title: Synthesis and comparative study of Co(pym)(VO3)2 and [Co(H2O)2(VO3)2]·2H2O.
abstract: The three-dimensional Co(pym)(VO(3))(2), 1, hybrid compound, where pym is pyrimidine, has been synthesized under mild hydrothermal conditions at 120 °C. The compound has been characterized by FT-IR spectroscopy, elemental analysis, thermogravimetric measurements, thermodiffractometry, UV-Vis spectroscopy, temperature-dependent magnetic susceptibility and magnetization, and finally a study of specific heat has been performed. The crystal structure of 1 was solved using single-crystal X-ray diffraction data, taking into account that the crystals of this compound are twins of two components. It crystallizes in the monoclinic system, space group C2/c, a = 12.899(5) Å, b = 9.859(2) Å, c = 7.051(1) Å, β = 111.41(3)°, Z = 4. The crystal structure is built up from edge sharing VO(5) trigonal bipyramid double chains and [CoO(4)pym](n) chains. This resembles the structure of the [Co(H(2)O)(2)(VO(3))(2)]·2H(2)O compound, 2. For this reason a comparative study of their properties was carried out. Magnetic measurements of 1, performed in the 2.0 to 300 K range, reveal the existence of a weak ferromagnetic order near 3 K. This fact was confirmed with magnetization measurements, which show irreversibility characteristic of soft ferromagnets. Magnetic measurements of 2 show a 3D antiferromagnetic ordering at 2.5 K. The magnetization shows a small change of curvature indicating the occurrence of a metamagnetic transition. Specific heat measurements of both compounds confirm the 3D nature of the magnetic order. The comparative study of the magneto-structural correlations reveals that the pyrimidine molecules are responsible for the different magnetic behaviour between 1 and 2.
authors.affiliation: Dpto. de Mineralogía y Petrología, Facultad de Ciencia y Tecnología, Universidad del País Vasco/Euskal Herriko Unibertsitatea, Apdo. 644, 48080 Bilbao, Spain.
authors.forename: Edurne S
authors.initials: ES
authors.lastname: Larrea
authors.forename: José L
authors.initials: JL
authors.lastname: Mesa
authors.forename: José L
authors.initials: JL
authors.lastname: Pizarro
authors.forename: Roberto
authors.initials: R
authors.lastname: Fernández de Luis
authors.forename: Jesús
authors.initials: J
authors.lastname: Rodríguez Fernández
authors.forename: Teófilo
authors.initials: T
authors.lastname: Rojo
authors.forename: María I
authors.initials: MI
authors.lastname: Arriortua
mesh_terms: D060326:Chemistry Techniques, Synthetic; D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006358:Hot Temperature; D060328:Magnetic Phenomena; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D017968:Vanadium Compounds / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D017968:Vanadium Compounds; D003035:Cobalt