Synthesis, structure and magnetic properties of two μ-oxo and thiocyanato-bridged manganese(II)-mercury(II) coordination polymers

Mixed-metal thiocyanate complexes [MnHg(SCN)₄(NOP)] (1) and [MnHg(SCN)₄(DMSO)] (2) (NOP = 3-methyl-4-nitropyridine-N-oxide, DMSO = dimethylsulfoxide) have been synthesized and structurally characterized by single crystal X-ray analysis. Complex 1 and 2 both contain a [Mn₂(μ₂-O)₂] lozenge, which is bridged to Hg(II) ions by end-to-end thiocyanate groups to form a 2-D and 3-D polymeric network, respectively. Magnetic studies indicate that both complexes are anti-ferromagnets, with 1 showing anti-ferrimagnetic ordering below 8.0 K.     

Synthesis, structure and magnetic property of μ-phenoxo-μ-acetato-bis(η-acetato)dicobalt(II, II) complexes

Dinuclear cobalt(II) complexes Co₂(bpmp)(OAc)₃ (1) and Co₂(bpcp)(OAc)₃ (2) have been synthesized by using acyclic ligands 2,6-bis((4-(pyridin-2-yl)pyrimidin-2-ylthio)methyl)-4-methylphenol [H(bpmp)] and 2,6-bis((4-(pyridin-2-yl)pyrimidin-2-ylthio)methyl)-4-chlorophenol [H(bpcp)] with versatile coordination sites. X-ray analysis uncovered that complex 1 · 3H₂O contains a μ-phenoxo-μ-acetato-bis(η²-acetato) dicobalt(II, II) core. Magnetic susceptibility was measured for 1 over the temperature range 1.8-300 K, and the best theoretical fitting parameters were g = 2.12(6), J = −3.63(9) cm⁻¹ and D = −12(4) cm⁻¹.     

Dicyanamido-metal(II) complexes. Part 4: Synthesis, structure and magnetic characterization of polynuclear Cu(II) and Ni(II) complexes bridged by μ-1,5-dicyanamide

The one pot aqueous reaction of M(ClO₄)₂ (M = Cu²⁺ or Ni²⁺) with N-methylbis[2-(2-pyridylethyl)]amine (MeDEPA) and N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)ethylenediamine (bpmen) and 1,4,7,10-tetraazacyclododecane (cyclen) in presence of sodium dicyanamide (Nadca) yielded dicyanamido-bridged polynuclear complex {[Cu(MeDEPA)(μ-1,5-dca)]ClO₄}_n (1), and two dinuclear complexes [Cu₂(bpmen)₂(μ-1,5-dca)]₂(ClO₄)₅dca (2) and [Ni(cyclen)(μ-1,5-dca)]₂(ClO₄)₂ (3). These complexes were characterized by IR and UV-Vis spectroscopy. Room temperature single-crystal X-ray studies have confirmed that the Cu(II) centers in 1 and 2 adopt geometries that are more close to trigonal bipyramidal (TBP) in 1 and close to square pyramidal (SP) in 2, whereas in 3, the Ni(II) centers are located in octahedral environment with doubly bridged μ-1,5-dca bonding mode. The intermolecular M···M distances in these complexes are in the range of 7.3-8.6 Å. Variable temperature magnetic susceptibility studies have confirmed that the dca-bridges mediate very weak antiferromagnetic interaction between the M(II) centers with J values of −0.35, −0.18 and −0.43 cm⁻¹ for 1, 2 and 3, respectively. The results are compared and discussed in the light of other related bridged μ-1,5-dca Cu(II) and Ni(II) complexes.     

Syntheses, structures, and magnetic properties of two new μ-alkoxo-μ-pyrazolato bridged dicopper(II) complexes

The syntheses, structures, and magnetic properties of two new μ-alkoxo-μ-pyrazolato heterobridged compounds, [Cu ^II₂(L¹-F)(μ-prz)] (1) and [Cu ^II₂(L¹-2OMe) (μ-prz)] · 0.5 CH₃CN (2) (prz=pyrazolato; H₂L¹-F=1,3-bis(3-fluorosalicylideneamino)-2-propanol; H₂L¹-2OMe=1,3-bis(4,6-dimethoxy salicylideneamino)-2-propanol) have been reported. Compound 1 crystallizes in triclinic space group with a=8.6392(10) Å, b=10.6431(9) Å, c=11.6809(13) Å, α=85.972(8)°, β=71.492(9)°, and γ=72.221(9)°, while the unit cell parameters of 2 are as follows: space group: monoclinic C2/c, a=28.2948(5) Å, b=7.3033(2) Å, c=26.3933(5) Å, and β=96.243(1)°. The variable-temperature magnetic susceptibility measurements reveal that the metal centers in both the compounds are antiferromagnetically coupled with J=−200 cm⁻¹ for 1 and J=−175 cm⁻¹ for 2. The magnetic behaviors have been explained on the basis of two opposing factors, complementarity and countercomplementarity of magnetic orbitals.     

Asymmetric μ2-1,1-azido bridged copper(II) complex: Synthesis, X-ray structure, magnetic study and DFT calculations

A new rare variety asymmetric μ₂-1,1-azido bridged copper(II) complex has been synthesized and characterized structurally and magnetically. The complex [Cu₂L₂(μ₂-1,1-N₃)₂] · H₂O · CH₃OH (L = 1-(N-ortho-hydroxyacetophenimine)-2-aminoethane) (1), crystallizes in monoclinic space group, P2₁/n, with a = 9.469(4) Å, b = 12.526(8) Å, c = 12.899(10) Å, β = 105.79(6)°, V = 1472.2(16) Å³. X-ray study reveals that he Cu-N(azide)-Cu angles in this complex is 90.4°. This is unusually low in comparison to that of the same angle in other end-on azido-bridged binuclear complexes. Though a strong ferromagnetic interaction between the metal centers is expected in the complex, the coupling has actually been found to be antiferromagnetic (J = −4.2 cm⁻¹), instead. To rationalize this paradoxical magnetic behavior, DFT calculation of this and other four complexes with very similar structure have been performed within broken symmetry framework. The calculated magnetic coupling constants (J) are in excellent agreement, both in sign and in the magnitude of the exchange interaction, with the experimental data, and the spin density map is correctly reproduced.     

Synthesis and antimicrobial activity of copper(II) and manganese(II) α,ω-dicarboxylate complexes

Copper(II) ,-dicarboxylate complexes of general formulae, [Cu(O₂C(CH₂)_nCO₂)]·xH₂O, [Cu(O₂C(CH₂)_nCO₂) (phen)₂]·xH₂O and [Cu(O₂C(CH₂)_nCO₂)(bipy)_y]·xH₂O (n=1–8; y=1, 2; phen = 1,10-phenanthroline; bipy = 2,2-bipyridine) were synthesised. These copper complexes, some related manganese(II) complexes and the metal-free ligands were screened in vitro for their ability to inhibit the growth of Candida albicans. Metal-free 1,10-phenanthroline and all of the copper(II) and manganese(II) phenanthroline complexes were potent growth inhibitors, with only one bipyridine complex, [Cu(O₂C(CH₂)CO₂)(bipy)₂]·2H₂O, having moderate activity. The remaining substances were effectively inactive. Complexes which were active against C. albicans also proved effective against C. glabrata, C. tropicalis and C. kreusi with the manganese complexes retaining superior activity. For the phenanthroline complexes the active drug species is thought to be the dication [M(phen)₂(H₂O)_n]²⁺ (M = Cu, Mn). Escherichia coli and Staphylococcus aureus were resistant to all of the metal complexes and also to metal-free 1,10-phenanthroline. Only the copper phenanthroline complexes showed intermediate activity against Pseudomonas aeruginosa.     

Synthesis, structure and properties of unsymmetrical μ-alkoxo-dicopper(II) complexes: biological relevance to phosphodiester and DNA cleavage and cytotoxic activity

The unsymmetric dinucleating ligand N-(2-hydroxybenzyl)-N,N′,N′-tris(2-pyridylmethyl)-1,3-diaminopropan-2-ol (L = H₂btppnol) and the corresponding copper(II) complex [Cu₂(Hbtppnol)(μ-CH₃COO)](ClO₄)₂ (1) have been recently reported in part in a short communication [Inorg. Chem. Commum. 8 (1999) 334]. In this study, we investigated the ability of complex 1 to promote the hydrolysis of P-O phosphate diester bonds in bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) and the cleavage of genomic and plasmid DNA molecules. Reaction of 1 with excess of the diester 2,4-BDNPP, at pH 7.0, results in the formation of the monoester phosphate coordinated [Cu₂(Hbtppnol)(μ-((NO₂)₂-C₆H₃)PO₄)]ClO₄ (3) complex, which was also characterized by X-ray crystallography. In addition, the stable μ-phosphate complex [Cu₂(Hbtppnol)(μ-(NO₂-C₆H₄)PO₄)](ClO₄) (2) obtained from the reaction of 4-nitrophenyl phosphate with complex 1 was also characterized by X-ray crystallography, indicating that 1 is unable to cleave monoester-phosphate bonds. The kinetics for the promotion of bis(2,4-dinitrophenyl) phosphate (2,4-BDNPP) hydrolysis by complex 1 was investigated as a function of pH, catalyst concentration and substrate concentration. On the basis of kinetic and potentiometric studies, the deuterium isotope effect (k^H/k^D ∼ 1) and the X-ray structure of the monoester phosphate coordinated [Cu₂(Hbtppnol)(μ-((NO₂)₂-C₆H₃)PO₄)]ClO₄ (3) complex as the product of the reaction, we demonstrated that the aquo/hydroxo complex is the active species and the reaction occurs through the formation of a ternary complex in which one Cu^II binds the substrate and the second copper center has a terminal bound hydroxide to attack the phosphorus atom, at physiological pH. A rate enhancement factor of ∼100 was calculated relative to that measured for the uncatalyzed reaction under identical conditions. Complex 1 effectively promotes the cleavage of double-stranded genomic and plasmid DNA, at physiological pH, probably through a hydrolytic mechanism in agreement with that proposed for the reaction of 1 with 2,4-BDNPP. Finally, cytotoxic activity of 1 in a human small cell lung carcinoma cell line (GLC4) and its cisplatin resistant subline (GLC4/CDDP) was studied and the IC₅₀ values were determined.     

Synthesis,X-ray structures,and magnetic properties of heterometal dinuclear Cr(III)–M(II) complexes

New 3,5-bis(2-pyridyl)pyrazolato (bpypz) bridged heterometal dinuclear complexes [(nta)Cr(μ-bpypz)M^II(picen)]⁺ (M = Mn(II), Ni(II)) and [(acac)₂Cr(μ-bpypz)Ni^II(picen)]²⁺ (nta = nitrilotriacetate, picen = N,N′-bis(2-pyridylmethyl)ethylenediamine, acac = acetylacetate) were synthesized and characterized by the X-ray analysis, ESI-MS and the magnetic measurements, and/or ²H NMR spectra. The molecular structures were compared from a viewpoint of the conformation of the picen depending on M^II ionic radii or different modes of hydrogen bonds. The picen in [(nta)Cr(μ-bpypz)Mn^II(picen)]BF₄ takes an abnormal conformation with intramolecular bifurcated three-center hydrogen bonds between two carboxylate oxygens of nta and an amine proton of the picen as found for the previously reported corresponding Fe(II) complex [K. Ni-iya, A. Fuyuhiro, T. Yagi, S. Nasu, K. Kuzushita, S. Morimoto, S. Kaizaki, Bull. Chem. Soc. Jpn. 74 (2001) 1891]. On the other hand, for both Ni(II)-nta and Ni(II)-acac complexes, the picen takes a normal conformation with only a two-center hydrogen bond between non-bridging ligands. The magneto-structural relation is discussed for the Cr(III)–Ni(II) complexes in connection with the orthogonality or orbital overlap arising from the difference in distortion around Cr(III) moiety.     

Binuclear metal complexes. 59. Synthesis and magnetism of dicopper(II) and copper(II)-nickel(II) complexes with N,N′-ethylenedisalicylamidatocuprate(II)

The complexes [Cu(samen)Cu(L)] and [Cu(samen)Ni(L)₂] (Lbpy, phen) have been synthesized by the reaction of sodium N,N′-ethylenedisalicylamidatocuprate(II) pentahydrate (Na₂- [Cu(samen)]·5H₂O), a divalent metal ion, and 2,2′- dipyridyl or 1,10-phenanthroline. Cryomagnetic data for the CuCu complexes did not fit the Bleaney- Bowers equation; but the data did fit a modified Bleaney-Bowers equation

with a large negative J and a significant negative θ, suggesting that a considerable magnetic interaction operates between essentially planar [Cu(samen)Cu(L)] molecules. The magnetisms of the CuNi complexes were well interpreted in terms of the susceptibility equation based on the Heisenberg model. An antiferromagnetic spin-exchange interaction (J= −13∼−14 cm⁻¹) was suggested between the metal ions.     

Theoretical description of the magnetic properties of μ3-hydroxo bridged trinuclear copper(II) complexes

A theoretical study of the magnetic properties, using density functional theory, of a family of trinuclear μ₃-OH copper(II) complexes reported in the literature is presented. The reported X-ray crystal structures of [Cu₃(μ₃-OH)(aat)₃(H₂O)₃](NO₃)₂·H₂O (HUKDUM), where aat: 3-acetylamine-1,2,4-triazole; [Cu₃(μ₃-OH)(aaat)₃(H₂SO₄)(HSO₄)(H₂O)] (HUKDOG), where aaat: 3-acetylamine-5-amine-1,2,4-triazole; [Cu₃(μ₃-OH)(PhPyCNO)₃(tchlphac)₂] (HOHQUR), where PhPyCNO: phenyl 2-pyridyl-ketoxime and tchlphac: acid 2,4,5-trichlorophenoxyacetic; [Cu₃(μ₃-OH)(PhPyCNO)₃(NO₃)₂(CH₃OH)] (ILEGEM); [Cu₃(μ₃-OH)(pz)₃(Hpz)₃(ClO₄)₂] (QOPJIP), where Hpz?=?pyrazole; [Cu₃(μ₃-OH)(pz)₃(Hpz)(Me₃CCOO)₂]?2Me₃CCOOH (DEFSEN) and [Cu₃(μ₃-OH)(8-amino-4-methyl-5-azaoct-3-en-2-one)₃][CuI₃] (RITXUO), were used in the calculations. The magnetic exchange constants were calculated using the broken-symmetry approach. The calculated J values are for HUKDUM J₁?=??68.6 cm^?1, J₂?=??69.9 cm^?1, J₃?=??70.4 cm^?1; for HUKDOG, J₁?=??73.5 cm^?1, J₂?=??58.9 cm^?1, J₃?=??62.1 cm^?1; for HOHQUR J₁?=??128.3 cm^?1, J₂?=??134.1 cm^?1, J₃?=??120.4 cm^?1; for ILEGEM J₁?=??151.6 cm^?1, J₂?=??173.9 cm^?1, J₃?=??186.9 cm^?1; for QOPJIP J₁?=??118.3 cm^?1, J₂?=??106.0 cm^?1, J₃?=??120.6 cm^?1; for DEFSEN J₁?=??74.9 cm^?1, J₂?=??64.0 cm^?1, J₃?=??57.7 cm^?1 and for RITXUO J₁?=??10.9 cm^?1, J₂?=?+14.3 cm^?1, J₃?=??35.4 cm^?1. The Kahn-Briat model was used to correlate the calculated magnetic properties with the overlap of the magnetic orbitals. Spin density surfaces show that the delocalization mechanism is predominant in all the studied compounds.

Studies on metal-drug complexes. Crystal structure and characterization of μ-sulfato bromazepam copper(II) complex

The compound Cu(Bromazepam) SO₄ having been synthesized, its crystal structure shows distorted octahedral environment for the Copper(II) ion. Because of the long Cu-O(4) length (2.90 Å), we can consider that there is a semicoordinative interaction with the sulfate group acting as tridentate bridging ligand. The structure is a polymeric chain where dimeric units are linked by the oxygen (C-O(5)) atom of the Bromazepam carbonyl group. The drug consequently acts as a tridentate ligand in this compound. The magnetic results show a very weak antiferromagnetic interaction.     

Structure, solution equilibria and magnetic properties of copper(II) complexes with new sulfurated triazoline derivatives of α-amino acids

Two new sulfurated triazoline ligands have been synthesized by functionalization of glycine and l-alanine (HL¹ and HL², respectively) at the carboxylate site with retention of chirality in the latter case. The ligands and their copper(II) complexes have been characterized by spectroscopic methods and their structures were determined by X-ray diffraction. The compound [Cu(H₂L²)₂](H₅O₂)(SO₄)₂(HSO₄) presents a very disordered structure with regard to the anionic counterion and a very unusual elongated crystal cell. In all the complexes the ligands are (N,S) coordinated to copper(II), while the amino groups remain protonated and uncoordinated. The ligands have also been studied in solution and their dissociation constants were determined both by potentiometry and ¹H NMR titrations. Potentiometric studies on the complex [Cu(H₂L²)₂](H₅O₂)(SO₄)₂(HSO₄) were performed to determine the dissociation constants of the ligand once coordinated to the metal. The complex [CuCl₂(H₂L¹)]Cl was studied also by magnetic susceptibility measurements, showing an interesting antiferromagnetic behavior at low temperature which has been interpreted on the basis of its crystal packing.     

Synthesis,characterization and antitumour properties of some metal(II) complexes of 2-pyridinecarboxaldehyde 2′-pyridylhydrazone and related compounds

Metal complexes of 2-pyridinecarboxaldehyde 2′-pyridylhydrazone (PCPH) and related compounds with manganese(II), iron(II), cobalt(II), nickel(Il), copper(II), zinc(II) and platinum(II) were synthesized and characterized by magnetic susceptibility measurements down to liquid nitrogen temperature and also by electronic, infrared, electron spin resonance and Mössbauer spectra. All the metal(II) complexes appeared to be monomeric, high-spin, five-coordinate (square-pyramidal) (X = Cl⁻ or OAc⁻), except for Ni(PCPH)Cl₂ which is polymeric, high-spin, six-coordinate. Each ligand behaved as a tridentate NNN donor, via the pyridine nitrogen, azomethine nitrogen, and pyridine or quinoline nitrogen. One of the most active agents of this series, Cu(PCPH)Cl₂, showed antitumour activity against a variety of transplanted tumours, including Sarcoma 180, Ehrlich carcinoma and L1210 leukaemia sensitive to α(N)-heterocyclic carboxaldehyde thiosemicarbazones. This agent caused inhibition of ³H-thymidine and ³H-uridine incorporation into DNA and RNA, respectively, of Sarcoma 180 ascites cells; protein biosynthesis was relatively insensitive to the action of this agent.     

Mesogenic and magnetic properties of nickel(II) complexes formed from 2′-(4-alkyloxyphenyl)malondialdehydes

The synthesis, characterization, thermal behavior and magnetic properties of a number of bis[2-(4-alkyloxyphenyl)malondialdehyde] nickel(II) complexes are reported. X-ray studies of the nickel(II) complexes were performed. It was found that the nickel(II) complexes show liquid-crystalline smectic A phases over a broad temperature range with low melting points. The temperature-dependent magnetic susceptibility measurements of the bis[2-(4-decyloxyphenyl)malondialdehyde] nickel(II) complex were carried out in the range of 4.2–480 K. The temperature dependent magnetic susceptibilities and magnetic moments of this compound (_eff=3.27 _B at 300 K) indicate that the nickel centers are octahedrally coordinated. Models for the molecular arrangement in the crystalline and liquid-crystalline phases are discussed on the basis of the magnetic data. In spite of the oxygen bridge between the nickel centers, no exchange interactions were found in the crystalline and liquid-crystalline phases.     

Synthesis, crystal structures and magnetic properties of two bis(μ-phenoxido)dicopper(II) complexes derived from reduced Schiff base ligands

Two phenoxido bridged dinuclear Cu(II) complexes, [Cu₂(L¹)₂(NCNCN)₂] (1) and [Cu₂(L²)₂(NCNCN)₂]·2H₂O (2) have been synthesized using the tridentate reduced Schiff-base ligands 2-[1-(2-dimethylamino-ethylamino)-ethyl]-phenol (HL¹) and 2-[1-(3-methylamino-propylamino)-ethyl]-phenol (HL²), respectively. The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. Both the complexes present a diphenoxido bridging Cu₂O₂ core. The geometries around metal atoms are intermediate between trigonal bipyramid and square pyramid with the Addison parameters (τ) = 0.57 and 0.49 for 1 and 2, respectively. Within the core the Cu–O–Cu angles are 99.15° and 103.51° and average Cu–O bond distances are 2.036 and 1.978 Å for compounds 1 and 2, respectively. These differences have marked effect on the magnetic properties of two compounds. Although both are antiferromagnetically coupled, the coupling constants (J = −184.3 and −478.4 cm⁻¹ for 1 and 2, respectively) differ appreciably.     

Synthesis,crystal structure,and DNA-binding properties of a new copper (II) complex containing mixed-ligands of 2,2′-bipyridine and p-methylbenzoate

A novel copper complex of [Cu(bpy)(pba)₂ · H₂O] · 0.5H₂O (bpy = 2,2′-bipyridine, pba = p-methylbenzoate) was synthesized. The interaction of the complex to native fish sperm DNA was investigated through electrochemistry, electronic absorption spectroscopy and viscosity experiments. In the X-ray crystallography structure, the copper (II) ion is coordinated by two oxygen atoms of two p-methylbenzoate groups, two nitrogen atoms of 2,2′-bipyridine and one water molecule. The observed changes in the physicochemical features of the copper (II) complex on binding to DNA suggested that the complex bind to DNA with intercalation mode via 2,2′-bipyridine ring into DNA base pairs. Electrochemical studies revealed that the complex prefer to bind to DNA in Cu(I) form rather than Cu(II) oxidation state form. Additionally, the nuclease activity of the title complex was assessed by gel electrophoresis assay and the results shown that the copper complex can cleave pBR322 DNA effectively in the presence of ascorbic acid.     

Synthesis and non-linear optical properties of (η-pentaphenylcyclopentadienyl)dicarbonylruthenium(II) σ-alkenyl complexes

The complexes [Ru{(Z)-HCCHPh}(CO)₂(η⁵-C₅Ph₅)] (1) and [Ru{(Z)-HCCHC₆H₄NO₂}(CO)₂(η⁵-C₅Ph₅)] (2) have been synthesized and their identity confirmed by single-crystal X-ray diffraction studies. Reaction of 2 with PMe₂Ph and Me₃NO in tetrahydrofuran afforded [Ru{(Z)-HCCHC₆H₄NO₂}(CO)(PMe₂Ph)(η⁵-C₅Ph₅)] (3). Cyclic voltammetry confirms the expected increase in ease of oxidation on proceeding from 2 to 1 and from 2 to 3. Hyper-Rayleigh scattering studies at 1064 nm reveal a dramatic increase in quadratic non-linearity on co-ligand replacement of CO by PMe₂Ph, in proceeding from 2 to 3. Z-scan studies at 800 nm are consistent with significant contribution from two-photon states, and with an increase in γ_real on co-ligand replacement of CO by PMe₂Ph in proceeding from 2 to 3.