Cocrystals of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides and 1,5-dioxides: step-by-step development of crystal engineering of energetic materials

Abstract

In this work, the cocrystallization of both benzotrifuroxan (BTF) and [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide (furazanotetrazine dioxide, FTDO) with [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide (FCO), 1,5-dioxide (FCDO) and some of their nitro derivatives was investigated, focusing on the cocrystal structural features and their detonation performance. First, cocrystallization energies using crystal structure prediction (CSP) methods, identifying energetically favorable component ratios for BTF and FTDO with cinnoline oxides, were calculated. Then two novel cocrystals, the BTF–FCDO 4 (1 : 2) and the FTDO–FCDO 3 (1 : 2) compositions, were prepared and characterized by X-ray diffraction and Hirshfeld surface analysis. The primary intermolecular interactions in BTF cocrystals include dominant n(NO₂)⋯π(BTF) contacts and π-stacking motifs, and in FTDO cocrystals, hydrogen-bonded synthons. The calculated energetic parameters were 7.37 km s⁻¹ and 23.99 GPa for the FTDO (1 : 2) cocrystal, and 7.69 km s⁻¹ and 26.4 GPa for the BTF (1 : 2) cocrystal. Their cocrystals (1 : 2) with FCDOs exhibited, compared to pure parent compounds, lower detonation velocities and pressures due to high FCDOs molar content, yet still outperformed conventional energetic compounds such as 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB).