title: 1D magnetic interactions in Cu(II) oxovanadium phosphates (VPO), magnetic susceptibility, DFT, and single-crystal EPR.
abstract: We report the crystal face indexing and molecular spatial orientation, magnetic properties, electron paramagnetic resonance (EPR) spectra, and density functional theory (DFT) calculations of two previously reported oxovanadium phosphates functionalized with Cu(II) complexes, namely, [Cu(bipy)(VO2)(PO4)]n (1) and [{Cu(phen)}2(VO2(H2O)2)(H2PO4)2 (PO4)]n (2), where bipy = 2,2'-bipyridine and phen = 1,10-phenanthroline, obtained by a new synthetic route allowing the growth of single crystals appropriate for the EPR measurements. Compounds 1 and 2 crystallize in the triclinic group P1̅ and in the orthorhombic Pccn group, respectively, containing dinuclear copper units connected by two -O-P-O- bridges in 1 and by a single -O-P-O- bridge in 2, further connected through -O-P-O-V-O- bridges. We emphasize in our work the structural aspects related to the chemical paths that determine the magnetic properties. Magnetic susceptibility data indicate bulk antiferromagnetism for both compounds, allowing to calculate J = -43.0 cm(-1) (dCu-Cu = 5.07 Å; J defined as Hex(i,j) = -J Si·Sj), considering dinuclear units for 1, and J = -1.44 cm(-1) (dCu-Cu = 3.47 Å) using the molecular field approximation for 2. The single-crystal EPR study allows evaluation of the g matrices, which provide a better understanding of the electronic structure. The absence of structure of the EPR spectra arising from the dinuclear character of the compounds allows estimation of weak additional exchange couplings |J'| > 0.3 cm(-1) for 1 (dCu-Cu = 5.54 Å) and a smaller value of |J'| ≥ 0.15 cm(-1) for 2 (dCu-Cu = 6.59 Å). DFT calculations allow evaluating two different exchange couplings for each compound, specifically, J = -36.60 cm(-1) (dCu-Cu = 5.07 Å) and J' = 0.20 cm(-1) (dCu-Cu =5.54 Å) for 1 and J = -1.10 cm(-1) (dCu-Cu =3.47 Å) and J' = 0.01 cm(-1) (dCu-Cu = 6.59 Å) for 2, this last value being in the range of the uncertainties of the calculations. Thus, these values are in good agreement with those provided by magnetic and single-crystal EPR measurements.
authors.affiliation: †Facultad de Química y Biología, Universidad de Santiago de Chile, USACH, Santiago, Chile.|‡Centro para el Desarrollo de Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile.
authors.forename: Diego
authors.initials: D
authors.lastname: Venegas-Yazigi
authors.affiliation: ‡Centro para el Desarrollo de Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile.|§Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile.
authors.forename: Evgenia
authors.initials: E
authors.lastname: Spodine
authors.affiliation: ‡Centro para el Desarrollo de Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile.|§Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile.
authors.forename: Marianela
authors.initials: M
authors.lastname: Saldias
authors.affiliation: ‡Centro para el Desarrollo de Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile.|⊥Departamento de Ciencias Químicas, Universidad Andrés Bello, Santiago, Chile.
authors.forename: Andrés
authors.initials: A
authors.lastname: Vega
authors.affiliation: ‡Centro para el Desarrollo de Nanociencias y Nanotecnología, CEDENNA, Santiago, Chile.|⊥Departamento de Ciencias Químicas, Universidad Andrés Bello, Santiago, Chile.
authors.forename: Verónica
authors.initials: V
authors.lastname: Paredes-García
authors.affiliation: ¶Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, and Instituto de Física del Litoral, CONICET-Universidad Nacional del Litoral, 3000 Santa Fe, Argentina.
authors.forename: Rafael
authors.initials: R
authors.lastname: Calvo
authors.affiliation: ∥Instituto de Física, Universidade Federal de Goiás, CP 131, 74001-970 Goiânia, Brazil.
authors.forename: Ricardo Costa
authors.initials: RC
authors.lastname: de Santana
mesh_terms: D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D060328:Magnetic Phenomena; D008958:Models, Molecular; D010710:Phosphates / Q000737:chemistry*; D011789:Quantum Theory; D014638:Vanadates / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D010710:Phosphates; D014638:Vanadates; D003300:Copper