Synthesis, crystal structures and magnetic properties of the copper(II) complexes containing isophthalate anion as coligand

Two new dinuclear isophthalato-bridged copper(II) complexes [Cu₂(ntb)₂(μ-ipt)](ClO₄)₂·4CH₃OH·0.33H₂O (1), [Cu₂(bbma)₂(μ-ipt)(NO₃)(CH₃OH)]NO₃·CH₃OH (2) and one mononuclear complex [Cu(bbma)(ipt)(CH₃OH)_0.67(H₂O)_0.33]·2CH₃OH (3) containing tetradentate and tridentate poly-benzimidazole ligands were synthesized, where ntb is tris(2-benzimidazolylmethyl)amine, bbma is bis(benzimidazol-2-yl-methyl)amine and ipt is isophthalate dianion. All of the complexes were characterized by elemental analysis, IR spectra and X-ray crystallography. The structures of complexes 1 and 2 consist of μ-ipt bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions of both compounds has a distorted square pyramidal geometry. The Cu···Cu distances are 9.142 and 10.435 Å for 1 and 2, respectively. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the bbma ligand, one isophthalate-oxygen atom and one oxygen atom from a coordinated methanol molecule. The magnetic susceptibility measurements at variable temperature over the 2-300 K range for complexes 1 and 2 are reported, with J values to be −0.013 and −0.32 cm⁻¹, respectively. The results show that the two complexes exhibit very weak antiferromagnetic interactions between the dinuclear copper(II) centers.     

Different coordination modes of 5,5-diethylbarbiturate in the copper(II) complexes with some aliphatic amines: Synthesis, spectroscopic, thermal and structural studies

Three new copper(II) complexes of 5,5-diethlybarbiturate (barb), [Cu(barb)₂(dmen)]·0.5H₂O (dmen = N,N-dimethylethylenediamine) 1, [Cu(barb)₂(bapa)] (bapa = bis(3-aminopropyl)amine) 2, and [Cu(barb)(apen)](barb)·2H₂O (apen = N,N′-bis(3-aminopropyl)ethylenediamine) 3, have been synthesized and characterized by chemical, spectroscopic and thermal methods. Single crystal X-ray diffraction studies revealed that all complexes are mononuclear. The copper(II) ion exhibits a square-pyramidal coordination geometry in 1 and 3, but a trigonal-bipyramidal geometry in 2. The barb ligand shows different coordination modes. 1 presents the unequal coordination of the barb ligands: one is monodentate (N) and the other one is bidentate (N, O). In 2, both barb ligands are N-coordinated, whereas in 3, one barb ligand is N-coordinated, while the second barb ligand behaves as a counter-ion. The dmen, bapa and apen ligands act as bi-, tri- and tetradentate ligands, respectively. All complexes display a hydrogen-bonded network structure. The IR spectroscopic analysis shows that the ν(CO) stretching frequencies do not correlate predictably with the coordination mode of the barb ligand in 1. Thermal analysis data for 1-3 are in agreement with the crystal structures.     

Effect of anionic co-ligands on structure and magnetic coupling of bis(μ-phenoxo)-bridged dinuclear copper(II) complexes

Two phenoxo bridged dinuclear Cu(II) complexes, [Cu₂L₂(NO₂)₂] (1) and [Cu₂L₂(NO₃)₂] (2) have been synthesized using the tridentate reduced Schiff-base ligand 2-[(2-dimethylamino-ethylamino)-methyl]-phenol (HL). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. The structures of the two compounds are very similar having the same tridentate chelating ligand (L) and mono-dentate anionic ligand nitrite for 1 and nitrate for 2. In both complexes Cu(II) is penta-coordinated but the square pyramidal geometry of the copper ions is severely distorted (Addison parameter (τ) = 0.33) in 1 while the distortion is quite small (average τ = 0.11) in 2. These differences have marked effect on the magnetic properties of two compounds. Although both are antiferromagnetically coupled, the coupling constants (J = −140.8 and −614.7 cm⁻¹ for 1 and 2, respectively) show that the coupling is much stronger in 2.     

Chlorido-bridged polymeric and dinuclear copper(II) complexes with tridentate Schiff base: Synthesis, crystal structure and magnetic properties

Two copper(II) complexes, [Cu(qsal)Cl](DMF) (1) and [Cu₂(qsalBr)₂Cl₂](DMF) (2), with tridentate Schiff base ligands, 8-(salicylideneamino)quinoline (Hqsal) and 8-(5-bromo-salicylideneamino)quinoline (HqsalBr), respectively, were synthesised and structurally characterized. Each copper(II) ion in the two complexes is in a distorted square pyramidal N₂OCl₂ environment. Complex 1 exists as a polymeric species via equatorial-apical chloride bridges, whereas 2 is a di-chlorido-bridged dinuclear complex, where each bridging chloride simultaneously occupies an in-plane coordination site on one copper(II) ion and an apical site on the other copper(II) ion. Variable-temperature magnetical susceptibility measurements on the two complexes in the temperature range 2-300 K indicate the occurrence of intrachain ferromagnetic (J = +6.58 cm⁻¹) and intramolecular antiferromagnetical (J = −6.91 cm⁻¹) interactions.     

The key role of hydrogen bonding in the nuclearity of three copper(II) complexes with hydrazone-derived ligands and nitrogen donor heterocycles

Three new Cu(II) complexes of formula [Cu(L¹)(pyz)(CH₃OH)]ClO₄ (1), [Cu(L¹)(4,4′-bpy)(ClO₄)]·0.5H₂O (2) and [{Cu(L²)(ClO₄)}₂(μ-4,4′-bpy)] (3) have been synthesised by using pyrazine (pyz) and 4,4′-bipyridine (4,4′-bpy) and tridentate O,N,O-donor hydrazone ligands, L¹H and L²H, obtained by the condensation of 1,1,1-trifluoro-2,4-pentanedione with salicyloylhydrazide and benzhydrazide, respectively. The ligands and their complexes have been characterized by elemental analyses, FT-IR, and UV-Vis spectroscopies. Single crystal X-ray structure analysis evidences the metal ion in a slightly deformed square pyramidal geometry in all the complexes. However complexes 1 and 2 are mononuclear with pyz and 4,4′-bpy, respectively, showing an unusual monodentate behavior, while complex 3 is dinuclear with 4,4′-bpy adopting the typical bridging coordination mode. Self assembly of the complex units by hydrogen bonding interactions produces one-dimensional arrangement in each crystal packing. The magnetic characterization of complex 3 indicates a weak antiferromagnetic exchange interaction between the Cu(II) ions (J = −0.96 cm⁻¹) mediated through the long 4,4′-bpy bridge. Electrochemical behavior of the complexes is also discussed.     

A family of polyamino phenolic macrocyclic ligands. Acid-base and coordination properties towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) ions

The acid-base and coordination properties towards Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) of four polyamino-phenol macrocycles 15-hydroxy-3,6,9-triazabicyclo[9.3.1]pentadeca-11,13,1¹⁵-triene L1, 18-hydroxy-3,6,9,12-tetraazabicyclo[12.3.1]octadeca-14,16,1¹⁸-triene L2, 21-hydroxy-3,6,9,12,15-pentaazabicyclo[15.3.1]enaicosa-17,19,1²¹-triene L3 and 24-hydroxy-3,6,9,12,15,18-hexaazabicyclo[18.3.1]tetraicosa-20,22,1²⁴-triene L4 are reported. The protonation and stability constants were determined by means of potentiometric measurements in 0.15 mol dm⁻³ NMe₄Cl aqueous solution at 298.1 K. L1 forms highly unsaturated Co(II), Cu(II), Zn(II) and Cd(II) mononuclear complexes that are prone to give dimeric dinuclear species with [(MH₋₁L1)₂]²⁺ stoichiometry, in solution. L2 forms stable Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) mononuclear complexes that can coordinate external species as OH⁻ anion, giving hydroxylated complexes at alkaline pH. L3 forms stable Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) mononuclear complexes and Co(II), Ni(II), Cu(II) and Zn(II) dinuclear [M₂H₋₁L3]³⁺ species. L4 forms stable mono- and dinuclear Co(II), Cu(II), Zn(II) and Cd(II) complexes, but only mononuclear species with Pb(II). The effect of macrocyclic size is considered in the discussion of results.     

Synthesis, crystal structure, spectroscopic and magnetic properties of copper(II) complexes with 2-(2-pyridyl)imino-N-(2-thiazolin-2-yl)thiazolidine (PyTT)

The copper(II) complexes [Cu(PyTT)₂(H₂O)](NO₃)₂ (A) and [CuCl₂(μ-PyTT)₂CuCl(H₂O)]Cl · 3H₂O (B) were synthesized and characterized by single crystal X-ray diffraction, IR spectroscopy, UV-Vis-NIR diffuse reflectance and magnetic susceptibility measurements. In the mononuclear compound A the copper ion is in a distorted square pyramidal geometry, with the equatorial plane formed by two thiazoline nitrogen atoms, one imino nitrogen atom and one water molecule, whereas the axial site is occupied by one imino nitrogen atom. The compound B is dinuclear and both Cu(II) centres present environments that can be described as slightly distorted square pyramidal geometries. The observed molar magnetic susceptibility for A (μ=2.13 BM) allows to exclude metal-metal interactions, supporting a monomeric structural formulation for this compound. In compound B, magnetic susceptibility measurements in the temperature range 6.2-288 K show an intradimer antiferromagnetic interaction (J=−11.8 cm⁻¹).     

Dinuclear triply-bridged copper(II) compounds containing carboxylato bridges and di-2-pyridylamine as a ligand: synthesis, crystal structure, spectroscopic and magnetic properties

Three new triply-bridged dinuclear copper(II) compounds with carboxylato bridges, [Cu₂(μ-O₂CH)(μ-OH)(μ-Cl)(dpyam)₂](PF₆) (1), [Cu₂(μ-O₂CH)₂(μ-OH)(dpyam)₂](PF₆) (2) and [Cu₂(μ-O₂CCH₂CH₃)₂(μ-OH)(dpyam)₂](ClO₄) (3) (dpyam = di-2-pyridylamine) have been synthesized and characterized crystallographically and spectroscopically. Compound 1 consists of a dinuclear unit in which both copper(II) ions are bridged by three different ligands, i.e., formate, chloride and hydroxide anions, providing a distorted trigonal bipyramidal geometry with a CuN₂O₂Cl chromophore. Compounds 2 and 3 have two bridging formato ligands and two bridging propionato ligands, respectively, together with a hydroxo bridge. The carboxylato ligands in both compounds 2 and 3 exhibit different coordination modes. One is in a syn, syn η¹:η¹:μ₂ bridging mode and the other is in a monoatomic bridging mode. The structure of compound 2 involves a dinuclear unit, with a distorted trigonal bipyramidal geometry around each Cu(II) ion with a CuN₂O₃ chromophore. Compound 3 contains a non-centrosymmetric unit; the coordination environment around Cu(1) is a distorted square-pyramidal geometry and an intermediate geometry of sp and tbp around the Cu(II) ion. The Cu?Cu separations are 3.061, 3.113 and 3.006 Å for compounds 1, 2 and 3, respectively. The EPR spectra of all three compounds show a broad isotropic signal with a g value around 2.10.The magnetic susceptibility measurements, measured from 5 to 280 K, revealed a moderate ferromagnetic interaction between the Cu(II) ions with a singlet-triplet energy gap (J) of 79.7, 47.8 and 24.1 cm⁻¹, for compounds 1, 2 and 3, respectively. Also a very weak intermolecular antiferromagnetic interaction was observed between the dinuclear units.     

Synthesis and structures of morpholine substituted new vic-dioxime ligand and its Ni(II) complexes

N,N^′-bis[4-(2-aminoethyl)morpholino]glyoxime (H₂L) (Fig. 1), has been prepared in various yields using three different methods. The most efficient of these methods is the technique of microwave irradiation. The crystal structures of H₂L, and of two nickel(II) complexes 1 and 2 have been determined by single crystal X-ray diffraction. Both nickel(II) complexes have a metal-ligand ratio of 1:2 in which the ligand coordinates through the two nitrogen atoms as do most vic-dioximes. The nickel(II) complexes are either hydrogen (1) or boron diphenyl bridged (2). Complex 1 was synthesized by reacting H₂L with nickel(II) chloride in refluxing ethanol. Complex 2 was prepared at room temperature in an ethanol solution containing excess NaBPh₄. Elemental analyses, NMR(¹H, ¹³C), IR and mass data are also presented.     

Synthesis of new compartmental amino-phenolic ligands. Basicity, coordination properties towards Cu(II) and Zn(II) ions. A fluorescent chemosensor for H and Zn(II)

The syntheses of three new compartmental ligands are reported. Each ligand shows two 1,4,7-triazaheptane (dien) moieties separated by different rigid aromatic groups. The dien unit is linked to the spacer through its central N-atom, while each aromatic moiety contains two hydroxyl-phenolic functions. The synthetic aspects involved in attaching two dien subunits to an aromatic group containing two hydroxyl functions were explored. Each ligand synthesized can coordinate two metal ions positioned far from each other; the single dinuclear units will be useful as building blocks in new supramolecular aggregates. The basicity and binding properties of one of the synthesized ligands (3,3′-bis[N,N-bis(2-aminoethyl)aminomethyl]-4,4′-dihydroxybiphenyl (L2)) were potentiometrically studied in aqueous solution. L2 was found to behave as a diprotic acid and as a pentaprotic base under the experimental conditions used. L2 forms stable mononuclear and dinuclear complexes with Cu(II) and Zn(II) ions; the mononuclear species show a tendency to dimerize, while the dinuclear ones are predominant in the presence of two equivalents of M(II) ions in solution.Both protonation and the presence of Zn(II) strongly affect the fluorescence emission properties of L2, which can be used as a new chemosensor for H⁺ and Zn(II) ions. L2 exhibits pH-dependent fluorescence and the emission due to the different protonation of L2 and can be ascribed, above all, to the degree of protonation of the 4,4′-biphenol unit; thus, L2 is more emitting at acidic pH values where the aromatic unit is fully protonated. On the contrary, the Zn-dinuclear species are more emitting from neutral to alkaline pH values exhibiting a CHEF effect which reaches its maximum values (seven times those of the free ligand) at pH 9 with the [Zn₂H₋₂L2]²⁺ species, thus highlighting the sensing properties of this new chemosensor towards Zn(II).     

Chiral 2-pyridyl alcoholate copper complexes: crystal structures of [bis(2-pyridyl alcoholate)copper(II)] and the use of [(2-pyridyl alcoholate)copper(II)]and [(2-pyridyl alcoholate)copper(I)] in asymmetric cyclopropanation of styene and allylic oxidation of cyclohexene

Chiral N,O pyridine alcohols HL¹-HL⁶ were used to form complexes with copper(II) ions. Ligands HL¹ and HL² formed complexes with copper(II) ions when Cu(OAc)₂ and HL were refluxed in methanol/ethanol mixture. Ligand HL³ formed a complex with copper(II) when deprotonated with NaH and stirred in a Cu(II) acetate THF solution. Ligands HL⁴-HL⁶ did not form complexes with copper(II) under similar conditions. Two complexes, [Cu(L¹)₂] and [Cu(L²)₂], were isolated as single crystals and characterized by X-ray crystallography. These complexes showed low catalytic activities in asymmetric reactions. However, they became active when reacted with triflic acid. Copper complexes, [Cu(L)] or [Cu(L)]⁺, formed in situ by reacting ligands HL with copper(I) or (II) ions, respectively, were also found to be active copper catalysts for asymmetric cyclopropanation of styrene with ethyl diazoacetate and allylic oxidation of cyclohexene with t-butylperoxybenzoate. Enantioselectivities up to 56% and 38% were obtained in asymmetric cyclopropanation of styrene and asymmetric allylic oxidation of cyclohexene, respectively.     

Synthesis, crystal structure, and catalytic studies on dinuclear copper(II) mesocates

Imine based bis-bidentate ligands H₂-m-xysal, (L₁H₂); H₂-m-xysal-Cl, (L₂H₂); H₂-m-xysal-Br, (L₃H₂); H₂-m-xysal-OCH_3, (L₄H₂); H₂-m-xysal-(t-Bu)_2, (L₅H₂) were synthesized and characterized. These substituted 1,3-bis(hydroxylbenzyl)-diaminoxylene dianion ligands upon treating with copper(II) acetate in 2:2 equivalent of L:M ratio, resulted in a series of binuclear [Cu₂(m-xysal)₂] neutral complexes 1-5. The crystal structures determined for the complexes 1 and 2 indicate a dinuclear association. The CH?π interaction observed between the metal-chelate ring and the hydrogens associated with m-xylene spacer moiety being first in this series of complexes, is demonstrated to stabilize the helical conformation through intramolecular self assembly process. The position of the resonance on the EPR spectra and the absence of ΔMs = ±1 feature for the complexes 2, 3, and 5 obtained for room temperature solid state samples revealed that the metal centers though exist in the dinuclear unit, they are separated from each other and possess a non-interacting monomer-type metal-metal association. The Cu(II) centers in all these complexes possessing an intermediate geometry between tetrahedral and square planar, an appropriate catalytic study converting 4-nitrobenzaldehye to corresponding nitroaldol was carried out using complex 5.     

Transition metal complexes with pyrazole based ligands, part 18: new binuclear Cu(I), Cu(II) and Co(II) complexes with 3,5-dimethyl-1-thiocarboxamide pyrazole: synthesis, structural and magnetic studies

Three new binuclear metal complexes of the formulas (L = 3,5-dimethyl-1-thiocarboxamide pyrazole) have been synthesized and characterized by chemical analysis, FT-IR spectroscopy, solution conductivity, solid state magnetic measurements and X-ray single crystal and variable temperature powder diffraction. Complex 1 forms doubly chloro-bridged dimers, with Cu(II) in distorted trigonal bipyramidal coordination with the apical positions occupied by chlorine atoms. Magnetic measurements indicate an antiferromagnetic interaction between the Cu(II) centres in the dimer, with the singlet-triplet exchange parameter of J = −19.40 cm⁻¹. Complex 2 forms doubly sulfur-bridged dimers, with Cu(I) in distorted tetrahedral coordination with apical positions occupied by bromine atoms. Complex 3 is a cobalt analogue of 1. It contains dinuclear units formed by five-coordinate high-spin Co(II) in a distorted trigonal bipyramidal environment. The magnetisation of 3 shows no significant departure from Curie-Weiss behaviour between room temperature and 5 K. All crystal structures are stabilized by two-dimensional hydrogen bonding networks between the carboxamide nitrogen donors and the terminal halide acceptors.     

Synthesis, structures, spectral and electrochemical properties of copper(II) complexes of sterically hindered Schiff base ligands

The Schiff base ligands 2-(2,6-diisopropylphenyliminomethyl)phenol H(L1), 5-diethylamino-2-(2,6-diisopropylphenyliminomethyl)phenol H(L2), 2,4-di-tert-butyl-6-(2,6-diisopropylphenyliminomethyl)phenol H(L3), 3-(2,6-diisopropylphenyliminomethyl)naphthalen-2-ol H(L4) and 4-(2,6-diisopropylphenyliminomethyl)-5-hydroxymethyl-2-methylpyridin-3-ol H(L5) have been synthesized by the condensation, respectively, of salicylaldehyde, 4-(diethylamino)salicylaldehyde, 3,5-di-tert-butylsalicylaldehyde, 2-hydroxy-1-napthaldehyde and pyridoxal with 2,6-diisopropylaniline. The copper(II) bis-ligand complexes [Cu(L1)₂] 1, [Cu(L2)₂] 2, [Cu(L3)₂] 3, [Cu(L4)₂] 4 and [Cu(L5)₂] · CH₃OH 5 of these ligands have been isolated and characterized. The X-ray crystal structures of two of the complexes [Cu(L1)₂] 1 and [Cu(L5)₂] · CH₃OH 5 have been successfully determined, and the centrosymmetric complexes possess a CuN₂O₂ chromophore with square planar coordination geometry. The frozen solution EPR spectra of the complexes reveal a square-based CuN₂O₂ chromophore, and the values of g_‖ and g_‖/A_‖ index reveal enhanced electron delocalization by incorporating the strongly electron-releasing -NEt₂ group (2) and fusing a benzene ring on sal-ring (4). The Cu(II)/Cu(I) redox potentials of the Cu(II) complexes reveal that the incorporation of electron-releasing -NEt₂ group and fusion of a benzene ring lead to enhanced stabilization of Cu(II) oxidation state supporting the EPR spectral results. The hydrogen bonding interactions between the two molecules present in the unit cell of 5a generate an interesting two-dimensional hydrogen-bonded network topology.     

Synthesis, X-ray structures, electrochemical properties and cytotoxic effects of Co(II) complexes

1-Benzothiazol-2-yl-3,5-dimethyl-1H-pyrazole (1a) and 1-benzothiazol-2-yl-5-(2-hydroxyphenyl)-3-methyl-1H-pyrazole-4-carboxylic acid methyl ester (1b) were reacted with the hexahydrates of cobalt(II) chloride, cobalt(II) nitrate and cobalt(II) perchlorate to give the corresponding complexes 2a-4a and 2b-5b, respectively. Obtained compounds differ in coordination spheres of central atoms. The complex 2a includes a fivefold coordinated cobalt(II) ion, whereas 3a shows a distorted octahedral configuration around the cobalt(II) ion. All complexes were characterised by FTIR spectroscopy, MS and elemental analysis. The X-ray structures of 2a, 3a and 5b complexes were also solved. The cytotoxic properties of the ligand 1a and both series of Co(II) complexes were examined on human leukemia NALM-6 and HL-60 cells and melanoma WM-115 cells. The ligands, were found to have very low cytotoxicity. Complex 3b exhibited the highest cytotoxic activity with IC₅₀ values in the range of 6.9-17.1 μM for three examined cell lines.     

Extended structures of three new coordination polymers based on 1,10-phenanthroline derivatives and 1,4-benzenedicarboxylate mixed ligands: Preparation, structural characterization and properties

Three coordination polymers, namely, [Cd(HOIP)₂(1,4-bdc)] (1), [Cu(HOIP)(1,4-bdc)] (2) and [Cu(PDIP)(1,4-bdc)] (3) (HOIP = 2-(4-hydroxylbenzene) imidazo[4,5-f]1,10-phenanthroline, PDIP = 2-(3-pyridine) imidazo[4,5-f]1,10-phenanthroline, and 1,4-bdc = 1,4-benzenedicarboxylate), have been synthesized under the hydrothermal conditions. All complexes have been characterized by elemental analyses, IR and single-crystal X-ray diffraction. Structural analyses reveal that complex 1 possesses infinite one-dimensional (1D) chain bridged by 1,4-bdc ligands, complexes 2 and 3 both exhibit two-dimensional (2D) (4,4) network structures based on dinuclear [Cu₂O₂] units. However, the weak interactions are different in complexes 1-3. Moreover, the thermal properties of all complexes, fluorescence property of 1, and the electrochemical behavior of 3 are also reported in this paper.     

Synthesis, structures and DNA binding of ternary transition metal complexes M(II)L with the 2,2-bipyridylamine (L = p-HB, M = Co, Ni, Cu and Zn)

New ternary transition metal complexes of formulations [Co(bpa)(p-HB)₂](bpa = 2,2′-bipyridylamine, p-HB = p-hydroxybenzenecarboxylic acid) (1), [Ni(bpa)(p-HB)(H₂O)₂]⁺(NO₃)⁻ · H₂O (2), , [Cu(bpa)(p-HB)Cl] (4) and [Zn(bpa)(p-HB)₂]₂ · 0.5H₂O (5) are prepared, their structural features are characterized by crystal structural studies, and their DNA binding propensity has been evaluated by fluorescence method. The molecular structure of complex 1 shows the six coordinate octahedral geometry with one bpa and two p-HB ligands, complex 2 is the cationic complex and has the six coordinate octahedral structure with one bpa, one p-HB and two aqua ligands, complex 3 is also the cationic complex of octahedral coordination with two bpa and one p-HB ligands, complex 4 is five coordinate distorted square pyramidal with one bpa, one p-HB and chloride ligands and complex 5 has the distorted octahedral coordination with two p-HB and one bpa ligands. In all of the complexes, both bpa and p-HB act as the bidentate N and O-donor ligands, respectively. The intermolecular H-bond networks, together with π-π interaction in their solid state are also described. The complexes show the competitive inhibition of ethidium binding to DNA, and the DNA binding propensity can be reflected as the relative order: 3 > 2 > 1 > 5 > 4, in which the cationic charged Ni(II) complexes 2 and 3 show the most effective inhibition ability.     

Synthesis and in vitro evaluation of palladium(II) salicylaldiminato thiosemicarbazone complexes against Trichomonas vaginalis

Eight mononuclear Pd(II) complexes containing salicylaldiminato thiosemicarbazones (saltsc-R; where R = H (1), 3-OMe (2), 3-^tBu (3) and 5-Cl (4)) as dinegative tridentate ligands were prepared by the reaction of the corresponding thiosemicarbazone with the precursor Pd(L)₂Cl₂ (L = phosphatriazaadamantane or 4-picoline) in the presence of a weak base. These complexes (9-16) were characterised by a range of spectroscopic and analytical techniques including NMR spectroscopy and X-ray diffraction. These complexes along with four other Pd(II) analogues (5-8) were screened for activity in vitro against the Trichomonas vaginalis parasite. Preliminary results show that the type of ancillary ligand as well as the substituents on the aromatic ring of the salicylaldiminato thiosemicarbazone ligand influences the antiparasitic activity of these complexes.     

Synthesis, structure, cytotoxic activities and DNA-binding properties of tetracopper(II) complexes with dissymmetrical N,N′-bis(substituted)oxamides as ligands

To compare the cytotoxicities and the DNA-binding properties in tetranuclear complexes with different bridging ligands, two tetracopper(II) complexes with formulae of [Cu₄(oxbe)₂Cl₂(bpy)₂]·4H₂O (1) and [Cu₄(oxbm)₂Cl₂(bpy)₂]·2H₂O (2) were synthesized, where H₃oxbe and H₃oxbm stand for N-benzoato-N′-(2-aminoethyl)oxamide and N-benzoato-N′-(1,2-propanediamine)oxamide, respectively, and bpy is 2,2′-bipyridine. Complex 1 was characterized by elemental analyses, IR and electronic spectra and single-crystal X-ray diffraction. The crystal structure reveals the presence of the circular tetranuclear copper(II) cations which are assembled by a pair of cis-oxamido-bridged dinuclear copper(II) units through carboxyl bridges. The crystal structure of complex 2 has been reported in our previous paper. However, the bioactivities were not studied. Cytotoxicities experiments reveal that both the two complexes exhibit cytotoxic effects against human hepatocellular carcinoma cell SMMC-7721 and human lung adenocarcinoma cell A549, and complex 1 has the better activities than those of complex 2. The results of the interactions between the two complexes and herring sperm DNA (HS-DNA) suggest that the two complexes interact with HS-DNA in the mode of intercalation with the intrinsic binding constants of 3.93 × 10⁴ M⁻¹ (1) and 2.48 × 10⁴ M⁻¹ (2). These results indicated that the bridging ligands may play an important role in the cytotoxicities and the DNA-binding properties of tetranuclear complexes.     

Hydrothermal syntheses, crystal structures and characterizations of three new copper coordination polymers

Three new copper complexes, [Cu^IICu^I(ip)(ipH)(4,4′-bipy)_3/2]_n (1), [Cu(ip)(4,4′-bipy)]_n · 3nH₂O (2), and [Cu(ipH)₂(4,4′-bipy)]_n (3), have been hydrothermally synthesized by the reaction of Cu(NO₃)₂ · 3H₂O with isophthalic acid (ipH₂) and 4,4′-bipyridine (4,4′-bipy) under different reaction conditions. Complex 1, a mixed-valence copper(I,II) complex, exhibits a 2-D interpenetrating grid framework, in which five-coordinated Cu^II and three-coordinated Cu^I environments are established. The oxidation states of center Cu atoms have been confirmed by X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectra (EPR). Complex 2 features a 2-D box-like bilayer architecture, in which Cu^II atoms are linked by ip ligands to form a 1-D double-chain and the resulting chains are further strutted by the 4,4′-bipy ligands. In complex 3, two bridging 4,4′-bipy ligands and two terminal ipH ligands confine the Cu^II center in a square plane coordination geometry. The whole molecule of 3 was arranged into a 1-D linear chain structure. Additionally, the thermogravimetric analyses (TGA) for complexes 1-3 are also discussed in this paper.