Topology and Spin Polarization in Sheetlike Metal(II) Polymers: [ML2X2] (M ˭ Mn, Fe, Co or Ni, L = Pyrimidine or Pyrazine and X = NCS or NCO)

The preparation and the structural and magnetic characterization of a series of sheetlike transition metal polymers of formula [ML2X2] [M ˭ Mn(II), Fe(II), Co(II) and Ni(II): L = pyrazine (pyz) and...

[Cr(phen)(ox)2]-: a versatile bis-oxalato building block for the design of heteropolymetallic systems. Crystal structures and magnetic properties of AsPh4[Cr(phen)(ox)2]·H2O, [NaCr(phen)(ox)2(H2O)]·2H2O and {[Cr(phen)(ox)2]2[Mn2(bpy)2(H2O)2(ox)]}·6H2O

The new complexes of formula AsPh4[Cr(phen)(ox)2]·H2O (1), [NaCr(phen)(ox)2(H2O)]·2H2O (2) and {[Cr(phen)(ox)2]2[Mn2(bpy)2(H2O)2(ox)]}·6H2O (3) (AsPh4=tetraphenylarsonium cation; phen=1,10-phenanthroline; ox=oxalate dianion; bpy=2,2′-bipyridine) have been prepared and characterized by single-crystal X-ray diffraction. The structure of 1 consists of discrete [Cr(phen)(ox)2]− anions, tetraphenylarsonium cations and uncoordinated water molecules. The chromium environment in 1 is distorted octahedral with Cr–O bond distances between 1.959(3) and 1.947(3) A and Cr–N bonds of 2.083(4) and 2.072(4) A. The angles subtended at the chromium atom by the two oxalates are 83.6(2) and 83.3(1)° whereas th…

Nuclearity controlled cyanide-bridged bimetallic CrIII-MnII compounds: synthesis, crystal structures, magnetic properties and theoretical calculations.

The preparation, X-ray crystallography and magnetic investigation of the compounds PPh4[Cr(bipy)(CN)4].2 CH3CN.H2O (1) (mononuclear), [[Cr(bipy)(CN)4]2Mn-(H2O)4].4H2O (2) (trinuclear), [[Cr(bipy)(CN)4]2Mn(H2O)2] (3) (chain) and [[Cr(bipy)(CN)4]2Mn(H2O)].H2O.CH3CN (4) (double chain) [bipy=2,2'-bipyridine; PPh4 (+)=tetraphenylphosphonium] are described herein. The [Cr(bipy)(CN)4]- unit act either as a monodentate (2) or bis-monodentate (3) ligand toward the manganese atom through one (2) or two (3) of its four cyanide groups. The manganese atom is six-coordinate with two (2) or four (3) cyanide nitrogens and four (2) or two (3) water molecules building a distorted octahedral environment. In 4…

Pyrophosphate-mediated magnetic interactions in Cu(II) coordination complexes.

The reaction in water of Cu(NO(3))(2)·2.5H(2)O with 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), or 1,10-phenanthroline-5-amine (phenam), and sodium pyrophosphate (Na(4)P(2)O(7)), at various pHs, afforded three new copper(II)-pyrophosphate complexes, namely, {[Cu(bipy)(cis-H(2)P(2)O(7))](2)}·3H(2)O (1a), {[Cu(phen)(H(2)O)](4)(HP(2)O(7))(2)}(ClO(4))(2)·4H(2)O (2), and {[Cu(2)(phenam)(2)(P(2)O(7))](2)·25H(2)O}(n) (3). A solvent free crystalline phase of 1a was also isolated with formula {[Cu(bipy)(trans-H(2)P(2)O(7))](2)} (1b), which can be regarded as a pseudo-polymorph of 1a. Single crystal X-ray analyses revealed these compounds to have uncommon molecular architectures, with 3 being…

Cooperative layer-2 based routing approach for hybrid wireless mesh networks

In a Wireless Mesh Network (WMN), the convenience of a routing strategy strongly depends on the mobility of the intermediate nodes that compose the paths. Taking this behaviour into account, this paper presents a routing scheme that works differently accordingly to the node mobility. In this sense, a proactive routing scheme is restricted to the backbone to promote the use of stable routes. Conversely, the reactive protocol is used for searching routes to or from a mobile destination. Both approaches are simultaneously implemented in the mesh nodes so that the routing protocols share routing information that optimises the network performance. Aimed at guaranteeing the IP compatibility, the …

Syntheses, crystal structures and magnetic properties of one- and two-dimensional pap-containing copper(II) complexes (pap = pyrazino[2,3-  f  ][4,7]phenanthroline)

Three polynuclear complexes containing copper(II) and pyrazino[2,3-f][4,7]phenanthroline (pap) as the basic building blocks have been prepared [Cu2(pap)(H2O)2(NO3)3]n[NO3]n1, [Cu4(pap)4Cl7]nCln·15nH2O 2, and [Cu4(pap)4(H2O)4(C4O4)2]n[C4O4]n[NO3]2n·12nH2O 3, and their crystal structures and variable-temperature magnetic susceptibilities determined. Compound 1 is a single stranded zigzag chain where pap and nitrate alternate as bridges between the copper atoms. The copper coordination geometry is to a first approximation distorted square pyramidal, but with an additional semi-coordinated oxygen from non-bridging nitrate groups. The bridging nitrate coordinates in the apical position to both c…

Spinpolarisierung und Ferromagnetismus in zweidimensionalen CoII-Schichtpolymeren: [Co(L)2(NCS)2] (L = Pyrimidin, Pyrazin)

Wie vorhergesagt antiferro- und ferromagnetisch sind die beiden Schichtpolymere [Co(NCS)2(pyz)2] 1 bzw. [Co(NCS)2(pym)2] 2 (Strukturausschnitt im Bild). Die Verbindungen sowie der einkernige Komplex [Co(NCS)2(pyd)4] 3, der zu Vergleichszwecken synthetisiert wurde, konnten aus Losungen von Co(NCS)2 und Pyrazin (pyz; 1), Pyrimidin (pym; 2) bzw. Pyridazin (pyd; 3) in Methanol erhalten, strukturell charakterisiert und ihre magnetischen Eigenschaften untersucht werden.

An Azide-Bridged Copper(II) Ferromagnetic Chain Compound Exhibiting Metamagnetic Behavior

The one-dimensional chain complex [Cu(2)(mgr;(2)-1,1-N(3))(2)(mgr;(2)-1,3-NO(3))(2)(mgr;(2)-1,3-Me(3)NCH(2)CO(2))(2)](n)() (1) contains three different bridge groups,mgr;(2)-1,1-azide (end-on),mgr;(2)-nitrate, andmgr;(2)-syn,syn-carboxylate, arranged so that the azide and carboxylate groups bridge equatorially and dictate the intrachain magnetic behavior between the copper magnetic orbitals. Variable-temperature magnetic susceptibility studies at low field, and magnetization studies at variable field, reveal dominant intrachain ferromagnetism (J = 26 cm(-)(1)) but also much weaker interchain ferromagnetism (THETAV; = 2.3 K) and antiferromagnetism (J(eff) = -0.18 cm(-)(1)). The structure has…

Host molecules containing electroactive cavities obtained by the molecular assembly of redox-active ligands and metal ions

Self-assembly processes of nickel ions with the redox-active ligand 1,4,8,11-tetra(ferrocenylmethyl)-1,4,8,11-tetraazacyclotetradecane (Fc4cyclam) induces the formation of a redox-active cavity of potential use in electrocatalysis.

Spin Polarization and Ferromagnetism in Two-Dimensional Sheetlike Cobalt(II) Polymers: [Co(L)2(NCS)2] (L=Pyrimidine or Pyrazine)

Synthesis, characterization and crystal structure of 2-dicyanomethylene-1,3-bis(ferrocenylmethyl)-1,3-diazolidine

By reaction of N,N′-ethylenebis(ferrocenylmethylamine)1 with tetracyanoethylene in dichloromethane the yellow compound 2-dicyanomethylene-1,3-bis(ferrocenylmethyl)-1,3-diazolidine 2 can be isolated. The single-crystal structure of 2 has been determined. It crystallizes in the non-centrosymmetric trigonal space group P3221, a= 12.255(2), c= 13.831(7)A, Z= 3. Refinement of the atomic parameters by least-squares techniques gave a final R factor of 0.038 (R′= 0.034) for 1782 observed reflections having I > 2.5δ(I). Anomalous values of the bond distances and the vinyl carbon chemical shift in the 13C NMR spectrum of 2 are explained on the basis of a polarization due to a combination of the elect…

Ferrocene containing chelating ligands 3. Synthesis, spectroscopic characterization, electrochemical behaviour and interaction with metal ions of new ligands obtained by condensation of ferrocenecarboxaldehyde with 2-amino-benzoic acid derivatives. Crystal structures of 2-ferrocenylmethylamino-5-methyl-benzoic acid and 2-bis(ferrocenylmethyl)ammonium-5-methyl-benzoic acid perchlorate

Abstract Ferrocenecarboxaldehyde reacts with 2-amino-benzoic acid, 2-amino-5-methyl-benzoic acid or 3-amino-2-naphthoic acid to give the corresponding Schiff-base derivatives 2-ferrocenylmethylidenimino-benzoic acid (1), 2-ferrocenylmethylidenimino-5-methyl-benzoic acid (2) and 3-ferrocenylmethylidenimino-2-naphthoic acid (3). 1, 2 and 3 are stable in the solid state but easily hydrolyze in solution. This hydrolysis has been studied kinetically in a methanol-water medium. In order to increase the stability in solution to use these compounds as ligands, the imino group from 1, 2 and 3 was reduced by NaBH4 to give the amino derivatives 2-ferrocenylmethylamino-benzoic acid (4), 2-ferrocenylmet…

A Ferromagnetic [Cu3(OH)2]4+Cluster Formed inside a Tritopic Nonaazapyridinophane: Crystal Structure and Solution Studies

Prediction of Magnetic Properties in Oxovanadium(IV) Phosphates: The Role of the Bridging PO4 Anions

Oxovanadium phosphates constitute a crystallochemically very rich family that, in turn, results in a seemingly intricate magnetochemistry including from isolated dimers to 3-D systems. This magnetic diversity is due, in part, to the possible participation of phosphate groups in the spin transfer between VIV centers. This way, 31P solid-state NMR becomes a key tool in determining the exchange paths involving phosphorus orbitals. The magnetic behavior of several layered oxovanadium phosphates M(VOPO4)2·4H2O (M = Na+, Ca2+, Ba2+, and Pb2+) has been investigated. Like it occurs in the case of other previously studied lamellar derivatives, the best fit of the temperature-dependent magnetic susce…

Synthesis, spectroscopic characterization and electrochemical behaviour of nickel(II) complexes with C-meso-5,5,7,12,12,14-hexamethylcyclotetradecane (Me6[14]aneN4). Crystal structure of {Ni(Me6[14]aneN4)|I2

A series of complexes of formula {Ni(Me6[14]aneN4)X2| (Me6[14]aneN4) = C-meso-5,5,7,12,12,14-hexamethyl-1,4,-8,11-tetraazacyclotetradecane and X = N3(1), NCO (2), NCS (3), AcO (4) or I (5) has been synthesized. The crystal structure of (5) has been determined by X-ray diffraction methods. The nickel atom is surrounded by a square-planar array of nitrogen atoms, giving a low-spin complex. The macrocyclic ligand shows the most stable conformation, the six-membered rings exhibiting the chair form while the gauche conformation is adopted by the five-membered rings. Spectroscopic and magnetic data for (1)–(4) are consistent with octahedral coordination around the nickel atom, which is achieved b…