ic7b02390_si_001.pdf (1.23 MB)
Slow Magnetic Relaxation in a Dysprosium Ammonia Metallocene Complex
journal contribution
posted on 2017-11-25, 07:06 authored by Selvan Demir, Monica D. Boshart, Jordan F. Corbey, David H. Woen, Miguel I. Gonzalez, Joseph W. Ziller, Katie R. Meihaus, Jeffrey R. Long, William J. EvansWe report the serendipitous
discovery and magnetic characterization of a dysprosium bis(ammonia)
metallocene complex, [(C5Me5)2Dy(NH3)2](BPh4) (1), isolated
in the course of performing a well-established synthesis of the unsolvated
cationic complex [(C5Me5)2Dy][(μ-Ph)2BPh2]. While side reactivity studies suggest that
this bis(ammonia) species owes its initial incidence to impurities
in the DyCl3(H2O)x starting material, we were able to independently prepare 1 and its tetrahydrofuran (THF) derivative, [(C5Me5)2Dy(NH3)(THF)](BPh4) (2), from the reaction of [(C5Me5)2Dy][(μ-Ph)2BPh2] with ammonia
in THF. The low-symmetry complex 1 exhibits slow magnetic
relaxation under zero applied direct-current (dc) field to temperatures
as high as 46 K and notably exhibits an effective barrier to magnetic
relaxation that is more than 150% greater than that previously reported
for the [(C5Me5)2Ln][(μ-Ph)2BPh2] precursor. On the basis of fitting of the
temperature-dependent relaxation data, magnetic relaxation is found
to occur via Orbach, Raman, and quantum-tunneling relaxation processes,
and the latter process can be suppressed by the application of a 1400
Oe dc field. Field-cooled and zero-field-cooled dc magnetic susceptibility
measurements reveal a divergence at 4 K indicative of magnetic blocking,
and magnetic hysteresis was observed up to 5.2 K. These results illustrate
the surprises and advantages that the lanthanides continue to offer
for synthetic chemists and magnetochemists alike.