Lanthanide complexes of 3-methoxy-salicylaldehyde

The reaction of a lanthanide(III) nitrate (Ln = Pr, Nd, Gd, Dy, Er) with 3-methoxy-salicylaldehyde(3-OCH(3)-saloH), afforded neutral complexes of the general formula [Ln(3-OCH(3)-salo)(3)], which were characterized by means of elemental analysis, FT-IR spectra, TG-DTA curves, and magnetic measurements. The released products, due to the thermal decomposition were analyzed by on-line coupling MS spectrometer to the thermobalance in argon, allowed to prove the proposed decomposition stages. In order to confirm the stability scale provided on the basis of the onset decomposition temperature, a kinetic analysis of the three decomposition stages was made using the Kissinger equation, while the complex nature of the decomposition kinetics was revealed by the isoconvertional Ozawa-Flynn-Wall method

New Type of Single Chain Magnet: Pseudo-One-Dimensional Chain of High-Spin Co(II) Exhibiting Ferromagnetic Intrachain Interactions

Two new six-coordinated high-spin Co­(II) complexes have been synthesized through the reactions of Co­(II) salts with dipyridylamine (dpamH) and 5-nitro-salicylaldehyde (5-NO₂-saloH) or 3-methoxy-salicylaldehyde (3-OCH₃-saloH) under argon atmosphere: [Co­(dpamH)₂(5-NO₂-salo)]­NO₃ (<b>1</b>) and [Co­(dpamH)₂(3-OCH₃-salo)]­NO₃·1.3 EtOH·0.4H₂O (<b>2</b>). According to the crystal packing of compound <b>1</b>, two coordination cations are linked with two nitrate anions into a cyclic dimeric arrangement via N–H···O and C–H···O hydrogen bonds. In turn, these dimers are assembled into (100) layers through π–π stacking interactions between inversion-center related pyridine rings of the dpamH ligands. The crystal packing of compound <b>2</b> reveals a 1D assembly consisting solely from the coordination cations, which is formed by π–π stacking interactions between pyridine rings of one of the dpamH along the [010] and another 1D assembly of the coordination cations and nitrate anions through the N–H···O hydrogen-bonding interactions along the [001] direction. All complexes were magnetically characterized, and a new approximation method was used to fit the magnetic susceptibility data in the whole temperature range 2–300 K on the basis of an empirical expression which allows the treatment of each cobalt­(II) ion in axial symmetry as an effective spin <i>S</i>_eff = ¹/₂. In zero-field, dynamic magnetic susceptibility measurements show slow magnetic relaxation below 5.5 K for compound <b>2</b>. The slow dynamics may originate from the motion of broad domain walls and is characterized by an Arrhenius law with a single energy barrier Δ_r/<i>k</i>_B = 55(1) K for the [10–1488 Hz] frequency range. In order to reveal the importance of the crystal packing in the SCM behavior, a gentle heating process to 180 °C was carried out to remove the solvent molecules. The system, after heating, undergoes a major but not complete collapse of the network retaining to a small percentage its SCM character

New Type of Single Chain Magnet: Pseudo-One-Dimensional Chain of High-Spin Co(II) Exhibiting Ferromagnetic Intrachain Interactions

Two new six-coordinated high-spin Co­(II) complexes have been synthesized through the reactions of Co­(II) salts with dipyridylamine (dpamH) and 5-nitro-salicylaldehyde (5-NO₂-saloH) or 3-methoxy-salicylaldehyde (3-OCH₃-saloH) under argon atmosphere: [Co­(dpamH)₂(5-NO₂-salo)]­NO₃ (<b>1</b>) and [Co­(dpamH)₂(3-OCH₃-salo)]­NO₃·1.3 EtOH·0.4H₂O (<b>2</b>). According to the crystal packing of compound <b>1</b>, two coordination cations are linked with two nitrate anions into a cyclic dimeric arrangement via N–H···O and C–H···O hydrogen bonds. In turn, these dimers are assembled into (100) layers through π–π stacking interactions between inversion-center related pyridine rings of the dpamH ligands. The crystal packing of compound <b>2</b> reveals a 1D assembly consisting solely from the coordination cations, which is formed by π–π stacking interactions between pyridine rings of one of the dpamH along the [010] and another 1D assembly of the coordination cations and nitrate anions through the N–H···O hydrogen-bonding interactions along the [001] direction. All complexes were magnetically characterized, and a new approximation method was used to fit the magnetic susceptibility data in the whole temperature range 2–300 K on the basis of an empirical expression which allows the treatment of each cobalt­(II) ion in axial symmetry as an effective spin <i>S</i>_eff = ¹/₂. In zero-field, dynamic magnetic susceptibility measurements show slow magnetic relaxation below 5.5 K for compound <b>2</b>. The slow dynamics may originate from the motion of broad domain walls and is characterized by an Arrhenius law with a single energy barrier Δ_r/<i>k</i>_B = 55(1) K for the [10–1488 Hz] frequency range. In order to reveal the importance of the crystal packing in the SCM behavior, a gentle heating process to 180 °C was carried out to remove the solvent molecules. The system, after heating, undergoes a major but not complete collapse of the network retaining to a small percentage its SCM character