New Series of Triply Bridged Dinuclear Cu(II) Compounds: Synthesis, Crystal Structure, Magnetic Properties, and Theoretical Study

Five new triply bridged dinuclear Cu(II) compounds have been synthesized, and their magnetic properties have been measured and characterized. The magnetic coupling constants (<i>J</i>) of these compounds plus a previously structurally characterized compound of the same type have been derived by appropriate fitting of the experimentally measured molar susceptibility variation with the temperature. Two of the compounds are ferromagnetically coupled, and three are antiferromagnetically coupled with <i>J</i> values in the [+150, −40] cm^–1 range. The validity of the structural aggregate Addison’s parameter as a qualitative magneto-structural correlation is confirmed. The origin of the magnetic interactions and the magnitude of the magnetic coupling have been analyzed by means of density functional theory-based calculations using a variety of state of the art exchange-correlation potentials. It is shown that the long-range separated LC-ωPBE provides the overall best agreement with experiment for this family as well as for a set of previously reported hetero triply bridged dinuclear Cu(II) compounds, especially for ferromagnetic systems

Drastic Effect of Lattice Propionitrile Molecules on the Spin-Transition Temperature of a 2,2′-Dipyridylamino/s-triazine-Based Iron(II) Complex

Reaction of iron­(II) selenocyanate (obtained from Fe­(ClO₄)₂ and KNCSe) with 2-(<i>N</i>,<i>N</i>-bis­(2-pyridyl)­amino)-4,6-bis­(pentafluorophenoxy)-(1,3,5)­triazine (<b>L1</b>^<b>F</b>) in propionitrile produces the compound [Fe­(<b>L1</b>^<b>F</b>)₂(NCSe)₂]·2CH₃CH₂CN (<b>1</b>^<b>NCSe</b><b>·2PrCN</b>), which shows spin-crossover (SCO) properties characterized by a <i>T</i>_1/2 of 283 K and a Δ<i>T</i>₈₀ (i.e., temperature range within which 80% of the transition considered occurs) of about 65 K. Upon air exposure, <b>1</b>^<b>NCSe</b><b>·2PrCN</b> gradually converts to a new SCO species that exhibits different properties, as reflected by <i>T</i>_1/2 = 220 K and Δ<i>T</i>₈₀ = 70 K. Various characterization techniques, namely, IR spectroscopy, thermogravimetric analysis, and thermodiffractometric studies, reveal that the new phase is obtained through the loss of the lattice propionitrile molecules within several days upon air exposure or several hours upon heating above 390 K