Diazine Bridging Research Articles

Hydrolysis of the Amide Bond in L-Methionine- and L-Histidine-Containing Dipeptides in the Presence of Dinuclear Palladium(II) Complexes with Benzodiazines Bridging Ligands

1H NMR spectroscopy was applied to study the catalytic activity of dinuclear Pd(II)-aqua complexes with different benzodiazine bridging ligands, [{Pd(en)(H2O)}2(μ-qx)]4+ (Pd1), [{Pd(en)(H2O)}2(μ-qz)]4+ (Pd2) and [{Pd(en)(H2O)}2(μ-phtz)]4+ (Pd3) (qx, qz and phtz denote quinoxaline, quinazoline and phthalazine, respectively), in the hydrolytic cleavage of the amide bond in N-acetylated L-methionylglycine (Ac–L–Met–Gly) and L-histidylglycine (Ac–L–His–Gly) dipeptides. All reactions were investigated with an equimolar amount of the reactants at pH = 2.0–2.5 in D2O and at 37 °C. The obtained data for the catalytic activity of Pd1–Pd3 complexes are compared with those previously reported for [{Pt(en)(H2O)}2(μ-L)]4+ (L denotes benzodiazine: qx, qz and phtz), [{Pd(en)(H2O)}2(μ-L)]4+ and [{Pt(en)(H2O)}2(μ-L)]4+ (L denotes diazine: pyrazine and pyridazine) complexes. It was found that catalytic activity of these complexes in peptide cleavage is strongly related to the position of the nitrogen atoms in the benzodiazine or diazine bridging ligand. The investigated dinuclear Pd(II) and Pt(II) complexes show catalytic activity in the selective hydrolysis of the Met–Gly amide bond of Ac–L–Met–Gly dipeptide. Moreover, all the above mentioned Pd(II) complexes were also able to catalyze the regioselective hydrolysis of the His–Gly amide bond of Ac–L–His–Gly dipeptide. However, in the reaction with Ac–L–His–Gly, only Pt(II) aqua complexes containing bridging ligands with two nitrogen atoms in the para-position (quinoxaline and pyrazine) were able to cleave this dipeptide.

The formation of a metallosupramolecular porous helicate through salicylaldehydethiosemicarbazone: Synthesis, Characterization, Cytotoxic activity, DNA binding and DFT calculations

The reaction of salicylaldehyde‐S‐methylisothiosemicarbazone in the presence of ethylenediamine base and iron (III)chloride generated unforeseen homotopic dinuclear triple‐stranded iron (III)helicate. The synthesized helicate was characterized by elemental analysis, IR, UV–Vis spectroscopy, magnetic moment measurement, and evaluated cytotoxic activities against K562, HL‐60 and THP‐1 leukemia cells. In addition, solid‐state structure has been determined by single‐crystal X‐ray diffraction technique. In the complex, three dinucleating O, N, N, O donor ligands provide three diazine (═N─N═) bridges between the metal ions and facial O3N3 coordination spheres around them. The ligands are folded about the N─N single bond and coordinated to the two metal ions in a helical fashion to form the triple helical structure. In the crystal lattice, chains of centrosymmetric rings, which are connected to one another via π─π stacking interactions, are generated by C─H···O intermolecular interactions. The results are also confirmed by the density functional theory (DFT) calculations. The results obtained from the cytotoxicity test showed to be effective in low concentrations on the leukemia cells. An intercalative binding mode of helicate‐DNA complex was confirmed with the high intrinsic binding constant (Kb = 8×106 M−1) and competitive displacement assay of Ethidium bromide with high Ksv value.

A linear tetranuclear Cu(II) complex exhibiting both ferro and antiferromagnetic couplings: Synthesis, characterization and magneto-structural studies

The pyrimidinyl hydrazone ligand OC{NHNC(Me)(pm)}2 (pm = 2-pyrimidinyl) (L3H2) has two potentially protic H atoms and multiple donor atoms. The reaction of L3H2 with CuCl2·2H2O yielded the tetranuclear complex [Cu4(L3H)2Cl6(CH3OH)2] (1). Structural studies on 1 reveal the molecule is located about a crystallographic inversion centre, affording two crystallographically independent Cu(II) centres with the two symmetry equivalent [Cu2(L3H)Cl3CH3OH] units connected via µ2-Cl bridges to generate a linear tetranuclear copper complex. The ligand is singly deprotonated (L3H−) and twisted around the diazine NN′ bond, affording an N3 donor set for the Cu1 centre and an N2O donor set for the Cu2 centre. The Cu1 ion is five coordinate with an [N3] donor set from the L3H− ligand and the remaining two sites occupied by Cl− anions. The Cu2 ion is six coordinate with the L3H− ligand offering a mer [N2O] donor set, with the three remaining sites occupied by two Cl− anions and a MeOH molecule. Magnetic studies reveal the presence of strong antiferromagnetic interactions via the diazine bridge linking the Cu1 and Cu2 ions and moderate ferromagnetic interactions via the chloro bridges located about the inversion centre, connecting the Cu2 and Cu2i ions.

Synthesis, characterization and magnetic studies on mono-, di-, and tri-nuclear Cu(ii) complexes of a new versatile diazine ligand.

The synthesis and coordination chemistry of a new open-chain diazine ligand (L4H2) containing bipyridine, oxime and hydrazone functionalities is reported. Reaction of L4H2 with CuCl2·2H2O affords the mononuclear complex [Cu(L4H2)Cl2] (1) in which the ligand acts as a neutral tridentate N,N',N'' donor, whereas treatment with a large excess of CuCl2·2H2O affords the dinuclear complex [Cu2(L4H)Cl3(CH3OH)(H2O)] (2) in which the ligand is singly-deprotonated at the diazine, offering N,N',N'' and N,N' donor sets to two Cu(ii) ions. Reaction with Cu(NO3)2·3H2O yields the trinuclear complex, [Cu3(L4H)2(CH3OH)4(NO3)4] (3) in which the ligand is again singly deprotonated, but now presents a tetradentate N,N',N'',N'''-donor set to the first Cu(ii) and behaves as an N,O-chelate to a second Cu(ii), with a conformational change from cis to trans at the diazine moiety. When the latter reaction is repeated in the presence of a mild base, a second trinuclear complex is isolated, [Cu3(L4)2(CH3CH2OH)](NO3)2 (4) in which both the diazine and oxime functionalities of the ligand are deprotonated which subsequently bridges all three Cu(ii) ions, acting as an N,N',N'' donor to the first Cu(ii), a N,N' donor to a second Cu(ii) (similar to 2) and as a terminal O-donor to a third Cu(ii) ion. The Cu(ii) ions are linked mutually cis via the two-atom diazine bridge in the case of 2 and 4 and trans in the case of 3. Magnetic studies reveal the presence of weak ferromagnetic interactions in 2 (g = 2.2, J/k = +12.8 K) and strong antiferromagnetic interactions in both 3 and 4 (g = 2.093 J/k = -140 K and g = 2.24 J/k = -300 K respectively).

Crystal structure of a trinuclear complex of zinc(II) with 2,6-Di-tert-butyl-p-quinone 1′-phthalazinylhydrazone

2,6-Di-tert-butyl-p-quinone 1′-phthalazynylhydrazone (HL) is synthesized; the total energies and geometry of the possible hydrazone tautomeric forms are calculated by quantum chemical methods. The hydrazone phthalazone tautomer is shown to be the most stable, which is well consistent with the 1H NMR spectroscopic data for hydrazone. An X-ray crystallographic analysis is performed of the hydrazone-based Zn(II) trinuclear complex, in which zinc atoms are linked by the diazine bridge of the phthalazine cycle and two pivalate bridges. The geometric properties of the monodeprotonated hydrazone residue in the complex are similar to the calculated data for the phthalazone hydrazone tautomeric form.

Pyrazole-bridged late first row transition metal complexes derived from hexadentate compartmental ligand: synthesis, characterization, antibacterial activity, and DNA binding/cleavage studies

A series of binuclear CoII, NiII, CuII, and ZnII complexes having μ-1,2 diazine bridging have been prepared and characterized by various physicochemical methods. The hexadentate ligand is synthesized by condensing pyrazole-3,5-dicarbohydrazide with 2-hydroxynaphthaldehyde (LH3) in 1:2 ratio. All the complexes were found to be monomeric in nature with octahedral geometry and act as nonelectrolytes. Ligand and complexes were screened for antibacterial activity against Escherichia coli and made to interact with its DNA to investigate the binding/cleaving ability by absorption, hydrodynamic, thermal denaturation, and electrophoresis studies. An intercalative binding mode is predicted by the results. Gel electrophoresis data indicate cleavage of DNA to a greater extent by both ligand and complexes.

Synthesis and structure of transition metal complexes derived from a novel polynucleating oxaza macrocycle having diazine and phenoxo bridging components

Novel CoII, NiII, CuII and ZnII complexes of the polynucleating oxaza macrocyclic ligand (LH4) derived from the 2:2 condensation of pyrazole-3,5-dicarbohydrazide and 2,6-diformyl-4-methylphenol have been synthesized. Ligand and complexes were characterized on the basis of elemental analysis, IR, 1HNMR, UV–Visible, magnetic susceptibility, ESR and conductivity measurements, FAB-mass and thermal analysis. Present ZnII and CuII complexes are binuclear in nature with octahedral geometry, where as CoII and NiII complexes are tetranuclear with square-planar geometry. CuII and CoII complexes are paramagnetic whereas ZnII and NiII complexes are diamagnetic. Only the copper complex has shown redox property in the applied potential range while the ligand and other complexes are found to be electrochemically innocent.

A Rare μ4‐O Centred Dy4 Tetrahedron with Coordination‐Induced Local Chirality and Single‐Molecule Magnet Behaviour

AbstractCoordination‐induced chirality was achieved in a uniquetetrahedral [Dy4(μ4‐O)(μ‐OMe)2(beh)2(esh)4]·3MeOH complex through a twisted diazine bridge from a Schiff base ligand. Magnetic measurements reveal weak intramolecular antiferromagnetic interactions (J = –0.3 cm–1) with single‐molecule magnet behaviour (Ueff = 23.42 K).

Interaction of E. coli DNA with diazine-bridged late first row transition metal complexes derived from hexadentate compartmental ligands: an approach to DNA cleavage/binding studies

A series of binuclear CoII, NiII, CuII and ZnII complexes having μ-1,2 diazine bridging have been prepared and characterized by various physico-chemical methods. The hexadentate ligands were synthesized by condensing 3,5-dichloroformyl-1H-pyrazole with 2-hydrazinobenzothiazole (L1H) or 4-aminoantipyrine (L2H) in 1:2 ratio. Gel electrophoresis data indicate cleavage of E. coli DNA to a minute extent by both [Co2L2(μ-Cl)Cl2(H2O)2]·H2O and [Ni2L2(μ-Cl)Cl2(H2O)2]. Conversely, the data for the remaining complexes indicated binding but not cleavage. These results were confirmed by viscosity measurements and absorption spectral studies. An intercalative binding mode is predicted when the title complexes interact with DNA.

Metal-pyrazolyl diazine interaction: Synthesis, structure and electrochemistry of binuclear transition metal(II) complexes derived from an ‘end-off’ compartmental Schiff base ligand

Pyrazolyl diazine (μ-NN) bridged late first row transition metal(II) complexes have been prepared by the interaction of metal(II) chlorides with an ‘end-off’ compartmental Schiff base ligand. The ligand system has a strong diazine bridging component and obtained as a condensation product between 1 H-pyrazole-3,5-dicarbohydrazide and 3-acetylcoumarin in absolute ethanol. All synthesized compounds are characterized on the basis of various spectral and analytical techniques. Complexes are found to be non-electrolytes and monomeric in nature. The magnetic exchange interactions are very weak because of the more electronegative exogenous chloride, though diazine bridging group bring metal centers in a close proximity.

Bi- and tetranuclear ligational deeds of a polyaza macrocycle having four diazine (N2) bridging components headed for CoII, NiII, CuII and ZnII ions: An emphasis on electrochemistry of non-innocent ligand system

Novel bi- and tetranuclear CoII, NiII, CuII and ZnII complexes having diazine bridging units have been prepared and characterised on the basis of analytical and spectroscopic techniques. With the help of electronic spectra and magnetic moment measurements, it is predicted that the CoII and NiII complexes have octahedral geometry while CuII and ZnII complexes found to be square pyramidal. Present ZnII and CuII complexes are binuclear in nature, where as CoII and NiII complexes are tetranuclear with feeble antiferromagnetic exchange interactions. UV–visible spectral studies, in the range 275–425 nm, evidence the significant blue shift in π → π* transition which provide the ease of stabilization of bonding molecular orbitals in the complexes. All complexes are monomeric in nature. Ligand and all complexes were found to be electrochemically active compounds. One electron transfer process is observed in ligand similarly, there is no significant change in the cyclic voltammograms of CoII and ZnII complexes, while CuII and NiII complexes show one and two electron transfer redox behaviours, respectively in the present macrocyclic ligand field.

Crystal structures and magnetic properties of triple helical binuclear complexes with bis(bidentate) diazine ligands

Three triple helical binuclear complexes [Ni 2(L 1) 3] · (ClO 4) 4 · (H 2O) 3 ( 1) (L 1 = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), [Ni 2(L 2) 3] · (ClO 4) 4 · (H 2O) 3 ( 2) (L 2 = 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene) and [Mn 2(L 1) 3] · (ClO 4) 4 · (H 2O) 3 ( 3) have been studied, where the L i ligand possesses a rotationally flexible single N–N bond. In complexes 1– 3, the three bis(bidentate) diazine ligands wrap around two metal cations with a spiral conformation, leading to a triple helicate with C 3 symmetry. Magnetic investigations revealed that antiferromagnetic interactions are operative between the two metal ions linked by the triple diazine bridges, with J = −2.97 and −5.40 cm −1 for 1 and 2, respectively. Variable temperature magnetic data for 3 indicates a weak ferromagnetic interaction between the two manganese(II) centers with J = 1.24 cm −1. The X-ray powder diffraction of 3 is also discussed.

High-dimensional azido-bridged cadmium(ii) polymeric complexes with bis(bidentate) diazine ligands

Five new Cd(II)-azido polymeric complexes with bis(bidentate) diazine Schiff bases as auxiliary bridging ligands have been synthesized and crystallographically characterized. The differences in side constituents of the coligands lead to different diazine-bridged binuclear units and hence to three different types of polymeric networks, all being 3-connected nets. In complex 1, [Cd2(L1)2(N3)4]n (L1 = 1,4-bis(2-pyridyl)-2,3-diaza-1,3-butadiene), a single diazine ligand links two metal ions into a centrosymmetric binuclear unit, and each unit is connected with four neighbors via double azido bridges in the end-on (EO) mode, yielding 2-D layers with the (6,3) net topology. Complex 2, [Cd2(L2)2(N3)2]n(ClO4)n·nH2O (L2 = 1,4-bis(2-pyridyl)-1-amino-4-methyl-2,3-diaza-1,3-butadiene), shows a layer structure with the (6,3) net topology, but the binuclear unit contains two diazine bridges and the neighboring units are interlinked via single azido bridges in the end-to-end (EE) mode. The remaining three complexes, [Cd2(L)2(N3)4]n (L = 1,4-bis(2-pyridyl)-1-amino-2,3-diaza-1,3-butadiene for 3, 1-(2-pyridyl)-4-(2-pyrazinyl)-4-amino-1-methyl-2,3-diaza-1,3-butadiene for 4, and 2,5-bis(2-pyridyl)-3,4-diaza-2,4-hexadiene for 5), are isostructural and form the 3-D (10,3)-b net with three different connectors around each node (the cadmium ion): adjacent cadmium ions are alternately bridged by double EO azido bridges and mixed EO azido-diazine double bridges to produce a chain, and each chain is connected to four neighboring chains by single EE azido bridges to generate the 3D framework.

Competition studies on the activation of the C_H bond of diazines by the unsaturated triangular cluster anion [Re3(μ-H)4(CO)10

Abstract The reactions of the unsaturated cluster anion [Re3(μ-H)4(CO)10]− (1) with 1,2-, 1,3- and 1,4-diazines (used as solvents) have been investigated. The reaction with 1,2-diazine at room temperature gives quantitatively the anion [Re3(μ-H)2(μ-η2-N2C4H4)(CO)10]− (3), containing a diazine bridging through the two N atoms, characterised by single crystal X-ray analysis. The orthometallated isomer [Re3(μ-H)3(μ-η2-N2C4H3)(CO)10]− (4) was obtained by refluxing 3 in toluene. The reaction of [NEt4]1 in molten 1,4-diazine (60 °C) affords the anion [Re3(μ-H)3(μ-η2-N2C4H3)(CO)10]− (5), containing orthometallated pyrazine. The slow reaction of [NEt4]1 with 1,3-diazine at room temperature gives two orthometallated isomers 6, corresponding to the metallation of carbon C2 (6a) and C6 (6b), respectively (6b/6a ratio ca. 1.2). Differently from what previously found for the analogous cluster anion containing orthometallated pyridine, the metallation reaction of diazines showed little reversibility, and poor conversion of 5 and 6 to the starting anion 1 was observed after several days under 100 atm of H2. Competition experiments, performed by dissolving [NEt4]1 in equimolar mixtures of pyridine/pyrazine or pyridine/pyrimidine, showed that the anion with metallated pyridine was the kinetically preferred product and that at longer times it slowly converted to the derivatives with metallated diazines (5 or 6).

5,5'-Bridged bis(1,2,3-dithiazoles): spin states and charge-transfer chemistry.

Bifunctional 1,2,3-dithiazoles bridged with azine and phenylenediamine spacers have been prepared, with a view to determining the extent of communication between the two dithiazole rings as a function of the electronic and steric demands of the bridge. The crystal structure of the closed-shell diazine derivative [S(2)NClC(2)=NN=C(2)ClNS(2)] is rigorously planar. Cyclic voltammetry on this compound indicates two reversible one-electron oxidations. The radical cation state has been characterized by EPR spectroscopy and by crystal structure determination of its 1:1 PF(6)(-) salt. The latter reveals little interaction between neighboring radical cations; consistently, the material exhibits a conductivity of sigma < 10(-5) S cm(-1). Insertion of a phenylene group into the diazine bridge to afford [S(2)NClC(2)=NC(6)H(4)N=C(2)ClNS(2)] leads to significant torsional motion between the phenylene ring and the two end groups, as a result of which the two DTA rings are electronically independent; no radical cation state has been observed for this species. Crystal data for Cl(2)S(4)N(4)C(4): a = 5.1469(15), b = 13.343(2), c = 14.2031(17), orthorhombic, Pbca, Z = 4. Crystal data for Cl(2)S(4)N(4)C(4)PF(6): a = 11.699(4), b = 12.753(5), c = 10.461(4), beta = 112.17(1) degrees, monoclinic, C2/c, Z = 4. Crystal data for C(l2)S(4)N(4)C(10)H(4): a = 3.9477(6), b = 23.790(3), c = 7.3769(9), beta =90.793(12) degrees, monoclinic, P2(1)/c, Z = 2.

Trinuclear copper(II) complexes with bridging (N–N) diazine ligands: structural and magnetic studies

The polytopic ligands 2poap and po2p have a linear disposition of coordination pockets suitably disposed to bind metal ions in close proximity and produce linear trinuclear copper(II) complexes. The complexes [Cu3(2poap − 2H)(CH3CO2)4]·3H2O (1), [Cu3(2poap − 2H)(H2O)(DMF)3(CH3OH)2](BF4)4 (2), and [Cu3(po2p − H)2(H2O)2](ClO4)4·2H2O (3) have a linear arrangement of Cu(II) centres linked by a trans arrangement of N–N single bonds. Each metal is assigned a dx2 − y2 magnetic ground state, and the trans diazine bridging arrangement leads to strong antiferromagnetic coupling in complete agreement with previous magnetostructural correlations relating the twist of the copper magnetic planes around the N–N bond to the exchange integral.

Tetranuclear Copper(II) and Nickel(II) Cluster Complexes Derived by Self-Assembly from a Series of Tetradentate Diazine Ligands: Structural and Magnetic Studies

A series of tetranuclear copper(II) and nickel(II) complexes is described, all of which form by a strict self-assembly process involving just a single ligand and the metal salt. The ligands POAP, POAPZ, PZOAP, and 6POAP contain terminal pyridine and pyrazine residues bound to a central flexible diazine subunit (N−N) and contain two potentially bridging groups (alkoxo and diazine). In all cases but one the metals are linked by alkoxo oxygens alone, forming essentially square [M4(μ2-O)4] clusters. A rectangular copper(II) complex [Cu4(μ2-N2)2(μ2-O)2] involves a mixture of two alkoxo and two diazine bridges. The square Cu4O4 clusters exhibit ferromagnetic coupling between the metal centers, associated with the orthogonal arrangement of magnetic orbitals, while for the Ni4O4 clusters the nickel(II) centers are coupled antiferromagnetically. The [Cu4(μ2-N2)2(μ2-O)2] cluster exhibits strong antiferromagnetic coupling through a trans Cu(N-N)Cu bridging arrangement, typical for systems of this sort. X-ray structures are reported for [Cu4 (POAP-H)4(H2O)2](NO3)4·4H2O (2), [Cu4(POAPZ-H)4(H2O)](NO3)4·3H2O (3), [Cu4(6POAP-H)4](ClO4)4 (4), [Cu4(PZOAP-H)4](NO3)4·3H2O (5), [Ni4(POAP-H)4 (H2O)4](NO3)4·8H2O (6), and [Ni4(PZOAP-H)4(H2O)4](ClO4)4·5H2O (9). 2 crystallized in the monoclinic system, space group C2/c, with a = 20.479(3) Å, b = 14.920(2) Å, c = 19.671(3) Å, β = 90.591(4)°, and Z = 8. 3 crystallized in the monoclinic system, space group P21/c, with a = 14.12(1) Å, b = 14.116(3) Å, c = 29.043(4) Å, β = 94.50(3)°, and Z = 4. 4 crystallized in the monoclinic system, space group C2/c, with a = 22.646(4) Å, b = 25.842(5) Å, c = 12.349(5) Å, β = 110.34(2)°, and Z = 4. 5 crystallized in the monoclinic system, space group P2/n, with a = 14.3573(4) Å, b = 10.8910(6) Å, c = 20.5360(10) Å, β = 96.975(4)°, and Z = 4. 6 crystallized in the triclinic system, space group P1̄, with a = 12.0509(6) Å, b = 12.7498(6) Å, c = 23.1208 Å, α = 93.1050(10)°, β = 100.1500(10)°, γ = 108.5050(11)°, and Z = 2. 9 crystallized in the orthorhombic system, space group Pbcn, with a = 14.368(4) Å, b = 25.469(7) Å, c = 18.479(5) Å, and Z = 4.

Dicopper(II) Complexes Bridged by Single N−N Bonds. Magnetic Exchange Dependence on the Rotation Angle between the Magnetic Planes

A series of dicopper(II) complexes with two tetradentate (N4) diazine ligands (PAHAP (1), PMHAP (2)) is reported, in which the two dx2-z2 type copper centers are bridged by a single N−N bond. Varying the coligands leads to a situation where the angle between the copper planes can be varied. For small angles (<80°) ferromagnetic coupling prevails, whereas at larger angles antiferromagnetic exchange is observed between the copper(II) centers. This is associated with the degree of alignment of the nitrogen p orbitals in the diazine bridge, and is supported by molecular orbital calculations on the complexes and appropriate models. Structures are reported for PAHAP (1) (picolinamide azine), [Cu2(PAHAP)Cl4]·H2O (3), [Cu2(PAHAP)Br4]·H2O (5), [Cu2(PAHAP)(H2O)6](NO3)4 (6), and [Cu2(PMHAP-H)(NO3)3] (8). 1 crystallized in the orthorhombic system, space group Pbca (No. 61), with a = 19.845(4) Å, b = 13.178(5) Å, c = 9.383(8) Å, and Z = 8. 3 crystallized in the monoclinic system, space group C2/c (No. 15), with a = 26.732(6) Å, b = 8.670(9) Å, c = 16.436(4) Å, β = 100.88(2)°, and Z = 8. 5 crystallized in the monoclinic system, space group C2/c (No. 15), with a = 27.336(2) Å, b = 8.859(4) Å, c = 16.795(3) Å, β = 100.78(1)°, and Z = 8. 6 crystallized in the monoclinic system, space group C2/c (No. 15), with a = 20.983(4) Å, b = 7.505(4) Å, c = 17.219(3) Å, β = 104.22(1)°, and Z = 4. 8 crystallized in the triclinic system, space group P1̄ (No. 2), with a = 7.8380(14) Å, b = 8.015(3) Å, c = 15.655(4) Å, α = 99.81(3)°, β = 101.74(2)°, γ = 94.524(17)°, and Z = 2. The antiferromagnetically coupled complexes [Cu2(PAHAP)Cl4] (4) and [Cu2(PAHAP-H)(N3)2(NO3)] (7) are also reported.

Synthesis and magnetostructural characterization of dinuclear copper(II) complexes with the diazine ligand, 3,6-bis(di-2-pyridylmethyl)pyridazine

The crystal structures of [Cu2(bdpdz)Br4]·2CH3CN 1, [Cu2(bdpdz)Cl3(H2O)]Cl·3.5H2O 2 and [Cu2(bdpdz)2][ClO4]43 were determined by X-ray analysis, where bdpdz, represents the binucleating ligand 3,6-bis(di-2-pyridylmethyl)pyridazine, formed by the reaction of 3,6-dichloropyridazine and di-2-pyridylmethyllithium. Compounds 1 and 2 consist of discrete binuclear units, in which copper atoms are linked by the diazine bridge and two halide ions. The pyridazine acts as a hexadentate ligand. In complex 2 the two copper(II) ions have a distorted octahedral co-ordination geometry, 4 + 2. Compound 3 also consists of discrete binuclear units, in which the copper centres are linked by two organic ligands. Here bdpdz acts as a pentadentate ligand, with one of the diazine nitrogen atoms not bonded. The two copper(II) ions have a square pyramidal co-ordination geometry, 4 + 1. The magnetic susceptibility was investigated in the temperature range 300–5 K. These measurements reveal an antiferromagnetic interaction for all three compounds (–2J= 98.1 for 1, 79.6 for 2 and 6.4 cm–1 for 3). The lack of a diazine bridge, N–N, for the perchlorate salt 3 substantially reduces the antiferromagnetic interaction.

Tetranuclear, spin-coupled, copper(II) complexes of a novel octadentate bis-diazine ligand

The octadentate, benzodipyridazine ligands L1 and L2 form tetranuclear copper(II) complexes involving hydroxide and diazine bridges and exhibit strong antiferromagnetic coupling between adjacent pairs of copper atoms, but also significant antiferromagnetic coupling across the extended, fused aromatic ring system.