ic3021244_si_001.pdf (1.43 MB)
A Family of Binuclear Dysprosium(III) Radical Compounds with Magnetic Relaxation in ON and OFF States
journal contribution
posted on 2012-12-03, 00:00 authored by Tian Han, Wei Shi, Xiao-Ping Zhang, Lei-Lei Li, Peng ChengFour binuclear dysprosium compounds incorporating the
radical ligand
2-(4-oxidopyridyl)-4,4,5,5-tetramethylimidazolin-1-oxyl-3-oxide (PyNONIT)
have been successfully synthesized under appropriate conditions. Centrosymmetric
bimetallic Dy2O2 cores in all of the compounds
through double-μ2-oxygen atoms of the N-oxide groups are realized in a metal–radical approach for
the first time. Dimers 1 and 2, of the same
formula {[Dy(hfac)3(PyNONIT)]2}2 (hfac
= hexafluoroacetylacetonate) but obtained by different methods, which
contain almost identical local symmetry of D4d and Dy–(O)2–Dy
bridging fashion, however, display no out-of-phase alternating-current
(ac) signal for 1 and slow relaxation of the magnetization
for 2 corresponding to the difference of the crystal
packing mode. The adduct ([Dy(hfac)3(PyNONIT)]2[Dy0.5(hfac)1.5(H2O)]2) (3) consists of two items, the dimer [Dy(hfac)3(PyNONIT)]2 and the monomer [Dy(hfac)3(H2O)2], where the symmetry of DyIII ion in Dy2O2 decreases to D2d, showing slow relaxation of the magnetization
at lower temperature. Interestingly, a moisture-mediated reversible
solid transformation between 1 and ([Dy(hfac)3(H2O)(PyNONIT)]2) (4) has been
investigated. Spongelike 1 can undergo a transition from
eight to nine coordination at room temperature through hydration.
A different coordination field is mostly responsible for no ac signal
noticed for 4. The structural diversity of the Dy2 family provides an opportunity to expand the investigation
on 4f single-molecule magnets. Approaches that the relaxation of the
supramolecular dimer can be tuned to ON and OFF states modulated by
the packing mode and ligand field are presented.
