Squarato-metal(II) complexes. 1: Structural and magnetic characterization of squarato-bridged dinuclear nickel(II) and copper(II) complexes

A new series of dinuclear squarato-bridged nickel(II) and copper(II) complexes [Ni₂(2,3,2-tet)₂(μ_1,3-C₄O₄)(H₂O)₂](ClO₄)₂ (1), [Ni₂(aepn)₂(μ_1,3-C₄O₄)(H₂O)₂](ClO₄)₂ (2), [Cu₂(pmedien)₂(μ_1,3-C₄O₄)(H₂O)₂](ClO₄)₂.4H₂O (3) and [Cu₂(DPA)₂(μ_1,2-C₄O₄)(H₂O)₂](ClO₄)₂ (4) where is the dianion of 3,4-dihydroxycyclobut-3-en-1,2-dione (squaric acid), 2,3,2-tet = 1,4,8,11-tetraazaundecane, aepn = N-(2-aminoethyl)-1,3-propanediamine, pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine and DPA = di(2-pyridylmethyl)amine were synthesized and structurally characterized by X-ray crystallography. The spectral and structural characterization as well as the magnetic behaviour of these complexes is reported. In this series, structures consist of the groups as counter ions and the bridging the two M(II) centers in a μ-1,3- (1-3) and in a μ-1,2-bis(monodentate) (4) bonding fashions. The coordination geometry around the Ni(II) ions in 1 and 2 is six-coordinate with distorted octahedral environment achieved by N atoms of the amines and by one or two oxygen atoms from coordinated water molecules, respectively. In the Cu(II) complexes 3 and 4, a distorted square pyramidal geometry is achieved by the three N-atoms of the aepn or DPA and by an oxygen atom from a coordinated water molecule. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the M(II) centers. The complexes show weak antiferromagnetic coupling with ∣J∣ = 1.8-4.2 cm⁻¹ in the μ-1,3- bridged squarato compounds 1-3, and J = −16.1 cm⁻¹ in the corresponding μ-1,2- bridged squarato complex 4. The magnetic properties are discussed in relation to the structural data.     

Cyanato bridged binuclear nickel(II) and copper(II) complexes with pyridylpyrazole ligand: Synthesis, structure and magnetic properties

Binuclear cyanate bridged nickel(II) complex [Ni(L)(NCO)]₂(PF₆)₂ (1) and copper(II) complex [Cu(L)(NCO)]₂(PF₆)₂ (2), where L is N,N-bis(3,5-dimethylpyrazol-1-ylmethyl)aminomethylpyridine, a tetradentate N₄-coordinated ligand have been synthesized and characterized by physicochemical method. The structures of complexes 1 and 2 have been studied by single crystal X-ray diffraction analysis. The structure analysis reveals that both nickel(II) and copper(II) center are coordinated in distorted octahedral fashion and coordination mode of cyanate ligand is end-to-end (μ-1,3) for complex 1 but it is double end-on (μ-1,1) mode for complex 2. The variable temperature magnetic susceptibility data, measured from 2 to 300 K, show weak antiferromagnetic interaction with J value −6.2(1) cm⁻¹ for complex 1, whereas complex 2 has very weak ferromagnetic interaction with J value +0.5(1) cm⁻¹.     

Ladder-like azido-bridged copper(II) complexes: Synthesis, X-ray structure and magnetic study

Two mixed-ligand copper(II) complexes [{Cu(L¹)(μ_1,3-N₃)}{Cu(L)(μ_1,3-N₃)(μ_1,1-N₃)}]_n (1) [HL¹ = 1-(N-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane; L = 2-(dimethylamino)-ethylamine] and [{Cu(L²)(μ_1,3-N₃)}{Cu(L)(μ_1,3-N₃)(μ_1,1-N₃)}]_n (2) [HL² = 1-(N-5-methoxy-ortho-hydroxyacetophenimino)-2,2-dimethyl-aminoethane] have been formed upon addition of aqueous solution of sodium azide to a methanolic solution of copper nitrate trihydrate and corresponding Schiff-base ligands. The ligands, HL¹ and HL² undergo partial hydrolysis of their imine bond during the course of reaction. Both the complexes contain single end-to-end (μ_1,3) azido bridged 1D infinite chains (rail) which propagate parallel to the crystallographic b-axis; neighboring chains are interconnected by pairs through double asymmetric end-on (μ_1,1) azido bridges (rung) to yield a ladder-like structure. In both complexes, rungs (end-on azido bridges) do not connect copper centers of the chains like in a regular ladder; instead they connect only the alternating copper sites of the 1D chain. In a chain the coordination environment around copper(II) ions are not the same: while the {Cu(L¹)(μ_1,3-N₃)} and {Cu(L²)(μ_1,3-N₃)} moieties have a penta-coordinated copper(II) center, the copper(II) ion of the neighboring {Cu(L¹)(μ_1,3-N₃)(μ_1,1-N₃)} or {Cu(L²)(μ_1,3-N₃)(μ_1,1-N₃)} moiety has an octahedral coordination environment. The variable temperature (2-300 K) magnetic susceptibility measurements showed that the magnetic interaction between the metal centers in complexes 1 and 2 is dominantly antiferromagnetic. The results of magnetic model are in good agreement with the experimental data.     

Three ion-pair complexes containing bis(maleonitriledithiolate)copper(II) anion and substituted 4-dimethylaminopyridinium: Syntheses, crystal structures, and magnetic properties

Three new ion-pair complexes, [4RBzDMAP]₂[Cu(mnt)₂] (mnt²⁻ = maleonitriledithiolate; [4RBzDMAP]⁺ = 1-(4′-R-benzyl)-4-dimethylaminopyridinium, R = F(1), Cl(2) and Br(3)) were synthesized and characterized by elemental analyses, IR, UV, single crystal X-ray diffraction and magnetic measurements. The [Cu(mnt)₂]²⁻ anions and the cations stack alternately and form a 1D column via C-H···S, C-H···π or C-H···Cu interactions for 1 and 2. While the cations stack into a column though π···π or C-H···π interactions between pyridine and phenyl rings for 1 and 3. The change of the molecular topology of the counteraction when the 4-substituted group in the benzyl ring have been changed from F or Cl to Br atom, results in the difference in the crystal system, space group and the stacking mode of the cations and anions of 1, 2 and 3. Some weak hydrogen bonds between the adjacent columns further generate a 3D network structure. It is interesting that 1 and 2 exhibits antiferromagnetic coupling with θ = −2.372 K and θ = −14.732 K, while 3 shows weak ferromagnetic coupling feature with θ = 0.381 K.     

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.     

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.     

The use of trans-4-cotininecarboxylate to construct a polymeric copper(II) azido complex: Hydro(solvo)thermal synthesis, structure and magnetic properties

A new pyridyl-carboxylate ligand, the anion of trans-4-cotininecarboxylic acid, HL, 1, has been used to prepare a new polymeric copper(II) complex, [CuLN₃]_2n, 2, based on a [CuLN₃]₂ dimeric building block. The single crystal structures of both 1 and 2 have been determined and 1 has been found to be in its zwitterionic configuration. The structure of 2 is a one-dimensional tape-like polymeric structure based on an end-on azido-bridged binuclear [Cu₂N₃]₂ backbone moiety. Magnetic studies reveal that 2 is close to paramagnetic from 2 to 300 K with a Curie constant of 1.094 emu K/mol, a Weiss temperature of 0.73 K and a corresponding μ_eff of 2.09 μ_B. A fit of χ_MT for 2 with S₁ = S₂ = ½, yields g = 2.441(6), J = −0.49(3) cm⁻¹, zJ = −0.38(2) cm⁻¹ and N(α) = 0.00053(12) emu/mol, a fit that indicates the presence of both very weak intramolecular intrachain antiferromagnetic exchange coupling within the one-dimensional tape-like chains and very weak interchain antiferromagnetic exchange coupling between these chains.     

Synthesis, crystal structure, spectroscopic and magnetic properties of doubly and triply bridged dinuclear copper(II) compounds containing di-2-pyridylamine as a ligand

The dihydroxo-bridged dinuclear copper(II) compound [Cu₂(dpyam)₂(μ-OH)₂]I₂ (1) and the triply bridged dinuclear copper(II) compounds with a formato bridge [Cu₂(dpyam)₂(μ-O₂CH)(μ-OH)(μ-OMe)](ClO₄) (2) and [Cu₂(dpyam)₂(μ-O₂CH)(μ-OH)(μ-Cl)](ClO₄) · 0.5H₂O (3) (in which dpyam=di-2-pyridylamine) have been synthesized and their crystal structures determined by X-ray crystallographic methods. All three compounds are either centrosymmetric, or have a symmetry plane in the molecule. Compound 1 contains the [Cu₂(dpyam)₂(μ-OH)₂]⁺ unit and iodide anions. Each copper(II) ion is in a slightly tetrahedrally distorted square planar coordination with the square plane consisting of two nitrogen atoms of the dpyam ligand and two bridging hydroxo groups. The Cu-I distances of 3.321 Å are quite long and only involve a weak semi-coordination. Compound 2 contains a triply bridged dinuclear copper(II) species, the coordination environment around each copper(II) ion involves a distorted trigonal-bipyramidal CuN₂O₃ chromophore. In the dinuclear unit of compound 3, the triply bridged copper(II) ions show a distorted trigonal-bipyramidal coordination of the CuN₂O₂Cl chromophore. The Cu-Cu distances are 2.933(2), 3.023(1) and 3.036(1) Å for compounds 1, 2 and 3, respectively.The magnetic susceptibility measurements, measured from 5 to 280 K, revealed a weak antiferromagnetic interaction between the Cu(II) atoms for compound 1 with a singlet-triplet energy gap (J) of −15.3 cm⁻¹, whereas compounds 2 and 3 are ferromagnetic with J=62.5 and 79.1 cm⁻¹, respectively.     

Synthesis, crystal structure, magnetic property and nuclease activity of a new binuclear cobalt(II) complex

One new binuclear Co(II) complex of N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxyl-1,3-diaminopropane (HL), [Co(2)L(mu(2)-Cl)](ClO(4))(2) x 3CH(3)CN x C(2)H(5)OC(2)H(5) (1), has been synthesized and its crystal structure and magnetic properties are shown. In 1, each Co(II) atom has a distorted trigonal bipyramidal geometry with a N(3)OCl donor set. The central two Co(II) atoms are bridged by one alkoxo-O atom and one Cl atom with the Co1-Co2 separation of 3.239 A. Susceptibility data of 1 indicate strong intramolecular antiferromagnetic coupling of the high-spin Co(II) atoms. In this paper, the interaction with calf thymus DNA was investigated by UV absorption and fluorescent spectroscopy. Results show the complex binds to ct-DNA with a intercalative mode. The interaction between complex 1 and pBR322 DNA has also been investigated by submarine gel electrophoresis, noticeably, the complex exhibits effective DNA cleavage activity in the absence of any external agents.     

Dinuclear terephthalato-bridged nickel(II) complexes. Structural characterization and magnetic properties

The dinuclear terephthalato-bridged nickel(II) complexes [Ni₂(cyclen)₂(μ-tp)](ClO₄)₂ (1) [Ni₂(trpn)₂(μ-tp)(H₂O)₂](ClO₄)₂ (2) and [Ni₂(3,3,3-tet)₂(μ-tp)(H₂O)₂](ClO₄)₂ · 2H₂O (3), where tp = terephthalate dianion, cyclen = 1,4,7,10-tetraazacyclododecane, trpn = tris(3-aminopropyl)amine and 3,3,3-tet = 1,5,9,13-tetraazatridecane, were synthesized and structurally characterized by X-ray crystallography. Their magnetic susceptibilities were also determined at variable temperatures over the range 2-300 K. The structures of these complexes consist of μ-tp bridging two Ni(II) centers in a bis(bidentate) bonding fashion in 1 and in bis(monodentate) bonding fashion in 2 and 3. The coordination geometry around the Ni(II) ions in these compounds has a distorted octahedral geometry with four nitrogen atoms from the amine ligand (cyclen, trpn or 3,3,3-tet) and two coordinated oxygen atoms supplied by the chelated carboxylate group of the bridged terephthalate ligand in 1, and by one tp-carboxylate-oxygen in 2 and 3. The sixth coordination site in the last two complexes 2 and 3 is achieved via an oxygen atom from a coordinated water molecule. The intradimer Ni…Ni distances in these complexes are 10.740, 11.428 and 11.537 Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Ni(II) centers. Also, the analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(bidentate) and bis(monodentate) coordination modes for the bridged terephthalate ligand in 1, 2 and 3, respectively. Despite the different coordination modes of the tp bridging ligand in these complexes, they all exhibit very weak antiferromagnetic coupling. The coupling constants J were found to be −2.2, −0.6 and −1.5 cm³ K mol⁻¹ for the complexes 1, 2 and 3, respectively. The structural and magnetic results of 1-3 are discussed in relation to the other related published μ-terephthalato dinuclear Ni(II) compounds.     

1D/2D coordination polymers of copper(II) having two superexchange pathways: syntheses, crystal structures and magnetic properties

Two new polynuclear complexes of Cu(II), [(μ-1,1,3-N₃)₂{Cu₂(me₂tn)₂(N₃)₂}]_n (1) (me₂tn=2,2-dimethylpropane-1,3-diamine) and [Cu₂(μ-C₂O₄)(μ-N₃)(ipr₂en)₂]_n(ClO₄)_n (2) (ipr₂en=N,N^′-di-isopropylethane-1,2-diamine) have been synthesized and structurally characterized by X-ray crystallography. The crystal structure of 1 displays a 2D network in which distorted octahedral copper(II) centers, chelated by a me₂tn ligand and bound to a terminal azide, are connected through μ-1,1,3 bridging azide anions. The structure of 2 shows 1D chains comprising alternating [(ipr₂en)Cu-Ox-Cu(ipr₂en)] units and end-to-end azide ligand. The chains on mutual H-bonding interaction through ClO₄⁻, give rise to a 2D supramolecular architecture. The magnetic data of complexes were recorded in the temperature range, 300-2 K. In case of complex 1, the magnetic data are consistent with a ferromagnetic interaction through the end-on azide bridge (J_FM=10 cm⁻¹) and a weak antiferromagnetic interaction (zj=−0.8 cm⁻¹) between the ferromagnetically coupled dimers and an average g-value of 2.05. The susceptibility data of 2 were fitted using an alternating AF-AF chain spin 1/2 law which leads to the following parameters J_oxalate=−180 cm⁻¹, J_azide=−43 cm⁻¹ and g=2.25 cm⁻¹.     

Dinuclear fumarato- and terephthalato-bridged copper(II) complexes: Structural characterization and magnetic properties

The dinuclear dicarboxylato-bridged copper(II) complexes [Cu₂(TPA)₂(μ-tp)](ClO₄)₂ · H₂O (1), [Cu₂(TPA)₂(μ-fum)](ClO₄)₂ · 2H₂O (2) and [Cu₂(pmedien)₂(μ-fum)(H₂O)₂](ClO₄)₂ (3) (tp = terephthalate dianion, fum = fumarate dianion, TPA = tris(2-pyridylmethyl)amine and pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) were synthesized and structurally characterized by X-ray crystallography. The structures of the TPA complexes 1 and 2 consist of μ-tp or μ-fum bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions in these compounds has a distorted trigonal bipyamidal geometry, TBP with four nitrogen atoms from the TPA ligand and a coordinated oxygen atom supplied by the carboxylate group of the bridged dicarboxylato ligand. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the pmedien, one fum-carboxylate-oxygen and by an oxygen atom from a coordinated water molecule. The intradimer Cu…Cu distances in these complexes are 11.078(3), 8.663(4) and 9.520(3) Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(mondentate) coordination mode for the bridged dicarboxylato ligands in compounds 1 and 2. The susceptibility measurements at variable temperature over the 2-300 K range are reported. For 1-3, it has been observed slight antiferromagnetic coupling with J values of −0.8, −3.0 and −2.9 cm⁻¹, respectively.     

Dinuclear terephthalato-bridged copper(II) complexes: Syntheses, spectral and structural characterization, and magnetic properties

Herein, we report the syntheses, spectral and structural characterization, and magnetic behavior of four new dinuclear terephthalato-bridged copper(II) complexes with formulae [Cu₂(trpn)₂(μ-tp)](ClO₄)₂ · 2H₂O (1), [Cu₂(aepn)₂(μ-tp)(ClO₄)₂] (2), [Cu₂(Medpt)₂(μ-tp)(H₂O)₂](ClO₄)₂ (3) and [Cu₂(Et₂dien)₂(μ-tp)(H₂O)](ClO₄)₂ (4) where tp = terephthalate dianion, trpn = tris(3-aminopropyl)-amin, aepn = N-(2-aminoethyl)-1,3-propanediamine, Medpt = 3,3′-diamino-N-methyldipropylmine and Et₂dien = N,N-diethyldiethylenetriamine. The structures of these complexes consist of two μ-tp bridging Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry of the Cu(II) ions in these compounds may be described as close to square-based pyramid (SP) with severe significant distortion towards trigonal bipyramid (TBP) stereochemistry in 1. The visible spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, the solid infrared spectral data for the stretching frequencies of the tp-carboxalato groups, the ν(COO⁻) reveals the existence of bis(monodentate) coordination mode for the bridged terephthalate ligand. The susceptibility measurements at variable temperature over the range 2-300 K are reported. Despite the same bonding mode of the tp bridging ligand, there has been observed slight antiferromagnetic coupling for the compounds 1 and 4 with J values of −0.5 and −2.9 cm³ K mol⁻¹, respectively, and very weak ferromagnetic coupling for 2 and 3 with J values of 0.8 and 10.1 cm³ K mol⁻¹, respectively. The magnetic results are discussed in relation to other related μ-terephthalato dinuclear Cu(II) published compounds.     

Discrete and 1D coordination polymeric chloro-bridged copper(II) dimers exhibiting ferro- and antiferromagnetic exchange coupling: Magneto-structural correlations and non-covalent interactions

The synthesis and characterization of two 1D coordination polymers [Cu₂(MHL)Cl₂][ClO₄]₂ · CH₃CN · THF (2 · CH₃CN · THF) and [Cu₂(MPyPz)Cl₂][ClO₄]₂ · CH₃CN (3 · CH₃CN), having repetitive units, of m-xylyl-based ligands with terminal tridentate (2-pyridyl)alkylamine (MHL = α,α′-bis[N-(2-pyridylethyl)-N-(2-pyridylmethyl)amino]-m-xylene) and (2-pyridyl)alkylamine/pyrazole (MPyPz = α,α′-bis[N-(2-pyridylethyl)-N-(pyrazol-1-ylmethyl)amino]-m-xylene) coordination have been accomplished. X-ray crystallographic studies reveal that the copper(II) centers in the recently reported dichloro-bridged discrete complex [{Cu(MeL)Cl}₂][ClO₄]₂ (1) of a tridentate (2-pyridyl)alkylamine ligand [MeL = methyl[2-(2-pyridyl)ethyl](2-pyridylmethyl)amine], 2 · CH₃CN · THF, and 3 · CH₃CN have distorted square-pyramidal geometry, sharing a base-to-apex edge with parallel basal planes. Variable-temperature susceptibility measurements in the range of 2-300 K reveal antiferromagnetic for 1 [J (singlet-triplet energy gap) = −3.89 cm⁻¹] and 2 · CH₃CN · THF (J = −1.84 cm⁻¹), and ferromagnetic for 3 · CH₃CN (J = +6.27 cm⁻¹) coupling. The complexes provide useful information for the magneto-structural correlations.     

Fluorous interactions in complexes of lead(II) hexafluoroacetylacetonate

Structure determinations for 2,2′-bipyridine and 1,10-phenanthroline adducts of lead(II) hexafluoroacetylacetonate, [Pb(bipy)₂(hfacac)₂] (1), [Pb(bipy)(hfacac)₂] (2), and [Pb(phen)(hfacac)₂] (3), show that the balance of intermolecular forces within the lattices is seemingly sensitive to the adduct stoichiometry but not to the nature of the heteroaromatic base. In 3, a structure, in which there is an apparent preference for CF/aromatic interactions over separate CF/CF and aromatic/aromatic interactions, is essentially identical at both 120 and 293 K.     

Electrochemical synthesis and crystal structure of iron(II), cobalt(II), nickel(II) and copper(II) complexes of dianionic tetradentate N4 Schiff base ligand

The electrochemical oxidation of anodic metal (iron, cobalt, nickel and copper) in an acetonitrile solution of the potentially chelating Schiff base N,N(dithiodiethylenebis-(aminylydenemethylydene)-bis(1,2-phenylene)ditosylamide (H₂L) afforded stable complexes of empirical formula [ML]. The compounds obtained have been characterized by microanalysis, IR spectroscopy and ES-MS mass spectrometry. The crystal and molecular structures of [FeL]·CH₃CN (1) [CoL]·CH₃CN (2), [NiL]·CH₃CN (3) and [CuL]·CH₃CN (4) have been determined by X-ray diffraction in all complexes, the metal atom is in a distorted tetrahedral environment with the Schiff base acting as a tetradentate N4 donor.     

Structural and magnetic properties of O-bridged tetranuclear and binuclear Cu(II) complexes

Two copper(II) complexes [Cu₄(L¹)₄] (1) and [Cu₂(phen)₂(HL²)₂] (ClO₄)₂ (2) have been synthesized from two potentially tridentate ligands N-(2-hydroxybenzyl) propanolamine (H₂L¹) and N-(2-hydroxybenzyl) ethanolamine (H₂L²). X-ray analyses revealed that 1 contains a Cu₄O₄ cubane core, with each two Cu(II) atoms bridged by a pair of alkoxides; 2 has a bis(μ₂-phenoxo)-bridged dicopper(II) structure. Variable temperature magnetic measurements of 1 have revealed that the correlation between 2J and the bridge angles φ for 1 shows a very strong antiferromagnetic tendency, i.e. the ferromagnetic and antiferromagnetic interactions cross at the φ of 94.5°. The relatively weak antiferromagnetic interactions (2J=−226.8 cm⁻¹) with respect to the bridge angles (φ=100.4°) for 2 have been ascribed to the pyramidal distortions at the phenoxide oxygen atoms in addition to the unfavorable overlaps of the magnetic orbitals for the highly distorted copper coordination polyhedra.     

Studies of copper(II) and nickel(II) complexation by bis(1,4,7-triazacyclononane) ligands containing alkene and alkyne bridging groups

The copper(II) and nickel(II) complexes of three new 1,2-bis(1,4,7-triazacyclononane) ligands containing unsaturated four carbon bridging groups is studied by continuous variation UV-Vis spectroscopic and pH potentiometric equilibrium experiments. The cis-butene-2 (L_C) linked ligand may form monomeric MN₆-type complexes while the trans-butene-2 (L_T) and butyne-2 (L_Y) ligands are prevented by their stereochemistry from forming monomeric complexes and form oligomeric complexes. It is determined that the stability of the CuL_C²⁺ complex is not appreciably different from the oligomeric complexes of L_T and L_Y. Single-crystal X-ray structure determinations are made on three square pyramidal Cu₂L⁴⁺ complexes: [Cu₂L_CCl₄] (1), [Cu₂L_YCl₄] (2), and [Cu₂L_T(NO₃)₂(H₂O)₂](NO₃)₂ (3). The structure of [Ni₂(L_C)₂](ClO₄)₄ · 2H₂O (4) is a binuclear dimer that contains two nickel(II) ions sandwiched between two ligands, indicating that bis([9]aneN₃) ligands with four linker atom chains may form either monomeric or oligomeric structures.     

Manganese(II) coordination polymers with bis(5-tetrazolyl)methane: Synthesis, structure and magnetic properties

Two new Mn(II) coordination polymers with bis(5-tetrazolyl)methane (H₂btm), [Mn(btm)(phen)(H₂O)] · H₂O (1) and [Mn(btm)(2,2′-bpy)] · 1.5H₂O (2), have been synthesized and their structures determined by X-ray diffraction. In complex 1, the btm ligands assume the μ₂-1,1′:4 coordination mode and interlink Mn(II) ions into infinite one-dimensional chains. The chains are assembled into a three-dimensional architecture via hydrogen bonds and π-π interactions. For 2, Mn(II) ions are connected by btm ligands in the μ₃-1,1′:2:3′ mode to produce two-dimensional (6,3) coordination network. Magnetic investigations revealed that interactions through the btm bridges in both 1 and 2 are antiferromagnetic.     

Synthesis, structure, sorption and magnetic properties of Ni(II) and Cu(II) complexes with thiosemicarbazone of 2-hydroxybenzaldehyde, bridged by 4,4′-bipyridine

(ML)₂(bipy) complexes (LH₂ = thiosemicarbazone of 2-hydroxybenzaldehyde, bipy = 4,4′-bipyridine, M = Ni(II), 1, or Cu(II), 2) were synthesized and characterized by X-ray crystallography. Compound 1 possessed porous structure due to peculiarities of crystal packing, whereas 2 formed infinite zig-zag chains with dense non-porous packing. It was shown that 1 absorbed 0.013 cm³/g of methanol vapor in two steps. Complex 1 was diamagnetic; for 2, the dependency of χ versus T could be interpreted by Bleaney-Bowers expression in 20-300 K temperature range (J = −6.8 cm⁻¹, g = 2.07).