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A leitmotiv in the field of molecular magnetism is the study of the electron exchange (EE) magnetic interactions among distant metal centers through the corresponding bridging ligands in polynuclear coordination compounds. The present review provides a historical perspective on the use of dinuclear copper(II) complexes with either simple inorganic or extended organic bridging ligands as experimental and theoretical models for the fundamental research on the relative importance of the spin delocalization and spin polarization mechanisms of the EE interaction across σ- and π-type orbital pathways. Particular focus is placed on the work by Professor Miguel Julve, outstanding researcher and an excellent teacher, best friend and colleague, in recognition of his invaluable contributions to molecular magnetism on the occasion of his 65th anniversary.

Five new complexes were obtained from solution of transition metal salts (M=Co(II), Cu(II)) with 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt) in different molar ratios. X-ray structural elucidation revealed low-dimensional compounds with the metal ions assembled in monomers, dimers or chains. Two similar polymorphs were obtained for the monomer synthesized from Cu(II) chloride. Temperature-dependent magnetic susceptibility measurements were conducted for the non-monomeric compounds, and efficient super-exchange interaction was found for the mostly planar dinuclear Co(II) complex.

A new copper(II) complex of formula {[Cu 2 (H 2 btc) 2 (dmf) 2 ] 4dmf} n (1)[H 4 btc = 1,2,4,5-benzenetetracarb-oxylic acid, dmf = dimethylformamide] has been synthesised and its structure determined by X-raydiffraction. The structure displays a new square grid of ‘‘paddle-wheel’’ tetracarboxylate-bridgeddicopper(II) units with an intradimer copper–copper separation of 2.619(2) A. The dmf molecules areretained through weak axial coordinative bonds and hydrogen bonding interactions with the carboxylicgroups of the porous neutral network of 4 4 net topology. The magnetic behaviour of 1 corresponds to astrong antiferromagnetic coupling within each dicopper(II) unit (J = 343 cm 1 with the Hamiltonianbeing defined by H = J S 1 S 2 ). Complex 1 does not adsorb N but it exhibits certain absorption of COwith a hysteretic desorption behaviour typical of flexible MOFs. 2014 Elsevier Ltd. All rights reserved. 1. IntroductionThe rational design and synthesis of porous coordination poly-mers, known as metal–organic frameworks (MOFs), is a very inter-esting subject of current research in the field of crystal engineering[1,2]. Due to their diverse structural architectures and net topolo-gies, this new class of multifunctional materials has potentialapplications in different areas, like catalysis, gas storage, ionexchange, molecular electronics and spintronics [3–9]. The selec-tion of an appropriate ligand is one of the most important stepsin order to obtain the desired compound in the reticular synthesisof porous coordination polymers. Aromatic carboxylate ligandshave been widely used for the construction of new coordinationpolymers of variable dimensionality. Among them, 1,2,4,5-benzenetetracarboxylic acid (hereafter noted H

The preparation and crystal structures of six new copper(II) compounds of formula [Cu(dppn)2(ClO4)]ClO4 (1), [Cu2(dppn)(OH)(ClO4)3(H2O)3]·H2O (2), [Cu2(dppn)2(H2O)2](ClO4)4 (3), [Cu2(dppn)2(ClO4)4] (4), {[Cu2(dppn)(N3)4]·H2O/[Cu2(dppn)(N3)4(H2O)]}n (5) and {[Cu2(dppn)(OH)(dca)3]·H2O}n (6) [dppn = 3,6-bis(2′-pyridyl)pyridazine and dca = dicyanamide] are reported. 1 is a mononuclear complex where two bidentate dppn molecules and a monodentate perchlorate build an intermediate square pyramidal/trigonal bipyramidal (sp/tbp) five-coordinate environment around the copper(II) ion, the overall positive charge being balanced by a free perchlorate anion. 2–4 are dinuclear complexes with either one (2) or two bis-bidentate dppn ligands (3, 4) and a single hydroxo bridge (2). One (2) or two water molecules (3) and three (2) or four perchlorate groups (4) complete the metal coordination sphere, describing elongated octahedral (2 and 4) or intermediate sp/tbp environments (3). Free perchlorate anions neutralize the pos...

The crystal structure of (µ3-Oxo)-hexakis(µ2-cyanoacetato)-triaqua-tri-iron(III) nitrate pentahydrate shows that the trinuclear ferric complex has an equilateral molecular structure which is manifested in the 57Fe Mössbauer spectrum single doublet. The magnetic measurements reveal antiferromagnetic exchange interactions of –22.85 cm-1, between the metal centers, that compel the system to a total spin ground state of S = ½.

A novel series of copper(II) complexes of formula [Cu(tren)(mpda)](ClO4)2 · 1/2H2O (1), [Cu2(tren)2(mpda)](ClO4)4 · 2H2O (2), and [Cu2(tren)2(ppda)](ClO4)4 · 2H2O (3) containing the tetradentate tris(2-aminoethyl)amine (tren) terminal ligand and the potentially bridging 1,n-phenylenediamine [n = 3 (mpda) and 4 (ppda)] ligand have been prepared and spectroscopically characterized. X-ray diffraction on single crystals of 1 and 3 show the presence of mono- (1) and dinuclear (3) copper(II) units where the mpda (1) and ppda (3) ligands adopt terminal monodentate (1) and bridging bis(monodentate) (3) coordination modes toward [Cu(tren)]2+ cations with an overall non-planar, orthogonal disposition of the phenylene group and the N–Cu–N threefold axis of the trigonal bipyramid of each copper(II) ion [values of the Cu–N–C–C torsion angle ( ϕ ) in the range of 50.8(3)–79.2(2) (1) and 80.9(2)–86.5(2)° (3)]. Variable-temperature magnetic susceptibility measurements on the dinuclear complexes 2 and 3 show the occurrence of moderate ferromagnetic (J = +8.3 cm−1, 2) and strong antiferromagnetic (J = −51.4 cm−1, 3) couplings between the two copper(II) ions across the meta- and para-phenylenediamine bridges, leading to S = 1 (2) and S = 0 (3) ground spin states [H = −JS1 · S2 with S1 = S2 = SCu = 1/2]. Density functional theory (DFT) calculations on the triplet (2) and broken-symmetry (BS) singlet (3) ground spin states, support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction through the predominantly π-type orbital pathway of the 1,n-phenylenediamine bridge. Finally, a new magneto-structural correlation between the magnitude of the magnetic coupling (J) and the Cu–N–C–C torsion angle ( ϕ ) has been found which reveals the role of σ- versus π-type orbital pathways in the modulation of the magnetic coupling for m- and p-phenylenediamine-bridged dicopper(II) complexes.

Two novel dinuclear copper(II) complexes of formulae [Cu2(tren)2(bpda)](ClO4)4 (2) and [Cu2(tren)2(tpda)](ClO4)4 (3) containing the tripodal tris(2-aminoethyl)amine (tren) terminal ligand and the 4,4′-biphenylenediamine (bpda) and 4,4″-p-terphenylenediamine (tpda) bridging ligands have been synthesized and structurally, spectroscopically, and magnetically characterized. Their experimentally available electronic spectroscopic and magnetic properties have been reasonably reproduced by DFT and TDDFT calculations. Single crystal X-ray diffraction analysis of 2 shows the presence of dicopper(II) cations where the bpda bridging ligand adopts a bismonodentate coordination mode toward two [Cu(tren)]2+ units with an overall non-planar, orthogonal anti configuration of the N–Cu–N threefold axis of the trigonal bipyramidal CuII ions and the biphenylene group. The electronic absorption spectra of 2 and 3 in acetonitrile reveal the presence of four moderately weak d–d transitions characteristic of a slightly distorted trigonal bipyramid stereochemistry of the CuII ions. TDDFT calculations on 2 identify these transitions as those taking place between the four lower-lying, doubly occupied a2 (dyz)2, b2 (dxz)2, b1 (dxy)2, and a1 ( d x 2 - y 2 )2 orbitals and the upper, singly occupied a1 ( d z 2 )1 orbital of each trigonal bipyramidal CuII ion. Variable-temperature magnetic susceptibility measurements of 2 and 3 show the occurrence of moderate (J = −8.5 cm−1) to weak intramolecular antiferromagnetic couplings (J = −2.0 cm–1) [H = −JS1·S2 with S1 = S2 = SCu = ½] inspite of the relatively large copper–copper separation across the para-substituted biphenylene- (r = 12.3 A) and terphenylenediamine (r = 16.4 A) bridges, respectively. DFT calculations on 2 and 3 support the occurrence of a spin polarization mechanism for the propagation of the exchange interaction between the two unpaired electrons occupying the d z 2 orbital of each trigonal bipyramidal CuII ion through the predominantly π-type orbital pathway of the oligo-p-phenylenediamine bridges, as reported earlier for the parent compound [Cu2(tren)2(ppda)](ClO4)4·2H2O (1) with the 1,4-phenylenediamine (ppda) bridging ligand. Finally, a rather slow exponential decay of the antiferromagnetic coupling (–J) with the number of phenylene repeat units, –(C6H4)n– (n = 1–3), has been found both experimentally and theoretically along this series of oligo-p-phenylenediamine-bridged dicopper(II) complexes. These results further support the ability of linear π-conjugated oligo-p-phenylene spacers to transmit the exchange interaction between the unpaired electrons of the two CuII centers with intermetallic distances in the range of 7.5–16.4 A.

International audience; The copper(II) complexes of formula [Cu2(2,5-dpp)(H2O)4(CF3SO3)4] · 2H2O (1) and [Cu2(2,5-dpp)(H2O)2(tcnoet)4]n (2) [2,5-dpp = 2,5-bis(2-pyridyl)pyrazine and tcnoet− = 1,1,3,3-tetracyano-2-ethoxypropenide anion] have been prepared and their structures determined by X-ray crystallographic methods. Compound 1 is a dinuclear complex where the 2,5-dpp molecule acts as a bis-bidentate bridge between the two copper centers, the electroneutrality being achieved by four terminally bound triflate anions. Each copper(II) ion presents an elongated octahedral CuN2O4 environment with two nitrogen atoms from 2,5-dpp and two water molecules in the basal plane and two triflate-oxygen atoms in the axial positions. Compound 2 is a zigzag chain of copper(II) ions with regular alternating 2,5-dpp and double tcnoet groups as bridges. Each copper(II) ion exhibits an elongated octahedral CuN5O surrounding with four nitrogen atoms, two from 2,5-dpp, one from a terminally bound tcnoet and the other from a bridging tcnoet occupying the equatorial positions and a water oxygen and a nitrogen from a monodentate tcnoet in the axial sites. The values of the copper–copper separation across 2,5-dpp are 6.763(1) (1) and 6.754(1) Å (2) whereas that through the double tcnoet bridge is 9.559(1) Å (2). The investigation of the magnetic properties of 1 and 2 in the temperature range 1.9–295 K reveal a Curie law behaviour for 1 and a very weak ferromagnetic interaction for 2. The poor ability of the 2,5-dpp ligand to mediate magnetic interactions between the copper(II) ions in the 2,5-dpp-bridged copper(II) complexes contrast with the somewhat better ability of the pyrazine ring in related pyrazine-bridged copper(II) complexes.

Three new copper(II) complexes of formulae [Cu(bpcam)(tcm)(H2O)] · 2H2O (1), [Cu(bpcam)(tcm)(H2O)] (2) and [Cu(bpcam)(tcm)]n (3) [bpcam = bis(2-pyrimidylcarbonyl)amidate and tcm = tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Complexes 1 and 2 are mononuclear species where each copper atom is five-coordinated in a somewhat distorted square pyramidal environment with a tridentate bpcam ligand and a terminally bound tcm group building the basal plane and a water molecule in the apical position. Compound 3 is a uniform copper(II) chain where the [Cu(bpcam)]+ units are connected through single μ-1,5-tcm bridges which link one equatorial position at one copper atom with the apical position of the adjacent copper. The intrachain meal–metal separation in 3 is 7.678(2) A. Magnetic susceptibility measurements of 3 in the temperature range 1.9–295 K show the occurrence of a weak intrachain antiferromagnetic interaction [J = −0.39 cm−1 with the Hamiltonian being defined as H ˆ = - J ∑ i S ˆ i · S ˆ i + 1 ]. This value of the magnetic coupling is analyzed through simple orbital symmetry considerations and compared with those observed through this bridge in other magneto-structurally characterized copper(II) complexes.

C44H28ClMnN4, monoclinic, P21/c (no. 14), a = 12.3044(6) A, b = 21.688(1) A, c = 17.0016(8) A, $ = 123.536(3)°, V = 3781.9 A, Z = 4, Rgt(F) = 0.0645, wRref(F ) = 0.0939, T = 293 K. Source of material Tetraphenylporphyrin (TPP) was synthesized from pyrrole (5 mL, 72 mmol) and benzaldehyde (8 mL, 70 mmol) following the procedure described by Adler et al. in 1967 [1]. Complexation with the metal was performed using manganese (II) chloride in dimethylformamide (80% yield), following the procedure described by Adler et al. in 1970 [2]. Experimental details The structure was solved by direct methods. All H atomswere refined as riding on their parent atoms, with C–H=0.93-0.98A, Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C) using SHELXL defaults [3]. There is a small amount of void space per unit cell which is filled with disordered solvent molecules. The intensity contribution of the disordered solvent molecules was removed by applying the SQUEEZE procedure in PLATON [4]. SQUEEZE estimated the electron counts in the voids of 315 A to be 87. Discussion This work is part of a project of synthesising porphyrins and porphyrin percursors [5-11]. Our aim is to obtain materials with Single Chain Magnet behaviour such as cyano bridged metalloporphyrins or multi-porous materials for CO2 sequestring. In the title compound (Fig. 1) chloro-(5,10,15,20tetraphenylporphyrinato)-manganese, the porphyrin moiety shows a saddle conformation with pairs of pyrrole $-C atoms alternately displaced above and below the porphyrin mean plane. The Mn(III) ion is penta-coordinated, and located 0.2663(8) A above the plane formed by the four nitrogen atoms. The averaged manganese nitrogen distance is 2.005(4)A. The phenyl rings are rotated nearly 60°with respect to the porphyrin ring except for the C39–C44 ring that is disordered, with torsion angles, C16–C15–C39B–C40B -80.9(11)° and C16–C15–C39A–C40A -88.9(15)°. The metallo-porphyrins assemble in pairs with the porphyrin planes nearly parallel, the Mn···Mn distance is 5.666(3) A, i: -x+2, -y, -z. There are solvent acessible voids in the crystal structure that accomodate solvent molecules in a very disordered way, possibly two dimethylformamide molecules per unit cell. The crystal structures of the chloroform and acetone solvates are very similar to this one [12-13]. 138 Z. Kristallogr. NCS 228 (2013) 138-140 / DOI 10.1524/ncrs.2013.0004 © by Oldenbourg Wissenschaftsverlag, Munchen Crystal: green blocks, size 0.10#0.12#0.25 mm Wavelength: Mo K! radiation (0.71073 A) #: 4.55 cm Diffractometer, scan mode: Bruker APEX CCD area-detector, ' and & 2"max: 51.58° N(hkl)measured, N(hkl)unique: 40354, 7243 Criterion for Iobs, N(hkl)gt: Iobs > 2 !(Iobs), 3202 N(param)refined: 446 Programs: SHELX [3], PLATON [4] Table 1. Data collection and handling.

The reaction of the mononuclear complex [Cr(dpa)(ox)2]− (dpa = 2,2-dipyridylamine) with Ag+ in aqueous solution affords the two-dimensional compound {Ag3(H2O)[Cr(dpa)(ox)2]3}n·2nH2O (1) whose structure has been determined by single-crystal X-ray diffraction. Six crystallographically independent metal atoms (three chromium and three silver atoms) occur in 1. The three [Cr(dpa)(ox)2]− units in 1 act as ligands towards the silver atoms through the two oxalate groups. Each oxalate group acts as bridging ligand adopting five coordination modes: bis-bidentate, bis-bidentate/monodentate (outer), bis-bidentate/monodentate (inner), bidentate/bis-monodentate (outer) and bidentate/monodentate (outer). The use of the [Cr(AA)(ox)2]− (AA = bidentate nitrogen donor) building block in the design of heterometallic species of different dimensionalities is discussed in the light of the available structural results.

In the title Schiff base, C21H14N4O4, the dihedral angle between the two nitro groups and the central benzene ring are 83.6 (5) and 2.6 (6)°. The anthracene ring system and the benzene ring make a dihedral angle of 0.7 (2)°. Intra­molecular N—H⋯O and C—H⋯N hydrogen bonds occur. In the crystal, C—H⋯O hydrogen bonds link the mol­ecules, forming chains along the b-axis direction.

Six new manganese(II) complexes of formulas [Mn 2(Rmal) 2(H 2O) 2(azpy)] n (1-3), [Mn(Phmal)(H 2O)(azpy)] n (4), [Mn 2(Et 2mal) 2(H 2O) 4(azpy) 2] n (5), and [Mn(Bzmal)(H 2O) 3(azpy)] (6) [azpy = 4,4′-azobispyridine (1-6), Rmal = methylmalonate (Memal) (1), dimethylmalonate (Me 2mal) (2), and butylmalonate (Butmal) (3), Phmal = phenylmalonate (4), Et 2mal = diethylmalonate (5), and Bzmal = benzylmalonate (6)] were synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1-3 are three-dimensional compounds whose structure consists of corrugated layers of manganese(II) linked through syn-anti carboxylate (Rmal) bridges, which are pillared through the bis-monodentate azpy molecule. Complex 4 has a layered structure of manganese(II) ions connected by carboxylate (Phmal) bridges in the syn-anti coordination mode as in 1-3, the azpy group acting here as a terminally bound monodentate ligand. The structure of 5 consists of Et 2mal-Mn(II) neutral chains linked through the azpy ligand, giving rise to a complex three-dimensional network. Complex 6 is constituted by neutral [Mn(Bzmal)(H 2O) 3(azpy)] mononuclear units, which are interlinked through O-H•••O, O-H•••N, and π-π type intermolecular interactions to afford a three-dimensional supramolecular structure. The topological analysis of these crystallographic structures shows the occurrence of four different nets: a (3,4)-connected InS-type (1-3), a binodal layered hcb (4), a uninodal CdS-type (5), and a (4,5)-connected tcs topology (6). The magnetic properties of 1-5 were investigated in the 2.0-300 K temperature range. Overall antiferromagnetic behavior occurs in 1-4 with susceptibility maxima in the range 2.8-5.5 K, the exchange pathway being provided by the syn-anti carboxylate (substituted malonate) bridge [manganese-manganese separation in the range 5.4365(3)-5.5274(1) Å]. Very weak antiferromagnetic interactions are observed in 5 through the trans-bis-monodentate Et 2mal ligand, the intrachain manganese-manganese separation being 7.328(3) Å. The much larger manganese-manganese separation through the bis-monodentate azpy ligand in 1-5 (values greater than 13.5 Å) accounts for the lack of any significant magnetic interaction though this extended bridge. © 2012 American Chemical Society., Financial support by the Spanish Ministerio de Ciencia e Innovación through projects MAT2010-16981, CTQ2010-15364, DPI2010-21103-C04-03, “Factoría de Crystalización” (Consolider Ingenio2010 CSD2006-0015), Molecular Nanoscience (Consolider Ingenio CSD2007-00010), ACIISI Gobierno de Canarias (PIL2070901), and Generalitat Valenciana (PROMETEO/2009/108, and ISIC/2012/002) is gratefully acknowledged. M. Déniz thanks the Spanish Ministerio de Ciencia e Innovación for a predoctoral fellowship.

The synthesis, crystal structure, thermal analysis and spectroscopic studies of five zinc(II) complexes of formulae [Zn(Memal)(H2O)]n (1) and [Zn2(L)(Memal)2(H2O)2]n (2-5) [H2Memal = methylmalonic acid, and L = 4,4′-bipyridine (4,4′-bpy) (2), 1,2-bis(4-pyridyl)ethylene (bpe) (3), 1,2-bis(4-pyridyl)ethane (bpa) (4) and 4,4′-azobispyridine (azpy) (5)] are presented here. The crystal structure of 1 is a three-dimensional arrangement of zinc(II) cations interconnected by methylmalonate groups adopting the μ3-κ2O:κO’:κO”:κO”’ coordination mode to afford a rare (10,3)-d utp-network. The structures of the compounds 2-5 are also three-dimensional and they consist of corrugated square layers of methylmalonate-bridged zinc(II) ions which are pillared by bis-monodentate 4,4′-bpy (2), bpe (3), bpa (4) and azpy (5) ligands. The Memal ligand in 2-5 adopts the μ3-κO:κO′:κO′′:κO′′′ coordination mode. Each zinc(II) ion in 1-5 is six-coordinated with five (1)/four (2-5) methylmalonate-oxygen atoms, a water molecule (1-5) and a nitrogen atom from a L ligand (2-5) building distorted octahedral environments. The rod-like L co-ligands in 2-5 appear as useful tools to control the interlayer metal-metal separation, which covers the range 8.4311(5) Å (2) – 9.644(3) Å (5). The influence of the co-ligand on the fluorescence properties of this series of compounds has been analyzed and discussed by steady-state and time resolved spectroscopy on all five compounds in the solid state. © 2012 Académie des sciences. des sciences. Published by Elsevier Masson SAS. All rights reserved., Funding for this work provided by the Ministerio de Ciencia e Innovación through the projects MAT2010-16981, Consolider Ingenio2010–CSD2006-0015, DPI2010-21103-C04-03 and by the Agencia Canaria de Investigación, Innovación y Sociedad de la Información, Gobierno de Canarias through projects PIL2070901, SolSubC200801000088 and structuring NANOMAC is gratefully acknowledged. M.D. thanks the Spanish Ministerio de Educación y Cultura for a predoctoral fellowship.

A screening of naproxen cocrystals with coformers picolinamide, nicotinamide, isonicotinamide, and pyrazinamide is performed by the Kofler contact method and mechanochemistry. The solids obtained by mechanochemistry are characterized by differential scanning calorimetry, DSC, polarized light thermomicroscopy, PLTM, infrared spectroscopy, FTIR, and X-ray powder diffraction, XRPD. No cocrystal could be prepared under the experimental conditions investigated between naproxen and pyrazinamide, which bears two aromatic nitrogen atoms, ortho and meta to the amide group. For the o-, m-, and p-pyridinecarboxamide isomers, regardless of the aromatic nitrogen position, the coformer interacts with naproxen to give rise to new cocrystals: naproxen:picolinamide, naproxen2:nicotinamide, and naproxen:isonicotinamide. A supramolecular acid:aromatic nitrogen heterosynthon is found in all these cocrystals. The structure of the new naproxen:isonicotinamide compound was solved by single-crystal X-ray diffraction, SXD. As nic...

12 páginas, 10 figuras, 6 tablas.-- et al., Five manganese(II) complexes of formulas [Mn2(Etmal)2(H2O)2(L)]n (1–4) and {[Mn(Etmal)2(H2O)][Mn(H2O)4]}n (5) with H2Etmal = ethylmalonic acid (1–5) and L = 1,2-bis(4-pyridyl)ethane (bpa) (1), 4,4′-azobispyridine (azpy) (2), 4,4′-bipyridyl (4,4′-bpy) (3), and 1,2-bis(4-pyridyl)ethylene (bpe) (4) were synthesized and structurally characterized by single crystal X-ray diffraction. Their thermal behavior and variable-temperature magnetic properties were also investigated. The structure of the compounds 1–4 consists of corrugated layers of aquamanganese(II) units with intralayer carboxylate-ethylmalonate bridges in the anti-syn (equatorial-equatorial) coordination mode which are linked through bis-monodentate bpa (1), azpy (2), 4,4′-bpy (3), and bpe (4) ligands to build up a three-dimensional (3D) framework. The structure of compound 5 is made up by zigzag chains of manganese(II) ions with a regular alternation of [Mn(H2O)4]2+ and chiral (either Δ or λ enantiomeric forms) [Mn(Etmal)2(H2O)]2– units within each chain. In contrast to the bidentate/bis-monodentate coordination mode of the Etmal ligand in 1–4, it adopts the bidentate/monodentate coordination mode in 5 with the bridging carboxylate-ethylmalonate also exhibiting the anti-syn conformation but connecting one equatorial and an axial position from adjacent metal centers. The manganese–manganese separation through the carboxylate-ethylmalonate bridge in 1–5 vary in the range 5.3167(4)–5.5336(7) Å. These values are much shorter than those across the extended bis-monodentate N-donors in 1–4 with longest/shortest values of 11.682(3) (3)/13.9745(9) Å (4). Compounds 1–5 exhibit an overall antiferromagnetic behavior, where the exchange pathway is provided by the carboxylate-ethylmalonate bridge. Monte Carlo simulations based on the classical spin approach (1–5) were used to successfully reproduce the magnetic data of 1–5., Financial support by the Spanish Ministerio de Ciencia e Innovación through projects MAT2007-60660, MAT2010-16981, CTQ2010-15364, DPI2010-21103-C04-03, “Factoría de Crystalización” (Consolider Ingenio2010 CSD2006-0015), Molecular Nanoscience (Consolider Ingenio CSD2007-00010), ACIISI Gobierno de Canarias and Generalitat Valenciana (PROMETEO/2009/108) is gratefully acknowledged. M.D. and J.F.-S. thank the Spanish Ministerio de Ciencia e Innovación (M.D.) and the Generalitat Valenciana (J.F.-S.) for predoctoral fellowships. J.P. also thanks the Proyecto Estructurante NANOMAC (ACIISI-Gobierno de Canarias) for a postdoctoral contract.

The preparation and structural characterization of three new copper(II) complexes of formula [Cu(3)(dipyatriz)(2)(H(2)O)(3)](ClO(4))(6) x 2 H(2)O (1), {[Cu(4)(dipyatriz)(2)(H(2)O)(2)(NO(3))(2)(ox)(2)](NO(3))(2) x 2 H(2)O}(n) (2), and [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](NO(3))(3) x 4 H(2)O (3) [dipyatriz = 2,4,6-tris(di-2-pyridylamine)-1,3,5-triazine and ox = oxalate] are reported. The structure of 1 consists of trinuclear units [Cu(3)(dipyatriz)(2)(H(2)O)(3)](6+) and uncoordinated perchlorate anions. The two dipyatriz molecules in 1 act as tris-bidentate ligands with the triazine cores being in a quasi eclipsed conformation. Each copper atom in 1 exhibits a distorted square pyramidal geometry CuN(4)O with four pyridyl-nitrogen atoms from two dipyatriz ligands building the basal plane and a water molecule occupying the axial position. The values of the intratrimer copper-copper separation are 8.0755(6) and 8.3598(8) A. Compound 2 exhibits a layered structure of copper(II) ions which are connected through bis-bidentate dipyatriz ligands and bidentate/outer monodentate oxalato groups. The copper atoms in 2 exhibit six- [Cu(1)N(4)O(2)] and five-coordination [Cu(2)N(2)O(3)]. A water molecule and three pyridyl-nitrogen atoms [Cu(1)] and two pyridyl-nitrogen plus two oxalate-oxygen atoms [Cu(2)] define the equatorial plane whereas either an oxalate-oxygen and a pyridyl-nitrogen [Cu(1)] or a nitrate-oxygen [Cu(2)] fill the axial positions. The copper-copper separation through the bridging oxalato is 5.6091(6) A whereas those across dipyatriz vary in the range 7.801(1)-9.079(1) A. The structure of compound 3 contains discrete cage-like hexacopper(II) units [Cu(6)(dipyatriz)(2)(H(2)O)(9)(NO(3))(3)(ox)(3)](3+) where two trinuclear [Cu(3)(dipyatriz)](6+) fragments are connected by three bis-bidentate oxalate ligands, the charge being balanced by three non-coordinated nitrate anions. The values of the intracage copper-copper distance are 5.112(3)-5.149(2) A (across oxalato) and 7.476(2)-8.098(2) A (through dipyatriz). Magnetic susceptibility measurements of polycrystalline samples of 1-3 in the temperature range 1.9-295 K show the occurrence of a weak antiferromagnetic interaction across dipyatriz in 1 [J = -0.08(1) cm(-1), the Hamiltonian being defined as (wedge)H = -J ((wedge)S(1).(wedge)S(2) + (wedge)S(1) x (wedge)S(3) + (wedge)S(2) x (wedge)S(3))] and weak ferro- (2) and strong antiferromagnetic (3) interactions through the oxalato bridge in 2 [J = +0.45(2) cm(-1)] and 3 [J = -390(1) cm(-1)]. The use of the dipyatriz-containing copper(II) species as a building block to design homo- and heterometallic magnetic compounds is analyzed and discussed.

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(2)(tppz)(H(2)O)(2)(CF(3)SO(3))(4)] (1), [Cu(tppz)(CrO(4))](n) x 3nH(2)O (2) and [Cu(4)(tppz)(4)(H(2)O)(4)(MoO(4))(2)](CF(3)SO(3))(4) x 7 H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where the copper atoms are bridged by two oxygen atoms of the chromate group (mu(1,2)-CrO(4)), the value of the intrachain metal-metal separation being 4.2614(5) A. Each copper(II) ion in 2 exhibits a somewhat distorted square pyramidal geometry with three nitrogen atoms from a tridentate tppz ligand and a chromate oxygen atom in the basal plane and an oxygen atom of a symmetry-related chromate group in the apical position. Complex 3 is a cyclic tetranuclear compound where peripheral [Cu(tppz)(H(2)O)](2+) units are connected through two molybdate groups, each one adopting the mu(1,1,2)-MoO(4) bridging mode. Regular alternating five [Cu(1) and Cu(4)] and six [Cu(2) and Cu(3)] coordinated copper(II) ions occur in 3 with distorted square pyramidal CuN(3)O(2) and elongated octahedral CuN(3)O(3) surroundings, respectively. The four copper atoms in 3 have in common the presence of a molybdate-oxygen and three tppz-nitrogen atoms in the basal [Cu(1) and Cu(4)]/equatorial [Cu(2) and Cu(3)] planes and a water molecule in the apical [Cu(1) and Cu(4)]/one axial [Cu(2) and Cu(3)] positions whereas the remaining axial position is occupied by a molybdate-oxygen [Cu(2) and Cu(3)]. The shorter intramolecular copper-copper separation is 3.371(1) A [Cu(2)...Cu(3)], the other ones varying in the range 5.537(1)-6.301(1) A. The investigation of the magnetic properties of 1-3 in the temperature range 1.9-295 K has shown the occurrence of intermediate antiferro- [J = -48.0(1) cm(-1) with H = -JS(1) x S(2) (1)], weak ferro- [J = +0.28(1) cm(-1) with H = -JSigma(i)S(i) x S(i+I) (2)] and coexistence of weak ferro- and antiferromagnetic interactions [J(1) = +2.38(2) cm(-1), J(2) = +0.56(2) cm(-1) and J(3) = -1.53(2) cm(-1) with H = -J(1) (S(2) x S(3)) + J(2) (S(1) x S(3) + S(2) x S(4)) + J(3) (S(1) x S(2) + S(3) x S(4)) (3)] between the copper(II) ions across bis-tridentate tppz (1), mu(1,2)-CrO(4) (2), di-mu(1,1)-MoO(4) and mu(1,2)-MoO(4) (3) bridges. The values of the magnetic interactions are analyzed in terms of simple orbital symmetry considerations and compared with those reported for parent systems.

The preparation, crystal structure and magnetic properties of four heteroleptic copper(II) complexes with the tricyanomethanide (tcm(-)) and the heterocyclic nitrogen donors 3,6-bis(2-pyridyl)pyridazine (dppn), 2,5-bis(2-pyridyl)pyrazine (2,5-dpp), 2,3-bis(2-pyridyl)pyrazine (2,3-dpp) and 2,3-bis(2-pyridyl)quinoxaline (2,3-dpq) are reported, {[Cu(2)(dppn)(OH)(tcm)(2)] x tcm}(n) (1), {[Cu(2,5-dpp)(tcm)] x tcm}(n) (2), {[Cu(2)(2,3-dpp)(2)(tcm)(3)(H(2)O)(0.5)] x tcm x 0.5H(2)O}(n) (3) and [Cu(2,3-dpq)(tcm)(2)](n) (4). 1 has a ladder-like structure with single mu-1,5-tcm ligands forming the sides and a bis-bidentate dppn and a single mu-hydroxo providing the rung. Each copper atom in 1 exhibits a distorted square pyramidal CuN(4)O surrounding: the basal plane is built by the hydroxo-oxygen, a nitrile-nitrogen atom from a tcm group and one pyrazine and a pyridyl nitrogen atoms from the dppn whereas the apical position is filled by a nitrile-nitrogen atom from a symmetry-related tcm ligand. The structures of 2-4 consists of zig-zag (2 and 3)/linear (4) chains of copper(II) ions which are bridged by either bis-bidentate 2,5-dpp (2) and 2,3-dpp (3) molecules or single mu-1,5-tcm (4) groups. The copper atoms in 2 and 4 are five coordinated with distorted trigonal bipyramidal (2) and square pyramidal (4) CuN(5) surroundings. The axial positions in 2 are occupied by two pyridyl-nitrogen atoms from two 2,5-dpp ligands whereas the trigonal plane is built by a nitrile-nitrogen from a terminally bound tcm group and two pyrazine nitrogen atoms from two 2,5-dpp molecules. The basal plane in 4 is defined by a pyridyl and a pyrazine nitrogen atoms from the bidentate 2,3-dpq ligand and two nitrile nitrogen atoms from two tcm groups (one terminal and the other bridging) whereas the apical position is filled by a nitrile nitrogen from another tcm ligand. The crystallographically independent copper atoms in 3 [Cu(1) and Cu(2)] exhibit elongated octahedral geometries being defined by four nitrogen atoms from two 2,3-dpp groups [Cu(1) and Cu(2)] either two terminally bound tcm ligands [Cu(1)] or a water molecule and a monodentate tcm ligand [Cu(2)] in cis positions. Magnetic susceptibility measurements for 1-4 in the temperature range 1.9-295 K reveal the occurrence of strong [J ca.-1000 cm(-1) (1); H = -JS(A) x S(B)] and weak [J = -0.13 (2), -0.67 (3) and -0.18 cm(-1) (4); H = -J Sigma(I)S(i) x S(i+1)] antiferromagnetic interactions in agreement with the different nature of the exchange pathways involved, diazine and single mu-hydroxo (1) and the extended 2,5-dpp (2), 2,3-dpp (3) and single mu-1,5-tcm (4) bridges with copper-copper separations of 3.363(8) (1), 7.111(1) (2), 6.823(1) and 7.056(1) (3) and 7.446(1) A (4).

The structure of the title compound, [Cu(C14H9NO4)(C12H8N2)] n , consists of zigzag polymeric chains along the c axis. The asymmetric unit contains one Cu(II) atom which is coordinated by one 2,2'-imino-dibenzoate ligand and a one phenanthroline unit. Two intra-molecular N-H⋯O hydrogen bonds occur. The supra-molecular structure is characterized by weak C-H⋯O hydrogen bonds and π-π stacking inter-actions, forming a three-dimensional supramolecular network. The shortest centroid-centroid distances between neighbouring phenanthroline aromatic rings and 2,2'-imino-dibenzoate rings are 3.684 (1) and 3.640 Å, respectively. The shortest intra-chain Cu⋯Cu distance is 7.2885 (9) and the shortest Cu⋯Cu distance between Cu atoms in different chains is 7.1103 (6) Å.

The asymmetric unit of the title compound, (C(6)H(9)N(2))[Co(C(7)H(3)NO(4))(C(7)H(4)NO(4))]·C(7)H(5)NO(4)·3H(2)O, contains one (6-carb-oxy-pyridine-2-carboxyl-ato)(pyridine-2,6-dicarboxyl-ato)cobaltate(II) anion, one phenyl-hydrazinium cation, one pyridine-2,6-dicarb-oxy-lic acid mol-ecule and three uncoordin-ated water mol-ecules, part of which are disordered. The Co(II) ion is coordinated by a pyridine-2,6-dicarboxyl-ate ion and a 6-carb-oxy-pyridine-2-carboxyl-ate ligand almost perpendicular to each other [the angle between the least-squares planes is 87.38 (4)°] and is surrounded by two O atoms and two N atoms in the equatorial plane and two O atoms in axial positions, resulting in a distorted octa-hedral coordination geometry. There is an extensive three-dimensional network of O-H⋯O and N-H⋯O hydrogen bonds, which link the components.

Four new high-spin cobalt(II) complexes of formulae [Co2(bta)(4,4′-bpy)2(H2O)2]n (1), {Hbpe[Co(Hbta)(bpe)(H2O)2]}n (2), {[Co(H2bta)(azpy)(H2O)2]·azpy}n (3) and {[Co2(bta)(bpa)2(H2O)4]·8H2O}n (4) with H4bta = 1,2,4,5-benzenetetracarboxylic acid, 4,4′-bpy = 4,4′-bipyridine, bpe = trans-1,2-bis(4-pyridyl)ethene, azpy = 4,4′-azobispyridine and bpa = trans-1,2-bis(4-pyridyl)ethane, have been prepared and characterized by single crystal X-ray diffraction. Compounds 1–4 exhibit two-dimensional networks where the fully (1 and 4) or partially (2 and 3) deprotonated tetracarboxylic ligand connects two (2 and 3) or four (1 and 4) cobalt(II) ions through two trans-carboxylate (1–3) or all the carboxylate groups (4) whereas the co-ligands 4,4′-bpy (1), bpe (2), azpy (3) and bpa (4) act as two-fold connectors in trans- (bpe and azpy) and gauche- (bpa) conformations. The cobalt(II) ions in 1 are five-coordinated with two nitrogen atoms from two 4,4′-bpy ligands in the axial positions and a water molecule and two carboxylate-oxygens building the trigonal plane. Six-coordinated cobalt(II) ions occur in 2–4 with two pyridyl-nitrogen atoms, two carboxylate-oxygens and two trans-coordinated water molecules in a somewhat distorted octahedral surrounding. The magnetic properties of 1–4 have been investigated in the temperature range 1.9–300 K. Compound 1 shows a weak antiferromagnetic interaction between the five-coordinated cobalt(II) ions (0.13 ≤ |J| ≤ 0.28 cm−1, Ĥ = −JŜ1·Ŝ2), the exchange pathway involved being the double carboxylate bridges in the syn–syn conformation [cobalt–cobalt separation] of 3.6465(9) A. As the magnetic interactions between the cobalt(II) ions through the phenyl ring of the bta group in 2–4 and those across the extended bpe (2), azpy (3) and bpa (4) bridges are negligible, the strong decrease of χMT upon cooling observed for 2–4 is mainly due to the depopulation of the higher Kramer doublets of the six-coordinated cobalt(II) ions.

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(pyim)(tcm)(2)](n) (1), [Cu(bpy)(tcm)(2)](n) (2), [Cu(4)(bpz)(4)(tcm)(8)] (3), {[Cu(terpy)(tcm)].tcm}(n) (4) and {[Cu(2)(tppz)(tcm)(4)].3/2H(2)O}(n) (5) [pyim = 2-(2-pyridyl)imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2''-terpyridine and tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complexes, 1, 2 and 4 are uniform copper(II) chains with single- (1 and 4) and double-(2) micro-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) A (4). Each copper atom in 1, 2 and 4 is five-coordinate with bidentate pyim (1)/bpy (2) and tridentate terpy (4) ligands and nitrile-nitrogen atoms from bridging (1,2 and 4) and terminal (1) tcm groups building a distorted square pyramidal surrounding. The structure of 3 is made up of neutral centrosymmetric rectangles of (2,2'-bipyrazine)copper(II) units at the corners, the edges being built by single- and double-micro-1,5-tcm bridges with copper-copper separations of 7.969(1) and 7.270(1) A, respectively. Five- and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in . Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double micro-1,5-tcm bridges, the intrachain copper-copper distances being 6.549(7) and 7.668(1) A, respectively. The two crystallographically independent copper atoms in 5 have an elongated octahedral geometry with three tppz nitrogen atoms and a nitrile-nitrogen atom from a bridging tcm group in the equatorial positions, and two nitrile nitrogen atoms from a terminal and a bridging tcm ligand occupying the axial sites. The investigation of the magnetic properies of 1-5 in the temperature range 1.9-295 K has shown the occurrence of weak ferro- [J = +0.11(1) cm(-1) (2)] and antiferromagnetic interactions [J = -0.093(1) (1), -0.083(1) (4), -0.04(1) and 1.21(1) cm(-1) (3)] across the micro-1,5-tcm bridges and intermediate antiferromagnetic coupling [-J = 37.4(1) cm(-1) (5)] through bis-tridentate tppz. The values of the magnetic interactions are analyzed through simple orbital symmetry considerations and compared with those previously reported for related systems.