Oxamido Bridge Research Articles

Incorporating Trigonal-Prismatic Cobalt(II) Blocks into an Exchange-Coupled [Co2Cu] System

Taking advantage of a rigid tetradentate ligand of bis(pyrazoly)(3-pyrazolypyridinyl)methane (PyPz3) and the [CuII(opba)]2- unit [opba4- = o-phenylenebis(oxamato)], the trinuclear complex [{CoII(PyPz3)}2CuII(opba)][ClO4]2·5MeCN·MeOH (1) was constructed, in which the CoII centers adopt a trigonal-prismatic geometry, while considerable intramolecular magnetic coupling was successfully introduced through the oxamido bridges, representing another very first example of single-molecule magnets marrying both selected coordination geometry and magnetic exchanges.

Synthesis, structures and magnetic properties of tetranuclear heterometallic complexes [Cu3M] (M = Mn(II) Co(II) and Ni(II)) based on an oxamido-bridged ligand

Three tetranuclear heterometallic coordination compounds of the general formula [(CuL)2M(CuL·CH3OH)](ClO4)2 [(M = Mn(for 2), Co(for 3) and Ni(for 4)] were synthesized by the reaction of the precursor CuL·0.5H2O (1) (H2L = 2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclotetradeca-7,12-diene) with M(ClO4)2·6H2O under solvothermal conditions. The compounds were fully characterized by elemental analysis, FTIR, UV–Vis spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction analysis. In addition, compound 2–4 were studied by magnetic susceptibility measurements. All three heterometallic compounds are isomorphous, and the central ions Mn(II), Co(II) and Ni(II) are connected to three CuL fragments via exo-cis oxamido bridges. Magnetic susceptibility studies of complexes 2–4 indicate the occurrence of antiferromagnetic coupling between the paramagnetic metals. The experimental data have been fitted according to the following Heisenberg Hamiltonian $$\hat{H} = - 2J\hat{S}_{{\text{M}}} (\hat{S}_{{{\text{Cu}}1}} + \hat{S}_{{{\text{Cu}}2}} + \hat{S}_{{{\text{Cu}}3}} )$$ , leading to J = − 15.24 cm−1, gCu = 2.06, gMn = 1.96 for complex 2, J = − 22.58 cm−1, gCu = 2.1, gCo = 2.55 for complex 3, and J = − 108.2 cm−1, gCu = 2.09, gNi = 2.27 for complex 4, respectively.

Synthesis and structure of a new trinuclear nickel(II) complex bridged by N-[3-(Dimethylamino)propyl]-N'-(2-hydroxyphenyl)oxamido: in vitro anticancer activities, and reactivities toward DNA and protein.

A new trinickel(II) complex bridged by N-[3-(dimethylamino)propyl]- N'-(2-hydroxylphenyl)oxamido (H3 pdmapo), namely [Ni3 (pdmapo)2 (H2 O)2 ]⋅4CH3 OH, was synthesized and characterized by X-ray single-crystal diffraction and other methods. In the molecule, two symmetric cis-pdmapo3- mononickel(II) complexes as a "complex ligand" using the carbonyl oxygen atoms coordinate to the center nickel(II) ion situated on an inversion point. The Ni···Ni distance through the oxamido bridge is 5.2624(4) Å. The center nickel(II) ion and the lateral ones have octahedral and square-planar coordination geometries, respectively. In the crystal, a three-dimensional supramolecular network dominated by hydrogen bonds is observed. The reactivity toward DNA/protein bovine serum albumin (BSA) revealed that the complex could interact with herring sperm DNA (HS-DNA) through the intercalation mode and quench the intrinsic fluorescence of BSA via a static mechanism. The in vitro anticancer activities suggested that the complex is active against the selected tumor cell lines.

Synthesis, characterization and X-ray crystal structures of trinuclear zinc(II) and cadmium(II) complexes derived from an oxovanadium(IV) complex ligand

By using a macrocyclic oxovanadium(IV) complex ligand VOL (H2L=2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) as precursor, two new trinuclear complexes [(VOL)2Zn(CH3OH)2](ClO4)2·5CH3OH (1) and [(VOL)2Cd(CH3OH)2](ClO4)2·3CH3OH·1.82H2O (2) have been synthesized. Their structures were determined by single-crystal X-ray diffraction and further characterized by elemental analyses, FT-IR, UV–Vis spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analyses (TGA). In the two complexes, the central zinc(II) and cadmium(II) ions are connected with two VOL fragments via exo-cis oxamido bridge. Magnetic susceptibility studies (2–300K) of complex 1 indicate the occurrence of weak antiferromagnetic coupling between the paramagnetic metals. The experimental data have been fitted according to Heisenberg Hamiltonian Ĥ=-2JŜ1Ŝ2, leading to J=−0.31cm−1, g=2.01.

Synthesis, crystal structures, and magnetic properties of trinuclear cobalt(II) and nickel(II) complexes with oxamido vanadium(IV)-oxo complex ligand

By using a macrocyclic vanadium(IV)-oxo complex ligand VOL (H2L=2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) as a precursor, two new trinuclear complexes [(VOL)2Co(C2H5OH)2](ClO4)2·2C2H5OH (1) and [(VOL)2Ni(CH3OH)2](ClO4)2 (2) have been synthesized and characterized by elemental analyses, IR spectroscopy, and power and single-crystal X-ray diffraction. In the two complexes, the central ions cobalt(II) and nickel(II) are connected with two VOL fragments via exo-cis oxamido bridge. Magnetic susceptibility measurements indicate that both complexes 1 and 2 show weak ferromagnetic interactions.

In Vitro Cytotoxic Activities, DNA-, and BSA-Binding Studies of a New Dinuclear Copper(II) Complex withN-[3-(Dimethylamino)propyl]-N′-(2-carboxylatophenyl)- Oxamide as Ligand

A new dinuclear copper(II) complex bridged by N-[3-(dimethylamino)propyl]-N'- (2-carbo-xylatophenyl)oxamide (H3 dmapob), and endcapped with 2,2'-diamino-4,4'-bithiazole (dabt), namely [Cu₂(dmapob)(dabt)(CH₃OH)(pic)]·(DMF)₀.₇₅ ·(CH₃OH)₀.₂₅ has been synthesized and characterized by elemental analysis, molar conductivity measurement, infrared and electronic spectra studies, and single-crystal X-ray diffraction. In the crystal structure, both copper(II) ions have square-pyramidal coordination geometries. The Cu···Cu separation through the oxamido bridge is 5.176(9) Å. A two-dimensional supramolecular framework is formed through hydrogen bonds and π-π stacking interactions. The reactivities toward herring sperm DNA and bovine serum albumin (BSA) show that the complex can interact with the DNA via intercalation mode and bind to the BSA responsible for quenching of tryptophan fluorescence by the static quenching mechanism. The in vitro anticancer activities suggest that the copper(II) complex is active against the selected tumor cell lines. The influence of different bridging ligands in dinuclear complexes on the DNA- and BSA-binding properties as well as anticancer activities is preliminarily discussed.

Synthesis, crystal structure, cytotoxicities and DNA-binding properties of a tetracopper(II) complex with N-benzoato-N′-[2-(2-hydroxyethylamino)ethyl-amino]oxamide ligand

A new dissymmetrical N,N’-bis(substituted)oxamide ligand, N-benzoato-N′-[2-(2- hydroxyethylamino)ethyl]oxamide (H3bhyox), and its tetranuclear copper(II) complex, [Cu4(bhyox)2(dabt)2](ClO4)2 (1) have been synthesized and characterized (dabt = 2,2′-diamino- 4,4′-bithiazole). The crystal structures of H3bhyox and complex 1 have been determined by X-ray single-crystal diffraction. Complex 1 has a cyclic tetranuclear cation with an embedded inversion center, in which the Cu–Cu separations through the oxamido and carboxyl bridges are 5.2246(6) and 5.3141(6) A, respectively. Both Cu(II) centers at the inner and outer sites of the cis-bhyox3− ligand have square pyramidal geometries. There is a 3D hydrogen-bonding network in the crystal. The cytotoxicities and DNA-binding properties of H3bhyox and complex 1 were studied. Both compounds can interact with HS–DNA by intercalation, and the DNA-binding affinities are consistent with their in vitro cytotoxicities.

Two new dicopper(II) complexes with oxamido-bridged ligand: Synthesis, crystal structures, DNA binding/cleavage and BSA binding activity

New oxamido-bridged copper(II) complexes, [Cu2(oxbp)(H2O)2(NCS)2] (1) and [Cu2(oxbp)(μ-DMSO)2(NCS)2][Cu2(oxbp)(DMSO)2(NCS)2] (2) (H2oxbp=N,N′-bis(2-(diethylamino)ethyl)oxalamide), were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, IR, and electronic spectra. X-ray analysis revealed that complex 1 consists of neutral binuclear [Cu2(oxbp)(H2O)2(NCS)2] units which forms a two-dimensional network through intermolecular hydrogen bonds and complex 2 is constructed by neutral [Cu2(oxbp)(μ-DMSO)2(NCS)2] (2a) and [Cu2(oxbp)(DMSO)2(NCS)2] (2b) entities which alternately distribute to form a two-dimensional network by means of quasi μ-DMSO bridge and intermolecular hydrogen bonds. In both 1 and 2, bicopper centers are linked by the “trans-form” oxamido bridges with the distances of 5.272Å for 1 and av. 5.296Å for 2, respectively. The interaction of Cu(II) complexes with DNA was investigated by UV-visible, fluorescence emission spectrometry and agarose gel electrophoresis. The apparent binding constant (Kapp) values of 3.16×105M−1 for 1 and 4.9×105M−1 for 2 suggest moderate intercalative binding modes between the complexes and DNA. Complex 1 displayed efficient oxidative cleavage of supercoiled DNA, which might indicate that the underlying mechanism involves singlet oxygen (1O2) as reactive oxygen species. Complex 2 is characteristic of the involvement of a singlet oxygen-like entity and hydrogen peroxide in the cleavage process. In addition, our present work showed, by fluorescence spectrometry of BSA with complexes, both 1 and 2 bind to BSA with a medium affinity through a static mode which is tentatively assigned binding to Trp134 in BSA.

A new oxamido-bridged dinuclear copper(II) complex with large antiferromagnetic exchange interactions

A new oxamido-bridged dinuclear compound [Cu2(µ-pmox)(DMF)4] · 2ClO4 (1) (H2pmox = N,N′-bis-(2-methylpyridyl)oxalamide, DMF = dimethylformamide) was synthesized and structurally characterized. The five-coordinate Cu(II) is bridged by oxamido groups and further cross-linked by C–H···O hydrogen bonds between the uncoordinated oxygen of perchlorate and methyl of DMF. The complex was also characterized by infrared spectroscopy and magnetic measurement. The copper complex exhibits strong antiferromagnetic interactions via the trans oxamido bridge with J of −414 cm−1, where J is the exchange parameter in the isotropic Hamiltonian H = −JS1S2.

A trigonal-prismatic Ag(I) complex and an octahedral Cu(II) complex incorporating with oxamide Ni(II) complex ligand: Syntheses, crystal structures and oxidative nuclease activities

A mononuclear macrocyclic complex NiIIL3a (L3a=dianion of 2,3-dioxo-5,6:13,14-dibenzo-9,10-cyclohexyl-7,12-bis(methoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene), which shows high DNA cleavage activity in the presence of H2O2, was reported in our previous work. Considering that many systems for natural enzyme-mediated DNA cleavage contain two or more metal active sites, two new trinuclear complexes [Cu(NiL3a)2(dca)2]·2CH3OH (abbreviated as Cu(NiL3a)2) and [Ag(NiL3a)2(NO3)]·2CH3OH·0.5H2O (abbreviated as Ag(NiL3a)2) were synthesized in this work, where dca is the dicyanamide. The complexes were structurally characterized by single crystal X-ray analysis. The central Cu(II) or Ag(I) atom is linked to two [NiL3a] ligands by oxamido bridges forming a trinuclear structure. In Cu(NiL3a)2, the central Cu(II) ion is in an octahedral coordination geometry. Whereas in Ag(NiL3a)2, the central Ag(I) ion is in a rarely reported trigonal-prismatic coordination geometry. The DNA cleavage behavior of the complexes in the presence of H2O2 was studied in detail. Comparing with the NiL3a, the trinuclear complex Ag(NiL3a)2 nearly has no ability to cleave DNA, whereas Cu(NiL3a)2 is a much better DNA cleavage agent. Cu(NiL3a)2 can efficiently convert supercoiled DNA to nicked DNA with a rate constant of 0.074±0.002min−1 when 40μM Cu(NiL3a)2 and 0.6mM H2O2 are used. The cleavage mechanism between the complex Cu(NiL3a)2 and plasmid DNA is likely to involve singlet oxygen as reactive oxygen species. Circular dichroism (CD) and fluorescence spectroscopy indicate that both Cu(NiL3a)2 and NiL3a bind to DNA by a groove binding mode, and the binding between Cu(NiL3a)2 and DNA is much stronger than that between NiL3a and DNA. The present results may provide some information for the design of efficient multinuclear artificial nucleases.

Oxamido‐bridged N4 Macrocyclic Complexes CuII/MII/CuII (M = Mn, Co): Synthesis, Crystal Structures and Magnetic Properties

AbstractTwo new oxamido‐bridged N4 macrocyclic complexes [(CuL)2Mn(C2H5OH)2](ClO4)2·2C2H5OH (1) and [(CuL)2Co‐(C2H5OH)2](ClO4)2·2C2H5OH (2) (H2L = 2,3‐dioxo‐5,6:14,15‐di‐benzo‐7,13‐diphenyl‐1,4,8,12‐tetraazacyclo‐pentadeca‐7,13‐diene) have been synthesized and structurally characterized by X‐ray crystallographic investigations. In the two complexes, all copper(II) ions adopt a slightly distorted square‐planar configuration and the central manganese(II) and cobalt(II) ions are set in a distorted octahedral coordination sphere, connected to the other CuL fragments through exo‐cis oxamido bridges. The analyses of the magnetic properties were carried out by means of the theoretical expression of the magnetic susceptibility deduced from the spin Hamiltonian Ĥ = –2JŜ1Ŝ2, leading to J = –14.58 cm–1 for complex 1 and J = –26.95 cm–1 for complex 2, respectively.

A macrocyclic oxamido vanadium(IV)-oxo ligand and its derivative VO IV2M II (M = Cu, Mn) trinuclear complexes: synthesis, structures and magnetic properties

A new oxamido-bridged vanadium(IV)-oxo complex ligand VOL (H 2L = 2,3-dioxo-5,6:13,14-dibenzo-7,12-diphenyl-1,4,8,11-tetraazacyclo-tetradeca-7,12-diene) ( 1) has been synthesized. Based on the mononuclear ligand, two trinuclear complexes [Cu(VOL) 2(H 2O) 2](ClO 4) 2 · 1.5H 2O ( 2) and [Mn(VOL) 2(CH 3OH) 2](ClO 4) 2 · 5CH 3OH ( 3) have been prepared and structurally characterized by X-ray crystallography. In complexes 2 and 3, the central ions Cu(II) and Mn(II) are connected to two VOL fragments via an exo-cis oxamido bridge. Magnetic susceptibility studies (2–300 K) indicate the occurrence of ferromagnetic coupling between the paramagnetic metals in complex 2, while a weak antiferromagnetic interaction is detected in complex 3. The experiment data have been fitted according to the Heisenberg Hamiltonian H ˆ = - 2 J S ˆ 1 S ˆ 2 , leading to J = 9.09 cm −1, zJ′ = 5.0 × 10 −3 cm −1 for complex 2 and J = −0.27 cm −1, θ = −0.03 K for complex 3.

Magnetic interactions in a new heterospin complex involving nitroxide radical and oxamido-bridged copper(II)

A new binuclear copper(II) complex [Cu2(oxpn)(IM2py)2](ClO4)2, containing four spin carriers with pyridyl-substituted nitroxide radicals has been synthesized and characterized structurally and magnetically (oxpn = N,N′-bis(3-aminopropyl)oxamido, IM2py = 2-(2′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl). The structure of the complex consists of centrosymmetric trans oxamido-bridged copper(II) binuclear units and nitroxide radicals. The coordination geometry around each copper atom is distorted square pyramidal and the apical position is occupied by a nitrogen atom of the imidazoline ring of a radical ligand. Magnetic analysis indicates that the complex exhibits strong antiferromagnetic coupling between copper(II) ions through the oxamido bridge and a ferromagnetic interaction between copper(II) ions and radical ligands. The magnetic behaviour is discussed with reference to the crystal structure.

Three trinuclear Cu–M–Cu (M = Co, Ni and Zn) complexes including macrocyclic oxamido bridge: Synthesis, structures and magnetic properties

Based on the complex ligand (CuL H2L = 2,3-dioxo-5,6:15,16-dibenzo-1,4,8,13-tetraazacyclotetradeca-7,13-diene), which includes macrocyclic oxamido bridge, three trinuclear complexes were prepared. They are of the formula [(CuL) 2M(ClO 4) 2] (M = Co( 1), Ni( 2)) and [(CuL) 2Zn(CH 3OH) 2] · (ClO 4) 2 ( 3). The crystal structures of the three complexes have been determined and the M(II) of the three complexes all exist on the mirror plane. Complex 1 is the first Cu–Co complex bridged by oxamido. Their magnetic properties were studied by susceptibility versus temperature measurement, the best fitting of the experimental data led to J = −28.12 cm −1 for 1, J = −42.88 cm −1 for 2, and J = −2.13 cm −1 for 3.

Oxamido-Bridged Bimetallic Complexes Involving Nitronyl Nitroxide Radical Ligands: Crystal Structure and Magnetic Behavior

Two novel dinuclear copper(II) complexes containing four spin carriers have been synthesized and characterized structurally and magnetically. These complexes are formulated as [Cu2(apox)(NIT-4Py)2](ClO4)2·2H2O (1) and [Cu2(apox)(NIT-2Py)2](ClO4)2 (2), where apox = N,N‘-bis(3-aminopropyl) oxamido, NIT-4Py = 2-(4‘-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, and NIT-2Py = 2-(2‘-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide. The structure of complexes 1 and 2 consists of centrosymmetric trans oxamido-bridged copper(II) binuclear units. In complex 1, the coordination geometry of the copper atom is distorted square plane and the radical ligands (NIT-4Py) coordinate to the copper atoms via the nitrogen atoms of the pyridine ring, whereas in complex 2, the coordination geometry around each copper atom is distorted square pyramidal and the apical position is occupied by an oxygen atom of the radical ligand. Magnetic analyses indicate that both compounds 1 and 2 exhibit strong antiferromagnetic coupling between copper(II) ions through the oxamido bridge and there are ferro- and antiferromagnetic exchange interactions between copper(II) ions and radical ligands for compounds 2 and 1, respectively.

Synthesis and ferromagnetically coupled heterodinuclear oxamido-bridged copper(II)–oxovanadium(IV) complexes

Three novel copper(II)-oxovanadium(IV) heterodinuclear complexes bridged by dianions of N,N′-oxamidobis(propionato)cuprate, [Cu(obp)], and endcapped with 2,9-dimethyl-1,10-phenanthroline (Me 2phen), 4,7-diphenyl-1,10-phenanthroline (Ph 2phen) or 5-methyl-1,10-phenanthroline (Mephen), respectively, have been synthesized and identified as [Cu(obp)VO(Me 2phen)] (1), [Cu(obp)VO(Ph 2phen)] (2) and [Cu(obp)VO(Mephen)] (3). The three dinuclear complexes have not yet been isolated in crystalline form suitable for X-ray structure analysis, but based on elemental analyses, IR and electronic spectra studies, magnetic moments at room temperature and molar conductivity measurements, these complexes are proposed to have an extended oxamido-bridged structure consisting of planar copper(II) and square-pyramidal oxovanadium(IV) ions. The three heterodinuclear complexes were further characterized by variable-temperature magnetic susceptibility (4.2–300 K) measurements and the magnetic data have been used to deduce the indicated heterodinuclear structure. The results derived from least-squares fit of the experimental data have confirmed that the operation of a ferromagnetic interaction between the adjacent copper(II) and oxovanadium(IV) ions through the oxamido bridge within each molecule takes place. Based on spin Hamiltonian, H ^ = - 2 J S ^ 1 · S ^ 2 , the exchange integral ( J) was evaluated as J = + 21.9 cm - 1 for (1), J = + 18.8 cm - 1 for (2) and +26.5 cm −1 for (3). The influence of the symmetry of the magnetic orbitals and different terminal ligands on the nature and magnitude of the magnetic interaction between the paramagnetic centers is also discussed.

Synthesis, structure and magnetic properties of the novel heteropolynuclear complex bridged by azido

Synthesis of the first heterometallic hexapolynuclear complex [(CuL) 4Mn 2(N 3) 4] · 2MeOH which is bridged by azido and macrocyclic oxamido bridge and especial the azido bridge links to two different metal ions, has been reported in this paper and the complex was characterised by low-temperature magnetic measurements.

Synthesis, spectral and magnetic studies of copper(II)–manganese(II) heterobinuclear complexes bridged by oxamido groups

Two new μ-oxamido-bridged heterobinuclear complexes have been synthesized and identified as [Cu(dmoxpn)Mn(Me 2phen) 2](ClO 4) 2 ( 1) and [Cu(dmoxae)Mn(Me 2phen) 2](ClO 4) 2 ( 2), where Me 2phen denotes 2,9-dimethyl-1,10-phenanthroline; dmoxpn and dmoxae represent N, N′-bis[3-(dimethylamino)-propyl]oxamido and N, N′-bis[2-(dimethylamino)ethyl]oxamido dianions, respectively. Based on elemental analyses, conductivity measurements, IR and electronic spectra studies, it is proposed that the two complexes have oxamido-bridged structures consisting of a copper(II) and a manganese(II) ions, which have a square-planar environment and a distorted octahedral environment, respectively. The electronic reflectance spectra indicate the presence of exchange-coupling interaction between bridging copper(II) and manganese(II) ions. Variable-temperature magnetic susceptibility (4.2–300 K) measurements of ( 1) and ( 2) complexes revealed the occurrence of an intramolecular antiferromagnetic interaction between the adjacent manganese(II) and copper(II) ions through the oxamido bridge within each molecule. On the basis of spin Hamiltonian, H ̂ =−2J S ̂ 1· S ̂ 2 the magnetic analysis was carried out for the two complexes and the spin coupling constant ( J) was evaluated as −26.9 cm −1 for ( 1) and −38.2 cm −1 for ( 2). The influence of the chelate ring arrangement around the copper(II) in the copper(II)–manganese(II) heterobinuclear complexes on magnetic interactions between the metal ions of this kind of complexes is also discussed.

Synthesis of and magnetic interactions in binuclear Cu(II)M(II) (M=Cu, Ni and Mn) complexes of macrocyclic oxamido ligands

Six oxamido-bridged binuclear Cu(II)M(II) (M=Cu, Ni and Mn) complexes containing macrocyclic oxamido ligands have been synthesized and characterized by IR, ESR and electronic spectra. They are of the formula [Cu(L 2)M(L) n ](ClO 4) 2, where H 2L 2=2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, L=2,2′-bipyridine and 1,10-phenanthroline (phen), n=1 for M=Cu and n=2 for M=Ni and Mn. The magnetic properties of the complexes with L=phen have been investigated and quantitatively interpreted using the Hamiltonian H ̂ =−2J S ̂ 1 · S ̂ 2 , suggesting antiferromagnetic interactions through the oxamido bridge with J=−210.2, −53.9 and −14.1 cm −1 for the Cu 2, CuNi and CuMn complexes, respectively. Finally, the magnitudes of the Cu(II)M(II) interactions with M=Cu, Ni and Mn have been compared and qualitatively justified.

Synthesis and Magnetic Studies of Copper (II)‐Manganese (II) Heterobinuclear Complexes with an Oxamido Bridge

AbstractFour new copper (II)‐manganese (II) heterobinuclear complexes bridged byN, N'‐bis[2‐(dimethylamino)ethyl)]oxamido dianion (dmoxæ) and end‐capped with 1, 10‐phenanthroline (phen), 5‐methyl‐1, 10‐phenanthroline (Mephen), diaminoethane (en) or 1,3‐di‐aminopropane (pn). respectively, namely, [Cu(dmoxae)MnL2] (CIO4)2 (L=phen, Mephen, en, pn), have been synthesized and characterized by elemental analyses, IR, electronic spectral studies, and molar conductivity measurements. The electronic reflectance spectrum indicates the presence of spin exchange‐coupling interaction between bridged copper(II) and manganese (II) ions. The cryomagnetic measurements (4.2‐300 K) of [Cu(dmoxae)Mn(phen)2](CIO4)2 (1) and [Cu(dmoxae)Mn(Mephen)2](CIO4)2(2) complexes demonstrated an antiferromagnetic interaction between the adjacent manganese(II) and copper (II) ions through the oxamido‐bridge within each molecule. On the basis of spin Hamiltonian, H= ‐ 2JS1. S2. the magnetic analysis was carried out for the two complexes and the spin‐coupling constant (J) was evaluated as −35.9 cm−1 for 1 and ‐ 32.6 cm−1 for 2. The influence of methyl substitutions in the amine groups of the bridging ligand on magnetic interactions between the metal ions of this kind of complexes is also discussed.