Details

Autor(en) / Beteiligte

• Vaidya, Shefali
• Tewary, Subrata
• Singh, Saurabh Kumar
• Langley, Stuart K
• Murray, Keith S
• Lan, Yanhua
• Wernsdorfer, Wolfgang
• Rajaraman, Gopalan
• Shanmugam, Maheswaran

Titel

What Controls the Sign and Magnitude of Magnetic Anisotropy in Tetrahedral Cobalt(II) Single-Ion Magnets?

Ist Teil von

• Inorganic chemistry, 2016-10, Vol.55 (19), p.9564-9578

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2016

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• A family of mononuclear tetrahedral cobalt­(II) thiourea complexes, [Co­(L1)4]­(NO3)2 (1) and [Co­(L x )4]­(ClO4)2 where x = 2 (2), 3 (3), 4 (4) (where L1 = thiourea, L2 = 1,3-dibutylthiourea, L3 = 1,3-phenylethylthiourea, and L4 = 1,1,3,3-tetramethylthiourea), has been synthesized using a rationally designed synthetic approach, with the aim of stabilizing an Ising-type magnetic anisotropy (−D). On the basis of direct-current, alternating-current, and hysteresis magnetic measurements and theoretical calculations, we have identified the factors that govern the sign and magnitude of D and ultimately the ability to design a single-ion magnet for a tetrahedral cobalt­(II) ion. To better understand the magnetization relaxation dynamics, particularly for complexes 1 and 2, dilution experiments were performed using their diamagnetic analogues, which are characterized by single-crystal X-ray diffraction with the general molecular formulas of [Zn­(L1)4]­(NO3)2 (5) and [Zn­(L2)4]­(ClO4)2 (6). Interestingly, intermolecular interactions are shown to play a role in quenching the quantum tunneling of magnetization in zero field, as evidenced in the hysteresis loop of 1. Complex 2 exhibits the largest U eff value of 62 cm–1 and reveals open hysteresis loops below 4 K. Furthermore, the influence of the hyperfine interaction on the magnetization relaxation dynamics is witnessed in the hysteresis loops, allowing us to determine the electron/nuclear spin S(Co) = 3/2/I(Co) = 7/2 hyperfine coupling constant of 550 MHz, a method ideally suited to determine the hyperfine coupling constant of highly anisotropic metal ions stabilized with large D value, which are otherwise hard to determine by conventional methods such as electron paramagnetic resonance.