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Correlating Mechanical Sensitivity with Spin Transition in the Explosive Spin Crossover Complex [Fe(Htrz)3][ClO4]2.

Thuy-Ai D Nguyen, Jacqueline M Veauthier, Gary F Angles-Tamayo

  • 1Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States.

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This study reveals that explosive spin crossover complexes can have switchable impact sensitivity. The sensitivity of [Fe(Htrz)3][ClO4]2 changes with its spin transition, offering new possibilities for smart materials.

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Area of Science:

  • Materials Science
  • Chemistry
  • Physics

Background:

  • Spin crossover (SCO) complexes exhibit changes in physical properties during spin transitions.
  • These transitions can influence the sensitivity of energetic materials, suggesting potential for switchable explosives.

Purpose of the Study:

  • To investigate the relationship between spin transition and mechanical impact sensitivity in an explosive SCO compound.
  • To develop and utilize a variable temperature impact test to assess sensitivity changes.

Main Methods:

  • Synthesized and characterized [Fe(Htrz)3][ClO4]2 (1) and a non-SCO Ni analog (2).
  • Employed a variable temperature impact test to measure impact sensitivity of compound 1 in different spin states (low spin, high spin, mixed).
  • Utilized density functional theory (DFT) to predict structural changes associated with spin transition.

Main Results:

  • A direct correlation between impact sensitivity and spin transition was observed for compound 1.
  • Impact sensitivity was lower in the low spin state and increased upon transition to the high spin state.
  • DFT calculations predicted structural changes that correlate with observed sensitivity variations.

Conclusions:

  • Demonstrates the first explosive spin crossover compound (ExSCO) with switchable impact sensitivity.
  • The ExSCO exhibits a fully reversible internal switching mechanism for sensitivity modulation.
  • This work opens avenues for developing new classes of sensitivity-switchable energetic materials.