Regulating the distortion degree of the square antiprism coordination geometry in Dy–Na single ion magnets

A DyNa complex (1) and a DyNa₂ 1D chain (2) have been obtained; their square antiprism coordination geometries were changed from the bicapped triangular prism of the reported DyNa₂ complex. Compounds 1 and 2 exhibit single ion magnet behavior.

Seven-coordinate LnIII complexes assembled from a bulky MesacacH ligand: their synthesis, structure, photoluminescence and SMM behaviour

The reaction of a bulky acetyl acetone ligand 1,3-dimesitylpropane-1,3-dione (MesacacH) with hydrated lanthanide chlorides in the presence of tetramethylammonium hydroxide afforded a new family of neutral mononuclear LnIII complexes [Ln(Mesacac)3(DMF)] (Ln = Dy (1); Tb (2); Y0.91Dy0.09 (3); and Er (4)). The molecular structures of these complexes were confirmed by single crystal X-ray diffraction studies. The coordination geometries of the LnIII centre were analysed by SHAPE analysis which revealed a capped octahedral geometry in 1-4. Photoluminescence studies showed ligand-sensitized green emissions for 2 with an appreciable quantum yield of 0.83%. Static (dc) and dynamic (ac) magnetic studies of complexes 1 and 3 were performed. The dynamic magnetic study revealed that complex 1 exhibits zero-field slow relaxation of the magnetization without showing a clear maximum in the out-of-phase ac susceptibility plots. However, magnetic dilution of 1 with the YIII metal ion (complex 3) and/or the application of a dc magnetic field induces a strong frequency dependence of the ac susceptibility signals with χ''M peaks in the 3-10 K temperature range, thus supporting field-induced SMM behaviour of 1. The relaxation process takes place through a combination of the Orbach and Raman mechanisms. The fitting of the temperature dependence of the relaxation time to the equation τ-1 = τ0-1 exp(-Ueff/kBT) + BTn, allows the extraction of the effective energy barrier Ueff/kB = 70 K (48.7 cm-1) and pre-exponential parameter of τ0 = 2.7 × 10-7 s for the Orbach mechanism (first term) and the parameters B = 0.04 s-1 K-n and n = 6.11, for the Raman mechanism (second term).

A nitronyl nitroxide and its two 1D chain Cu–Tb complexes: synthesis, structures, and magnetic properties

A new nitronyl nitroxide, namely NIT-Ph-p-OCH₂trz (1), and two types of one-chain Cu–Tb complexes, namely [TbCu(hfac)₅NIT-Ph-p-OCH₂trz·0.5C₆H₁₄]_n (2a) and [LnCu(hfac)₅NIT-Ph-p-OCH₂trz]_n (2b) (NIT-Ph-p-OCH₂trz = 2-(4-((1H-1,2,4-triazol-1-yl)methoxy)phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; hfac = hexafluoroacetylacetonate), have been successfully synthesized simultaneously through reacting nitronyl nitroxide radical NIT-Ph-p-OCH₂trz with Cu(hfac)₂ and Ln(hfac)₃, and the molecular structures have been elucidated via single-crystal X-ray structural analysis. 2a features a ‘ladder-like’ chain structure, while 2b displays a linear chain structure built up by Ln(hfac)₃ units bridged with the NO groups of radical ligands. The additional Cu(ii) ions are coordinated to the nitrogen atoms of the triazole units. Nonzero out-of-phase signals are observed for the Tb derivatives (2a and 2b) and they exhibit frequency-dependent out-of-phase signals indicating a single-chain magnet behavior.

A new nitronyl nitroxide and two types of one-chain Cu–Tb complexes have been successfully synthesized, and the molecular structures have been elucidated via single-crystal X-ray structural analysis.

Magnetic Cationic Copper(II) Chains and a Mononuclear Cobalt(II) Complex Containing [Ln(hfac)4]- Blocks as Counterions

Four new heterospin compounds with molecular formula {[Cu₂(hfac)₃(TlTrzNIT)₂][Ln(hfac)₄]} _n·C₇H₁₆ (Ln^III = Gd (1), Tb (2), or Dy (3)) and [Co(hfac)(TlTrzNIT)₂][Dy(hfac)₄] (4), where hfac is hexafluoroacetylacetonato and TlTrzNIT is the nitronylnitroxide radical 1-( m-tolyl)-1 H-1,2,3-triazole-4-(4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), were obtained. All structures were determined by single-crystal X-ray diffraction. In compounds 1-3, the TlTrzNIT radical is bridge-coordinated to copper(II) ions, leading to positively charged copper(II)-radical chains containing [Ln(hfac)₄]^- as counterions. In compound 4, the cobalt(II) ion is coordinated to two TlTrzNIT radicals and one hfac ligand in bidentate mode leading to a mononuclear cationic complex that contains [Dy(hfac)₄]^- as counterion. Magnetic measurements of all complexes were performed. Magnetic data were fit considering the contributions of the copper(II)-radical chain and a paramagnetic gadolinium(III) ion for 1. The sign and magnitude of the magnetic coupling constants extracted from the fit were confirmed by density functional theory calculations. The obtained spin topology shows an alternated ferro-antiferromagnetic chain. Field-induced single molecule magnet behavior was observed for the Dy derivatives 3 and 4, in agreement with CASSCF calculations performed for the latter system.