Cocrystallization of Photosensitive Energetic Copper(II) Perchlorate Complexes with the Nitrogen-rich Ligand 1,2-D-(1H-tetrazol-5-yl)ethane

Two recently introduced concepts in the design of new energetic materials, namely complexation and cocrystallization, have been applied in the synthesis and characterization of the energetic copper(II) compound [Cu(dt-5-e)(2)(H2O)](ClO4)(2), which consists of two different complex cations and can be described as a model energetic ionic cocrystal. The presence of both the N-rich 1,2-di(1H-tetrazol-5-yl)ethane ligand and oxidizing perchlorate counterion results in a new type of energetic material. The ionic complex cocrystal consists of a mononuclear and a trinuclear complex unit. It can be obtained by precipitation from perchloric acid or by dehydration of the related mononuclear coordination compound [Cu(dt-5-e)(2)(H2O)(2)](ClO4)(2).2H(2)O at 70 degrees C in the solid state. The transformation starting at 60 degrees C was monitored by X-ray powder diffraction and thermal analysis. The energetic ionic cocrystal was shown to be a new primary explosive suitable for laser ignition. The different coordination spheres within the ionic cocrystal (octahedral and square pyramidal) were shown by UV/vis/NIR spectroscopy to result in excellent light absorption.