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The synthesis, crystal structure, and magnetic properties of a one-dimensional compound, {[Mn(hfac)2]2(biradical)}n (1), resulting from the coordination of bis(hexafluoroacethylacetonato)manganese(II) [Mn(hfac)2] with a biradical obtained by grafting two nitronyl nitroxide radicals in the 5 and 5' positions of a 2,2'-bipyridine ligand are described. Compound 1 crystallizes in the triclinic P space group with the following parameters: a = 11.905(2) A, b = 12.911(2) A, c = 20.163(3) A, alpha = 73.556(3) degrees , beta = 80.850(3) degrees , gamma = 82.126(3) degrees , Z = 2. The bipyridyl moiety acts as a chelate toward one [Mn(hfac)2] unit, while the pendent nitronyl nitroxide radicals are symmetrically bound in trans-configuration to additional [Mn(hfac)2] units. The result is infinite chains running along the c axis direction with the biradical bridging [Mn(hfac)2] units with pending bipyridine/Mn(hfac)2 cores. The magnetic behavior is characteristic of ferrimagnetic chains. Qualitatively we observe first the antiferromagnetic coupling (J2) of each manganese(II) center with two nitronyl nitroxide moieties, leading to a minimum in the chiT product of 6.63 emu K mol(-1) observed at 70 K and corresponding to a ground spin state S = 3/2 plus one extra spin S = 5/2 coming from the pending manganese(II) center. The increase of chiT at lower temperature is understood as a fictive ferromagnetic coupling related to the true antiferromagnetic coupling J1 of the pseudospin S = 3/2 with spin S = 5/2 of the pending manganese(II). Along this approach (H = -JSiSj) the best fit (300-8 K) of the experimental data leads to J1 = -0.622 +/- 0.022 cm(-1) and J2 = -203 +/- 3 cm(-1) with g(Rad) = 2.0017 +/- 0.0015 and g(Mn) = 2.0017 +/- 0.0015.

The reaction of the trimetallic species [Fe(3)O(PhCOO)(6)(H(2)O)(3)]NO(3) with 1,1,1-tris(hydroxymethyl)ethane (H(3)thme) affords either the octametallic species [Fe(8)(PhCOO)(12)(thme)(4)] 1 or the hexadecametallic species [Fe(16)(EtO)(4)(PhCOO)(16)(Hthme)(12)](NO(3))(4) 2, depending on the nature of the solvent used for crystallization. The structure of 1 can be described as a nonplanar wheel of eight Fe(III) ions bridged by a combination of PhCOO(-) and thme(3)(-) ligands, and 2 as a nonplanar wheel of sixteen Fe(III) ions bridged by PhCOO(-), Hthme(2)(-), and EtO(-) ligands. Both compounds can be broken down into simple units of two metal ions and the bridging ligands that connect them. The best fits of the chi vs T curves in the 300-10 K temperature range were obtained with the parameters g = 2.0, J(1) = -24.0 cm(-1), and J(2) = -8.59 cm(-1) for [Fe(8)] and g = 2.0, J(1) = -25.0 cm(-1), J(2) = -11.73 cm(-1), and J(3) = -69.3 cm(-1) for [Fe(16)]. Density functional theory (DFT) calculations show that the antiferromagnetic interactions between the metals in the dinuclear units decrease when two types of bridging ligands are present, as expected for an orbital counter-complementarity effect.

The dinuclear copper(II) complexes {[Cu2(1,3-tpbd)(H2O)(OAc)2](ClO4)2}0.23{[Cu2(1,3-tpbd)(H2O)2(OAc)](ClO4)3}0.77·0.77H2O (1), [Cu2(1,3-tpbd)(H2O)2(OAc)2](ClO4)2·2H2O (2), and the tetranuclear copper(II) complex [Cu4(1,3-tpbd)2(H2O)2(SO4)4]·8H2O (3) {1,3-tpbd = 1,3-bis[bis(2-pyridylmethyl)amino]benzene} were synthesised and structurally characterised by X-ray diffraction. Variable-temperature (2.0−290 K) magnetic susceptibility measurements on these complexes as well as on the dinuclear copper(II) complex [Cu2(1,3-tpbd)(H2O)2(ClO4)3]ClO4 (4) (whose structure was published earlier) were performed. In contrast to 2 and 3, significant ferromagnetic coupling with J = +9.3 cm−1 was observed for 4 (the Hamiltonian being defined as Hˆ = −J Sˆ1·Sˆ2). Density functional theory (DFT) calculations were used successfully for the interpretation of the ferromagnetic coupling observed in 4. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

A novel mu-pyrazolato-mu-hydroxo-dibridged copper(II) complex has been synthesized and structurally characterized: [(Cu(mepirizole)Br)2(mu-OH)(mu-pz)] (mepirizole=4-methoxy-2-(5-methoxy-3-methyl-1H-pyrazol-1-yl)-6-methylpyrimidine; pz=pyrazolate). The title compound crystallizes in the monoclinic system, space group P2(1)/c, with a=15.618(2) A, b=15.369(3) A, c=16.071(3) A, and beta=112.250(1) degrees. The structure is built up of dinuclear [(Cu(mepirizole)Br)2(mu-OH)(mu-pz)] units with five-coordinated copper(II) ions (CuBrN3O chromophores) linked by mu2-OH and mu2-pyrazolato bridges that are well separated from each others. The intramolecular copper-copper distance is 3.378(3) A. Magnetic susceptibility data show that the copper atoms are strongly antiferromagnetically coupled with J=-770 cm(-1). The obtained triplet-singlet energy gap is compared with those reported for a series of related dimers. The strong antiferromagnetic coupling arising from the complementarity of the hydroxo and pyrazolato bridges has been discussed on the basis of DFT calculations.

A theoretical density functional study of the exchange coupling in hexanuclear polysiloxanolato-bridged complexes of Cu(II) and Ni(II) is presented. By calculating the energies of three different spin configurations, we can obtain estimates of the first-, second-, and third-neighbor exchange coupling constants. The study has been carried out for the complete structures of the Cu pristine cluster and of the chloroenclathrated Ni complex as well as for the hypotethical pristine Ni compound and for magnetically dinuclear analogues M(2)Zn(4) (M = Cu, Ni).

The application of theoretical methods based on the density functional theory with hybrid functionals provides good estimates of the exchange coupling constants for polynuclear transition metal complexes. The accuracy is similar to that previously obtained for dinuclear compounds. We present test calculations on simple model systems based on H · · · He and CH2 · · · He units to compare with Hartree–Fock and multiconfigurational results. Calculations for complete, nonmodeled polynuclear transition metal complexes yield coupling constants in very good agreement with available experimental data. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 982–989, 2003

Two distinct one-dimensional (1) and two-dimensional (2) mixed-metal-organic polymers have been synthesized by using the "complex-as-ligand" strategy. The structure of 1 consists of isolated ladderlike Mn(II)(2)Cu(II)(2) chains separated from each other by neutral Mn(II)(2) dimers, whereas 2 possesses an overall corrugated layer structure built from additional coordinative interactions between adjacent Mn(II)(2)Cu(II)(2) ladders. Interestingly, 1 and 2 show overall ferri- and antiferromagnetic behavior, respectively, as a result of their distinct crystalline aggregation in the solid state.

The use of the [ReCl(4)(bpym)] precursor as a ligand toward the fully solvated nickel(II) metal ion affords the first example of a 2,2'-bipyrimidine-bridged Re(IV)-Ni(II) complex, [ReCl(4)(μ-bpym)NiBr(2)(H(2)O)(2)] (1), whose intramolecular ferromagnetic coupling has been substantiated from both experimental and theoretical studies.

Self-assembly of the rigid rodlike ligand N,N'-4,4'-diphenylethynebis(oxamate) (dpeba) and Cu(2+) ions affords a novel dinuclear copper(II) metallacyclophane (nBu(4)N)(4)[Cu(2)(dpeba)(2)]·4MeOH·2Et(2)O (1) featuring a very long intermetallic distance (r = 15.0 Å). Magnetic susceptibility measurements for 1 reveal a moderately weak but nonnegligible intramolecular antiferromagnetic coupling between the two metal centers across the double para-substituted diphenylethynediamidate bridge (J = -3.9 cm(-1); H = -JS(1)S(2), where S(1) = S(2) = S(Cu) = (1)/(2)). Density functional electronic structure calculations on 1 support the occurrence of a spin polarization mechanism.

The use of the [Fe(III) (AA)(CN)4](-) complex anion as metalloligand towards the preformed [Cu(II) (valpn)Ln(III)](3+) or [Ni(II) (valpn)Ln(III) ](3+) heterometallic complex cations (AA=2,2'-bipyridine (bipy) and 1,10-phenathroline (phen); H2 valpn=1,3-propanediyl-bis(2-iminomethylene-6-methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu(II) (valpn)Ln(III) (H2O)3 (μ-NC)2 Fe(III) (phen)(CN)2 {(μ-NC)Fe(III) (phen)(CN)3}]NO3 ⋅7 H2O}n (Ln=Gd (1), Tb (2), and Dy (3)) and the trinuclear complex [Cu(II) (valpn)La(III) (OH2 )3 (O2 NO)(μ-NC)Fe(III) (phen)(CN)3 ]⋅NO3 ⋅H2O⋅CH3 CN (4) were obtained with the [Cu(II) (valpn)Ln(III)](3+) assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni(II) (valpn)Ln(III) (ONO2 )2 (H2 O)(μ-NC)3 Fe(III) (bipy)(CN)]⋅2 H2 O⋅2 CH3 CN}n (Ln=Gd (5), Tb (6), and Dy (7)) resulted with the related [Ni(II) (valpn)Ln(III) ](3+) precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu(II) (valpn)La(III) (OH2)3 (O2 NO)(μ-NC)Fe(III) (phen)(CN)3 ](+), nitrate counterions, and non-coordinate water and acetonitrile molecules. The heteroleptic {Fe(III) (bipy)(CN)4} moiety in 5-7 acts as a tris-monodentate ligand towards three {Ni(II) (valpn)Ln(III)} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu(II)-Ln(III) (1-3) and Ni(II)-Ln(III) (5-7) units, as well as through the single cyanide bridge between the Fe(III) and either Ni(II) (5-7) or Cu(II) (4) account for the overall ferromagnetic behavior observed in 1-7. DFT-type calculations were performed to substantiate the magnetic interactions in 1, 4, and 5. Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out-of-phase ac signals below 4.0 K in the lack of a dc field, the values of the pre-exponential factor (τo) and energy barrier (Ea ) through the Arrhenius equation being 2.0×10(-12) s and 29.1 cm(-1), respectively. In the case of 7, the ferromagnetic interactions through the double phenoxo (Ni(II)-Dy(III)) and single cyanide (Fe(III)-Ni(II)) pathways are masked by the depopulation of the Stark levels of the Dy(III) ion, this feature most likely accounting for the continuous decrease of χMT upon cooling observed for this last compound.

Two new dinuclear copper(II) metallacyclophanes with 1,4-disubstituted 9,10-anthraquinonebis(oxamate) bridging ligands are reported that can reversibly take and release electrons at the redox-active ligand and metal sites, respectively, to give the corresponding mono- and bis(semiquinonate and/or catecholate) Cu(II)2 species and mixed-valent Cu(II)/Cu(III) and high-valent Cu(III)2 ones. Density functional calculations allow us to give further insights on the dual ligand- and metal-based character of the redox processes in this novel family of antiferromagnetically coupled di- copper(II) anthraquinophanes. This unique ability for charge storage could be the basis for the development of new kinds of molecular spintronic devices, referred to as molecular magnetic capacitors (MMCs).

Two new trinuclear copper(ii) complexes without end-capping ligands, (Bu4N)2[Cu(dmso)2{Cu(dnopba)(dmso)}2] () and (Bu4N)2[Cu(dmso)2{Cu(dcopba)(dmso)}2] () [dnopba = 4,5-dinitro-ortho-phenylenebis(oxamate), dcopba = 4,5-dichloro-ortho-phenylenebis(oxamate), Bu4N(+) = tetra-n-butylammonium and dmso = dimethylsulfoxide], were synthesized and their structures were determined by single crystal X-ray diffraction. The crystal structures of and consist of two outer bis(oxamato)(dmso)cuprate(ii) units which act as bidentate ligands toward a trans-bis(dmso)copper(ii) inner entity leading to centrosymmetric tricopper(ii) complexes with copper-copper separations across the oxamate bridges of 5.1916(3) () and 5.1776(3) A (). The peripheral copper(ii) ions in and are five-coordinate in somewhat distorted square pyramidal environments with a dmso molecule filling the apical position whereas the inner copper(ii) ion is six-coordinate in an elongated octahedral environment with two dmso molecules in the axial sites. The investigation of their magnetic properties in the temperature range 2.0-300 K shows the occurrence of a strong intramolecular antiferromagnetic coupling between the copper(ii) ions through the oxamate bridges [J1 = -296(1) () and -334(1) cm(-1) (), the Hamiltonian being defined as Ĥ = -J1(ŜCu2·ŜCu1 + ŜCu2·ŜCu1')], which leads to a low-lying spin doublet at low temperatures. Density functional theory calculations (DFT) have been used to substantiate these magnetic couplings and also to analyse the influence exerted on these interactions by the type of substituent at the 4,5-positions from the phenylene ring of the bis(oxamate) ligand.

Three new 1,4-phenylenediacrylate bridged Mn(II) and Co(II) complexes of molecular formulas {[Mn2(ppda)(phen)4(H2O)2](ppda)2(H2O)} (1), {[Co(ppda)- (dpyo)(H2O)3]·4(H2O)}n (2), and {[Co(ppda)(bpe)]·(0.5H2O)}n (3) [ppda = 1,4- phenylenediacrylate; phen = 1,10-phenanthroline; dpyo = 4,4′-dipyridyl N,N′-dioxide; bpe = 1,2-bis(4-pyridyl)ethane] have been synthesized and characterized by elemental analysis, IR spectra, single-crystal X-ray diffraction studies, and low-temperature magnetic measurements. The structural determination reveals that complex 1 is a discrete dinuclear species, 2 is a 1D polymeric chain, while 3 is a three-fold interpenetrated α-polonium network. Hydrogen-bonding interactions, formed by coordinated and/or lattice water molecules with ppda oxygen and π−π stacking interactions of aromatic rings, lead to a 3D supramolecular architecture in both complexes 1 and 2. Low-temperature magnetic study shows antiferromagnetic coupling in all the complexes. In addition, their electronic and fluorescent spectral properties have been investigated.

Two pentanuclear complexes are obtained from the reaction of hexacyanochromate(III) with one to two molar equivalents of [Ni(H 2 O) 6 ] 2+ and bidentate organic ligands that chelate the metal ion, leaving two coordination sites in cis positions. Even though the crystal structure was not solved, the full characterization supports the formation of pentanuclear discrete species. [Cr(CN) 6 ] 2 [Ni(HIM2-py) 2 ] 3 ·7H 2 O, 1, has a ground spin state S=6 owing to the ferromagnetic interaction between Cr III ( S =3/2) and N II ( S =1). The presence of six organic radicals that couple ferromagnetically with Ni II in [Cr(CN) 6 ] 2 [Ni(IM2-py) 2 ] 3 ·7H 2 O, 2, leads to an S =9 ground state. A.c. susceptibility measurements below 2K indicate the occurrence of an antiferromagnetic order at 1.5 K in 2.

[EN] The new complexes of formulae PPh4[Cr(dpa)(ox)(2)] (1), AsPh4[Cr(dpa)(OX)(2)] (2), Hdpa[Cr(dpa)(ox)(2)]-4H(2)O (3), Rad[Cr(dpa)(ox)(2)] . H2O (4) and Sr[Cr(dpa)(ox)(2)](2) . 8H(2)O (5) [PPh4 = tetraphenylphosphonium cation; AsPh4 = tetraphenylarsoniurn cation; dpa = 2,T-dipyridylamine; ox = oxalate dianion; Rad = 2-(4-N-methylpyridinium)4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-a-oxyl-3-N-oxide] have been prepared and characterised by single-crystal X-ray diffraction. The structures of 1-4 consist of discrete [Cr(dpa)(ox)(2)](-) anions, tetraphenylphosphonium. (1), tetraphenylarsonium (2), monoprotonated Hdpa (3) and univalent radical (4) cations and uncoordinated water molecules (2-4). The chromium environment in 1-4 is distorted octahedral with Cr-O bond distances between 1.982(2)-1.946(2) Angstrom and Cr-N bonds of 2.0716(17)-2.048(3) Angstrom. The angles subtended at the chromium atom by the two oxalates are 83.6(2)-81.71(8)degrees, whereas the N-Cr-N angles are 87.76(7)-86.24(9)degrees. The [Cr(dpa)(ox)(2)](-) unit of 1-4 is also present in 5 but it acts as a chelating ligand through its two oxalato groups towards divalent strontium cations, yielding heterobimetallic zig-zag chains that run parallel to the a axis. Each chain is formed of diamond-shaped units sharing the strontium atoms, while the two other corners are occupied by two crystallographically independent chromium atoms. The [Cr(dpa)(ox)(2)](-) unit in 5 retains the environment observed in 1-4 and the strontium atom is coordinated to eight oxalate oxygens from four oxalate ligands. The two crystallographycally independent chromium centres within each double chain have opposite chirality. However, the adjacent double chains are related by an inversion centre resulting in achiral layers parallel to the ac plane. The magnetic properties of 1-5 have been investigated in the temperature range 1.9-290 K. A quasi Curie law behaviour is observed for 1-3 and 5 in agreement with their crystal structures, whereas a significant antiferromagnetic interaction between the chromium(m) and the radical centre occurs in the case of 4. The synthetic possibilities offered by the use of the heteroleptic species [CrL(ox)(2)](-) (L = alpha -diimine-type ligand) as a ligand towards metal ions is analysed and discussed in the fight of the available structural results., Financial support from the Spanish Dirección General de Investigación Científica y Técnica (DGICYT) through Projects PB97-1397 and PB98-1044, the Romanian Ministry of Education (Grants 30C/CNCSIS and 1D/CNCSIS) and the TMR Program from the European Union (Contract ERBFMRXCT98-0181) is acknowledged. Thanks are also extended to the Centre d'Informàtica de la Universitat de València for computer resource support.

Reaction of MnII and pyridine derivatives such as 4-methylpyridine (4-Mepy) and 4-ethylpyridine (4-Etpy) led to the new two-dimensional systems trans-[Mn(4-Mepy)2(N3)2]n (1) and trans-[Mn(4-Etpy)2(N3)2]n (2). Compound 1 crystallizes in the triclinic system, P1 group (a = 9.269(2) A, b = 9.635(3) A, c = 18.860(4) A, Z = 4), and compound 2 crystallizes in the monoclinic system, P2(1)/c group (a = 14.416(3) A, b = 8.515(2) A, c = 15.728(4) A, Z = 4). The two compounds show honeycomb structures based on dinuclear Mn-(mu-N3)2-Mn subunits linked to the four nearest-neighbor similar subunits by four end-to-end single azido bridges, but whereas the subunits of compound 1 show the end-to-end Mn-(mu 1,3-N3)2-Mn kind of bridges, compound 2 prefers the end-on Mn-(mu 1,1-N3)2-Mn fragment. Magnetically, compound 1 is an alternating 2-D system with two different antiferromagnetic interactions, whereas compound 2 corresponds to a two-dimensional ferro-antiferromagnetic system showing spin canting and permanent magnetization below 20 K. The coupling constant parameters J1 = -10.1 cm-1, J2 = -4.7 cm-1, and g = 2.019 for 1 and J1 = -5.3 cm-1, J2 = 2.9 cm-1, and g = 2.016 for 2 have been obtained from calculations using the Monte Carlo method based on the Metropolis algorithm.

The structural and magnetic data of the trinuclear compound [Cu3(L)2(CH3COO)2(OH)2(dmf)2] (HL = N-(2-methylpyridyl)toluensulfonylamide) are reported. The compound crystallizes in the monoclinic system, space group P2(1)/n (no. 14), with a = 11.6482(6) A, b = 13.5772(6) A, c = 13.5306(7) A, alpha = 90 degrees, beta = 92.859(5) degrees, gamma = 90 degrees, and Z = 2. The three copper atoms form an exact linear arrangement. Neighboring coppers are connected by a hydroxo bridge and a bidentate syn-syn carboxylato group. The coordination spheres of the terminal copper atoms are square pyramidal with a dmf molecule as the apical ligand. The central copper has a regular square planar geometry. The mixed bridging by a hydroxide oxygen atom and a bidentate carboxylato group leads to a noncoplanarity of the adjacent basal coordination planes with a dihedral angle of 51.96(9) degrees. Susceptibility measurements (2-300 K) reveal a strong ferromagnetic coupling, J = 93(6) cm-1, in the mixed-bridged moiety leading to a quartet ground state that is confirmed by the EPR spectra. The ferromagnetic exchange coupling is discussed using DFT calculations on model compounds that have shown a countercomplementary effect of the hydroxo and acetate bridges.

Three new thermotolerant species of Corynascus isolated from Indian and Argentinian soils are described and illustrated: C. sexualis sp. nov. characterised by small ascospores and the absence of a Myceliophthora anamorph (present in all other species of the genus); C. similis sp. nov. characterised by navicular ascospores with two lateral to sub-terminal germ pores; and C. verrucosus sp. nov. distinguished by the ellipsoid ascospores with two oblique to sub-terminal germ pores. A study to compare the ITS-region sequences of all species of the genus with representative species of related genera demonstrated that this region is very conserved in this group of fungi and of low taxonomic value. A key to the eight species of the genus now known is provided. The molecular data suggest the genus is best placed in the Chaetomiaceae rather than the Ceratostomataceae.

The influence of structural parameters on the exchange coupling J between metal atoms in end-to-end azido-bridged binuclear complexes of Cu(II) and Ni(II) has been studied by means of density functional calculations. For the case of double-bridged Cu(II) compounds, four ideal pentacoordinate models have been employed in which the coordination spheres of the two metal atoms are either a trigonal bipyramid or a square pyramid, connected through equatorial or axial bridges. The distortion from those ideal geometries along a Berry pathway has also been analyzed. For the hexacoordinate Ni(II) compounds, models with two or one bridging ligands have been studied. The effect of the bridging M-N-N bond angles on the exchange coupling has been analyzed for both the Cu(II) and Ni(II) complexes.

Unusual single N-bridging thiocyanato and double pyridazine (pdz) bridges occur in the linear trinuclear nickel(II) complex of formula [Ni3(pdz)6(NCS)6]. The compound exhibits a quasi Curie law behavior, the antiferromagnetic coupling through the double 1,2-diazine links being nearly compensated by the ferromagnetic exchange through the single N-bridging thiocyanato.

Two new polymeric manganese-azido systems with formula Cs(n)-[[Mn(N3)3]n] (1) and [[N(C2H5)4]n][[Mn2-(N3)5(H2O)]n] (2) were synthesised and structurally characterised. Compound 1 crystallises in the P2(1)/n group and consists of a three-dimensional system with end-to-end and end-on azido bridges with the caesium atoms in the holes of the net. Magnetically, compound 1 is a rare case of a three-dimensional network with alternate ferro-antiferromagnetic interactions. Compound 2 crystallises in the P1 group and consists of double chains of manganese atoms bridged by end-on and, the exceptional, (mu-1,1,1)-azido bridges. Magnetically, compound 2 shows net ferromagnetic behaviour. Exact fit of the magnetic data was performed for the two compounds by means of Monte Carlo simulations based on the Metropolis algorithm on sets of 10 x 10 x 10 (1) and 1 x 1 x 320 (2) S = 5/2 classical spin centres.

A density functional study of exchange coupling was carried out for a series of heterobinuclear oximato-bridged transition metal complexes. Model calculations were used to examine the influence of the electronic configuration of the metal atoms on the coupling constants. This analysis was complemented by a study of the variation of the coupling constant with the most usual structural distortions within this family of compounds. The influence of the nature of the terminal ligands as well as that of the symmetry on the bridge were also investigated.

A theoretical density-functional study has been carried out to analyze the exchange coupling in the chains of ${\mathrm{CuGeO}}_{3}$ using discrete models. The results show a good agreement with the experimental exchange coupling constant $(J)$ together with a strong dependence of J with the Cu-O-Cu angle. The calculation of the J values for a distorted model indicates a larger degree of dimerization than those reported previously.

Melanospora pascuensis sp. nov., isolated from soil of Easter Island, is described and illustrated. The ITS1, ITS2 and 5.8 S rRNA gene sequences are also provided. The fungus can be recognized by the setose perithecial ascomata and the peculiar ring-like structure surrounding the ascospore germ pores. It is compared with other species of Melanospora and related genera.

Two new rhenium(IV) compounds of formula (AsPh(4))(2)[ReCl(4)(ox)] (1) and [ReCl(4)(mgr;-ox)Cu(bipy)(2)] (2) (AsPh(4) = tetraphenylarsonium cation, ox = oxalate anion, and bipy = 2,2'-bipyridine) have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. 1 and 2 crystallize in the monoclinic system, space groups P2(1)/c and P2(1)/n, respectively, with a = 22.250(5) Å, b = 11.245(3) Å, c = 19.089(4) Å, beta = 96.59(2) degrees, and Z = 4 for 1 and a = 9.421(2) Å, b = 16.909(4) Å, c = 16.179(4) Å, beta = 93.97(2) degrees, and Z = 4 for 2. The structure of 1 is made up of [ReCl(4)(ox)](2)(-) anions and AsPh(4)(+) cations held united by electrostatic forces. Rhenium(IV) is hexacoordinate, with two oxygens of a chelating ox and four chlorine atoms building a distorted octahedron around the metal atom. There is no contact between the [ReCl(4)(ox)](2)(-) anions, the shortest Re.Re and Cl.Cl distances being 10.345 and 7.209 Å, respectively. This anionic complex is coordinated to a [Cu(bipy)(2)](2+) cation in 2, through one oxalate-oxygen, giving a neutral heterometallic dinuclear unit. The Cu(II) ion shows a very distorted five-coordinated geometry, four bipy-nitrogens occuping the equatorial positions and the oxygen atom the apical one. The basal plane geometry is distorted toward the tetrahedron, the dihedral angle between the mean planes of the two bipy ligands is 37.6(2) degrees. These [ReCl(4)(mgr;-ox)Cu(bipy)(2)] units are arranged in such a way that a chlorine atom of one of them points toward the copper atom of the neighboring one, forming helicoid chains. The intrachain Re.Cu distances through chloro and oxalato bridges are 4.658 and 4.798 Å, respectively. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.8-300 K. 1 is a magnetically diluted Re(IV) complex, the great value of zero-field splitting of the ground level (D = 60 cm(-)(1)) accounting for the variation of chi(M)T with T in the low-temperature range. 2 behaves as a ferrimagnetic chain, with weak antiferromagnetic interactions between Re(IV) and Cu(II) through oxalato and single chloro bridges.

The simulation of the magnetic properties of S=5/2 extended 1D, 2D and 3D networks using MonteCarlo method (MC) is presented in this paper. It is shown that the MC method gives better results at low temperature than the others approximate methods for simple systems with an unique interaction between the magnetic ions. The case of alternating chains and honeycomb networks with two different J values have been also treated. The J values obtained by MC simulation for alternating chains are comparable with those derived from Drillon's law. For the honeycomb networks, the J values found by the MC approach are in good agreement with the values found for dinuclear complexes with the same bridges.

Emericella indica sp. nov. and a peculiar morphological variant of E. quadrilineata are described and illustrated. The former is characterized by large, smooth, violet ascospores and the latter by apparently budding ascospores. Analysis of the sequences of the nuclear rDNA ITS region gene of these species and E. nidulans and E. variecolor support our concepts based on morphological criteria.

Random amplified polymorphic DNA (RAPD) fingerprinting was applied to Fusarium solani from a cutaneous hyalohyphomycosis in a loggerhead sea turtle. A total of seven F. solani isolates were examined, three from culture collections and four from the turtle infection (one from the turtle's lesions and three from the sand of the tank in which the turtle was kept). The banding patterns of the isolates from culture collections were markedly different from the patterns of the isolates from both the turtle and the sand. The RAPD banding patterns were the same with all the primers used, suggesting that this opportunistic infection may be related to the presence of F. solani in the tank. RAPD techniques can be particularly useful for large-scale epidemiological studies and for identifying sources of infection.

A theoretical density functional study of the exchange coupling has been carried out for binuclear copper(II) compounds with oxamidate and related bridging ligands: oxalate, oxamate, ethylenetetraamidate, dithiooxamidate, dithiooxalate, tetrathiooxalate, bipyrimidine and bisimidazole. Model calculations have been used to examine the influence of the donor atoms at the bridging ligand and of the ligands’ orientation on the coupling constant. Estimates for the singlet–triplet gap of complete structures of cis- and trans-oxamidato-bridged complexes are reported. Comparison of these results with those obtained from qualitative models provides some insight into the limits of applicability of these methods for the study of magnetostructural correlations.

A dodecanuclear copper(II) globular-shaped structure has been obtained with the cytidine nucleoside and the templating carbonate anion. It shows receptor properties through anion-cation and multiple anion-pi interactions toward ClO 4 (-) as well as an overall antiferromagnetic coupling.

Gelasinospora bonaerensis sp. nov., isolated from a soil sample collected in Argentina, is described and illustrated and the sequences corresponding to the ITS1/ITS2 regions and the 5.8 S ribosomal RNA are provided. Its taxonomic relationships with other species of the genus are discussed.

The effect of structural parameters on the exchange coupling constant of the title complexes of Cu(II), Ni(II), and Mn(II) is studied by means of density functional calculations on model compounds....

A recently developed computational strategy is applied to examine the influence of several factors on the exchange coupling constants of oxalato-bridged copper(II) binuclear complexes (shown schematically here); molecular topology, the nature of terminal ligands and selected structural parameters are discussed.

Sediments from eight river mouths along the Catalonian coast (Spain) were surveyed for keratinolytic fungi and related Onygenales. The actidione plating technique was employed. Of 532 actidione-treated sediment samples, 268 (50.3%) were positive for the fungi. Altogether, 384 fungal strains from 35 species were isolated from the samples. Narasimhella marginospora, Aphanoascus fulvescens, Neoarachnotheca keratinophila with its anamorph Myriodontium keratinophilum, Narasimhella hyalinospora, Beauveria alba, Sporothrix schenckii, Chrysosporium lobatum and Gymnoascus littoralis were the predominant species in sediments. Abundance of N. marginospora was clearly correlated with the degree of water pollution with sewage.

The spin density distribution in transition metal complexes is discussed in qualitative terms, taking into account the coexistence of spin delocalization and spin polarization mechanisms, with the help of numerical results for several complexes obtained from density functional calculations. The covalent character of the metal-ligand bonds as well as the σ- or π-characteristics of the partially filled d orbitals must be taken into account to qualitatively predict the sign of the spin density at a particular atom within a ligand. The same patterns can be applied to binuclear complexes and can be helpful in determining the ferro- or antiferromagnetic character of the exchange coupling between two paramagnetic ions when the energy gap between the partially occupied molecular orbitals is small. An attempt is made to establish a link between the qualitative-Hay-Thibeault-Hoffmann model of exchange coupling and the of spin polarization model.

The Catalonian river sediments were found to be rich in keratinolytic fungi. The keratinolytic fungal populations showed clear seasonal changes in the river sediments. The main factors ‘regulating’ these populations in such habitat were temperature, dissolved oxygen concentration, pH, ammonium, nitrates, total fungal number, BOD5, water poisons (cyanides, detergents, phenols), salinity and, presumably, strong insolation associated with low water levels. The last was probably of special importance in the deterioration of the fungal populations in the spring/summer season. A toxic effect on keratinolytic fungi in sediments was observed.Chrysosporium keratinophilum was found to be most resistant to industrial contaminants and salinity. Therefore, this species could be used as an indicator of water pollution.

Magnetic coupling constants (2J) of hydroxo- and alkoxo-bridged copper binuclear compounds have been evaluated to determine the accuracy of different density functional methods and to study the magnetic behavior of these compounds. Comparison between the calculated and experimental coupling constants for the complete structures of five compounds shows that the most successful computational strategy is the combination of the B3LYP method with the broken-symmetry approach. Calculations for model compounds of both families yield reasonable approximations to the values of magnetic coupling constants calculated for the full molecular structures. Our calculations show a correlation between the magnetic coupling constant and the Cu−O−Cu bridging angle and with the out-of-plane displacement of the hydroxo or alkoxo groups, in agreement with the experimental data. The counterions of the hydroxo-bridged complexes, when hydrogen bonded to the bridging hydroxo group, determine the extent of the out-of-plane displacem...

Neoarachnotheca is proposed as a new genus of Onygenales. The outstanding generic characteristics are white, spherical ascomata with a wall formed by a network of hyphae and spherical, subhyaline ascospores with an irregular sheath. Nt. keratinophila, the type species, characterized by wavy peridial hyphae has been isolated from marine and river sediments and Myriodontium keratinophilum is its anamorph. Nannizziopsis tropicalis is proposed as a new species based on a strain isolated from soil in Burundi. RFLPs analysis of ITS and 5.8S rDNA support these proposals. The differences with related genera are discussed.

Potentiometric studies were carried out in dimethyl sulfoxide–water (80∶20 w/w) at 25 °C and ionic strength 0.1 mol dm–3 in NaClO4 for the Schiff bases H2sal-m-phen [N,N′-bis(salicylidene)-m-phenylenediamine], H2sal-2,4-toluen [N,N′-bis(salicylidene)toluene-2,4-diamine] and H2sal-2,6-toluen [N,N′-bis(salicylidene)toluene-2,6-diamine] and their complexes with CuII, NiII, CoII and ZnII. These studies have shown that monomer, dimer, ligand∶metal ratio 2∶1 and 1∶2 complex species are found. The first reported stability constants for these systems have been determined. The molecular structure of the complex [Co2(sal-m-phen)2]·CHCl3 has been determined by single-crystal X-ray analysis. It consists of dimeric centrosymmetric units, with the two bis(salicylideneiminato)cobalt(II) residues bridged by two m-phenylene groups and with a chloroform molecule associated with each dimer molecule. The co-ordination geometry around each cobalt(II) can be best described as a distorted tetrahedron. Variable-temperature magnetic susceptibility measurements for the solid complexes [Co2(sal-m-phen)2]·CHCl3, [Co2(sal-2,4-toluen)2]·4H2O, [Co2(sal-2,6-toluen)2], [Ni2(sal-m-phen)2]·3H2O, [Ni2(sal-2,4-toluen)2]·3H2O, [Ni2(sal-2,6-toluen)2], [Cu2(sal-2,4-toluen)2] and [Cu2(sal-2,6-toluen)2] revealed a weak intradimer antiferromagnetic interaction.

The electrochemical behaviour of a family of monomeric copper(II) complexes of the related tetraanionic chelating ligands N,N′-o-phenylenebis(oxamate) (L 1 ) and its methylamide (L 2 ) and bis(methylamide) (L 3 ) has been investigated by cyclic voltammetry in acetonitrile at 25 °C and 0.1 mol dm -3 NEt 4 ClO 4 as supporting electrolyte. The copper(III)–copper(II) reduction potentials have been found to span a potential range from +0.41 to -0.02 V (vs. saturated calomel electrode), being reversible for all cases except the copper(II)–L 1 complex. The trend in formal potentials along this series is explained in terms of the stronger donor properties of the deprotonated-amido nitrogen atoms than those of the carboxylate oxygen ones. Hence, the stabilization of the trivalent oxidation state of copper is attributed to the increasing number of deprotonated-amido donor groups. A perfect correlation has been observed within this family between the Cu III –Cu II potentials and the visible absorption maxima of the copper(II) complexes. The relative gain in crystal-field stabilization energy for the change from the d 9 (Cu II , square planar) to the low-spin d 8 (Cu III , square-planar) electronic configuration is the main factor in the overall thermodynamic stability of the copper(III) complexes. The molecular structure of the stable copper(III) complex [PPh 4 ][CuL 3 ]·MeCN has been determined by single-crystal X-ray analysis. The metal is in a nearly square-planar environment formed by the four amido nitrogen atoms of the chelating ligand, with short Cu–N bond distances (1.84–1.88 A) typical of trivalent copper.

International audience

A new compound of formula (Bu4N)2[Mn2{Cu(opba)}2ox] (1) [Bu4N(+) = tetra-n-butylammonium cation, H4opba = 1,2-phenylenebis(oxamic acid), and H2ox = oxalic acid] has been synthesized and magneto-structurally investigated. The reaction of manganese(II) acetate, [Cu(opba)](2-), and ox(2-) in dimethyl sulfoxide yielded single crystals of 1. The structure of 1 consists of heterobimetallic oxamato-bridged Cu(II)Mn(II) chains which are connected through bis-bidentate oxalate coordinated to the manganese(II) ions to afford anionic heterobimetallic layers of 6(3)-hcb net topology. The layers are interleaved by n-Bu4N(+) counterions. Each copper(II) ion in 1 is four-coordinate in a square planar environment defined by two amidate-nitrogen and two carboxylate-oxygen atoms from the two oxamate groups of the obpa ligand. The manganese(II) ion is six-coordinate in a somewhat distorted octahedral surrounding that is built by two oxalate-oxygen and four carbonyl-oxygen atoms from two [Cu(opba)](2-) units. The magnetic properties of 1 in the temperature range 1.9-300 K correspond to those expected for the coexistence of intralayer antiferromagnetic interactions of the type copper(II)-manganese(II) across oxamato and manganese(II)-manganese(II) through oxalato bridges plus a weak spin canting in the very low temperature domain. Simulation of the magnetic data through quantum Monte Carlo methodology reveals the magnitude of the intralayer magnetic interactions [J(CuMn) = -32.5(3) cm(-1), and J(MnMn) = -2.7(3) cm(-1)], their values being within the range of those previously observed in lower nuclearity systems.

The new dinuclear copper(II) metallacyclophane with the non-innocent N,N'-1,4-bis(oxamate)-9,10-anthraquinone bridging ligand possesses a dual multielectron redox behavior featuring stepwise one-electron oxidation of the antiferromagnetically coupled Cu(II) ions and two-electron reduction of the anthraquinone spacers in a π-stacked anti conformation.

Two new hexanuclear oxamatocopper(II) complexes 3 and 4 have been synthesized from the binuclear copper(II) complexes of the meta- and para-phenylenebis(oxamate) ligands, respectively. Complexes 3 and 4 possess an overall ladderlike structure made up of two oxamate-bridged linear trinuclear units ("rails") connected through two phenylenediamidate bridges ("rungs") between the central copper atoms to give metallacyclic cores of the meta- and para-cyclophane type, respectively. They show different ground spin states, S = 1 (3) or S = 0 (4), depending on the substitution pattern in the aromatic spacers. The triplet state molecule 3 containing two spin doublet Cu(II)3 units connected by two m-phenylenediamidate bridges represents a successful extension of the concept of "ferromagnetic coupling units" to metal complexes, which is a well-known approach toward high spin organic radicals.

This article focuses on the study of the release rate in a family of modified silica mesoporous supports. A collection of solids containing ethyl, butyl, hexyl, octyl, decyl, octadecyl, docosyl, and triacontyl groups anchored on the pore outlets of mesoporous MCM-41 has been prepared and characterized. Controlled release from pore voids has been studied through the delivery of the dye complex tris(2,2¿-bipyridyl)ruthenium(II). Delivery rates were found to be dependent on the alkyl chain length anchored on the pore outlets of the mesoporous scaffolding. Moreover, release rates follow a Higuchi diffusion model, and Higuchi constants for the different hybrid solids have been calculated. A decrease of the Higuchi constants was observed as the alkyl chain used to tune the release profile is longer, confirming the effect that the different alkyl chains anchored into the pore mouths exerted on the delivery of the cargo. Furthermore, to better understand the relation between pore outlets decoration and release rate, studies using molecular dynamics simulations employing force-field methods have been carried out. A good agreement between the calculations and the experimental observations was observed., Financial support from the Spanish Government (projects MAT2009-14564-C04-01 and MAT2009-14564-C04-04) and the Generalitat Valencia (project PROMETEO/2009/016) is gratefully acknowledged.

International audience; The novel mononuclear Co(II) complex cis-[Co-II(dmphen)(2)(NCS)(2)]center dot 0.25EtOH (1) (dmphen = 2,9-dimethyl-1,10-phenanthroline) features a highly rhombically distorted octahedral environment that is responsible for the strong positive axial and rhombic magnetic anisotropy of the high-spin Co-II ion (D = +98 cm(-1) and E = +8.4 cm(-1)). Slow magnetic relaxation effects were observed for 1 in the presence of a dc magnetic field, constituting the first example of field-induced single-molecule magnet behavior in a mononuclear six-coordinate Co(II) complex with a transverse anisotropy energy barrier.

Two metallacyclic complexes of general formula Na-8[(M2L3)-L-II]center dot xH(2)O [M = Ni (4) and Co (5) with x = 15 (4) and 17 (5)] have been self-assembled in aqueous solution from N,N'-1,3-phenylenebis(oxamic acid) (H4L) and M2+ ions in a ligand/metal molar ratio of 3 : 2 in the presence of NaOH acting as base. X-Ray structural analyses of 4 and 5 show triple-stranded, dinuclear anions of the meso-helicate-type (so-called mesocates) with C-3h molecular symmetry. The two octahedral metal-tris(oxamate) moieties of opposite chiralities (Delta, Lambda form) are connected by three m-phenylene spacers at intermetallic distances of 6.822(2) (4) and 6.868(2) angstrom (5) to give a metallacryptand core. In the crystal lattice, the binding of these heterochiral dinickel(II) and dicobalt(II) triple mesocates to sodium(I) ions leads to oxamato-bridged heterobimetallic three-dimensional open-frameworks with a hexagonal diamond architecture having small pores of 17.566(4) (4) and 17.640(2) angstrom (5) in diameter where the crystallization water molecules and the sodium(I) countercations are hosted. Variable temperature (2.0-300 K) magnetic susceptibility measurements reveal relatively anisotropic S = 2 Ni-2(II) (4) and S = 3 Co-2(II) (5) ground states resulting from the moderate to weak intramolecular ferromagnetic coupling between the two high-spin Ni-II (S-Ni = 1) or Co-II (S-Co = 3/2) ions across the m-phenylenediamidate bridges [J = +3.6 (4) and +1.1 cm(-1) (5); H = -JS(1)center dot S-2]. A simple molecular orbital analysis of the electron exchange interaction identifies the p-type pathways of the meta-substituted phenylene spacers involving the d(z2) and d(x2-y2) pairs of magnetic orbitals of the two trigonally distorted octahedral high-spin M-II ions (M = Ni and Co) as responsible for the overall ferromagnetic coupling observed in 4 and 5 in agreement with a spin polarization mechanism. The decrease of the overall ferromagnetic coupling from 4 to 5 is in turn explained by the additional antiferromagnetic exchange contribution involving the d(xy) pair of magnetic orbitals of the two trigonally distorted octahedral high-spin Co-II ions across the sigma-type pathway of the meta-substituted phenylene spacers., This work was supported by the MICINN (Spain) (Projects CTQ2010-15364, MAT2010-16981, CSD2007-00010, and CSD2006-00015), the University of Valencia (Project UV-INVAE11-38904), the Generalitat Valenciana (Spain) (Projects PROMETEO/2009/108, GVACOMP2011-108, GV/2012/051 and ISIC/2012/002), the ACIISI-Gobierno Autónomo de Canarias (Spain) (Project PIL-2070901), the MFR and the CNRS (France). E. P. acknowledges the MICINN for a postdoctoral (‘‘Juan de la Cierva’’) contract. M.-C. Dul and M. C. thank the MFR and the MICINN respectively, for doctoral grants.

The compound (NBu 4) 5[Gd III{Re IVBr 4(μ-ox)} 4(H 2O)]·H 2O (1), with intramolecular antiferromagnetic coupling, is the first Re(iv) system incorporating a 4f ion. © 2012 The Royal Society of Chemistry., Financial support from the Spanish Ministerio de Ciencia e Innovación and the Generalitat Valenciana through the projects CTQ2010-15364 and PROMETEO/2009/108, respectively, is gratefully acknowledged.