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We have prepared and characterized three coordination polymers formulated as [Dy2(C6O4Cl2)3(fma)6] ⋅ 4.5fma (1) and [Dy2(C6O4X2)3(fma)6] ⋅ 4fma ⋅ 2H2O with X=Br (2) and Cl (3), where fma=formamide and C6O4X22−=3,6‐disubstituted‐2,5‐dihydroxy‐1,4‐benzoquinone dianion with X=Cl (chloranilato) and Br (bromanilato). Compounds 1 and 3 are solvates obtained with slow and fast precipitation methods, respectively. Compounds 2 and 3 are isostructural and only differ in the X group of the anilato ligand. The three compounds present (6,3)‐gon two‐dimensional hexagonal honey‐comb structures. Magnetic measurements indicate that the three compounds show slow relaxation of the magnetization at low temperatures when a continuous magnetic field is applied, although with different relaxation times and energy barriers depending on X and the crystallisation molecules. Compounds 1–3 represent the first examples of anilato‐based lattices with formamide and field‐induced slow relaxation of the magnetization. [ABSTRACT FROM AUTHOR]

We report a novel triangular trinuclear copper(II) complex with a central μ3-OH bridge, [(CuL)3(μ3-OH)(ClO4)2]·CH3OH·H2O (1), stabilised by the oxime-based Schiff base ligand, 3-(((5-bromothiophen-2-yl)methylene)hydrazineylidene)butan-2-one oxime (HL). Comprehensive characterization of 1 has been realised through different analytical and physical methods coupled with spectroscopic techniques. 1 has been structurally characterised by single crystal X-ray diffraction. The antiproliferative capacity of HL and 1 has been evaluated against human lung cancer cell line A549. Compound 1 shows promising efficacy in contrast to HL, which shows a limited cytotoxicity. Contrary to HL, 1 has distinctly impeded the proliferation of lung adenocarcinoma A549 cell lines in a dose-dependent way. Compound 1 has been employed as a potential therapeutic agent for promising cellular transformation of malevolent A549 cell lines. The programmed cell death mechanism of 1 reveals characteristic apoptotic changes in cellular morphology like chromatin condensation, fragmented nuclei, nuclear shrinkage along with blebbing, elevated number of nuclear body fragments and distorted nucleus, while round, clear edged, intact nucleus and uniformly stained round nuclei have been observed in the negative control. Variable-temperature magnetic studies show an antiferromagnetic Cu⋯Cu coupling of −44.6(2) cm−1. The g value as determined by EPR measurement of 1 in frozen N,N-dimethylformamide solution corroborates the experimental magnetic susceptibility values. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of a new triangular Cu3–μ3OH pyrazolato complex of formula, [Cu3(μ3−OH)(pz)3(Hpz)3][BF4]2 (1−Cu3), Hpz = pyrazole, is presented. The triangular unit forms a quasi-isosceles triangle with Cu–Cu distances of 3.3739(9), 3.3571(9), and 3.370(1) Å. This complex is isostructural to the hexanuclear complex [Cu3(μ3−OH)(pz)3(Hpz)3](ClO4)2]2 (QOPJIP). A comparative structural analysis with other reported triangular Cu3–μ3OH pyrazolato complexes has been carried out, showing that, depending on the pyrazolato derivative, an auxiliary ligand or counter-anion can affect the nuclearity and/or the dimensionality of the system. The magnetic properties of 1−Cu3 are analyzed using experimental data and DFT calculation. A detailed analysis was performed on the magnetic properties, comparing experimental and theoretical data of other molecular triangular Cu3–μ3OH complexes, showing that the displacement of the μ3−OH− from the Cu3 plane, together with the type of organic ligands, influences the nature of the magnetic exchange interaction between the spin-carrier centers, since it affects the overlap of the magnetic orbitals involved in the exchange pathways. Finally, a detailed comparison of the magnetic properties of 1−Cu3 and QOPJIP was carried out, which allowed us to understand the differences in their magnetic properties. [ABSTRACT FROM AUTHOR]

Here, we illustrate the use of formamide (fma) and anilato-type ligands to build two-dimensional lattices with lanthanoids. Thus, we describe the synthesis and crystal structure of four lattices formulated as [Ln2(C6O4X2)3(fma)6]·6fma with Ln/X = La/Cl (1), La/Br (2), Eu/Cl (3), and Eu/Br (4), where C6O4X22− = dianion of 3,6-disubstituted-2,5-dihydroxy-1,4-benzoquinone with X = Cl (chloranilato) and X = Br (bromanilato). Single crystal X-ray analysis shows that the four compounds crystallize in the triclinic P-1 space group and present two-dimensional, very distorted hexagonal lattices with the lanthanoids ions in the vertex coordinated by three anilato ligands forming the sides of the distorted hexagons that appear as rectangles. The rectangles are disposed parallel to their long sides in a brick wall fashion. The nona-coordination of the lanthanoids is completed by three formamide molecules. These layered compounds include three additional formamide molecules per lanthanoid atom, located in the interlayer space inside the channels formed by the eclipsed packing of the layers. We discuss the differences observed among these compounds due to the change of the lanthanoid ion (La and Eu) and of the substituent group X in the anilato ligand (Cl and Br). [ABSTRACT FROM AUTHOR]

Reactions of Fe(II) with the tripodal chelating ligand 1,1,1-tris(2-pyridyl)ethoxymethane (py3C-OEt) and (NCE)- co-ligands (E = S, Se, BH3) give a series of mononuclear complexes formulated as [Fe(py3C-OEt)2][Fe(py3C-OEt)(NCE)3]22CH3CN, with E = S (1) and BH3 (2). These compounds are the first Fe(II) spin cross-over (SCO) complexes based on the tripodal ligand tris(2-pyridyl)ethoxymethane and on the versatile co-ligands (NCS)- and (NCBH3)-. The crystal structure reveals discrete monomeric isomorph structures formed by a cationic [Fe(py3C-OEt)2]2+ complex and by two equivalent anionic [Fe(py3C-OEt)(NCE)3]- complexes. In the cations the Fe(II) is facially coordinated by two py3C-OEt tripodal ligands whereas in the anion the three nitrogen atoms of the tripodal ligand are facially coordinated and the N-donor atoms of the three (NCE)- co-ligands occupy the remaining three positions to complete the distorted octahedral environment of the Fe(II) centre. The magnetic studies show the presence of gradual SCO for both complexes: A one-step transition around 205 K for 1 and a two-step transition for compound 2, centered around 245 K and 380 K. [ABSTRACT FROM AUTHOR]

Two new copper(ii) polymeric complexes, {[Cu(HPymat)(H2O)](NO3)}n (1) and [Cu2(Pymat)2(H2O)3]n (2), have been synthesized using the Schiff base ligand H2Pymat [H2Pymat = (E)-2-(1-(pyridin-2-yl)-methyleneamino)terephthalic acid]. Complex 1 is a cationic 1D polymer, whereas complex 2 is a two dimensional polymer. Both complexes were crystallographically, spectroscopically and magnetically characterized. Theoretical studies were performed and the catecholase activity of the complexes was also examined. Complex 1 is a ferromagnetically coupled complex with J = 2.8 cm−1 and 2 shows antiferromagnetic coupling with J = −1.6 cm−1. Both complexes show notable features in the EPR study. They show rhombic spectra at 77 K in the solid state, but by varying the temperature or solvents the nature of the spectra can be changed or inverted. This behaviour indicates a change of the ground state from dx2−y2 to dz2 orbitals. Theoretical calculations of 1 focus on the evaluation and characterization of interesting anion–π–anion assemblies that are formed in the solid state. In 2 we have analysed the unconventional chelate ring…chelate ring π-stacking interactions that govern its solid state architecture. Both complexes act as functional models and show catechol oxidase activity with a kcat value of the order of 103 h−1. [ABSTRACT FROM AUTHOR]

Here we show the important role played by the size of the lanthanoid and the solvent used in the final structures of several two-dimensional magnetic coordination polymers with the ligand chlorocyananilato, (C6O4(CN)Cl)2. With this aim we have prepared five compounds: [Nd2(C6O4(CN)Cl)3(DMF)6] (1) (DMF = dimethylformamide), [Dy2(C6O4(CN)Cl)3(DMF)6]4H2O (2), [Ho2(C6O4(CN)Cl)3(DMF)6]·2H2O (3), and [Ln2(C6O4(CN)Cl)3(DMSO)6] with Ln = Ce (4) and Nd (5) (DMSO = dimethylsulfoxide). These compounds are formed by two dimensional networks with a (6,3)-topology but, depending on the size of the lanthanoid and on the solvent used, show important structural differences, including the size, shape, distortion and content of the cavities as well as the flatness of the layers. The comparison of compounds 1-3 and 4-5 shows the role played by the size of the lanthanoid while keeping constant the solvent, whereas, the comparison of compounds 1 and 5 shows the role of the solvent (DMF vs. DMSO) while keeping constant the lanthanoid. The magnetic properties of all of them show the absence of noticeable magnetic interactions, in agreement with previous results that can be explained by the internal character of the 4f electron and the weak magnetic coupling mediated by these anilato-based ligands. [ABSTRACT FROM AUTHOR]

We show the key role that the size and shape of the solvent molecules may play in the dimensionality and structure of a series of lanthanoid–chloranilato coordination polymers. We report the synthesis, structure and magnetic properties of six different coordination polymers prepared with Er(iii) and chloranilato (C6O4Cl22− = 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone) and six different solvents: [Er2(C6O4Cl2)3(H2O)6]·10H2O (1), [Er2(C6O4Cl2)3(FMA)6]·4FMA·2H2O (2) (FMA = formamide = NH2CHO), [Er2(C6O4Cl2)3(DMSO)4]·2DMSO·2H2O (3) (DMSO = dimethy sulfoxide = Me2SO), [Er2(C6O4Cl2)3(DMF)6] (4) (DMF = dimethylformamide = Me2NCHO), [Er2(C6O4Cl2)3(DMA)4] (5) (DMA = dimethylacetamide = Me2NC(Me)O) and [Er2(C6O4Cl2)3(HMPA)(H2O)3]·H2O (6) (HMPA = hexamethylphosphormamide = (Me2N)3PO). We show how the different solvent molecules modulate and determine important structural parameters such as the coordination number and geometry, the shape and distortions of the cavities, the presence of solvent molecules in these cavities, the interlayer space and even the dimensionality of the structure. [ABSTRACT FROM AUTHOR]

Five new anilato-based, Ln(III)-containing, layered compounds have been prepared with the asymmetric ligand chlorocyananilato (C6O4(CN)Cl)2-; different Ln(III) ions Ce(III), Pr(III), Yb(III), and Dy(III); and the three different solvents H2O, dimethylsolfoxide (DMSO), and dimethylformamide (DMF). Compounds [Ce2(C6O4(CN)Cl)3(DMF)6]•2H2O (1), [Pr2(C6O4(CN)Cl)3(DMF)6] (2), [Pr2(C6O4(CN)Cl)3(DMSO)6] (3), [Yb2(C6O4(CN)Cl)3(DMSO)4]•2H2O (4) and [H3O][Dy(C6O4(CN)Cl)2(H2O)]•4H2O (5) show the important role that the Ln(III) size, as well as the size and shape of the solvent may play in the crystal structure of each compound. Compounds 1-4 present (6,3)-2D hexagonal lattices, with important differences in the coordination number and geometry of the Ln(III) ion, as well as in the distortion of the hexagonal cavities, depending on the Ln(III) and solvent size. Compound 5 (the only one prepared with water) presents a (4,4)-2D square lattice, where the Dy(III) ions are surrounded by four chelating anilato ligands. Compounds 2-4 are essentially paramagnetic, confirming the presence of weak (if any) magnetic coupling mediated by the anilato ligands when connecting Ln(III) ions. Compounds 2-4 showed a red shift and a broadening of the emission band of the ligand. Compound 4 also showed a strong emission band attributed to the Yb(III), suggesting an antenna effect of the ligand. An energy transfer diagram is proposed to explain these luminescent properties. [ABSTRACT FROM AUTHOR]

A new iron(iii) complex, [Et3NH][FeIII(L2−Ṗ)2] (1) with a substituted o-aminophenol based ligand is reported. Complex 1 is an anionic complex with a triethylammonium cation in the lattice. It contains two O,O,N-coordinated o-iminobenzosemiquinonate(2−) radical anions with an Fe(iii) centre in a high-spin configuration. The crystal structure of 1 was determined by X-ray diffraction, which revealed a trigonal prismatic coordination environment whose electronic structure was established by various physical methods including EPR, Mössbauer spectroscopy and variable-temperature (2–300 K) magnetic susceptibility measurements. Electrochemical analysis indicated primarily ligand-centred redox processes. Complex 1 retained the high-spin character of Fe(iii) throughout the temperature range studied (2–300 K) and exhibited, as expected, strong antiferromagnetic coupling operating between two radicals (SR = 1/2) and the high-spin Fe(iii) centre (SFe = 5/2), yielding a St = 3/2 as the ground state. This was confirmed by means of DFT calculations (M06-2X/6-31+G*) and a spin density analysis of the high spin and low spin configurations. [ABSTRACT FROM AUTHOR]

Five new hetero-metallic nickel(II)–mercury(II) complexes, [(NiL 1 )HgCl 2 ] ( 1 ), [(NiL 1 ) 2 HgCl 2 ] ( 3 ), [(NiL 1 ) 2 Hg(N 3 ) 2 ] ( 4 ), [{(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )} 2 ] ( 5 ) and [{(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )HgCl 2 } 2 {Hg(N 3 )(μ 1,1 -N 3 )}] ( 6 ) have been synthesized by reacting metalloligands [NiL 1 ] or [NiL 2 ] (where H 2 L 1 is N,N′-bis(salicylidene)-1,2-ethylenediamine and H 2 L 2 is N,N′-bis(salicylidene)-1,3-propanediamine) with HgX 2 (X − = Cl − or N 3 − ) at different molar ratios. All five complexes have been characterised by X-ray single-crystal structural, elemental and spectroscopic analyses. In complex 1 , the Hg(II) ion is coordinated to two phenoxido oxygen atoms of one [NiL 1 ] moiety and two terminal chloride ions to form a NiHg dinuclear complex. In the trinuclear complexes 3 and 4 , the central Hg(II) ion is coordinated by two terminal [NiL 1 ] units through two phenoxido oxygens from each and two terminal chloride (in 3 ) or azide (in 4 ) ions. The centrosymmetric hexanuclear complex 5 consists of two trinuclear [(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )] units, where the phenoxido bridges connect two terminal Ni(II) atoms of the trinuclear units. In these trinuclear units, one azido ligand adopts a μ l,1 -briding mode between Hg and Ni whereas the other one is terminal. In the nonanuclear complex 6 , two tetranuclear [{(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )}HgCl 2 ] units are linked to a central Hg(II) positioned on a two fold axis, via chlorido, azido, and phenoxido bridges. The tetranuclear unit is formed by the addition of a HgCl 2 molecule to a trinuclear [(NiL 2 ) 2 Hg(N 3 )(μ 1,1 -N 3 )] unit, similar to that present in 5 . Complex 5 shows weak ferromagnetic interactions ( J = +2.1 cm −1 ) between the two octahedral Ni(II) ions through double phenoxido bridges with a Ni–O–Ni bond angle of 95.87(11)°. [ABSTRACT FROM AUTHOR]

The preparation by simple direct synthesis of a series of coordination polymers based on copper with chloride or bromide and dipyrimidinedisulfide is reported. The structural characterisations of these compounds reveal a rich structural variety as a result of the number of coordination modes available to the organosulfur ligand, in combination with the bridging capabilities of the halides. Interestingly, some of the polymers displayed fully reversible solvent exchange/removal crystal-to-crystal 2D to 0D and 2D to 2D transformations. These materials show multifunctional electronic properties. Thus, some of them are semiconductors and present weak antiferromagnetic interactions, and the CuI/CuII coordination polymers present coexistence of paramagnetism with weak red emission. These compounds present some of the lowest NIR energy luminescence in d10 transition-metal complexes. [ABSTRACT FROM AUTHOR]

Combining Fe(II) with the carboxylate-functionalized 2,6-bis-(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes. [ABSTRACT FROM AUTHOR]

A series of four dinuclear cobalt(III,II) complexes were synthesized and structurally characterized. The four complexes show field-induced single-molecule magnet behaviour and constitute the first examples of cobalt(III,II) SMM with reduced shift bases. [Display omitted] We present the synthesis, structure and magnetic characterization of four dinuclear cobalt(III,II) complexes: [(NCS)CoIII(L n)(µ–OAc)CoII(NCS)]·G, with n/G = 1/CH 3 OH (1), 2/CH 3 CN (2), 3/- (3) and 4/CH 3 OH (4), being H 2 L n , four closely related reduced Schiff base ligands: H 2 L1 = (1,3-propanediyl)bis(iminomethylene)bis(6-methoxyphenol), H 2 L2 = (1,3-propanediyl)bis(iminomethylene)bis(6-ethoxyphenol), H 2 L3= (2,2-dimethyl-1,3-propanediyl)-bis(iminomethylene)bis(6-methoxyphenol) and H 2 L4= (2,2-dimethyl-1,3-propanediyl)-bis(iminomethylene)bis(6-ethoxyphenol). The single crystal X-ray structures of complexes 1 – 4 show that both cobalt centres in the four complexes adopt a distorted octahedral geometry with Co(III) and Co(II) centres residing at inner N 2 O 2 and outer O 4 pockets of the reduced Schiff base, respectively. Magnetic measurements show that all complexes behave as Co(II) monomers, confirming the presence of diamagnetic low spin Co(III) ions, which have also been supported by the spin-density calculation using Density Functional Theory. Additionally, complexes 1 – 4 show a field-induced slow relaxation of the magnetization at low temperatures that follow direct and Raman mechanisms. [ABSTRACT FROM AUTHOR]

In this paper we report the temperature and pH dependent syntheses and systematic characterization of four new CoII/CoIIIand NiIIcomplexes with a pentadentate Schiff base ligand H3L obtained by condensing 1,3,-diaminopropan-2-ol with 2-hydroxyacetophenone in 1 : 2 molar ratio. The room temperature syntheses involving CoIIand NiIInitrates and the ligand H3L lead to the isolation of the dinuclear species [Co2L2(H2O)] (1), and the mononuclear complex [Ni(LH)] (3), respectively, whereas refluxing at basic pH leads to the tetranuclear complexes, [CoII2CoIII2L2(μ3-OMe)2(NO3)(H2O)2]NO3·2(H2O) (2), and [Ni4L2(μ3-OMe)2(H2O)2]·2H2O (4). 1is found to be a simple mono alkoxo-bridged CoIIIdinuclear species, whereas 2and 4are both rhomb-like tetrameric complexes with double oxo bridges and μ3-methoxo bridges, derived from the methanol solvent, in an open dicubane arrangement. Moreover 2shows six coordinate ordered CoIIand CoIIIions and 4has both six- and five-coordinate NiIIcenters. Compound 3is assigned a tentative mononuclear structure based on IR, UV-Vis spectroscopic, 1H-NMR and ESI mass study results and is supposed to have one NiIIcenter coordinated with a ligand fragment in square planar geometry. The variable temperature magnetic susceptibility study for 2and 4is performed which indicate for both 2and 4the presence of intracluster dominant ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Abstract: A Co-monosubstituted Keggin polyoxometalate with an antenna ligand linked to the Co(II) center with a Co(II)-containing cation has been prepared. The title compound, formulated as {Co(H2O)4(4,4′-bpy)}2(4,4′-Hbpy)2[SiW11Co(4,4′-bpy)O39]·5H2O (1) (4,4′-bpy=4,4′-bipyridine), was synthesized and characterized by elemental analysis, IR spectra, TG analysis, X-ray single crystal structure analysis and magnetic measurements. As far as we know, the title compound represents the first Co(II) substituted Keggin polyoxometalate with an antenna ligand structurally and magnetically characterized. [Copyright &y& Elsevier]

A new polymeric approach, based on cyanocarbanion ligands, for the design of spin crossover (SCO) compounds led us to the compound [Fe(abpt)2(tcpd)] (1) (tcpd2- = (C[C(CN)2]3)2-, abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole) which has been characterised as the first SCO molecular chain involving a cyanocarbanion as bridging ligand. [ABSTRACT FROM AUTHOR]

The combination of hexacyanoferrate(III) anions, [Fe(CN)[sub 6]][sup 3-] , with nickel(II) complexes derived from the chiral ligand trans-cyclohexane-1,2-diamine (trans-chxn) affords the enantiopure layered compounds [Ni(trans-(1 S,2S)-chxn)[sub 2]][sub 3][Fe(CN)[sub 6]][sub 2] · .2H[sub 2]0 (1) and [Ni(trans-(1R,2R)-chxn)[sub 2]]3[Fe(CN)[sub 6]][sub 2] · .2H[sub 2]O (2), These chiral systems behave as ferromagnets (To = 13.8 K) with a relatively high coercive field (H[sub c] = 0.17 T) at 2 K. They also exhibit an unusual magnetic behavior at low temperatures that has been attributed to the dynamics of the magnetic domains in the ordered phase. [ABSTRACT FROM AUTHOR]

Dimers based on lanthanoids and an asymmetric anilato ligand exhibit slow magnetic relaxation. [Display omitted] • Understanding the mechanisms behind slow magnetic relaxation in Tb and Er dimers contributes to the development of advanced magnetic materials. • Insights into the complex interplay of magnetic interactions at the molecular level. • Understanding and controlling quantum tunnelling processes at the molecular level. • Engineer molecular architectures to optimize magnetic relaxation dynamics. • Advancing steps towards practical quantum technologies with Tb and Er dimers as key building blocks. We report the synthesis, structure and magnetic properties of two dimers prepared with the asymmetric chloronitranilato ligand: 3-chloro-6-nitro-2,5-dihydroxy-1,4-benzo-quinone (C 6 O 4 (NO 2)Cl)2- and two lanthanoid ions as TbIII and ErIII. The two compounds, formulated as: [Tb 2 (C 6 O 4 Cl(NO 2)) 3 (H 2 O) 10 ]·6H 2 O (1) and [Er 2 (C 6 O 4 Cl(NO 2)) 3 (H 2 O) 10 ]·6H 2 O (2) are isostructural and present a dimeric structure where the LnIII ions are connected by a bridging bis-bidentate chloronitranilato ligand. Each metal completes its nona-coordination environment with a terminal bidentate chloronitranilato ligand and five water molecules in a slightly distorted capped square antiprismatic geometry. In addition, these dimers exhibit field-induced slow magnetic relaxation with energy barriers of ca. 5 and 24 K, respectively. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue is the group of Smail Triki from Université de Brest, France. The cover image shows the crucial effect of the counter ions and solvent molecules on the spin-crossover behavior of macrocycle-based FeII complexes. [ABSTRACT FROM AUTHOR]

A new hexanuclear Copper (II) complex has been synthesised with symmetrical N 2 O 3 -donor Schiff-base ligand and characterized fully by structurally and spectroscopically. The magnetic property indicates the presence of predominant antiferromagnetic Cu⋯Cu interactions in the Cu6 cluster. [Display omitted] • Based on a symmetrical N 2 O 3 -donor Schiff-base ligand an hexanuclear Cu(II) complex has been synthesised and characterized fully by spectroscopically and structurally. • In the cluster, Cu(II) ions are bridged by very unusual combinations of single hydroxido, single alkoxido and double phenoxido bridges. • The magnetic properties indicate the presence of antiferromagnetic interactions inside the cluster having two different J values. A new CuII 6 complex, formulated as [Cu 6 (L) 3 (µ 3 -OH)(H 2 O)(OH)(NO 3)]·2H 2 O·7CH 3 OH (1) has been prepared using the symmetrical N 2 O 3 -donor Schiff-base ligand H 3 L = N,N′-(2-hydroxypropane-1,3-diyl)bis(2-hydroxyacetophenimine). Compound 1 has been structurally and spectroscopically characterized. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the triclinic space group P -1 and consists of a CuII 6 complex where each deprotonated ligand chelates two CuII centres. Three of the six independent CuII centres are arranged in an almost equilateral triangle with double Cu-O-Cu bridges, formed by a μ 3 -hydroxido and phenoxido bridges. Each of the three CuII centres in the triangle is further connected to one CuII centre through a single alkoxido bridge. The magnetic properties indicate the presence of moderate and weak antiferromagnetic interactions through the double and single oxido bridges, respectively. [ABSTRACT FROM AUTHOR]

Two polynuclear copper(II) complexes with hydroxido-bridging ligands and polycyanide units, [Cu{Cu(tn)} 6 (μ 2 -OH) 2 (μ 3 -OH) 4 Cl 2 ](tcm) 4 Cl 2 ·2H 2 O ( 1 ) and [{Cu(bpy)} 4 (OH) 4 (dca) 2 ](dca) 2 ·bpy·2H 2 O ( 2 ) (tn = NH 2 (CH 2 ) 3 NH 2 ; tcm − = [C(CN) 3 ] − , bpy = 2,2′-bipyridyl, dca − = [N(CN) 2 ] − ) have been prepared by one-pot reactions. The structure of 1 consists of a centrosymmetric heptanuclear ion [Cu{Cu(tn)} 6 (μ 2 -OH) 2 (μ 3 -OH) 4 Cl 2 ] 6+ . The tcm − and the halide anions which appear as counter-ions in the formula unit, play an important role in the stabilization of the complex since the hydrogen bonding between nitrogen atoms of the tcm − anion and halide anions, and hydrogen atoms of the terminal water molecule and of the bridging hydroxido ligands generate an overall three-dimensional structure. The crystal structure of 2 is essentially built on discrete centrosymmetric tetranuclear [{Cu(bpy)} 4 (μ 2 -OH) 2 (μ 3 -OH) 2 (dca) 2 ] 2+ units including two μ 2 - and two μ 3 -OH ligands. As observed for 1 , the dca − anions form a network of hydrogen bonding between their nitrogen atoms and hydrogen atoms of water molecules generating a two-dimensional structure. The magnetic susceptibility data indicate antiferromagnetic interactions in 1 and ferromagnetic ones in 2 . [ABSTRACT FROM AUTHOR]

Abstract: Four new manganese(II) coordination polymers: [Mn(4,4′-azpy)(C6H5COO)2](4,4′-azpy)0.5 (1), [Mn(4,4′-azpy)(p-(NO2)C6H4COO)2] (2), [Mn(4,4′-azpy)(m-(NO2)C6H4COO)2] (3) and [Mn(4,4′-azpy)(o-(NO2)C6H4COO)2(H2O)2] (4), where 4,4′-azpy=4,4′-azobis(pyridine), have been synthesized by self-assembly of MnX2 (X=benzoate, p-, m-, or o-nitrobenzoates) together with 4,4′-azpy. All four complexes were characterized by elemental analyses, IR spectroscopy, thermal analyses, single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that complexes 1, 2 and 3 feature a 1D molecular ladder formed by syn–syn (complex 1) or syn–anti (complexes 2 and 3) carboxylate-bridged dimeric Mn(II) units which are joined together by 4,4′-azpy ligands. In complex 1, these ladders assemble with the help of π–π and C–H⋯π interactions to form a nanoporous framework that incorporates non coordinated 4,4′-azpy molecules by exploiting host–guest C–H⋯π and hydrogen bonding interactions. Complex 2 presents a 3D supramolecular framework by π–π and CH⋯π interactions, whereas, complex 3 having a similar ladder structure to 1 and 2, forms a 2D grid through π–π interactions. On the other hand, complex 4 is a 4,4′-azpy bridged fish-bone chain of carboxylate-coordinated mononuclear manganese(II) units, which are linked together by strong hydrogen bonds to form a 2D structure. Variable-temperature (2–300K) magnetic susceptibility measurements show the presence of weak antiferromagnetic interactions within the discrete Mn–(OCO)2–Mn dimers for complexes 1, 2 and 3 that have been fitted with a S =5/2 dimer model (J =−0.8, −0.5 and −0.4cm−1 respectively). The magnetic data of complex 4 can be reproduced with a S =5/2 monomer model including a Zero Field Splitting (|D|=1.7cm−1). [Copyright &y& Elsevier]

Two new polynuclear manganese(II) complexes [Mn(dptz)(N3)2]n (1) and [Mn(azpy)(N3)2]n (2) (where dptz = dipyridyl-tetrazine and azpy = 4,4′-azobis(pyridine)) have been synthesized by self-assembly of the ligand azide, together with dptz and azpy as secondary spacers. The compounds are characterized by single-crystal X-ray diffraction analyses and variable-temperature magnetic measurements. The structural analyses reveal that in complex 1, which is the first reported Mn(II) complex with the ligand dptz, two μ1,3 bridging azides connect neighboring manganese ions in a zigzag manner to generate a neutral two-dimensional (2D) sheet which is further connected by the dptz ligands to form a three-dimensional (3D) framework. By contrast, complex 2 contains dimeric [Mn2(μ1,1-N3)2]2+ fragments linked to four identical motifs by means of four single μ1,3-N3 bridges, that generates a neutral 2D MnII-azide sheet which is further interconnected by azpy ligands to neighboring manganese ions forming an unprecedented 3D network. Variable-temperature (2-300 K) magnetic susceptibility measurements show the presence of predominantly antiferromagnetic coupling for both complexes that has been reproduced with a regular antiferromagnetic S = 5/2 chain (J) with interchain interactions (j) modeled with the molecular field approximation with J = -7.1 cm-1 and j′ = -0.8 cm-1 for 1 and J = -4.2 cm-1 and j′ = 0.1 cm-1 for 2. [ABSTRACT FROM AUTHOR]

Abstract: A new two-dimensional (2D) thiocyanato-bridged cobalt(II) network formulated as [LCo2(NCS)2] n (1), has been synthesized with the Schiff base ligand N,N′-bis(3-methoxysalicylidenimino)-1,3-diaminopropane (H2L) and thiocyanate anions. This novel layered compound has been completely characterized by elemental analysis, FT-IR, UV–Vis spectroscopy and the structure has been established by single crystal X-ray diffraction studies. The structure of 1 consists of a doubly phenoxo-bridged dimer comprising two different cobalt(II) centers with different coordination geometries (octahedral and tetrahedral). The 2D network is accomplished by bridging thiocyanate ligands, connecting the dimeric motifs in an end-to-end fashion. Variable-temperature magnetic susceptibility and EPR measurements reveal predominant antiferromagnetic exchange interaction in the complex. [ABSTRACT FROM AUTHOR]

Five new nickel(II) complexes [Ni[sub2]L[sub2](N[sub3])[sub2](H[sub2]O)[sub2]] (2), Ni[sub2]L[sub2](O[sub2]CPh)(CH[sub3]OH)[sub2]]ClO[sub4].0.5CH[sub3]OH (3), [Ni[sub3]L[sub2](O[sub2]CPh)[sub4]] (4), and [Ni[sub2]L[sub2](NO[sub2])[sub2]][subn] (5) have been synthesized by using a tridentate schiff base ligand, HL (2-[3-Methylamino-propylimino)-methyl]-phenol), and the polyatomic monoanions N[sub3][sup-], NO[sub3][sup-], PhCOO[sup-], or NO[sub2][sup-]. The complexes have been structurally and magnetically characterized. The structural analysis reveals that in all five complexes, the Ni(II) ions possess a distorted octahedral geometry. Complexes 1 and 2 are dinuclear with di-μ-1, 1-azido and di-μ[sub2]-phenoxo bridges, respectively. Complex 3 is also a di-μ[sub2]-phenoxo-bridged dinuclear Ni(II) complex but has an additional syn—syn benzoate bridge. Compound 4 ossess a linear trinuclear structure with the tridentate Schiff base ligand coordinated to the terminal nickel atoms which are linked to the central Ni(II) by phenoxo and carboxylate bridges. Complex 5 consists of a dinuclear entity, bridged by di-μ[sub2]-phenoxo together with a cis-(μ-nitrito-1[subK]O:2[subK]N) nitrite ion. The dinuclear units are linked each other by another bridging trans-(μ-nitrito-1[subK]O:2[subK]N) nitrite to form a Ni(II) chain that shows the presence of unprecedented alternating cis- and trans-N,O bridging mode of the nitrite anion. Variable-temperature magnetic susceptibility measurements of complex 1 indicate the presence of ferromagnetic exchange interactions within the dimer (J=23.5(3) cm[sup-1]) together with antiferromagnetic interdimer interactions (J' = -0.513(3) cm[sup-1]), whereas compounds 2 and 3 show intradimer antiferromagnetic interactions (J=-24.27(6) and -16.48(4) cm[sup-1], respectively). Ferromagnetic coupling (J=6.14(2) cm[sup-1] is observed in complex 4 for linear centro-symmetric Ni(II) trimer, whereas complex 5 shows an alternating intra-chain antiferromagnetic coupling (J[sub1] = -32.1(1) cm[sup-1] and J[sub2] = -3.2(1) cm[sup-1]. [ABSTRACT FROM AUTHOR]

Structural and magnetic characterization of compound ([Ni[sub2](L)[sub2](OAc)[sub2]][Ni[sub3](L)[sub2](OAc)[sub4]])∙2CH[sub3]CN (3) (HL = the tridentate Schiff base ligand, 2-[(3-methylamino-propylimino)-methyl]-phenol) shows that it isa rare example of a crystal incorporating a dinuclear Ni(ll) compound, [Ni[sub2](L)[sub2](OAc)[sub2]), and a trinuclear one, [Ni[sub3](L)[sub2](OAc)[sub4]]. Even more unusual is the fact that both Ni (II) complexes, [Ni[sub2](L)[sub2](OAc)[sub2]) (1) and [Ni[sub3](L)[sub2](OAc)[sub4](H[sub2]O)[sub2]] CH[sub2]Cl[sub2]∙2CH[sub3]OH (2), have also been isolated and structurally and magnetically characterized. The structural analysis reveals that the dimeric complexes [Ni[sub2](L)[sub2](OAc)[sub2]] in cocrystal 3 and in compound 1 are almost identical-in both complexes, the Ni(ll) ions possess a distorted octahedral geometry formed by the chelating tridentate ligand (L), a chelating acetate ion, and a bridging phenoxo group with very similar bond angles and distances. On the other hand, compound 2 and the tnnuclear complex in the cocrystal 3 show a similar linear centrosymmetric structure with the tndentate ligand coordinated to the terminal Ni(ll) and linked to the central Ni(II) by phenoxo and carboxylate bridges. The only difference is that a water molecule found in 2 is not present in the tnnuclear unit of complex 3; instead, the coordination sphere is completed by an additional budging oxygen atom from an acetate ligand. Variable-temperature (2-300 K) magnetic susceptibility measurements show that the dinuclear unit is antiferromagnetically coupled in both compounds (2J= -36.18 and -29.5 cm[sup-1] in 1 and 3, respectively), whereas the trinuclear unit shows a very weak ferromagnetic coupling in compound 3 (2J= 0.23 cm[sup-1]) and a weak antiferromagnetic coupling in 2 (2J= -8.7(2) cm[sup-1]) due to the minor changes in the coordination sphere. [ABSTRACT FROM AUTHOR]

A new tridentate N2O donor Schiff base ligand [(C6H5C(OH)CHC(CH3)NCH2C5H4N)LH] was obtained by 1:1 condensation of benzoylacetone with 2-picolylamine and has been used to synthesise a mononuclear [CuLCl] (1) and an end-to-end dicyanamide bridged polynuclear {[Cu2(μ-L)2(μ2-1,5-(CN)2N)]ClO4}n (2) copper(II) complexes. The ligand, 1 and 2 were clearly characterised by elemental analysis, FT-IR, 1H NMR, UV–Vis spectral studies, electrochemical studies and in addition single crystal X-ray diffraction studies were performed for 1 and 2. The Schiff base ligand [LH] shows a significant variation in its coordination behaviour with copper(II) ion in absence and in presence of dicyanamide ion in 1 and 2 respectively. In absence of dicyanamide the deprotonated enolato oxygen of the tridentate Schiff base ligand [L]− coordinates the copper(II) ion in a monodentate fashion generating a mononuclear species (1) whereas in presence of the dicyanamide ion, the deprotonated enolato oxygen of [L]− bridges two adjacent [CuL(CN)2N] units through μ-OL bridges, forming dimers. The dimeric units are further linked to adjacent dimeric units through μ2-1,5-dicyanamide bridges to produce 1D polymeric chains in 2. Variable temperature magnetic susceptibility measurements for 2 in the temperature range 2-300 K reveal the presence of weak antiferromagnetic exchange interactions in the polymeric chain. [Copyright &y& Elsevier]

Abstract: A novel polynitrile ligand (tcnoprOH− =[(NC)2CC(OCH2CH2CH2OH)C(CN)2]−) with up to five potentially coordinating groups has been synthesized in a one-pot reaction from a cyclic acetal and malononitrile. The combination of this novel ligand with different transition metal ions has led to the synthesis of two different structural types with the same formula but with different coordination modes in the ligand. Mn(II) and Cu(II) lead to a μ2-N,O-coordinating mode in the series of compounds formulated as [M(N,O-tcnoprOH)2(H2O)2] (M=MnII (1) and CuII (2)), whereas Co(II) and, most probably Ni(II), lead to a μ2-N,N′-coordinating mode in [Co(N,N′-tcnoprOH)2(H2O)2] (3). Both structural types consist of linear chains of metal ions connected by a double tcnoprOH− bridge. These ligands are connected to the metal ions through one –CN and one –OH group in compounds 1 and 2 (N,O-coordinating mode) or through two –CN groups in compound 3. Magnetic measurements show that all compounds are paramagnetic with a low zero field splitting for the Mn derivative. [Copyright &y& Elsevier]

Abstract: A novel polynitrile anionic ligand, tcnoetOH−(=[(NC)2CC(OCH2CH2OH)C(CN)2]−), has been synthesized by a one-pot reaction from a cyclic acetal and malononitrile. This ligand has been successfully used to prepare, with 4,4′-bpy as co-ligand, a novel series of coordination polymers formulated as [M(tcnoetOH)2(4,4′-bpy)(H2O)2] with M(II)=Fe (1), Co (2) and Ni (3). These isostructural compounds present a linear chain structure consisting of octahedrally coordinated metal ions bridged by trans 4,4′-bpy ligands. The coordination sphere of the metal ions is completed with two terminal tcnoetOH− ligand and two water molecules. The magnetic properties indicate that the three compounds are paramagnetic, as expected from the long 4,4′-bpy bridge connecting the metal atoms. Their magnetic properties have been fitted with a model of isolated ions including a zero field splitting for the Fe(II) and Ni(II) derivatives. [Copyright &y& Elsevier]

Structural characterization and spectroscopic studies of the (2-acetyl-6-(1-TEMPO-imino)ethyl)pyridine (pat) and the 2,6-bis(1-TEMPO-imino)ethyl)pyridine (pbtMe) ligands are presented. Their electrochemical properties are also discussed. Two new nickel complexes, [Ni II (dip)(CH 3 CN)(H 2 O) 2 ](BF 4 ) 2 ( 1 ) (dip = 2,6-(di-iminepyridine)) and [Ni II (pbtMe)(CH 3 CN) 3 ](BF 4 ) 2 ( 2 ) have been characterized by X-ray diffraction. The reaction of 1 with the tetraethyl ammonium pentacyanopropenide salt (Et 4 N)(pcp) affords the new compound [Ni II (pcp)(dip)(CH 3 CN)](pcp) ( 3 ) for which X-ray diffraction studies evidence an usual bridging μ 2 coordination mode for the pentacyanopropenide anion, leading to chains running along the [1 0 0] direction with Ni⋯Ni intra-chains distances of 10.653 Å. Magnetic measurements for 3 indicate that it presents antiferromagnetic interactions that can be reproduced with a S = 1 regular chain model with g = 2.115(1) and J chain  = −0.589(5) cm −1 . [ABSTRACT FROM AUTHOR]

This work highlights the key role of the solvents in the structures of the series of 2D compounds [Ln 2 (C 6 O 4 Br 2 ) 3 ·(Solvent) n ]·G (G = Guest). This study is based on the affinity and ability of these solvents to coordinate to lanthanides and on their possibility to act as solvation molecules. For this purpose here we focus on the Er(III) ion and on the bromanilato bridging ligand ([C 6 O 4 Br 2 ] 2− = dianion of 3,6-dibromo-2,5-dihydroxy-1,4-benzoquinone) and we play with three solvents: H 2 O, DMSO (dimethylsulfoxide) and DMF (dimethylformamide). Here we report the synthesis, crystal structure and magnetic characterization of compounds [Er 2 (C 6 O 4 Br 2 ) 3 (H 2 O) 6 ]·12H 2 O ( 1 ), [Er 2 (C 6 O 4 Br 2 ) 3 (DMSO) 4 ]·2DMSO·2H 2 O ( 2 ) and [Er 2 (C 6 O 4 Br 2 ) 3 (DMF) 6 ] ( 3 ). We show the key role played by the shape and size of the three solvents in (i) the coordination number and geometry of the metal ion, (ii) the distortion of the hexagonal cavities of these (6,3)-2D lattices, (iii) the presence/absence of porosity in these hexagonal cavities and (iv) the interlayer separation. The magnetic characterization of the three compounds show the expected behavior for almost isolated Er(III) ions since the bridging (C 6 O 4 Br 2 ) 2− ligands give rise to very weak (if any) antiferromagnetic couplings. Finally we also show that this study can be extended to other lanthanide with other anilato-based ligands [C 6 O 4 X 2 ] 2− (X = Cl, Br, NO 2 , H,…) and using other solvents. [ABSTRACT FROM AUTHOR]

The synthesis, structure and magnetic properties of a novel Co(II) 1D coordination polymer, [Co(L)(µ 1,5 -dca)(ClO 4 ) 2 ·MeOH] n ( 1 ) are described. Compound 1 contains two independent cationic Co(II) chains (CoA and CoB) which are parallel to the c direction and present short π-π and C-H⋯π interactions with two neighbouring chains along the b direction, giving rise to alternating layers of chains A and B in the bc plane. Variable-temperature magnetic susceptibility measurements shows a weak antiferromagnetic coupling among the adjacent cobalt(II) centres mediated through μ 1,5 -dca − bridge. [ABSTRACT FROM AUTHOR]

Two new Cu(II) coordination polymeric neutral chains of formula [Cu 2 (1,4-tpbd)(μ-A) 2 (H 2 O) 2 ](A) 2 with A = tcnoet − ( 1 ) and tcnopr − ( 2 ) (1,4-tpbd = N,N,N′N′ -tetrakis(2-pyridylmethyl)benzene-1,4-diamine, tcnoet − = 1,1,3,3-tetracyano-2-ethoxypropenide and tcnopr − = 1,1,3,3-tetracyano-2-propoxypropenide) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. 1 and 2 show alternating chains where the 1,4-tpbd and the cyanocarbanion units (tcnoet − for 1 and tcnopr − for 2 ) alternate as bridging ligands. The molecular structure can be viewed as [Cu 2 (μ-tpbd)] 4+ dinuclear units (with Cu⋯Cu distances of 8.2233(3) for 1 and 8.2454(7) Å for 2 ) connected through double cyanocarbanion bridges (Cu(NCCCN) 2 Cu with Cu⋯Cu distances of 7.4226(6) Å for 1 and 7.4605(3) Å for 2 ) leading to alternating zig-zag chains running along the [0 1 0] direction. Both compounds exhibit a maximum in the thermal variation of the magnetic susceptibility (at ca . 30 K in both cases), characteristic of antiferromagnetic exchange interactions occurring mainly through the 1,4-tbpd organic ligand that can be very well reproduced with a S = ½ dimer model with g = 2.119, J = −35.0 cm −1 for 1 and g = 2.070 and J = −35.2 cm −1 for 2 . [ABSTRACT FROM AUTHOR]

The similar bis-bidentate coordination mode of oxalato and anilato-based ligands is exploited here to create the first examples of 2D and 3D heterometallic lattices based on anilato ligands combining M(I) and a M(III) ions, phases already observed with oxalato but unknown with anilato-type ligands. These lattices are prepared with alkaline metal ions and magnetic chiral tris(anilato)metalate molecular building blocks: [MIII(C6O4X2)3]3- (MIII = Fe and Cr; X = Cl and Br; (C6O4X2)2- = dianion of the 3,6-disubstituted derivatives of 2,5-dihydroxy-1,4-benzoquinone, H4C6O4). The new compounds include two very similar 2D lattices formulated as (PBu3Me)2[NaCr(C6O4Br2)3] (1) and (PPh3Et)2[KFe(C6O4Cl2)3](dmf)2 (2), both presenting hexagonal [MIMIII(C6O4X2)3]2- honeycomb layers with (PBu3Me)+ in 1 or (PPh3Et)+ and dmf in 2 inserted between them. Minor modifications in the synthetic conditions yield the novel 3D lattice (NEt3Me)[Na(dmf)][NaFe(C6O4Cl2)3] (3), in which hexagonal layers analogous to 1 and 2 are interconnected through Na+ cations, and (NBu3Me)2[NaCr(C6O4Br2)3] (4), the first heterometallic 3D lattice based on anilato ligands. This compound presents two interlocked chiral 3D (10,3) lattices with opposite chiralities. Attempts to prepare 4 in larger quantities result in the 2D polymorph of compound 4 (4'). Magnetic properties of compounds 1, 3, and 4' are reported, and in all cases we observe, as expected, paramagnetic behaviors that can be satisfactorily reproduced with simple monomer models including a zero field splitting (ZFS) of the corresponding S = 3/2 for Cr(III) in 1 and 4' or S = 5/2 for Fe(III) in 3. [ABSTRACT FROM AUTHOR]

The syntheses, structures, and magnetic properties of a family of bimetallic anilate-based compounds with inserted spin-crossover cationic complexes are reported. The structures of 1-4 present a two-dimensional anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands with inserted [FeIII(sal2-trien)]+ (1), [FeIII(4-OH-sal2-trien)]+ (2), [FeIII(sal2-epe)]+ (3), or [FeIII(5-Cl-sal2-trien)]+ (4) complexes. The structure of 5 is formed by anionic [MnIICl2CrIII(Cl2An)3]3- chains surrounded by [FeII(tren(imid)3)]2+, Cl-, and solvent molecules. The magnetic properties indicate that 1-4 undergo a long-range ferrimagnetic ordering at ca. 10 K. On the other hand, the inserted Fe(III) cations remain in the low-spin (in 4) or high-spin state (in 1, 2, and 3). In the case of 5, half of the inserted Fe(II) cations undergo a complete and gradual spin crossover from 280 to 90 K that coexists with a magnetic ordering below 2.5 K. [ABSTRACT FROM AUTHOR]

On the quest of heterometallic mixed-valence MM'X chains, we have prepared two stable discrete bimetallic compounds: the reduced (PPN)[ClNi(μ-OSCPh)4Pt] (PPN = bis(triphenylphosphine)iminium; OSCPh = benzothiocarboxylato) and the oxidized [(H2O)Ni(μ-OSCPh)4PtCl] species. The role of the aqua and chlorido axial ligands is crucial to facilitate oxidation of the {Ni(μ-OSCPh)4Pt} core. Experimental and theoretical analyses indicate that a NiPt-Cl/Cl-NiPt isomerization process occurs in the oxidized species. The electronic structure of the reduced system shows two unpaired electrons, one located in a ... orbital of the Ni(II) ion and a second in the antibonding ... combination from the Ni(II) and Pt(II) centers. Oxidation occurs by removing one electron from this second multicenter molecular orbital. Although the mixed-valence character of the oxidized species makes the isolation of MM'X chains very attractive, such polymeric structure is prevented by the low Pt-Cl⋯Ni interaction energy and the high tendency of Ni centers to coordinate water molecules. Thus, this work offers valuable insights and hints to engage the production of heterometallic mixed-valence MM'X chains, which still is a challenging task. [ABSTRACT FROM AUTHOR]

Abstract: Two new polynuclear complexes with hydroxyl-rich Schiff base ligand 3-[(2-Hydroxy-benzylidene)-amino]-propane-1,2-diol (H3L), namely [NiII 2(HL)(H2L)(SCN)]2·DMF (1) and [MnIII 2NiII 2(HL)2(L)2] (2) have been synthesized and characterized by single crystal X-ray diffraction, elemental analyses, FTIR, UV–Vis spectroscopy and variable temperature magnetic susceptibility measurements. The X-ray refinements reveal that both compounds present defective rhomb-like dicubane central cores (Ni4 in 1 and Mn2Ni2 in 2). Magnetic susceptibility measurements indicate the presence of overall antiferromagnetic exchange interactions in 1 along the side connected by a N and O atoms (J 1 =−43.6cm−1) and along the short diagonal of the rhomb (J 3 =−3.9cm−1) and a weak ferromagnetic coupling (J 2 =+5.8cm−1) along the side of the rhomb connected by a double O-bridge. In 2 the three exchange interactions are negative (J 1 = J 2 =−0.3cm−1 and J 3 =−0.7cm−1). A magneto-structural correlation with the ratio between the Ni–O–Mn bond angle and the Mn–O bond length is also discussed for double O-bridged Mn–Ni pairs. [Copyright &y& Elsevier]

New Fe(ll) coordination polymeric neutral chains of formula [Fe(aqin)2(μ2-M(CN)4)] (M = NiII (1) and PtII (2)) (aqin = Qwnolin-8-armne) have been synthesized and characterized by infrared spectroscopy, X-ray diffraction, and magnetic measurements. The crystal structure determinations of 1--2 reveal in both cases a one-dimensional structure in which the planar [M(CN)4]2- (M = NiII (1) and PtII (2)) anion acts as a μ-bridging ligand, and the two aqin molecules as chelating coligands. Examination of the intermolecular contacts in the two compounds reveals that the main contacts are ascribed to hydrogen bonding interactions involving the amine groups of the aqin chelating ligands and the nitrogen atoms of the two non bridging CN groups of the [M(CN)4]2- (M = NiII (1) and PtII (2)) anion. The average values of the six Fe--N distances observed respectively at room temperature (293 K) and low temperature (120 K), that is, 2.142(3) and 2.035(2) Å for 1, and 2.178(3) and 1.990(2) Å for 2, and the thermal variation of the cell parameters (performed on 2) are indicative of the presence of an abrupt HS-LS spin crossover (SCO) transition in both compounds. The thermal dependence of the product of the molar magnetic susceptibility times the temperature (XmT), in cooling and warming modes, confirms the SCO behavior at about 145 and 133 K in 1 and 2, respectively, and reveals the presence of a small thermal hysteresis of about 2 K for each compound. [ABSTRACT FROM AUTHOR]

In this work we have synthetized and characterized by X-ray diffraction five cobalt complexes with 6-thioguanine (6-ThioGH), 6-thioguanosine (6-ThioGuoH), or 2'-deoxy-6-thioguanosine (2'-d-6-ThioGuoH) ligands. In all cases, these ligands coordinate to cobalt via N7 and S6 forming a chelate ring. However, independendy of reagents ratio, 6-ThioGH provided monodimensional cobalt(n) coordination polymers, in which the 6-ThioG- acts as bridging ligand. However, for 2'-d-6-ThioGuoH and 6-ThioGuoH, the structure directing effect of the sugar residue gives rise to mononuclear cobalt complexes which form extensive H-bond interactions to generate 3D supramolecular networks. Furthermore, with 2'-d-6-ThioGuoH the cobalt ion remains in the divalent state, whereas with 6-ThioGuoH oxidation occurs and Co(Hl) is found. The electrical and magnetic properties of the coordination polymers isolated have been studied and the results discussed with the aid of DFT calculations, in the context of molecular wires. [ABSTRACT FROM AUTHOR]

The use of the recently prepared polynitrile ligand tcnopr3OH- ([(NC)2CC(OCH2CH2CH2OH)C(CN)2]-) with different salts of Fe(II), Co(II), and Ni(II) has led to a very rare example of linkage isomerism in a coordination chain. These pairs of linkage isomers can be formulated as [M(tcnopr3OH-κN,κO)2(H2O)2]; M = Fe (1), Co (3), and Ni(5) and [M(tcnopr3OH-κN,κN')2(H2O)2]; M = Fe (2), Co (4), and Ni (6). Compounds 1-2, 3-4, and 5-6 are three pairs of linkage isomers since they present the same formula and chain structure and they only differ in the connectivity of the polynitrile ligand bridging the metal ions in the chain: through a N and an O atom (1κN:2κO-isomer) or through two N atoms (1κN:2κN'-isomer). The magnetic properties show, as expected, very similar behaviors for both isomers. [ABSTRACT FROM AUTHOR]

Abstract: Three Cu(II)-azido complexes of formula [Cu2L2(N3)2] (1), [Cu2L2(N3)2]·H2O (2) and [CuL(N3)] n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical μ-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a μ-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N3 azido bridges (J =−2.59(4) and −0.10(1)cm−1, respectively). The single 1,1-N3 bridge in compound 3 mediates a negligible exchange interaction. [Copyright &y& Elsevier]

Abstract: A dicyanamide bridged 2D polynuclear complex of copper(II) having molecular formula [Cu2(L)(μ1,5-dca)2] n (1) has been synthesized using the Schiff base ligand N,N′-bis(salicylidene)-1,3-diaminopentane, (H2L) and sodium dicyanamide (dca). The complex presents a 2D hexagonal structure formed by 1,5-dca singly bridged helical chains connected through double 1,5-dca bridges. The chelating characteristics of the H2L Schiff base ligand results in the formation of copper(II) dimer with a double phenoxo bridge presenting a very strong antiferromagnetic coupling in the copper(II) derivative (1) (J =−510cm−1). The dimeric asymmetric unit of 1 is very similar to the active site of the catechol oxidase and, as expected, also presents catalytic activity for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone in presence of O2, as demonstrated by kinetic studies of this oxidation reaction monitored by absorption spectroscopy resulting in high turnover number (K cat =259h−1). [Copyright &y& Elsevier]

Abstract: A tridentate NNO donor Schiff base ligand [(1Z,3E)-3-((pyridin-2-yl)methylimino)-1-phenylbut-1-en-1-ol= LH] in presence of azide ions coordinates with cobalt(II) and copper(II) ions giving rise to three new coordination complexes [Co2(L)2(μ1,1-N3)2(N3)2] (1), [Cu2(L)2(μ1,3-N3)]·ClO4 (2) and [(μ1,1-N3)2Cu5(μ-OL)2(μ1,1-N3)4(μ1,1,1-N3)2] n (3). The complexes have been characterized by elemental analysis, FT-IR, UV–Vis spectral studies, and single crystal X-ray diffraction studies. These complexes demonstrate that under different synthetic conditions the azide ions and the Schiff base ligand (LH) show different coordination modes with cobalt(II) and copper(II) ions, giving rise to unusual dinuclear and polynuclear species (1, 2 and 3) whose structural variations are discussed. Magneto-structural correlation for the very rare singly μ1,3-N3 bridged CuII–Schiff base dinuclear species (2) has been studied. In addition, the catalytic properties of 1 for alkene oxidation and the general catalase-like activity behavior of 2 have been discussed. [Copyright &y& Elsevier]

Abstract: Three new Cu(II) complexes of formula [Cu(L1)(pyz)(CH3OH)]ClO4 (1), [Cu(L1)(4,4′-bpy)(ClO4)]·0.5H2O (2) and [{Cu(L2)(ClO4)}2(μ-4,4′-bpy)] (3) have been synthesised by using pyrazine (pyz) and 4,4′-bipyridine (4,4′-bpy) and tridentate O,N,O-donor hydrazone ligands, L1H and L2H, obtained by the condensation of 1,1,1-trifluoro-2,4-pentanedione with salicyloylhydrazide and benzhydrazide, respectively. The ligands and their complexes have been characterized by elemental analyses, FT-IR, and UV–Vis spectroscopies. Single crystal X-ray structure analysis evidences the metal ion in a slightly deformed square pyramidal geometry in all the complexes. However complexes 1 and 2 are mononuclear with pyz and 4,4′-bpy, respectively, showing an unusual monodentate behavior, while complex 3 is dinuclear with 4,4′-bpy adopting the typical bridging coordination mode. Self assembly of the complex units by hydrogen bonding interactions produces one-dimensional arrangement in each crystal packing. The magnetic characterization of complex 3 indicates a weak antiferromagnetic exchange interaction between the Cu(II) ions (J =−0.96cm−1) mediated through the long 4,4′-bpy bridge. Electrochemical behavior of the complexes is also discussed. [Copyright &y& Elsevier]

Abstract: This review focuses on new families of spin crossover (SCO) complexes based on polynitrile anions as new anionic ligands or on polyazamacrocycles as neutral macrocyclic ligands. We have shown that the structural and electronic characteristics (original coordination modes and high electronic delocalization) of the polynitrile anions can be tuned by slight chemical modifications such as substitution of functional groups or variation of the negative charge to design new discrete or polymeric SCO systems. In our ongoing work on the design of new molecular systems based on new ligands that can be fine-tuned via chemical modifications, another promising way which has been recently developed in our group concerns the use of new neutral polydentate ligands which are able to tune the ligand field energy around the metal centre. Here we report some recent original Fe(II) SCO complexes based on such polydentate ligands. [Copyright &y& Elsevier]

Abstract: The use of polynitrile anions as ligands (L) either alone or in combination with neutral co-ligands (L′) is a very promising and appealing strategy to get molecular architectures with different topologies and dimensionalities thanks to their ability to coordinate and bridge metal ions in many different ways. The presence of several potentially coordinating nitrile groups (or even other donor groups as –OH, –SH or –NH2), their rigidity and their electronic delocalization allow the synthesis of original magnetic high dimensional coordination polymers with transition metals ions. Furthermore, these ligands have shown coordinating and bridging capabilities in novel discrete and polymeric bistable materials (materials showing original magnetic behaviours or spin crossover (SCO) transitions). Here we report an overview of the results obtained with some of these modified polynitrile ligands, showing their rich coordination chemistry and their crucial role in new molecular materials exhibiting unusual magnetic transitions. [Copyright &y& Elsevier]

Abstract: Two new copper(II) complexes, [Cu3(L1)2(H2O)2](ClO4)2 (1) and [CuL2 (H2O)] (2) have been derived from two di-compartmental Schiff base ligands H2L1 and H2L2 , respectively. Depending on slight modification of the substituent group of the potentially N2O4 donor ligands, tri- and mononuclear structures are obtained, which have been confirmed by single-crystal X-ray diffraction studies. Both complexes have been characterized by elemental analysis, IR, UV–vis and EPR spectroscopy. Complex 1 consists of an angular trinuclear array of copper ions, while complex 2 consists of a mononuclear copper center. Variable temperature magnetic susceptibility measurements have been performed to investigate the magnetic behaviour of complex 1 and the result indicates a strong antiferromagnetic exchange interaction (J =−120.1(2)cm−1) between the adjacent copper(II) centers through two double μ2-phenoxo bridges. Complex 2 is a mononuclear inclusion compound encapsulating one water molecule in the vacant external compartment of the ligand through hydrogen-bonding interactions. [Copyright &y& Elsevier]

Abstract: Reactions of CuCl2 with different CN complexes in presence of a neutral ancillary ligand lead to two novel mixed-valence Cu complexes [CuII(bpy)CuI(CN)3] n , 1 (bpy=2,2′-bipyridine) and {[CuII(tn)2][CuI 4(CN)6]} n 2 (tn=1,3-diaminopropane). For compound 1, the asymmetric unit involves two Cu ions Cu1 and Cu2 (CuI and CuII centres, respectively) which strongly differ in their environments. The Cu1 ion presents a CuC4 pseudo-tetrahedral geometry, while the Cu2 ion presents a CuN5 slightly distorted square-pyramidal geometry. The extended structure of 1 is generated by three cyano ligands which differ in their coordination modes. One CN group has a μ3 coordination mode and bridges two CuI and one CuII ion, while the two other CN groups act as μ2 bridges leading to a sophisticated 3-D structure. As for 1, the asymmetric unit of 2 involves three crystallographically different Cu ions (Cu1A and Cu1B, presumably CuI centres, and Cu2 presumably CuII centres). The Cu2 ion presents centrosymmetric CuN4 coordination environments involving four nitrogen atoms from two bidentate tn ligands; while the Cu1A and Cu1B ions are three coordinated to cyano groups. The structure can be described as formed by 18-membered “[CuI(CN)]6” planar metallocycles that are connected to their six neighbors to generate 2-D sheets; these sheets stack forming infinite hexagonal channels in which the [Cu(tn)2]2+ units are located. Magnetic measurements show an unexpected weak ferromagnetic coupling (θ =0.239(1)K) of the CuII ions through the long and “a priori diamagnetic” –NC–CuI–CN– bridges in compound 1 and an essentially paramagnetic behavior in compound 2. [Copyright &y& Elsevier]

Abstract: One-pot reaction of copper(II) chloride dihydrate CuCl2 ·2H2O with 2,2′-bipyridyl (bpy=C10H8N2) in the presence of sodium adipate Na2adip (adip2− =[O2C(CH2)4CO2]2−) and potassium 1,1,3,3-tetracyano-2-ethoxypropenide (tcnoet− =[(NC)2CC(OEt)C(CN)2]−) gives the new compound [Cu4(bpy)4(adip)3](tcnoet)2 ·2H2O (1), which was characterized by single crystal X-ray diffraction analysis. The Cu(II) metal ion presents an elongated square pyramidal CuN2O3 environment, with an oxygen atom in apical position and a base plane involving almost equivalent bond lengths. The structure can be described as a pseudo dinuclear species in which two Cu(bpy) units are triply bridged by two unsymmetrical bridging oxygen atoms of two carboxylate groups and by an almost symmetrical OCO unit with a bidentate syn–syn bridging mode. Each Cu2 dinuclear unit is triply bonded by aliphatic chains of the three adipate ligands to generate a ladder-like infinite chain. Magnetic measurements exhibit a maximum in the χ m versus T plot (at ∼5.0K) which is characteristic of weak antiferromagnetic exchange interactions between the Cu(II) ions bridged by the carboxylate groups. Fit of the magnetic data with appropriate model led to J value of −3.26(1)cm−1 (the Hamiltonian is written as H =−2JS a S b ). [Copyright &y& Elsevier]