Joseba Orive

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.

Hybrid vanadates constructed from extended metal–organic arrays: crystal architectures and properties

The hybrid vanadates exhibit structural archetypes between the hybrid zeotypes, in which the inorganic framework is surrounding an organic cation acting as a template, and metal–organic frameworks whose crystal structures are constructed from metal nodes or clusters linked by organic bridges. Here we present the summary of the studies carried out on hybrid vanadates constructed from extended metal–organic arrays. The crystal structures are systematically described and classified according to the dimensionality of the inorganic and metal–organic frameworks. Finally, the magnetic, thermal and catalytic properties of different structural archetypes are discussed.

Fluorinated mixed valence Fe(II)–Fe(III) phosphites with channels templated by linear tetramine chains. Structural and magnetic implications of partial replacement of Fe(II) by Co(II)

Three new fluorinated mixed valence Fe(II)–Fe(III) phosphites were synthesized by employing mild hydrothermal conditions. (H4baepn)0.5[FeIII2.3FeII1.7(H2O)2(HPO3)4−(x+y)(HPO4)x(PO4)yF4] (x ≃ 0.13, y ≃ 0.3) (1) (baepn = N,N′-bis(2-aminoethyl)-1,3-propanediamine (C7N4H20)) and the Co(II)-substituted phase with the formula (H4baepn)0.5[FeIII2.0FeII0.71CoII1.29(H2O)2(HPO3)4−x(HPO4)xF4] (x ≃ 0.38) (2) were studied by single crystal X-ray diffraction. The phase with the major content of Co(II), (H4baepn)0.5[FeIII2.0FeII0.62CoII1.38(H2O)2(HPO3)4−x(HPO4)xF4] (x ≃ 0.38) (3) was obtained as a polycrystalline powder and studied by Rietveld refinement by using the structural model of 2. These compounds were characterized by ICP-Q-MS, thermogravimetric and thermodiffractometric analyses, and XPS, IR, UV/vis and Mossbauer spectroscopy. The single crystal data indicate that phases 1 and 2 crystallize in the P21/c space group with lattice parameters a = 13.6808(4), b = 12.6340(2), c = 12.7830(3) A and β = 116.983(4)° for 1 and a = 13.6823(4), b = 12.6063(3), c = 12.7535(4) A and β = 116.988(4)° for 2, with Z = 4. The reciprocal space of 1 shows satellite reflections with a modulation wavevector q = 0.284(2)a* which indicate an incommensurate long-range order. The average structure of these compounds is built up by a 3D lattice constructed by inorganic layers of Fe(III) chains and Fe(II) and Co(II) dimers joined by phosphite groups partially substituted by HPO4 and PO4 tetrahedral groups. These anionic layers stack along the [100] direction encapsulating linear tetramines in eight-membered open channels involving host–guest interactions. Magnetic measurements of 1 and 3 showed antiferromagnetic coupling as the major interactions, exhibiting a weak ferromagnetic component together with a spin glass transition at low temperature in the case of 1. Heat capacity measurements showed a small anomaly at 20.5 K for 1 and a sharp magnetic peak at 28 K for 3. Unexpectedly, the small anomaly observed in 1 increased with the magnetic field and became better defined.