been synthesized and characterized by both spectroscopic and electrochemical techniques. Single crystal X-ray diffraction studies of complexes 1 and 2 shows that the complexes belong to monoclinic crystal system, with the two Itpy ligands coordinated to the central metal ion. The binding behavior of both the cobalt complexes to calf thymus DNA has been investigated by UV–Vis, fluorescence spectroscopy, viscosity and electrochemical measurements. The results suggest that complexes 1 and 2 bind to DNA through intercalation. The intrinsic DNA binding constant values obtained from absorption spectral titration studies were found to be (5.07 ± 0.12) × 10³ M⁻¹ and (7.46 ± 0.16) × 10³ M⁻¹, respectively, for complexes 1 and 2. Gel electrophoresis studies with the cobalt complexes show that while complex 1 cleaves DNA in the presence of hydrogen peroxide, complex 2 cleaves DNA in the presence of ascorbic acid and hydrogen peroxide.     

Synthesis,crystal structure,spectroscopy, and nuclease activity of copper(II) complexes containing N,N-bis(2-pyridylmethyl)amine ligand

[Cu(bpea)Cl]ClO₄ (1) and a new copper(II) complex [Cu(bpma)(Ph-COO)(H₂O)]ClO₄ (2) [bpea?=?N,N-bis(2-pyridylmethyl)ethylamine; bpma?=?N,N-bis(2-pyridylmethyl)methylamine] have been synthesized. Complex 2 was crystallized in monoclinic space group P2₁/c with unit cell parameters a ?=?16.460(6)?Å, b ?=?11.222(4)?Å, c?=?12.522(5)?Å, and β?=?97.985(6)°. Interactions of the complexes with calf thymus DNA (CT-DNA) have been investigated by UV absorption, fluorescence, and cyclic voltammetry; thus, modes of CT-DNA binding for the complexes have been proposed. Furthermore, DNA cleavage activities by the complexes were performed in the absence of any external agents. The influence of complex concentration or reaction time on the DNA cleavage was studied.     

Formation of hydrogen-bonded complexes of 3,3′,5,5′-tetrabromo-2,2′-biphenol with MTBD and triethylamine

The complexes of 3,3′,5,5′-tetrabromo-2,2′-biphenol (TBBPh) with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) and triethylamine (TEA) were studied by FTIR spectroscopy. In chloroform and in acetonitrile a proton transfer from TBBPh to N-bases (MTBD, TEA) occurs. In chloroform solution the protonated N-base molecules are hydrogen-bonded to the deprotonated TBBPh molecules, whereas in acetonitrile the complexes dissociate. The intra- as well as intermolecular hydrogen bonds within the chains show large proton polarizability.     

Oxidative DNA cleavage promoted by multinuclear copper complexes: activity dependence on the complex structure

Polynuclear copper complexes with two or three Cu(BPA) (BPA, bis(2-pyridylmethyl)amine) motifs, [Cu2(mTPXA)Cl4]3 H2O (1), [Cu2(pTPXA)Cl4]3 H2O (2), [Cu3(HPTAB)Cl5]Cl3 H2O (3) (mTPXA = N,N,N',N'-tetra-(2-pyridylmethyl)-m-xylylene diamine; pTPXA = N,N, N',N'-tetra-(2-pyridylmethyl)-p-xylylenediamine; HPTAB = N,N,N',N',N',N'-hexakis(2-pyridylmethyl)-1,3,5-tris-(aminomethyl)benzene) have been synthesized and characterized. The crystal structures of compounds 2 and 3 showed each Cu(BPA) motif had a 4+1 square-pyramidal coordination environment with one chloride occupying the apical position and three N atoms from the same BPA moiety together with another Cl atom forming the basal plane. Fluorescence and circular dichroism (CD) spectroscopy studies indicated that the DNA binding followed an order of 3>2>1 in the compounds. These complexes cleave plasmid pUC19 DNA by using an oxidative mechanism with mercaptopropionic acid (MPA) as the reductant under aerobic conditions. Dinuclear Cu2+ complexes 1 and 2 showed much higher cleavage efficiency than their mononuclear analogue [Cu(bpa)Cl2] at the same [Cu2+] concentration, suggesting a synergistic effect of the Cu2+ centers. Moreover, the meta-dicopper centers in complex 1 facilitated the formation of linear DNA. Interestingly, the additional copper center to the meta-dicopper motif in complex 3 decreased the cleavage efficacy of meta-dicopper motif in complex 1, although it is able to cleave DNA to the linear form at higher [Cu2+] concentrations. Therefore, the higher DNA binding ability of complex 3 did not lead to higher cleavage efficiency. These findings have been correlated to the DNA binding mode and the ability of the Cu2+ complexes to activate oxygen (O2). This work is a good example of the rational design of multinuclear Cu2+ artificial nuclease and the activity of which can be manipulated by the geometry and the number of metal centers.     

The crystal and molecular structure of potassium aquapentachloroiridate(III) and the H, C, N NMR coordination shifts in iridium(III) chloride complexes with 2,2′-bipyridine or 1,10-phenanthroline

The crystal and molecular structure of potassium aquapentachloroiridate(III) (K₂[Ir(H₂O)Cl₅]) was reported. The [Ir(H₂O)Cl₅]²⁻ anions are nearly octahedral, the axial Ir–Cl bond (2.322(2) Å) being shorter than the equatorial ones (2.346(2)–2.360(2) Å); the Ir–O bond length is 2.090(4) Å. Ir(III) chloride complexes with 2,2′-bipyridine (LL = bpy) or 1,10-phenanthroline (LL = phen), of the general formulae K[Ir(LL)Cl₄] and cis-[Ir(LL)₂Cl₂]Cl, were studied by far-IR and ¹H–¹³C, ¹H–¹⁵N HMBC/HMQC/HSQC–NMR. High-frequency ¹H NMR coordination shifts (Δ^1H_coord = δ^1H_complex − δ^1H_ligand; max. ca. +1 ppm) were noted for [Ir(LL)Cl₄]⁻ anions, while for cis-[Ir(LL)₂Cl₂]⁺ cations they had variable sign and magnitude (max. ca. ±1 ppm); they were dependent on the proton position, being mostly expressed for the nitrogen-adjacent hydrogens (H(6) for bpy, H(2) for phen). ¹³C NMR signals were high-frequency shifted (by max. ca. 8 ppm), whereas all ¹⁵N nuclei were shifted to the lower frequency (by ca. 105–120 ppm). The experimental ¹H, ¹³C, ¹⁵N NMR chemical shifts were reproduced by semi-empirical quantum-chemical calculations (B3LYP/LanL2DZ+6-31G^**//B3LYP/LanL2DZ+6-31G*).     

Selective complexometric determination of copper in ores and alloys using 2,2′-bipyridyl as masking agent

An EDTA titration method is described for the determination of copper(II) in the presence of other ions based on the selective masking ability of 2,2′-bipyridyl. Copper and other ions in a given sample solution are initially complexed with an excess of EDTA and the surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as an indicator. A known excess of 2,2′-bipyridyl solution (1% in 50% alcohol) is then added, the mixture is shaken well and the released EDTA from the Cu–EDTA complex is titrated against standard lead nitrate solution. The interference of various ions are studied and the method is applied to the determination of copper in its ores and alloys. Reproducible and accurate results are obtained for 2.54–25.40 mg of copper with S.D. values <0.04 mg.     

Two complexes of PtIV and AuIII with 2,2′‐dipyridylamine and 2,2′‐dipyridylaminide ligands

Two noble metal complexes involving ancillary chloride ligands and chelating 2,2′‐bipyridylamine (Hdpa) or its deprotonated derivative (dpa), namely [bis(pyridin‐2‐yl‐κN)amine]tetrachloridoplatinum(IV), [PtCl₄(C₁₀H₉N₃)], and [bis(pyridin‐2‐yl‐κN)aminido]dichloridogold(III), [AuCl₂(C₁₀H₈N₃)], are presented and structurally characterized. The metal atom in the former has a slightly distorted octahedral coordination environment, formed by four chloride ligands and two pyridyl N atoms of Hdpa, while the metal atom in the latter has a slightly distorted square‐planar coordination environment, formed by two chloride ligands and two pyridyl N atoms of dpa. The difference in conjugation between the pyridine rings in normal and deprotonated 2,2′‐dipyridylamine is discussed on the basis of the structural features of these complexes. The influence of weak interactions on the supramolecular structures of the complexes, providing one‐dimensional chains of [PtCl₄(C₁₀H₉N₃)] and dimers of [AuCl₂(C₁₀H₈N₃)], are discussed.     

Crystal structure of 3-diethylaminomethyl-2,2′-biphenol

Crystals of 3-diethylaminomethyl-2,2′-biphenol were examined using X-ray diffraction and FT-IR spectroscopy. Their space group is P2₁/c with a=7.305(1), b=13.816(2), c=29.232(4) Å, β=92.411(3)° and Z=8. The unit cell contains two symmetry-independent zwitterions. The hydrogen atom of the protonated diethylaminomethyl group is linked to the negatively charged phenolate oxygen atom, which in turn is linked to the hydroxyl group by a short hydrogen bond (molecule a: NO=2.604(3), OO=2.512(3) Å; molecule b: NO=2.593(4), OO=2.489(4) Å). The OHO⁻H⁺N bifurcated intramolecular hydrogen bonds are crystallographically asymmetric. The IR spectrum of the crystals confirms very well the results obtained by the X-ray study. Instead of continuous absorption, only broad bands are found indicating relatively low proton polarisability in the two types of intramolecular hydrogen bonds.     

Synthesis,characterization, and biological and anticancer studies of mixed ligand complexes with Schiff base and 2,2′‐bipyridine

New mixed ligand complexes of transition metals were synthesized from a Schiff base (L¹) obtained by the condensation reaction of oxamide and furfural as primary ligand and 2,2′‐bipyridine (L²) as secondary ligand. The ligands and their metal complexes were studied using various spectroscopic methods. Also thermal analyses were conducted. The mixed ligand complexes were found to have formulae [M(L¹)(L²)]Cl_m ⋅n H₂O (M = Cr(III) and Fe(III): m  = 3, n  = 0; M = Cu(II) and Cd(II): m  = 2, n  = 1; M = Mn(II), Co(II), Ni(II) and Zn(II): m  = 2, n  = 0). The resultant data revealed that the metal complexes have octahedral structure. Also, the mixed ligand complexes are electrolytic. The biological and anticancer activities of the new compounds were tested against breast cancer (MCF‐7) and colon cancer (HCT‐116) cell lines. The results showed high activity for the synthesized compounds.     

Cu–Ni heterobimetallic compounds. Part 2: Study of the system Cu(II)–bpy–[Ni(CN)4] (bpy = 2,2′-bipyridine)

Two new complexes [Ni(bpy)₃][Cu(CN)₃]·4.5H₂O (1) and [Cu(bpy)₂(CN)]₂[Ni(CN)₄]·4H₂O (2) (bpy = 2,2′-bipyridine) have been synthesized from aqueous-ethanolic solution. The crystal structures of both 1 and 2 are ionic. The crystal structure of 1 is built up of [Ni(bpy)₃]²⁺ and [Cu(CN)₃]²⁻ complex ions, and disordered solvated water molecules. While the Ni(II) atom is octahedrally coordinated by three chelate bonded bidentate bpy ligands with Ni–N bond 2.0851(1) Å (6×), the Cu(I) atom is in trigonal coordination with Cu–C bond 1.9440(1) Å (3×). Crystal structure of 2 consists of a rare [Cu(bpy)₂(CN)]⁺ complex cations, [Ni(CN)₄]²⁻ complex anions (ratio 2:1) and solvated water molecules; in the complex cation the Cu(II) atom is penta-coordinated with terminal cyanido ligand. In both crystal structures the not coordinated water molecules are involved in hydrogen bonding. Thermal study on air of both 1 and 2 did not indicate formation of a stable intermediate; the solid residues are formed of a mixture of CuO and NiO. Magnetic susceptibilities of both 1 and 2 are described by Curie–Weiss behavior with θ values of −1.37 K (1) and −0.54 K (2) due to the action of weak antiferromagnetic interactions in 1 and 2, respectively.     

2-Benzothiazolylthioacetic acid and 4,4′-bipyridine as ligands in designing low-dimensional coordination polymers: Synthesis, architectures and magnetic properties

The combined use of 4,4′-bipyridine (4,4′-bipy) and 2-benzothiazolylthioacetic acid (HBTTAA) as ligands with Mn(II), Cd(II), Co(II) and Cu(II) ions afforded six polymeric complexes, namely {[Mn₃(BTTAA)₄(4,4′-bipy)₄](ClO₄)₂ · 2H₂O}_n (1), [Mn(BTTAA)₂(4,4′-bipy)₂]_n (2), [Cd(BTTAA)₂(4,4′-bipy)₂]_n (3), [Cd(BTTAA)(4,4′-bipy)(NO₃)(H₂O)]_n (4), [Co(BTTAA)₂(4,4′-bipy)(H₂O)₂]_n (5) and [Cu(BTTAA)₂(4,4′-bipy)]_n (6). All these complexes have been characterized by a combination of analytical, spectroscopic and crystallographic methods. Complex 1 is a novel 2D network formed by two different 4⁴ grid networks, whereas isomorphous complexes 2 and 3 exhibit a 2Dl coordination architecture formed by the same 4⁴ grid network. In 4–6, extended 1D chains are formed, with the 4,4′-bipy molecules acting as rigid rod-like links between adjacent metal centers. The carboxylato groups of BTTAA in these complexes exhibit four different coordination modes, namely monodentate, chelating, bridging and bridging-chelating modes. The magnetic properties of 1, 2, 5 and 6 were investigated in the temperature range 2.0–300.0 K. Variable temperature magnetic susceptibility measurements show weak antiferromagnetic interactions in these complexes.