[Sm(hfac)3(boaDTDA)]n is the first coordination compound of a thiazyl-based neutral radical ligand to exhibit ferromagnetic ordering; TC = 3 K. The [Sm(iii)-radical]n species is soluble in common organic solvents and can be sublimed quantitatively. A McConnell I mechanism is implicated in local exchange pathways that contribute to cooperative magnetic properties.
The
achiral molecule 2-cyano-4,6-dimethylpyrimidine (Me2pmCN)
meets simple criteria that predict a supramolecular arrangement
capable of exhibiting plastic bending. Indeed, crystals grown by sublimation
bend readily without breaking under manual manipulation at room temperature.
Compression of a crystal perpendicular to the bending direction easily
“squashes” the crystal, a mechanical response akin to
metal-like malleability. Single crystal X-ray diffraction (XRD) study
reveals net alignment of the molecular dipoles propagating along the
21 screw axis in the monoclinic space group P21. Columnar π-stacked arrays of the planar molecules
extend in [100], the long axis of the crystals. Weak interactions
between the columnar structures account for the observed mechanical
behavior. Variable temperature powder XRD and differential scanning
calorimetry measurements of the plastic crystals indicate a solid-to-solid
phase transition from one crystalline phase to another at 80.7 °C
prior to melting at 83.3 °C.
SbPh3Cl2is used to effect a dramatic rearrangement of the ligand sphere and “pancake bonding” in Ce(hfac)3(5′-Br-pyDTDA)2by forming a 2 : 1 host–guest complex.
We present the results of muon-spin relaxation (µ + SR) measurements on antiferromagnetic and ferromagnetic spin chains. In antiferromagnetic CuF 2 (pyz) we identify a transition to long range magnetic order taking place at T N = 0.6(1) K, allowing us to estimate a ratio with the intrachain exchange of T N /|J| ≈ 0.1 and the ratio of interchain to intrachain exchange coupling as |J /J| ≈ 0.05. The ferromagnetic chain [Sm(hfac) 3 (boaDTDA)] n undergoes an ordering transition at T c = 2.8(1) K, seen via a broad freezing of dynamic fluctuations on the muon (microsecond) timescale and implying T c /|J| ≈ 0.6. The ordered radical moment continues to fluctuate on this timescale down to 0.3 K, while the Sm moments remain disordered. In contrast, the radical spins in [La(hfac) 3 (boaDTDA)] n remain magnetically disordered down to T = 0.1 K suggesting T c /|J| < 0.17. arXiv:1905.04913v1 [cond-mat.str-el]
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