Synthesis, structure and properties of two bimetallic compounds [Co(bpy)2 (NiL)] (ClO4)2 and {[Co(phen)3](NiL)}(ClO4)2 containing a macrocyclic oxamide ligand

Two compounds, [Co(bpy)₂(NiL)](ClO₄)₂ (1)and {[Co(phen)₃](NiL)}(ClO₄)₂ (2), have been synthesized: (H₂L=2,3-dioxo-5,6,14,15-dibenzo-1,4,8,12-tetraazacylotetradeca-7,12-diene, bpy=2,2-bypyridine and phen = 1,10-phenanthroline). Compound (1) contains a discrete binuclear [Co(bpy)₂(NiL)]²⁺ cation, while compound (2) is composed of [Co(phen)₃]²⁺ cations and NiL neutral fragments. The magnetic properties of compound (1) have been dealt with by isotropic one-ion approximation of the Co^II ion with a spin--orbit coupling in an O_h symmetry environment. The electronic spectra of these two compounds have also been discussed.     

Three new copper(II)–nickel(II) heterodinuclear complexes with the <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N′</Emphasis>-bis(2-pyridyl-ethyl)oxamide dianion. Syntheses,spectra, and magnetic properties

Three new Cu(II)–Ni(II) heterodinuclear complexes: [Cu(PMoxd)Ni(phen)₂](ClO₄)₂ (1), [Cu(PMoxd)Ni(NO₂-phen)₂](ClO₄)₂ (2), [Cu(PEoxd)Ni(Me₂-bpy)₂](ClO₄)₂ (3), [where Cu(PMoxd)=N,N′-bis(pyridyl-methyl)oxamidatocopper(II), Cu(PExod)=N,N′-bis(2-pyridyl-ethyl)oxamidatocopper(II), phen=1,10-phenanthroline and NO₂-phen=5-nitro-1,10-phenanthroline and bpy=2,2′-bipyridine] were prepared and characterized by i.r. and electronic spectra, and by magnetic properties. The magnetic analysis was carried out by means of the theoretical expression of the magnetic susceptibility deduced from the spin Hamiltonian H=−2JS₁S₂, leading to J=−70.83 cm⁻¹ (1); −56.23 cm⁻¹ (2); −57.30 cm⁻¹ (3), indicating a weak antiferromagnetic spin–exchange interaction between Cu(II) and Ni(II) ions within three complexes.     

Synthesis and magnetic properties of binuclear cobalt(Ⅱ), nickel(Ⅱ) and copper(Ⅱ) complexes bridged by oxamidate group

Four binuclear Co(Ⅱ), Ni(Ⅱ) and Cu(Ⅱ) complexes bridged by oxamidate (oxd) group have been synthesized, namely Co2(byp)2(oxd)(ClO4)2 (1), Co2(Me2bpy)2(oxd)(ClO4)2.H2O (2), Ni2(bpy)2(oxd)(ClO4)2.2H2O (3) and Cu2(Me2bpy)2(oxd)(NO3)2 (4). (bpy=2,2'-bipyridyl, Me2-bpy=4,4'-dimethylbipyridyl, oxd=oxamidate) The complexes are characterized by IR, UV spectra, EPR and variable-temperature magnetic susceptibility (4-300 K). The susceptibility data for. complexes 1 and 3 were least-squares fit to the susceptibility equation derived from the spin Hamiltonian H=-2J . S1 . S2. The exchange integral, J, was found to be equal to -3.62 cm-1 in 1 and -1.82 cm-1 in 3. This indicates a weak antiferromagnetic spin exchange interaction between the metal ions.     

Synthetic,structural and spectroscopic studies of complexes derived from the copper(II) perchlorate/fumaric acid/N,N′-chelates tertiary reaction systems

The synthetic investigation of the Cu(ClO₄)₂·6H₂O/fumaric acid (H₂fum)/N,N’-chelates (1,10-phen, 2,2′-bpy) tertiary reaction systems has yielded mononuclear, dinuclear and tetranuclear complexes, and three coordination polymers. The chemical and structural identity of the products depends on the solvent, the absence or presence of external hydroxides in the reaction mixtures and the N,N’-donor. Three fumarato(−2) complexes, i.e. compounds [Cu₂(fum)(phen)₄](ClO₄)₂·2H₂O (1·2H₂O), [Cu(fum)(phen)(H₂O)]_n (3) and [Cu₂(fum)(bpy)₂(H₂O)₂]_n(ClO₄)_2n (6), were isolated and structurally characterized, and four non-fumarato complexes, i.e. compounds [Cu₄(μ₃-ΟΗ)₂(μ₂-ΟΗ)₂(phen)₄(H₂O)₂](ClO₄)₄·2H₂O (2·2H₂O), [Cu(ClO₄)(phen) (MeCN)₂(H₂O)](ClO₄) (4), [Cu(ClO₄)(phen)(MeCN)₂]_n(ClO₄)_n (5) and [Cu(ClO₄)₂(bpy)(MeCN)₂] (7), were simultaneously obtained from the reaction systems investigated. The coordination versatility of the fumarato(−2) ligand is reflected to the three different coordination modes observed in 1·2H₂O, 3 and 6; the monodentate bridging μ₂-κO:κO′ mode in 3, the asymmetric chelating bridging μ₂-κO:κO′:κO′′:κO′′′ mode in 1·2H₂O and 3, and the syn,syn bridging μ₄-κO:κO′:κO′′:κO′′′ mode in 6. The crystal structures of the complexes are stabilized by intra- and inter-molecular hydrogen bonding and π–π stacking interactions leading to interesting supramolecular architectures. Characteristic IR bands of the complexes are discussed in terms of the known structures, and the coordination modes of the fum²⁻ ligands.     

Synthesis,structures, and characterization of cadmium(II), cobalt(II), and copper(II) metal polymers with tetrazole-1-acetate

Three new coordination polymers {[Cd(tza)(2,2′-bpy)(H₂O)](ClO₄)} _n 1, {[Co(tza)(2,2′-bpy)(H₂O)](ClO₄)} _n 2, and {[Cu(tza)(phen)](ClO₄)} _n 3 (Htza = tetrazole-1-acetic acid, 2,2′-bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline) were synthesized and characterized by X-ray single-crystal diffraction, elemental analysis, and IR spectra. Complexes 1 and 2 exhibit 3-D architectures formed by π–π interaction of 2,2′-bpy ligands interlinking to the adjacent 2-D layers. Complex 3 is a 1-D zigzag double chain and the 3-D structure is formed by π–π stacking interaction of phen and nonclassical hydrogen bonding.     

Phosphoester binding,DNA binding,DNA cleavage and in vitro cytotoxicity studies of simple heteroleptic copper(II) complexes with bidentate ligands

Abstract

Two mononuclear heteroleptic copper complexes, [Cu(±trans-dach)(bpy)](ClO₄)₂ 1a and [Cu(±trans-dach)(phen)](ClO₄)₂ 2a [dach?=?1,2-diaminocyclohexane, bpy?=?2,2′-bipyridine and phen?=?1,10-phenanthroline], were synthesized and analyzed by CHN analysis, electronic absorption, FT-IR spectroscopy, EPR, and SXRD. The molecular structures of 1a and 2a showed octahedral geometry around Cu(II). Both complexes interacted with phosphoesters and DNA. Their binding affinities with diphenylphosphate, di n-butylphosphate, trimethylphosphate, and triphenylphosphate were studied by UV–vis spectroscopy. For understanding the stereochemical role of dach ligand toward DNA interaction, enantiopure DACH complexes [Cu(R,R-trans-dach(bpy)](ClO₄)₂ 1b, [Cu(S,S-trans-dach)(bpy)](ClO₄)₂ 1c, [Cu(cis-dach)(bpy)](ClO₄)₂ 1d, [Cu(R,R-trans-dach)(phen)](ClO₄)₂ 2b, [Cu(S,S-trans-dach)(phen)](ClO₄)₂ 2c, and [Cu(cis-dach)(phen)](ClO₄)₂ 2d were synthesized and analyzed. All complexes interacted with calf thymus-DNA (CT-DNA) as studied by UV–vis spectroscopy. The nature of binding to CT-DNA was groove/electrostatic as supported by circular dichroism, cyclic voltammetry, and docking studies. Complexes were able to cleave plasmid DNA at 12.5 µM (1a–d) and 6 µM (2a–d), where 2d showed 64% Form II and 36% Form III. The in vitro cytotoxic studies of two different cancer cell lines showed inhibition with low IC₅₀ value in comparison to reference control (cisplatin). These complexes are efficient in inducing apoptosis in cancer cells, making them viable for potent anticancer activity.     

ELECTRONIC STRUCTURES AND BONDING PROPERTIES OF MIXED LIGAND COPPER(II) COMPLEXES OF 2-(2-PYRIDYLETHYL)PICOLYLAMINE AND DIPICOLYLAMINE. MOLECULAR STRUCTURES OF (2,2′-BIPYRIDINE)[2-(2-PYRIDYLETHYL)PICOLYLAMINE]COPPER(II) PERCHLORATE AND (DIPICOLYLAMINE)(1,10-PHENANTHROLINE)COPPER(II) PERCHLORATE

Abstract

Mixed ligand copper(II) complexes of 2-(2-pyridylethyl)picolylamine (pepica) of [Cu(pepica)(pi-colinato)](ClO₄)(H₂O) and the [Cu(pepica)(L)](ClO₄)₂ type, where L stands for 2,2′-bipyridine (bipy), 1,10-phenanthroline, neocuproine, and ethylenediamine, and dipicolylamine(dipica) of the [Cu(dipica)(L)](ClO₄)₂(H₂O) _n type, where L for 2,2′-bipyridine (n = 0), 1,10-phenanthroline (phen, n = 0), and neocuproine (n = 1), have been synthesized and characterized by elemental analyses, and IR, electronic and EPR spectroscopic measurements. The molecular structures of [Cu(pepica)(bipy)](ClO₄)₂ (1) and [Cu(dipica)(phen)](ClO₄)₂ (2) have been determined using three dimensional X-ray diffraction data. Complex 1 consists of discrete distorted square pyramidal [Cu(pepica)(bipy)] cations, with a meridional pepica ligand and one of the pyridine rings of the bipy ligand forming a basal plane. The other pyridine nucleus of the bipy is bound at the apex having an elongated bond distance of 2.255 Å and tilted off the normal z axis by ～15°. Complex 2 comprises discrete distorted trigonal bipyramidal [Cu(dipica)(phen)] cations, with the two pyridine nuclei of the dipica ligand and one of the pyridine rings of the phen forming an equatorial trigonal plane and the remaining pyridine ring of the phen and the amine nitrogen of the dipica on the axial sites. The trigonal bipyramidal cation, distorted toward a square pyramidal structure, has an enlarged equatorial N(py)–Cu–N(py) angle of 132.4° and an elongated equatorial Cu–N(phen) bond of 2.156 Å. All of the complexes exhibit axial type EPR spectra. Gaussian resolved d-d spectra for these complexes, except the dipica-bipy and dipicaphen ones, yield an orbital sequence of d_x ²- _y ² ≥ d_z ² > d_xy > d_yz ～d_xz . The bonding properties of the tridentate and the bidentate ligands are elucidated.     

Synthesis and Single-crystal Structures of Two Copper(II) Complexes and One Iron(II) Complex Prepared by in situ Ligand Substitution at Room Temperature

Two hexa-coordinate copper(II) complexes formulated as [Cu(phen)(4-dmampy)₂(ClO₄)₂] and [Cu(bpy)(3-ampy)₂(ClO₄)₂] · 0.5CH₃OH · 0.5H₂O (phen = 1,10–phenanthroline bpy = 2,2′-bipyridine, 3-ampy = 3-aminopyridine, 4-dmampy = 4-dimethylaminopyridine), and one low-spin ferrous complex formulated as [Fe(dmbpy)₃](ClO₄)₂ · H₂O (dmbpy = 4,4′-dimethyl-2,2′-bipyridine), were synthesized by in situ ligand substitution at room temperature, and characterized by X-ray single-crystal diffraction. This is the first structural report where either 4-dmampy and phen molecules, or 3-ampy and bpy molecules, are located simultaneously around one metal center.     

Synthesis, crystal structures, electrochemical and spectroscopic properties of ruthenium(II) complexes containing diamino-1,3,5-triazine derivatives

Three Ru(II) complexes [Ru(bpy)₂(1-IQTNH)](ClO₄)₂ (1), [Ru(bpy)₂(2-QTNH)](ClO₄)₂ (2) and [Ru(bpy)₂(3-IQTNH)](ClO₄)₂ (3) (bpy = 2,2′-bipyridine, 1-IQTNH = 6-(isoquinolin-1-yl)-1,3,5-triazine- 2,4-diamine, 2-QTNH = 6-(quinolin-2-yl)-1,3,5-triazine- 2,4-diamine, 3-IQTNH = 6-(isoquinolin-3-yl)-1,3,5-triazine-2,4-diamine) have been synthesized and characterized by elemental analysis, ¹H NMR spectroscopy, electrospray ionization mass spectrometry and X-ray crystallography. The electrochemical and spectroscopic properties of the complexes differ from those of [Ru(bpy)₃]²⁺ owing to the structural differences between the ligands and their complexes.     

Antimycobacterial activity of mixed-ligand copper quinolone complexes

New mixed-ligand Cu^II, complexes: [Cu(cf)(phen)Cl)](BF₄) · 4H₂O (3), [Cu(cf)(bipy)(Cl)](BF₄) · 2H₂O (4) and [Cu(cf)(dafone)(Cl)](BF₄) · 2H₂O (5) (cf = ciprofloxacin, phen = 1,10-phenanthroline, bipy = 2,2-bipyridine and dafone = 4,5-diazafluoren-9-one) have been isolated and characterized by elemental analyses, i.r., u.v.–vis. spectra, magnetic susceptibility and cyclic voltammetry. Complex (4) crystallizes in the monoclinic space group P2₁/n with a = 13.8919(13) Å, b = 14.5718(13) Å, c = 14.0725(13) Å, = 95.150(2)°, V=2837.2(5) ų. All complexes possess square-pyramidal geometry. The antimycobacterial activity of ciprofloxacin and complexes (3–5) has been evaluated against Mycobacterium smegmatis, which shows clear enhancement in the antitubercular activity upon copper complexation with N—N donors.     

Ferromagnetically coupled heterobinuclear Cu(II)-Ln(III) complexes with N,N′-bis(2-aminoethyl)-oxamido dianion as a bridged ligand

Six novel μ-oxamido heterobinuclear complexes, namely Cu(oxae)Ln(Me₂bpy)₂-(ClO₄)₃ (Ln? La, Nd, Gd, Tb, Ho, Er), where oxae denotes N, N'-bis(2-aminoethyl)oxamido dianion, Me₂bpy is 4,4'-dimethyl-2,2'-bipyridyl, have been synthesized and characterised by elemental analyses, IR, conductivity measurements and electronic spectra. The temperature dependence of the magnetic susceptibility of Cu(oxae)Gd(Me₂bpy)₂(ClO₄)₃ has been measured over the range 4–300 K. The least-squares fit of the experimental susceptibilities yielded J = 1.87 cm^?1. The observed Gd(III)-Cu(II) coupling is ferromagnetic. One plausible mechanism that can cause a ferromagnetic coupling between Gd(III) and Cu(II) is discussed in terms of spin-polarization.     

Synthesis and magnetic properties of new nickel(II)-copper(II)-nickel(II) trinuclear complexes with irregular spin-state structure

Summary Four novel heterotrinuclear complexes were prepared, namely {[Ni(L)₂]₂[Cu(pba)]}(ClO₄)₂, where pba = pro-pylene-1,3-bis(oxamato) and L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂-phen), 2,2-bipyridyl (bpy), 4,4-dimethyl-2,2-bipyridyl (Me₂bpy). Based on i.r., elemental analyses, conductivity measurements and electronic spectra oxamato-bridged structures are proposed for these complexes, consisting of two nickel(II) ions, each in a distorted octahedral environment, and a copper(II) ion in a square planar environment, respectively. The temperature dependence of the magnetic susceptibility of {[Ni(phen)₂]₂[Cu(pba)]}(ClO₄)₂·H₂O was studied in the 4–300 K range, giving the exchange integral J = - 106 cm^–1. TheX _scm T versusT plot exhibited a minimum at ca. 98 K, characteristic of this kind of coupled polymetallic complex with an irregular spin-state structure. E.s.r. spectra of these complexes clearly indicated a strong rhombicity withg ₁ = 5.20,g ₂ = 2.29 andg ₃ = 2.02 (approximately), which agrees with an anisotropicS = ±1/2 Kramer doublet in the ground state.     

Synthesis,crystal structure and physicochemical properties of copper(II) complexes containing bis[(benzimidazol-2-yl)methyl] ether derivatives

A new benzimidazoyl ligand bis[(N-ethylbenzimidazol-2-yl)methyl]ether (EDGB) and Cu^II complexes [Cu(L¹) (L²)](ClO₄)·mEt₂O·nH₂O [L¹ = bis[(benzimidazol-2-yl)methyl]ether (DGB) or EDGB, L² = 2,2-bipyridine (bipy) or 1,10-phenanthroline (phen)] have been synthesized and characterized by elemental analyses and i.r. spectra. The single-crystal structure of the [Cu(phen)(DGB)(OClO₃)]ClO₄·Et₂O·0.5H₂O complex was determined by X-ray diffraction. The geometry around Cu is best described as a distorted octahedron with four nitrogen atoms from phen and DGB ligands forming the equatorial plane. The oxygen atoms of DGB and one perchlorate group are in the axial positions with semi-coordinated bonding modes. The electrochemical behavior of the complexes is described.     

Synthesis and magnetic properties of μ-oxalato-bridged Cu2 IIFeIII-type heterotrinuclear complexes

Three new -oxalato-bridged heterotrinuclear copper(II)–iron(III)–copper(II) complexes have been synthesized and identified: [Cu₂Fe(ox)₃L₂]ClO₄ [L = 5-nitro-1,10-phenanthroline (NO₂phen); 2,9-dimethyl-1,10-phenanthroline (Me₂phen) or 2,2-bipyridine (bpy), respectively]; ox = the oxalato dianions. Based on elemental analyses, molar conductivity and magnetic moment (at room-temperature) measurements, i.r. and electronic spectral studies, extended ox-bridged structures consisting of two copper(II) and an iron(III) ions, in which the central iron(III) ion has an octahedral environment and the end-capped two copper(II) ions a square-planar environment, are proposed for these complexes. The [Cu₂Fe(ox)₃(Me₂phen)₂]ClO₄ (1) and [Cu₂Fe(ox)₃(bpy)₂]ClO₄ (2) complexes were characterized further by variable-temperature magnetic susceptibility (4.2–300 K) measurements and the observed data were simulated by the equation based on the spin Hamiltonian operator, = –2J₁ · ₂, giving the exchange integrals J = –12.85 cm^–1 for (1) and J = –11.28 cm^–1 for (2). The results indicate the presence of an antiferromagnetic spin-exchange interaction between the copper(II) and iron(III) ions through the oxalato-bridge in both complexes (1) and (2).     

Solution-reaction Calorimetric Study of Coordination Compounds of Rare Earth Perchlorates with Alanine and Imidazole

Introduction Since Anghileri firstly reported that complex of LaCl3 with glycine had the antitumor function in 1975,1 coordination compounds of rare earth with amino acid have attracted increasing attention.2-4 People have found that some compounds of rare earth with amino acids possess disinfection, elimination of inflammation, de-crease of the level of blood sugar and anti-cruor func-tions. Imidazole is a wreath compound, and presents unique biological activities. Ternary coordination com-…     

Low-dimensional Compounds Containing Cyano Groups. XI. Preparation,Crystal Structure and Properties of Two Copper(II) Dicyanamide Complexes with PF<Stack><Subscript>6</Subscript><Superscript>−</Superscript></Stack> Anions

From the reaction mixtures containing Cu(NO₃)₂, Na[N(CN)₂], KPF₆ and 2,2′-bipyridine (bpy) or 1,10- phenanthroline (phen) in 1:1:1:2 molar ratios, [Cu(bpy)₂N(CN)₂][Cu(bpy)₂(H₂O)](PF₆)₃ (1b) and [Cu (phen)₂N(CN)₂]PF₆ (1p) complexes were isolated. Measured i.r. spectra confirm the presence of all functional groups in both complexes and, moreover, they indicate monodentate coordination of dicyanamide through the cyano nitrogen atom in (1p). The structure of (1b) contains two crystallographically independent complex cations. In both, Cu is coordinated by two chelating bpy molecules, and either dicyanamide anion or water molecule fills the fifth position, completing the basal plane. The Cu^II atoms in (1p) are coordinated by two chelating phen ligands and by one dicyanamide anion in the equatorial plane. Hexafluorophosphate anions in (1b) and (1p) remain uncoordinated. Besides the ionic forces in both structures, the structure of (1b) is stabilized by strong O—H···F and O—H···N hydrogen bonds and, moreover, both structures are stabilized by weak C—H···F hydrogen bonds and possible π-π interactions between pyridine rings of bpy or phen molecules.     

O-phenylenebis(oxamato) bridged trinuclear copper(II) complexes: synthesis and magnetic properties

Summary Four new trinuclear copper(II) complexes bridged by o-phenylenebis(oxamato) (opba) and end-capped with 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (NO₂-phen), 2,2-bipyridyl (bipy) or 4,4-dimethyl-2,2-bipyridyl (Me₂bipy), {[Cu(opba)][Cu(L)]₂}(ClO₄)₂ (L = phen, NO₂-phen, bipy or Me₂bipy), have been synthesized and characterized. Based on i.r., elemental analyses, conductivity measurements and electronic spectra, oxamato-bridged structures consisting of three copper(II) ions in which each copper(II) ion has a square-planar environment are proposed. The temperature-dependent magnetic susceptibility of {[Cu(opba)][Cu(phen)]₂} (ClO₄)₂ has been studied in the 4.2–300 K range, giving the exchange integral J = -134.4cm^–1. The result revealed the operation of an antiferromagnetic spin-exchange interaction between the adjacent copper ions.     

Preparation of a novel clay/metal complex hybrid film and its catalytic oxidation to chiral 1,1-binaphthol

An ITO electrode modified with a hybrid film of chiral metal complex (Λ-[Os(phen)₃]²⁺) and a clay (montmorillonite) has been prepared for the purpose of chiral sensing. As a first step, a floating monolayer of amphiphilic Os(II) complex, [Os(phen)₂(dC18bpy)](ClO₄)₂ (phen=1,10-phenanthroline, dC18bpy=4,4^′-dioctadecyl-2,2^′-bipyridyl), was formed on an aqueous dispersion of sodium montmorillonite. The monolayer acted as an organic part for the hybridization of clay particles in an aqueous phase. The hybrid film of clay and amphiphilic metal complex was transferred onto an indium tin oxide (ITO) substrate by the vertical dipping method. The next step was to immerse the electrode in chloroform, during which the amphiphilic Os(II) complex was removed from the clay surface. Thereafter the electrode was immersed in an aqueous solution of 0.5 mM Λ-[Os(phen)₃](ClO₄)₂ and rinsed with water. Cyclic voltammetric measurements were performed at each step of the above procedures. When the observed curves were simulated on the basis of a double-layered modified electrode, the electron transfer rate constant (k₁) for Λ-[Os(phen)₃]²⁺/Λ-[Os(phen)₃]³⁺ was determined to be 0.25 s⁻¹. This Os^II/Os^III redox couple was found to mediate the electrochemical oxidation of chiral 1,1^′-2-binaphthol in a stereoselective way: i.e., the S-isomer was oxidized at a 1.4 times higher rate than the R-isomer.     

Copper complexes as chemical nucleases

Redox active mononuclear and binuclear copper(II) complexes have been prepared and structurally characterized. The complexes have planar N-donor heterocyclic bases like 1,10-phenanthroline (phen), dipyridoquinoxaline (dpq) and dipyridophenazine (dppz) ligands that are suitable for intercalation to B-DNA. Complexes studied for nuclease activity have the formulations [Cu(dpq)₂(H₂O)] (ClO₄)₂.H₂O (1), [CuL(H₂O)₂(μ-ox)](ClO₄)₂ (L = bpy,2; phen,3; dpq,4; and dppz,5) and [Cu(L)(salgly)] (L = bpy,6; phen,7; dpq,8; and dppz,9), where salgly is a tridentate Schiff base obtained from the condensation of glycine and salicylaldehyde. The dpq complexes are efficient DNA binding and cleavage active species. The dppz complexes show good binding ability but poor nuclease activity. The cleavage activity of thebis-dpq complex is significantly higher than thebis-phen complex of copper(II). The nuclease activity is found to be dependent on the intercalating nature of the complex and on the redox potential of the copper(II)/copper(I) couple. The ancillary ligand plays a significant role in binding and cleavage activity.     

Binuclear iron(III) complexes bridged by terephthalato groups

Six new μ-terephthalato iron(III) binuclear complexes have been prepared and identified: [Fe₂(TPHA)(L)₄]-(ClO₄)₄ [L = 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy); 5-methyl-1,10-phenanthroline (Me-phen); 5-chloro-1,10-phenanthroline (Cl-phen) and 5-nitro-1,10-phenanthroline (NO₂-phen)]; where TPHA = the terephthalate dianion. Based on the elemental analyses, molar conductance and magnetic moments of room-temperature measurements, and spectroscopic studies, extended TPHA-bridged structures consisting of two iron(III) ions, each in an octahedral environment, are proposed for these complexes. The [Fe₂(TPHA)(Me-phen)₄](ClO₄)₄ (1) and [Fe₂(TPHA)(phen)₄](ClO₄)₄ (2) complexes were characterized by variable temperature magnetic susceptibility (4–300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, Ĥ = −2JŜ ₁ Ŝ ₂, giving the exchange integrals J = −1.05 cm⁻¹ for (1) and J = −9.28 cm⁻¹ for (2). This result indicates the presence of a weak antiferromagnetic spin-exchange interaction between the metal ions within each molecule. The influence of the terminal ligand methyl substituents on magnetic interactions between the metals is also discussed. This revised version was published online in June 2006 with corrections to the Cover Date.