José L. Pizarro

(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

Synthesis and spectroscopic properties of copper(II) complexes derived from thiophene-2-carbaldehyde thiosemicarbazone. Structure and biological activity of [Cu(C6H6N3S2)2].

The synthesis, structure and spectroscopic properties on complexes with the formula [Cu(Lm)2] (1) and Cu(NO3)2(HLm)2 (2), where HLm = thiophene-2-carbaldehyde thiosemicarbazone, have been developed. The molecular structure of compound 1 consists of monomeric entities. The copper(II) ions exhibit distorted square-planar geometry with both bidentate thiosemicarbazone ligands placed in a centrosymmetric way. Metal to ligand pi-backdonation is proposed to explain several structural and spectroscopic features in these complexes. The EPR spectra of compound 1 show an orthorhombic g tensor indicating the presence of weak magnetic exchange interactions. The reaction of compound 1 with glutathione causes the reduction of the metal ion and the substitution of the thiosemicarbazone ligand by the thiol ligand. This mechanism seems to be related to the cytotoxicity of this complex against Friend Erithroleukemia cells (FLC) and melanome B16F10 cells.

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].

Spectroscopic and magnetic properties of copper(II) complexes derived from pyridine-2-carbaldehyde thiosemicarbazone. Structures of [Cu(NO3)(C7H8N4S)(H2O)](NO3) and [{Cu(NCS)(C7H7N4S)}2]

Abstract Complexes with the formula CuX(L) (X=N3 1, NCO 2 and NCS 3) and [Cu(NO3)(HL)(H2O)](NO3) 4, where HL=C7H8N4S, (pyridine-2-carbaldehyde thiosemicarbazone), have been characterised. Single-crystal X-ray diffraction studies on compounds 3 and 4 have been carried out. The structure of compound 4 consists of monomeric distorted square pyramidal copper(II) species. The copper(II) ions are coordinated to the NNS atoms from the tridentate thiosemicarbazone ligand and one oxygen atom of a nitrate group in the equatorial position. The oxygen atom of the water molecule occupies the apical position. The structure of compound 3 consists of non-centrosymmetric {Cu2(μ-SR)2} entities in which the copper(II) ions exhibit five-coordinate square–pyramidal geometry. The thiosemicarbazone ligand and one nitrogen atom from the thiocyanate ion are in a basal position. The sulfur atom of the tridentate ligand acts as a bridge occupying the apical position. Structural and spectroscopic results suggest the presence of relevant σ ligand-to-metal charge transfer and metal-to-ligand π-backdonation character in these compounds. The ESR spectra of compounds 3 and 4 show rhombic symmetry. For complexes 1 and 2 the ESR spectra exhibit axial signals. Magnetic measurements on compounds 1, 2 and 3 show antiferromagnetic couplings. The susceptibility data were fitted by the Bleaney–Bowers’ equation for copper(II) dimers. The obtained J/k values are −4.22, −6.10 and −7.33 K for compounds 1, 2 and 3, respectively.

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.

Magnetic properties of the LiMPO4 (M = Co, Ni) compounds

Abstract Powder samples of LiNiPO 4 , LiCoPO 4 together with LiMgPO 4 doped with 0.1% of Co 2+ were prepared by solid state reactions. Magnetic susceptibility measurements of the LiNiPO 4 and LiCoPO 4 compounds are consistent with 3D antiferromagnetic behaviour. The magnetic exchange value for the LiNiPO 4 phase is −5.61 K, with a g -value of 2.15. The EPR study of LiMgPO 4 doped with 0.1% of Co 2+ shows the large magnetic anisotropy of the Co 2+ ion in a distorted octahedral geometry. The obtained values at 4.2 K for the spin Hamiltonian parameters are g 1 = 6.16, g 2 = 4.14, g 3 = 2.53 and A 1 = 246 × 10 −4 , A 2 = 89 × 10 −4 and A 3 −4 cm −1 .

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).

Synthesis, crystal structure and spectroscopic properties of the NH4NiPO4·nH2O (n= 1,6) compounds; magnetic behaviour of the monohydrated phase

NH4NiPO4·6H2O and NH4NiPO4·H2O have been obtained by adding different concentrations of H3PO4 to dilute solutions of NiCl2·6H2O with special attention to the control of the pH in the solvent medium, which was regulated by addition of NH4OH. The NH4NiPO4·6H2O compound crystallizes in the orthorhombic Pmn21space group with cell parameters a= 6.9032(8), b= 6.0907(5) and c= 11.1402(8)A, V= 468.39(7)A3, Z= 2, R= 23 and Rw= 2.3%. The structure is three-dimensional and consists of Ni[O(w)]6 octahedra [O(w)= oxygen from a water molecule] linked to PO4 and NH4 tetrahedra by hydrogen bonds. All polyhedra are quite regular in this compound. The NH4NiPO4·H2O phase crystallizes in the Pmn2l space group with cell parameters a= 5.5698(2), b= 8.7668(2) and c= 4.7460(2)A. The structure of this compound has been refined with the Rietveld method using the coordinates of the KMnPO4·H2O phase as a starting model. The final residual factors were Rwp= 7.37, RB= 2.68%. The structure is formed from sheets of distorted NiO6 corner-sharing octahedra bridged through the oxygen atoms of the phosphate tetrahedra. These layers are pillared along the b direction and are interconnected by hydrogen bonds with the NH4+ cations, which are inserted between the sheets. The spectroscopic properties of both compounds are in good agreement with the symmetry observed in each phase. The values of the nephelauxetic ratio, β, are 0.89 and 0.94 for the hexahydrated and monohydrated compounds respectively. Magnetic susceptibility and specific heat results obtained for NH4NiPO4·H2O show an essentially two-dimensional antiferromagnetic exchange coupling, which becomes of a more three-dimensional behaviour with decreasing temperature.

Trans-stereoselectivity in the reaction between homophthalic anhydride and imines.

The reaction between homophthalic anhydride and imines in the presence of TiCl4 and diisopropyl ethyl amine is trans-selective. Under these conditions, the reaction using homochiral imines can be highly diastereoselective, thus allowing the synthesis of enantiopure 1,2,3,4-tetrahydro-1-oxoquinoline-4-carboxylic acids.

Crystal structure and properties of the [Cu(C11H10N4)Br2] compound. Stereochemistry of [Cu(planar tridentate ligand)(unidentate ligand)2] complexes

Abstract The crystal structure of the dibromo(pyridine-2-aldehyde 2′-pyridylhydrazone) copper(II) is reported. The compound crystallizes in space group P21/n, with a = 12.86(2), b = 11.944(5), c = 8.770(7) A, β = 97.17(6)°, U = 1336(3) A3, Z = 4, Dm = 2.06(1), Dx= 2.10 g cm−3, μ(Mo-Kα) = 78.92 mm−1, F(000) = 812, T = 293 K. Final R is 0.047 (Rw = 0.049) for 854 observed reflections. The structure consists of discrete molecules in which the copper(II) ion is pentacoordinate with a distorted square pyramidal geometry. The spectroscopic data are in good agreement with the structural results. The stereochemistry of several pentacoordinate complexes of type [Cu(planar tridentate ligand) (unidentate ligand)2] is examined and the distortions of the coordination polyhedra are calculated.