Abstract
Single-molecule magnets (SMMs) are regarded as a class of promising materials for spintronic and ultrahigh-density storage devices. Tuning the magnetic dynamics of single-molecule magnets is a crucial challenge for chemists. Lanthanide ions are not only highly magnetically anisotropic but also highly sensitive to the changes in the coordination environments. We developed a feasible approach to understand parts of the magneto-structure correlations and propose to regulate the relaxation behaviors via rational design. A series of Co(II)-Dy(III)-Co(II) complexes were obtained using in situ synthesis; in this system of complexes, the relaxation dynamics can be greatly improved, accompanied with desolvation, via single-crystal to single-crystal transformation. The effective energy barrier can be increased from 293 cm−1 (422 K) to 416 cm−1 (600 K), and the tunneling relaxation time can be grown from 8.5 × 10−4 s to 7.4 × 10−2 s. These remarkable improvements are due to the change in the coordination environments of Dy(III) and Co(II). Ab initio calculations were performed to better understand the magnetic dynamics.
Highlights
The ground J manifold of the lanthanides could be regarded as the spin S in the case of classical spin magnets, such as Mn12Ac1
Large zero-field splitting of the latter is difficult to induce, i.e., the zero-field splitting parameter D is typically small, whereas the typical splitting of the ground J manifold of lanthanides in the absence of applied field is as large as several hundreds of wavenumbers
We go beyond the previous analysis and attempt to understand the structural reasons for such strong magnetic blocking in a series of Co-Dy-Co complexes having similar quasi-D5h symmetry of the Dy(III)
Summary
All procedures were conducted under an inert N2 atmosphere by using Schlenk techniques. After stirring for 1 min and slowly flowing dinitrogen for 3 h, light-pink crystals were grown in the remaining solution (~25 mL). The crystals were placed into a high-moisture atmosphere (up to 100% humidity at room temperature) for 2–3 h; ~80 mg light-pink crystals of 1∙3H2O were obtained after filtration (~43% yield based on Dy). Elemental analysis (calcd, found) for 1∙H2O: C (36.54, 36.55), H (3.63, 3.93), N (7.10, 7.26). CCDC 1058028 (1∙3H2O) 1058029 (1∙H2O) and 1058030 (1) contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Data were corrected for the diamagnetic contribution calculated from the Pascal constants
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