Engineering bistetrazoles: (E)-5,5′-(ethene-1,2-diyl)bis(1H-tetrazol-1-ol) as a new planar high-energy-density material

Abstract

Energetic properties of bistetrazole derivatives are improved by the step-by-step introduction of functionalities which improve heat of formation, density, and oxygen content. The incorporation of unsaturation between bis(1H-tetrazol-5-yl) and bis(1H-tetrazol-1-ol) derivatives leads to planarity which enhances the density of the final product. In this manuscript, we have synthesized compounds 1,2-di(1H-tetrazol-5-yl)ethane (4), (E)-1,2-di(1H-tetrazol-5-yl)ethene (5), and (E)-5,5′-(ethene-1,2-diyl)bis(1H-tetrazol-1-ol), (6) using readily available starting materials. Their corresponding dihydroxylammonium salts 7, 8 and 9 are obtained by reacting two equivalents of hydroxylamine (50% in water). New compounds are analyzed using IR, EA, DSC and multinuclear NMR spectroscopy (¹H, ¹³C and ¹⁵N). The solid-state structures of compounds 6, 7, 8 and 9 are confirmed by single-crystal X-ray diffraction. The energetic performances are calculated using the EXPLO5 (v6.06.02) code and the sensitivities towards external stimuli such as friction and impact are determined according to BAM standard. Compound 6 {(E)-5,5′-(ethene-1,2-diyl)bis(1H-tetrazol-1-ol)} exhibits a surprisingly high density of 1.91 g cm⁻³ at 100 K (1.86 g cm⁻³ at 298 K). Its detonation velocity (9017 m s⁻¹) is considerably superior to those of RDX (8795 m s⁻¹), which suggests it is a competitive high-energy-density material.