Energetic Chromophores: Low-Energy Laser Initiation in Explosive Fe(II) Tetrazine Complexes

The
synthesis and characterization of air stable Fe­(II) coordination
complexes with tetrazine and triazolo-tetrazine ligands and perchlorate
counteranions have been achieved. Time-dependent density functional
theory (TD-DFT) was used to model the structural, electrochemical,
and optical properties of these materials. These compounds are secondary
explosives that can be initiated with Nd:YAG laser light at lower
energy thresholds than those of PETN. Furthermore, these Fe­(II) tetrazine
complexes have significantly lower sensitivity than PETN toward mechanical
stimuli such as impact and friction. The lower threshold for laser
initiation was achieved by altering the electronic properties of the
ligand scaffold to tune the metal ligand charge transfer (MLCT) bands
of these materials from the visible into the near-infrared region
of the electromagnetic spectrum. Unprecedented decrease in both the
laser initiation threshold and the mechanical sensitivity makes these
materials the first explosives that are both safer to handle and easier
to initiate than PETN with NIR lasers.