Abstract
Single-molecule magnets (SMMs) have potential applications in high-density
data storage, but magnetic relaxation times at elevated temperatures must be
increased to make them practically useful. Bis-cyclopentadienyl
lanthanide sandwich complexes have emerged as the leading candidates for SMMs
that show magnetic memory at liquid nitrogen temperatures, but the relaxation
mechanisms mediated by aromatic C5 rings have not been fully
established. Here we synthesise a bis-monophospholyl
dysprosium SMM [Dy(Dtp)2][Al{OC(CF3)3}4]
(1, Dtp = {P(CtBuCMe)2})
by the treatment of in situ-prepared
“[Dy(Dtp)2(C3H5)]” with [HNEt3][Al{OC(CF3)3}4].
SQUID magnetometry reveals that 1 has
an effective barrier to magnetisation reversal of 1,760 K (1,223 cm–1)
and magnetic hysteresis up to 48 K. Ab
initio calculation of the spin dynamics reveal that transitions out of the
ground state are slower in 1 than in the first reported dysprosocenium SMM,
[Dy(Cpttt)2][B(C6F5)4]
(Cpttt = C5H2tBu3-1,2,4),
however relaxation is faster in 1 overall due to the compression of
electronic energies and to vibrational modes being brought on-resonance by the
chemical and structural changes introduced by the bis-Dtp framework. With the preparation and analysis of 1 we are thus able to further refine
our understanding of relaxation processes operating in bis-C5/C4P sandwich lanthanide SMMs, which is the
necessary first step towards rationally achieving higher magnetic blocking
temperatures in these systems in future.
Supplementary materials
Title
ChemRxiv 2019 DyDTP ESI
Description
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