Hui-Lien Tsai

A family of isostructural one-dimensional (1D) lanthanide compounds with the formula [Ln^III(L)(NO₃)(DMF)₂]_∞, where Ln = Tb (1), Dy (2), Ho (3) and Er (4), was synthesised and structurally characterised. The magnetic behaviour of these compounds is demonstrated, and their static and dynamic properties are discussed and analyzed. The results of dc magnetic susceptibility measurements regarding compounds 1–4 indicate the existence of thermal depopulation of the crystal field-induced splitting of m_J levels of Ln ions, while the observed frequency-dependent out-of-phase ac magnetic susceptibility signals under certain magnetic fields for compounds 1, 2, and 4 show a slow relaxation of the magnetisation with an energy barrier of 6.15, 54.45, and 28.14 K, respectively. Also, complex 2 shows peak maxima of χ_M′′ signals in temperature-dependent as well as frequency-dependent ac magnetic susceptibility measurements under an appropriate magnetic field, indicating that the relaxation process is dominantly thermally activated.

Two Mn₄ single-molecule-magnet (SMM)-based coordination polymers, {[Mn₄O(salox)₃(N₃)₃(DMF)₂(H₂O)(dpp)]·0.5MeOH}_n (1·0.5MeOH; H₂salox = salicylaldoxime; dpp = 1,3-di-4-pyridylpropane; DMF = N,N-dimethylformamide) and {[Mn₄O(Me-salox)₃(N₃)₃(dpp)_1.5]·1.5Et₂O}_n (2·1.5Et₂O; Me-H₂salox = hydroxyphenylethanone oxime), are self-assembled from Mn(ClO₄)₂·6H₂O/H₂salox and Mn(ClO₄)₂·6H₂O/Me-H₂salox systems with dpp and NaN₃ in DMF/MeOH, respectively. Both compounds comprise a mixed-valence tetranuclear manganese core, [Mn^IIMn^III₃O]⁹⁺, which serves as a building unit for subsequent assembly via oximate and azido ligands. The flexible dpp ligand links with a Mn₄ unit, leading to the formation of a one-dimensional helical structure in 1·0.5MeOH and a three-dimensional pcu network in 2·1.5Et₂O. The magnetic data analysis shows that antiferromagnetic interactions within the Mn₄ units resulted in S = ³/₂ and ⁷/₂ ground states for 1·0.5MeOH and 2·1.5Et₂O, respectively. Both compounds show SMM behavior, as evidenced by frequency-dependent out-of-phase signals in alternating-current magnetic susceptibility and magnetic hysteresis loop studies with an energy barrier of U_eff = 37 K for 2·1.5Et₂O.

A manganese single-chain magnet, [Mn₆O₂(4-MeOsalox)₆(N₃)₂(MeOH)₄]_n (4-MeO-H₂salox = 2-hydroxy-4-methoxybenzaldehyde oxime), is synthesized via the assembly of Mn₆ single-molecule magnets, which exhibits a large magnetic coercivity.