José L. Mesa

(C2H10N2)[Cr(HPO3)F3]: The First Organically Templated Fluorochromium(III) Phosphite†

� 3 gL � 1 ) with C32H66 ,C 44H90 ,C 50H102 (1.3 i 10 � 2 gL � 1 ) were spin-coated onto the basal plane of highly oriented pyrolytic graphite (HOPG, Advanced Ceramics Co., USA, quality ZYH at 40 rps). The coated graphite samples were dried for 10 min at 408C before SFM investigations were carried out with a Nanoscope IIIa (Digital Instruments, Santa Barbara, CA) in the tapping mode. An E-scanner over a range of scan lengths from 5 to 0.3 mm, and commercial Si cantilevers (length 125 mm and width 30 mm) with spring constants between 17 and 64 N m � 1

Hydrothermal synthesis of a new layered inorganic–organic hybrid cobalt(II) phosphite: (C2H10N2)[Co3(HPO3)4]: Crystal structure and spectroscopic and magnetic properties

The (C2H10N2)[Co3(HPO3)4] phosphite templated by ethylenediamine has been prepared by hydrothermal synthesis. It crystallizes in the triclinic space group P-1 with the parameters: a=5.351(2), b=5.347(4), c=14.010(6) A, α=80.98(5), β=85.66(4), γ=60.04(4)°, V=343.0(3) A3 and Z=1. The compound shows a layered structure stacked along the c-axis. The ethylenediammonium cations are placed between the sheets. Ionic interactions and hydrogen bonds are present between the ethylenediammonium cations and the inorganic layers. The layers are formed by Co3O12 trimeric entities which contain face-sharing CoO6 octahedra interconnected by (HPO3)2− tetrahedral phosphite anions. The spectroscopic study by diffuse reflectance allowed us to obtain the Dq=725 cm−1 and the Racah parameters, B=880 and C=3950 cm−1 for the high spin octahedral Co(II) ions. Magnetic measurements reveal the presence of antiferromagnetic exchange interactions in the trimeric units of (C2H10N2)[Co3(HPO3)4].

Organically templated open-framework phosphites

Here we present a summary of the work carried out in the last few years on the synthesis and characterization of a new type of organically templated inorganic–organic solid based on the (HPO3)2−phosphite oxoanion, with special focus on the magnetostructural properties of those systems containing open d-shell transition metal ions. As a result of the inherent connectivity of the metal-phosphite framework, the magnetic behaviour of the great majority of these materials is characterized by weak antiferromagnetic interactions that become relevant only at low temperature.

Crystal Structure and Spectroscopic Properties of the Monoaquobis (N-thiocyanate) (2,2′-dipyridylamine)copper(II) Complex

The monoaquobis (N-thiocyanate)(2,2′-dipyridylamine)copper(II) complex has been synthesized and characterized. Its crystal structure has been resolved at room temperature. The complex crystallizes in the monoclinic space group P21/n, with a = 10.688(1) A, b = 11.104(2) A, c = 12.982(2) A β = 102.63(1)° and Z = 4. The structure consists of discrete molecules in which the copper(II) ion is pentacoordinated with a distorted square pyramidal geometry. The ESR and diffuse reflectance spectra are in good agreement with the structural results. The covalence factor has been calculated from the ESR and reflectance measurements (K = 0.79).

Structure and magnetic properties of the ferromagnetically coupled nickel dimer [Ni(terpy)(NCO)(H2O)]2(PF6)2

SummaryThe crystal structure of the dimeric [{Ni(C15H11N3)(NCO)(H2O)}2](PF6)2 has been determined by x-ray diffraction methods. Crystal data are as follows: P 1,a=11.904(4) Å,b=10.392(4) Å,c=8.531(3) Å, α=111.87(2)o, β=90.61(3)o, γ=107.37(5)o, U=926.7(4) Å3, Z=2, Dm=1.77(2), Dx=1.78 g. cm−3, μ(Mo-Kα)=12.1 cm−1, F(000)=494. Least-squares refinement of 1230 reflections with I≥1.5σ(1) gave a final R =0.035 (Rω=0.038). The structure is formed by cationic [{Ni(C15H11N3)(NCO)(H2O)}2]2+ and anionic PF6− units, linked through hydrogen bonds between the water molecule and the hexafluorophosphate ion. The resulting coordination geometry around each nickel(II) ion is ferragonally elongated octahedral. The N-bridging cyanate groups occupy simultaneously an equatorial position in the coordination sphere of one of the nickel atoms and an axial position in the other. The remaining axial positions are occupied by the water molecules. Powder susceptibility data, between 2.0 and 300 K, show the existence of ferromagnetic exchange between nickel centres. The magnetic parameters are J/K=6.6K, D/K =−17.6 K, z′J′/K=0.57 and g-2.21.

Structure and magnetic properties of two new polynuclear copper(II) complexes [Cu(terpy)(NCO)(H2O)](Y) (Y = NO3, PF6)

Abstract Compounds [Cu(terpy)(NCO)(H 2 O)](NO 3 ) ( I ) and [Cu(terpy)(NCO)(H 2 O)](PF 6 ) ( II ) (terpy = 2,2′:6′,2″-terpyridine) have been synthesized and the crystal structures have been determined. Complex I is monoclinic with space group P 2 1 / n and lattice parameters a = 9.698(2), b = 10.391(2), c = 16.681- (2) A, β = 95.54(4)°, U = 1673(1) A 3 and Z = 4. Complex II is triclinic, with space group P 1 and lattice parameters a = 9.129(1), b = 10.489(2), c = 11.106(3) A, α = 104.90(2)°, β = 86.61(1)°, γ = 113.93(1)°, U = 938.1(5) A 3 and Z = 2. The complexes consist of [Cu(terpy)(NCO)(H 2 O)] + and NO 3 − or PF 6 − ions. The [Cu(terpy)(NCO)(H 2 O)] + cationic units are stacked to make a chain or dimeric arrangements for the nitrate and hexafluorophosphate compounds, respectively. Magnetic susceptibility measurements (2–100 K) and EPR spectra provide evidence of the existence of very weak antiferromagnetic exchange coupling for both complexes. The magnetic behaviour is discussed on the basis of the structural findings.

Enhancement of the Luminescent Properties of a New Red-Emitting Phosphor, Mn2(HPO3)F2, by Zn Substitution

The Mn(2)(HPO(3))F(2) phase has been synthesized as single crystals by using mild hydrothermal conditions. The compound crystallizes in the orthorhombic Pnma space group, with unit cell parameters of a = 7.5607(8), b = 10.2342(7), and c = 5.5156(4) Å, with Z = 4. The crystal structure consists of a three-dimensional framework formed by alternating (010) layers of [MnO(3)F(3)] octahedra linked up by three connected [HPO(3)] tetrahedra. Luminescence measurements were performed at different temperatures between 10 and 150 K. The 10 K emission spectrum of the octahedrally coordinated Mn(II) cation exhibits a broad band centered at around 615 nm corresponding to the (4)T(1) → (6)A(1) transition. In order to explore the effect of the Mn(II) concentration and the possibility of enhancing the luminescence properties of the Mn(II) cation in Mn(2)(HPO(3))F(2), different intermediate composition members of the finite solid solution with the general formula (Mn(x)Zn(1-x))(2)(HPO(3))F(2) were prepared and their luminescent properties studied. The magnetic and specific heat behavior of M(2)(HPO(3))F(2) (M = Mn, Fe) have also been investigated. The compounds exhibit a global antiferromagnetic ordering with a spin canting phenomenon detected at approximately 30 K. The specific heat measurements show sharp λ-type peaks at 29.7 and 33.5 K for manganese and iron compounds, respectively. The total magnetic entropy is consistent with spin S = 5/2 and S = 2 of Mn(II) and Fe(II) cations.

Thermal response, catalytic activity, and color change of the first hybrid vanadate containing Bpe guest molecules.

Four isomorphic compounds with formula [{Co2(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, CoBpe 1; [{CoNi(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, CoNiBpe 2; [{Co0.6Ni1.4(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, NiCoBpe 3; and [{Ni2(H2O)2(Bpe)2}(V4O12)]·4H2O·Bpe, NiBpe 4, have been obtained by hydrothermal synthesis. The crystal structures of CoBpe 1 and NiBpe 4 were determined by single-crystal X-ray diffraction (XRD). The Rietveld refinement of CoNiBpe 2 and NiCoBpe 3 XRD patterns confirms that those are isomorphic. The compounds crystallize in the P1̅ space group, exhibiting a crystal structure constructed from inorganic layers pillared by Bpe ligands. The crystal structure contains intralayer and interlayer channels, in which the crystallization water molecules and Bpe guest molecules, respectively, are located. The solvent molecules establish a hydrogen bonding network with the coordinated water molecules. Thermodiffractometric and thermogravimetric studies showed that the loss of crystallization and coordinated water molecules takes place at different temperatures, giving rise to crystal structure transformations that involve important reduction of the interlayer distance, and strong reduction of crystallinity. The IR, Raman, and UV-vis spectra of the as-synthesized and heated compounds confirm that the structural building blocks and octahedral coordination environment of the metal centers are maintained after the structural transformations. The color change and reversibility of the water molecules uptake/removal were tested showing that the initial color is not completely recovered when the compounds are heated at temperatures higher than 200 °C. The thermal evolution of the magnetic susceptibility indicates one-dimensional antiferromagnetic coupling of the metal centers at high temperatures. For NiCoBpe 3 and NiBpe 4 compounds magnetic ordering is established at low temperatures, as can be judged by the maxima observed in the magnetic susceptibilities. CoNiBpe 2 was proved as catalyst being active for cyanosilylation reactions of aldehydes.

Topological description of a 3D self-catenated nickel hybrid vanadate Ni(bpe)(VO3)2. Thermal stability, spectroscopic and magnetic properties

The three-dimensional Ni(bpe)(VO3)2 hybrid compound, where bpe is 1,2-di(4-pyridyl)ethene, (C12H10N2), has been synthesized using mild hydrothermal conditions under autogeneous pressure at 140 °C during five days, obtaining green emerald prismatic single-crystals suitable for X-ray structure determination. The compound crystallizes in the orthorhombic system, space groupPbcn, with a = 14.9066(5), b = 7.6269(2) and c = 26.9624(10) A, Z = 8, and R1 = 0.0373 for 4149 observed reflections. Single-crystal X-ray diffraction reveals that the crystal structure is composed of a 3D self-catenated 10-connected uninodal net constructed from 36-hxl like {NiV2O6} inorganic sheets linked through bpe ligands. The thermal evolution of the crystal parameters shows three different tendencies during the heating process: (i) initial contraction, (ii) thermal expansion, (iii) structural collapse due to the thermal instability of the organic ligand. The IR spectrum shows the vibrational modes of the bpe organic molecules and those of the (VO4)3− tetrahedral oxoanions. Diffuse reflectance electronic absorption spectroscopy shows the characteristic bands of the Ni(II) d8-high spin cation in slightly distorted octahedral geometry. From the positions of the bands in the electronic spectrum the Dq (940 cm−1) and Racah, B (930 cm−1) and C (3350 cm−1), parameters have been calculated. Magnetic measurements indicate the existence of antiferromagnetic interactions between the Ni(II) centres of the dinuclear units, with a value of the J/k = −59.4, with g = 2.076.

Magnetostructural correlations in parallel square-planar halo-bridged copper(II) dimers. Part II: Structure and magnetic properties of [Cu2(terpy)2Br2](PF6)2

Abstract The crystal and molecular structure of bis-μ- bromo-bis [(2,2′:6′,2″ - terpyridyl) copper (II) ] bis (hexafluorophosphate) has been determined from three dimensional single-crystal X-ray diffraction data, collected by counter techniques. The blue crystals belong to the monoclinic system, space group P21/a, with four formula units in a unit cell of dimensions a=20.40(2), b=13.35(2), c=6.453(8) A and β=97.74(9)°. The structure was solved using a refinement procedure and starting with the atomic positions of the isostructural complex [Cu(terpy)- Cl]2(PF6)2, to final agreement factors R=0.071 (Rw=0.077). The structure consists of dimeric molecules bridged by two bromine atoms. The coordination geometry about the copper(II) ion is based on a distorted square pyramid with the bridging ligands occupying the apical and equatorial positions. The other three basal coordination positions are occupied by nitrogen atoms from the terpiridyl ligand. The apical CuBr bond distance is 2.83(9) A, and the equatorial CuBr bond distance is 2.36(4) A. The three copper-nitrogen bond lengths are 1.90(4), 2.01(4) and 2.01(8) A. Both, magnetic susceptibility and ESR data evidenced the existence of exchange coupling. The best fit of the susceptibility data to the susceptibility expression for a pair of exchange coupled S=1/2 ions leads to an evaluation of the singlet-triplet energy gap (2J=−7.3 cm-1). A correlation is proposcd relating the magnetic behaviour to the topology of the coordination polyhedron about the copper(II) ion in bis (μ-halo)- bridged parallel planar dimers.