ja9b13835_si_001.pdf (2.53 MB)
Correlating Mechanical Sensitivity with Spin Transition in the Explosive Spin Crossover Complex [Fe(Htrz)3]n[ClO4]2n
journal contribution
posted on 2020-02-25, 21:45 authored by Thuy-Ai D. Nguyen, Jacqueline M. Veauthier, Gary F. Angles-Tamayo, David E. Chavez, Ekaterina Lapsheva, Thomas W. Myers, Tammie R. Nelson, Eric J. SchelterSpin crossover complexes are known
to undergo bond length, volume,
and enthalpy changes during spin transition. In an explosive spin
crossover complex, these changes could affect the mechanical and initiation
sensitivity of the explosive and lead to the development of a new
class of sensitivity switchable materials. To explore this relationship,
the well-known spin crossover compound [Fe(Htrz)3]n[ClO4]2n (1) was re-evaluated for its explosive properties,
and its mechanical impact sensitivity was correlated to spin transition.
A variable temperature impact test was developed and used to evaluate
the impact sensitivity of 1 in the low spin (LS, S =
0), thermally accessed high spin (HS, S = 2), and mixed LS and HS
states. For comparison, the structurally similar Ni compound, [Ni(Htrz)3]n[ClO4]2n (2), which does not undergo a spin
transition at accessible temperatures, was synthesized and characterized,
and its explosive properties and variable temperature impact sensitivity
measured. These results reveal a correlation between impact sensitivity
and spin transition, where 1 exhibits lower impact sensitivity
in the LS state and increases in sensitivity upon transition to the
HS state. Density functional theory was used to predict structural
changes that occur upon spin transition that correlate to the change
in sensitivity. This demonstrates, for the first time, an explosive
spin crossover compound (ExSCO) that exhibits switchable impact sensitivity
with a fully reversible internal switching mechanism.