Dinuclear and polynuclear Cu(II) azido-bridged compounds with 7-azaindole as a ligand. Synthesis, characterization and 3D structures

In this study three new dinuclear Cu(II) compounds with the ligand 7-azaindole (abbreviated as Haza) and bridging end-on azide anions with the general formula [Cu₂(Haza)₄(N₃)₂(A)₂] (in which A =  (1), (2) and (3)) are reported, as well as a dinuclear-based polymeric compound with the overall formula [Cu₄(L)₆(N₃)₆(ClO₄)₂]_n·(CH₃OH)_2n (4). The latter compound contains both end-on and end-to-end azide anions. Full characterization of all four compounds has been performed by spectroscopic methods and by using 3D X-ray structure analysis.     

Chromium(III) complexes with 2-(2′-pyridyl)imidazole: Synthesis, crystal structure and magnetic properties

The preparation, crystal structure and variable temperature-magnetic investigation of three 2-(2′-pyridyl)imidazole-containing chromium(III) complexes of formula PPh₄[Cr(pyim)(C₂O₄)₂]·H₂O (1), AsPh₄[Cr(pyim)(C₂O₄)₂]·H₂O (2) and [Cr₂(pyim)₂(C₂O₄)₂(OH₂)₂]·2pyim · 6H₂O (3) [pyim = 2-(2′-pyridyl)imidazole, , and ] are reported herein. The isomorphous compounds are made up of discrete [Cr(pyim)(C₂O₄)₂]⁻ anions, cations [X = P (1) and As (2)] and uncoordinated water molecules. The chromium environment in 1 and 2 is distorted octahedral with Cr-N and Cr-O bond distances varying in the ranges 2.040(3)-2.101(3) and 1.941(3)-1.959(3) Å, respectively. The angle subtended by the chromium(III) ion by the two didentate oxalate ligands cover the range 82.49(12)-82.95(12)°, values which are somewhat greater than those concerning the chelating pyim molecule [77.94(13) (1) and 78.50(13)° (2)]. Complex 3 contains discrete centrosymmetric [Cr₂(pyim)₂(C₂O₄)₂(OH)₂] neutral units where the two chromium(III) ions are joined by a di-μ-hydroxo bridge, the oxalate and pyim groups acting as peripheral didentate ligands. Uncoordinated water and pyim molecules are also present in 3 and they contribute to the stabilization of its structure by extensive hydrogen bonding and π-π type interactions. The values of the intramolecular chromium-chromium separation and angle at the hydroxo bridge in 3 are 2.9908(12) Å and 99.60(16)°, respectively. Magnetic susceptibility measurements of 1-3 in the temperature range 1.9-300 K show the occurrence of weak inter- (1 and 2) and intramolecular (3) antiferromagnetic couplings. The magnetic properties of 3 have been interpreted in terms of a temperature-dependent exchange integral, small changes of the angle at the hydroxo bridge upon cooling being most likely responsible for this peculiar magnetic behavior.     

Crystal structure of six and seven coordinate manganese(II) complexes with penta and hexadentate pyridylmethyl ligands

Two six-coordinated manganese(II) complexes [Mn(pydien)Cl](ClO₄) · C₂H₅OH (1), [Mn(pydien)NCS](ClO₄) (2) and two seven-coordinated manganese(II) complexes [Mn(pydado)Cl](ClO₄) (3), [Mn(pydado)NCS](ClO₄) (4) have been obtained using linear penta and hexadentate ligands pydien and pydado (pydien: 1,7-bis(2-pyridylmethyl)-1,4,7-triazaheptane and pydado: 1,10-bis(pyridylmethyl)-1,10-diaza-4,7-dioxadecane). The crystal structures for all compounds have been determined. 1 and 3 crystallize in the triclinic space group , 2 crystallizes in the orthorhombic space group Pbca, whereas 4 crystallizes in the monoclinic space group P2₁/c. The bound anion (chloro or isothiocyanato) in complexes 1 and 2 has no influence on the geometry of six-coordinate manganese(II) complexes, whereas the geometry and the wrapping of the hexadentate ligand (pydado) around Mn²⁺ cation depend on the nature of the bound anion. The complex 3 has a capped octahedron geometry with the two pyridyl groups in trans position, while the geometry of complex 4 can be described as pentagonal bipyramid with one pyridyl group and a thiocyanate anion in the axial positions.     

Complexes containing the [TeCl4X] moiety (X = Cl or an aryl group)

Treatment of TeCl₄ with either K[{N(C₆H₃Prⁱ₂-2,6)C(H)}₂CPh] [≡K(L)] (1) in thf/Et₂O or [H₂(L)]Cl (2) in Et₂O furnished [Cl₄Cl?HH?OEt₂]·0.5(Et₂O) (3), whilst 2TeCl₄ with a mixture of single equivalent portions of 2,6-Prⁱ₂C₆H₃NH₂ and H(L) produced [Cl₄] (4). The X-ray structures of each of crystalline 3 and 4 show that the Te atom is at the centre of an only slightly distorted square pyramid, with a Cl atom of 3 or a C of 4 in the axial position. The N1 and N2 atoms of the π-delocalised β-dialdiminium moiety of 3 have H-bond contacts, involving short N1-H?OEt₂ and N2-H?Cl5 distances. The two longer of the four Te-Cl bonds of 4 are close to the N atom of the neighbouring molecule; whilst two of the H atoms of each H₃ fragment are H-bonded to the O atoms of the two thf ligands, the third being close to two Cl atoms of an adjacent molecule, thus forming H-bonded chains of molecules.     

Synthesis and single crystal structural investigations on quaternary salts of tellurated alkylamine derivatives

Tellurated alkylamine derivatives , , and have been synthesized by reacting appropriate organic halides with the nucleophile 4-CH₃OC₆H₄Te⁻ or Te²⁻ generated in situ by borohydride reduction of (4-CH₃OC₆H₄Te)₂ or Te powder followed by reaction with HCl of appropriate concentration. The zwitterionic species was generated when single crystals of 2 were grown in methanol at 0 °C. Complexes 1-4 exhibit characteristic ¹H NMR spectra. The single crystal structures of 1-4 and 2a have been determined. In the crystals of 1, C-H?π distances have been found to be 3.31(7)-3.59(5) Å. In both 2 and 2a, weak Te?Cl interactions (3.54(2) -3.62(2) Å) are observed. The C-H?π distance in the crystal of 2 is 3.19(0) Å. In 2a and 3, water hydrogen bonds connect the water molecules with the end groups from different molecules. In the case of 3, Te?Cl weak interactions involving the Cl⁻ ions connect together two such chains. The geometry of Te in 1 is V shaped. In 2 and 3 it is pseudo trigonal bipyramidal, and in 2a, it is square pyramidal. However, in the latter case it becomes distorted octahedral due to weak Te?Cl secondary interactions. The geometry about Te in 4 is distorted octahedral due to weak Te?Cl interactions involving Cl⁻ ions. However, there are no intermolecular Te?Cl interactions.     

Synthesis and characterization of new AMTTO-imine-ligands and their silver(I) complexes: crystal structures of TAMTTO, [Ag2(TAMMTO)4](NO3)2 · 4MeOH, [Ag(TAMTTO)(PPh3)2]NO3 · 1.5THF, [Ag(FAMTTO)(PPh3)2]NO3

Reaction of 4-amino-6-methyl-1,2,4-triazin-thione-5-one (AMTTO, 1) with 2-thiophenecarboxaldehyde and 2-furaldehyde led to the corresponding iminic compounds 6-methyl-4-[thiophene-2-yl-methylene-amino]-3-thioxo-[1,2,4]-triazin-3,4-dihydro(2H)-5-one (TAMTTO, 2) and 4-[furan-2-yl-methylene-amino]-6-methyl-3-thioxo-[1,2,4]-triazin-3,4-dihydro(2H)-5-one (FAMTTO, 3). Treatment of 2 with AgNO₃ gave the complex [Ag₂(TAMMTO)₄](NO₃)₂ · 4MeOH (4) and of 2 and 3 with [Ag(PPh₃)₂]NO₃ gave the complexes [Ag(TAMTTO)(PPh₃)₂]NO₃ · 1.5THF (5) and [Ag(FAMTTO)(PPh₃)₂]NO₃ (6), respectively. All the compounds have been characterized by elemental analyses, IR spectroscopy and mass spectrometry. Compound 2 and all the complexes have been characterized by X-ray diffraction studies, respectively. In addition, 5 and 6 have been characterized by ³¹P NMR spectroscopy. Crystal data for 2 at −80 °C: monoclinic, space group C2/c, a=2319.6(2), b=609.8(1), c=1673.6(2) pm, β=106.14(1)°, Z=8, R₁=0.0523; for 4 at −80 °C: triclinic, space group , a=877.6(1), b=1085.2(1), c=1557.7(2) pm, α=77.14(1)°, β=80.87(1)°, γ=78.18(1)°, Z=1, R₁=0.0407; for 5 at 20 °C: triclinic, space group , a=1151.1(2), b=1225.1(2), c=1887.4(3) pm, α=78.04(1)°, β=86.20(1)°, γ=76.03(1)°, Z=2, R₁=0.0662; for 6 at −80 °C: triclinic, space group , a=1189.7(2), b=1387.8(2), c=1410.9(2) pm, α=94.74(2)°, β=95.12(2)°, γ=112.41(2)°, Z=2, R₁=0.0511.     

Synthesis and characterization of amine complexes of the cyclopentadienyliron dicarbonyl complex cation, [Cp(CO)2Fe]

The organometallic Lewis acid, [CpFe(CO)₂]⁺ (Cp = η⁵-C₅H₅) reacts with excess dry diethyl ether at low temperatures to form the labile complex [CpFe(CO)₂(Et₂O)]⁺[BF₄]⁻ (1) which is stable at low temperatures and has been fully characterized. Complex 1 in turn reacts with 1-aminoalkanes and α,ω-diaminoalkanes to form new complexes of the type [CpFe(CO)₂NH₂(CH₂)_nCH₃]BF₄ (n = 2-6) (2) and [{CpFe(CO)₂}₂μ-(NH₂(CH₂)_nNH₂)](BF₄)₂ (n = 2-4) (3), respectively. These complexes have been fully characterized and the mass spectral patterns of complexes 2 are reported. The structures of compounds 2a (n = 2) and 2b (n = 3) have been confirmed by single crystal X-ray crystallography. The single crystal X-ray diffraction data show that complex 2a, [CpFe(CO)₂NH₂(CH₂)₂CH₃]BF₄, crystallizes in a triclinic space group while 2b, [CpFe(CO)₂NH₂(CH₂)₃CH₃]BF₄, crystallizes in an orthorhombic Pca2₁ space group with two crystallographically independent molecular cations in the asymmetric unit. Furthermore, the reaction of 1 with 1-alkenes gives the η²-alkene complexes in high yield.     

New supramolecular complexes generated from Mn, Fe, Co, Zn, Fe with a bent dipyridyl ligand: Metal- and anion-directed assembly

Assemblies of an angular dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo) with a series of metal perchlorate afford five new supramolecular complexes with the general formula of [M(4-bpo)₂(H₂O)₄] · (4-bpo)₂ · (anion) · (solvent), in which M = Mn^II for 1, Fe^II for 2, Co^II for 3, Zn^II for 4, and Fe^III for 5. Although similar molecular structures and compositions are found for these mononuclear complexes, they display two types of supramolecular lattices. Complexes 1, 4 and 5 similarly crystallize in space group P2/n or P2/c. The complex cations, free 4-bpo and lattice water are linked to generate 2D layered frameworks with the aid of hydrogen bonding, and the counter anions are located within and between (also methanol in 5) these 2D arrays. However, complexes 2 and 3 are isostructural in space group . Two types of alternate 2D layers consisting of complex cations and free 4-bpo components, respectively, are observed with the anions and lattice water locating between them. These motifs are interlinked by complicated hydrogen-bonding to form a 3D intercalated network. Moreover, when Co(NO₃)₂ is used instead of Co(ClO₄)₂ in the assembly of 3, a 1D polymeric chain complex {[Co(4-bpo)(H₂O)₂(NO₃)₂](H₂O)₃}_n (6) is generated. These results indicate that the choice of metal ion and anion exerts a significant influence on governing the target complexes. A comparison of the structural features for all metal perchlorate complexes with 4-bpo is also briefly discussed.     

Chloro and acetato complexes of platinum(II) with functionalized thioethers

The chloro complexes [PtCl₂(RSR′)₂] (1-10) (RSR′ = MeSCH₂C(O)OMe, 1; MeSCH₂C(O)OEt, 2; MeSCH₂C(O)Omenthyl(−), 3; MeSCH₂CH₂C(O)OMe, 4; , 5; EtSCH₂C(O)Me, 6; MeSCH(Me)C(O)Me, 7; MeSPh, 8; MeS-o-C₆H₄Me, 9; and MeS-o-C₆H₄Et, 10) are obtained in high yield (63-90%) by reaction of [PtCl₂(PhCN)₂] with the proper thioether in 1/2 molar ratio, in anhydrous chloroform, at reflux under argon for ca. 10 h. The X-ray crystal structure of [PtCl₂(MeS-o-C₆H₄Me)₂] (9) shows an almost regular trans square planar geometry (triclinic, space group , a 6.806(1), b 7.789(2), c 10.085(3) Å, α 101.80(2)°, β 69.55(2)°, γ 115.27(2)°, R(F_o) 0.023, ). The dichloro complexes react with silver acetate in a complex manner, which depends on the nature of the thioether, and only with RSR′ = MeSPh the simple diacetato complex [Pt(OAc)₂(RSR′)₂] is obtained as the major product.     

Coordination and derivatization of 3, 4, and 6-membered nitrogen heterocycles at a chiral tungsten(II) center

Reaction of [Tp′W(CO)₂(PhCCPh)][OTf] (1b) (Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate) with excess aziridine or 2-methylaziridine followed by protonation with produces chiral tungsten(II) amine complexes (3, 4; R = Me, Ph). An azetidine amido complex, Tp′W(CO)(PhCCMe)(H₂) (5) is synthesized by reaction of [Tp′W(CO)₂(PhCCMe)][OTf] (1a) with excess azetidine. Oxidation of amido complex 5 with I₂ in the presence of a weak base provides the corresponding 1-azetine complex, (6). Addition of methylmagnesium bromide to complex 6 results in formation of predominantly one diastereomer (S_WR_C/R_WS_C) (96:4 dr) of the 2-methylazetidine complex, Tp′W(CO)(PhCCMe)(H₂) (7). Reaction of complex 5 with results in formation of a cationic azetidine complex, (8). Reaction of 1b with excess piperidine followed by oxidation affords 2,3,4,5-tetrahydropyridine complex 9b, . Formation of an enamido complex, Tp′W(CO)(PhCCPh)(H₂) (10), is observed upon addition of base to 9b. Subsequent addition of [D⁺] to the enamido β-carbon results in the formation of the deuterated product, 9b-d₁, as determined by ²H NMR. Seven X-ray crystal structures have been determined, and these encompass complexes with 3, 4, and 6-membered heterocyclic ligands. Crystal structures are reported for two aziridine adducts (2, 4) two neutral amido complexes (5, 7), one cationic imine complex (6), and one cationic amine (8) complex derived from azetidine, and the imine complex formed from piperidine (9).     

Anionic effects on the formation of tridentate 4′-chloro-2,2′:6′,2″-terpyridine copper(II) complexes having 1:1 or 1:2 ratio of metal and ligand and their crystal symmetry

A facile synthetic procedure has been used to prepare one five-coordinate and four six-coordinate copper(II) complexes of 4′-chloro-2,2′:6′,2″-terpyridine (tpyCl) ligand with different counterions (, , , , and ) in high yields. They are formulated as [Cu(tpyCl-κ³N,N′,N′′)(SO₄-κO)(H₂O-κO)] · 2H₂O (1), trans-[Cu(tpyCl-κ³N,N′,N″)(NO₃-κO)₂(H₂O-κO)] (2), [Cu(tpyCl-κ³N,N′,N″)₂](BF₄)₂ (3), [Cu(tpyCl-κ³N,N′,N″)₂](PF₆)₂ (4) and [Cu(tpyCl-κ³N,N′,N″)₂](ClO₄)₂ (5) and versatile interactions in supramolecular level including coordinative bonding, O-H?O, O-H?Cl, C-H?F, and C-H?Cl hydrogen bonding, π-π stacking play essential roles in forming different frameworks of 1-5. It is concluded that the difference of coordination abilities of the counterions used and the experimental conditions codominate the resulting complexes with 1:1 or 1:2 ratio of metal and ligand.     

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.     

Complexes of Cu with mixed-donor phenanthroline-containing macrocycles: analysis of their structural, redox and spectral properties in the context of Type-1 blue copper proteins biomimetic models

The macrocycles L¹-L³ having N₂S₂O-, N₂S₂-, and N₂S₃-donor sets, respectively, and incorporating the 1,10-phenanthroline unit interact in EtOH and MeCN solutions with Cu^II to give 1:1 [M(L)]²⁺ complex species. The compounds [Cu(L¹)(ClO₄)]ClO₄ (1), [Cu(L²)(ClO₄)]ClO₄ ·  (2) and [Cu(L³)](ClO₄)₂ (3) were isolated at the solid state and the first two also characterised by X-ray diffraction studies. The conformation adopted by L¹ and L² in the cation complexes reveals the aliphatic portion of the rings folded over the plane containing the heteroaromatic moiety with the ligands encapsulating the metal centre within their cavity by imposing, respectively, a square-based pyramidal and a square planar geometry. In both complexes, the metal ion completes its coordination sphere by interacting with a ClO₄⁻ ligand. The compound [Cu(L³)₂](PF₆)₂ (4) containing a 1:2 cation complex was also isolated at the solid state: EPR spectroscopy measurements suggest the presence of a CuN₄ chromophore in this complex. The EPR and electronic spectral features of 1-4 have been studied and their redox properties examined in comparison with those observed for Type-1 blue copper proteins.The reactivity of L¹-L³ has also been tested toward stoichiometric amounts of the Cu^I salt [CuCl(PPh₃)₃].     

Mononuclear cobalt(II) carboxylate complexes: Synthesis, molecular structure and selective oxygenation study

Some cobalt carboxylate (both mononuclear as well as binuclear) complexes have been prepared by using hindered hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (Tp^iPr2) as supporting ligand. The reaction of [Tp^iPr2Co(NO₃)] (2) with sodium benzoate resulted in the formation of acetonitrile coordinated complex [Tp^iPr2Co(OBz)(CH₃CN)] (3) whereas the reaction of 2 with sodium fluorobenzoate gave coordinately unsaturated five coordinate complex of the type [Tp^iPr2Co(F-OBz)] (4). The oxidation of compound 4 in the presence of 3,5-diisopropylpyrazole resulted in the formation of a unique compound (5) where only one methine carbon of isopropyl group on pyrazole ring of hydrotris(3,5-diisopropyl-1-pyrazolyl)borate oxidized and coordinated with cobalt center. In compound 5, the binding behavior of fluorobenzoate also changes from bidentate to monodentate and the nonbonded oxygen atom formed intramolecular hydrogen bond with the hydrogen atom of the NH fragment of the coordinated . X-ray crystallography and IR studies confirmed the existence of hydrogen bonding in complex 5. The pyrazolato bridged binuclear cobalt(II) complex (6) was prepared by the reaction of hydrated cobalt(II) nitrate, 3,5-diisopropylpyrazole and sodium nitrobenzoate where, each cobalt is four coordinate. The X-ray structure of 6 showed that the NH fragment of terminally coordinated formed intramolecular hydrogen bonding with nonbonded oxygen atom of monodentately coordinated nitrobenzoate.     

Ruthenium(II) complexes possessing the η-p-cymene ligand

Complexes possessing a soft donor η⁶-arene and hard donor acetylacetonate ligand, [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1) (OTf = trifluoromethanesulfonate; acac = acetylacetonate) and {Ar′ = 3,5-(CF₃)-C₆H₃}, were prepared and fully characterized. The lability of the μ-CH linkage for complex 1 and the THF ligand of 2 allow access to the unsaturated cation [(η⁶-p-cymene)Ru(κ²-O,O-acac)]⁺. The reaction of with KTp {Tp = hydridotris(pyrazolyl)borate} produces . The azide complex forms upon reaction of with N₃Ar (Ar = p-tolyl), and reaction of with CHCl₃ at 100 °C yields the chloride-bridged binuclear complex . The details of solid-state structures of [(η⁶-p-cymene)Ru(κ²-O,O-acac-μ-CH)]₂[OTf]₂ (1), and are disclosed.     

Imidazole-imidazole stacking in some inorganic complexes

Reaction of CuCl₂ · 2H₂O with the 1:1 condensate (L) of 2-(2-aminoethyl)pyridine and 1-methyl-2-imidazolecarboxaldehyde in methanol yields monomeric CuLCl₂.H₂O (1). Recrystallisation of 1 from aqueous methanol medium containing excess of affords the 1D coordination polymer [CuLCl]_n(PF₆)_n (2). A chloride bridge results in the coordination polymer. A face-to-face interaction is observed between the imidazole rings in 2. The interaction influences the structure and magnetic properties of 2 markedly. The complex 2 is ferromagnetic with a J value of 1.79 ± 0.01 cm⁻¹. The imidazole fragments in 2 are coordinated to the metal. In mononuclear (ClO₄)₂, where L′′ is the 1:2 condensate of ethylenediamine and 1-methyl-2-imidazolecarboxaldehyde, the imidazolyl moieties are not under the direct influence of the metal. Here the imidazole-imidazole interaction is angular and more distant.     

Reduction of diruthenium(II,III) carboxylate compounds with hydroquinone: a facile preparation of diruthenium(II) complexes

The synthesis of the diruthenium(II) compounds [Ru₂(μ-O₂CR)₄(MeOH)₂] [R = Me (1), Ph (2), CMePh₂ (3) C₆H₄-p-OMe (4), C₆H₄-p-CMe₃ (5)] by reaction of with hydroquinone, under a nitrogen atmosphere, in the presence of a base is described. This reaction constitutes an easy via to the preparation of diruthenium(II) compounds. The structure of the complexes [Ru₂(μ-O₂CMe)₄(MeOH)₂] (1) and [Ru₂(μ-O₂CPh)₄(thf)₂] (2b) is established by single crystal X-ray diffraction. These compounds show a diruthenium(II) unit bridged by four carboxylate ligands with the axial positions occupied by methanol and tetrahydrofuran molecules for 1 and 2b, respectively. Complex 1 shows, in the solid state, polymeric chains in which the molecules [Ru₂(μ-O₂CMe)₄(MeOH)₂] are linked by hydrogen bonds.     

Stabilization of Mn(II) and Mn(III) in mononuclear complexes derived from tridentate ligands with N2O donors: Synthesis, crystal structure, superoxide dismutase activity and DNA interaction studies

A new family of tridentate ligands PhimpH (2-((2-phenyl-2-(pyridin-2-yl)hydazono)methyl)phenol), N-PhimpH (2-((2-phenyl-2-(pyridin-2-yl)hydrazono)methyl)napthalen-1-ol), Me-PhimpH (2-(1-(2-phenyl-2-(pyridine-2-yl)hydrazono)ethyl)phenol) have been synthesized and characterized. The ligands PhimpH and N-PhimpH after deprotonation react with manganese(II) and manganese(III) starting materials affording [Mn(Phimp)₂] (1), [Mn(Phimp)₂](ClO₄) (2), [Mn(N-Phimp)₂] (3), [Mn(N-Phimp)₂](ClO₄) (4). Complexes [Mn(Phimp)₂] (1) and [Mn(N-Phimp)₂] (3) convert to [Mn(Phimp)₂]⁺ (cation of 2) and [Mn(N-Phimp)₂]⁺ (cation of 4) respectively upon oxidation. Ligand Me-PhimpH stabilized only manganese(III) centre resulting [Mn(Me-Phimp)₂](ClO₄) (5). The molecular structures of [Mn(Phimp)₂], 1 and [Mn(Phimp)₂](ClO₄), 2 were determined by single crystal X-ray diffraction. X-ray crystal structures of 1 and 2 have revealed the presence of distorted octahedral MnN₄O₂ coordination sphere having meridionally spanning ligands. Electrochemical studies for the complexes showed Mn(II)/Mn(III), (E_1/2 = 0.14-0.40 V) and Mn(III)/Mn(IV), (E_1/2 = 0.80-1.06 V) couples vs. Ag/AgCl. The redox properties were exploited to examine superoxide dismutase (SOD) activity using Mn(II)/Mn(III) couple. The complexes 1, 2, 4 and 5 have been revealed to catalyze effectively the dismutation of superoxide () in xanthine-xanthine oxidase-nitro blue tetrazolium assay and IC₅₀ values were found to be 0.29, 0.39, 1.12 and 0.76 μM respectively. DNA interaction studies with complex 2 showed binding of DNA in a non-intercalative pathway. Complexes 1, 2 and 4 exhibited nuclease activity in presence of H₂O₂ and inhibition of activity was noted in presence of KI.     

Magnetic properties and circular dichroism of 1D chains built from chiral mononuclear and non-chiral trinuclear Cu(II) complexes with α-aminocarboxylates

Coordination polymers Cu(l-Pro)(ClO₄)(H₂O)₂ (1) and Cu₃(Gly)₄(H₂O)₂(NO₃)₂ (2) were synthesized and characterized structurally. Compound 1 possesses the structure of 1D chain, where Cu(II) ions are linked by carboxyl-group in syn-anti conformation in equatorial-equatorial mode. Compound 2 is polymeric chain, consisting from trinuclear blocks Cu₃(Gly)₄(H₂O)₂²⁺. In each of these units Cu(II) ions are linked by carboxyl-group in the same way as in 1, while trinuclear units Cu₃(Gly)₄(H₂O)₂²⁺ are linked by NO₃⁻ ions, acting as the bridges between Cu(II) ions of neighboring trinuclear units. Circular dichroism properties of 1 were studied in solid state and solution. Magnetic measurements revealed that there were ferromagnetic exchange interactions between Cu(II) ions in 1 (J = +1.22(1) cm^-1 for Hamiltonian ) and 2 (J = +1.17(2) cm^-1 for Hamiltonian ).     

Synthesis, structure and reactions of a series of 1,2-dicyanoethylenedithiolate coordinated dimeric Mo(V) complexes

(where mnt = 1,2-dicyanoethylenedithiolate) (1), reacts with HX (X = SPh, Cl, Br) to form a series of complexes, . In acidic-alcoholic medium 1 with thiophenol yields another series of compounds, . Under similar conditions tertiary-butanol does not coordinate where a complex can only be isolated in the presence of bromide as . The use of excess of methanesulfonic acid in the presence of HSPh or HSEt facilitates methanesulfonate coordination in complexes, . All these complexes are structurally characterized by single crystal X-ray study. These complexes show pH dependent hydrolytic reaction leading to quantitative reversal to the starting complex, 1. Complexes 2a-c respond to hydrolysis in CH₂Cl₂ with the intermediate formation of EPR active molybdenum(V) species.