Impact of Positional Isomerism on Melting Point and Stability in New Energetic Melt-Castable Materials

For an energetic material with a definite composition,
the substituent
position is the most crucial factor to influence its physicochemical
properties. Thus, it is becoming increasingly important to understand
the impact of positional isomerism on multidimensional properties
differences. Herein, we reported two new potential energetic melt-castable
molecules, a pair of positional isomers (4-MMDNP and 5-MMDNP). These
two explosives exhibit obviously different properties, including densities
(Δρ = 0.03 g cm–3), melting point (ΔTm = 47.2 °C), decomposition temperature
(ΔTd = 27.3 °C), stability
(IS = 20 J, FS = 160 N vs IS = 10 J, FS = 40 N), etc., even though
they share similar compositions and structures. Simultaneously, by
analyzing crystal packing, intermolecular interactions, and monomolecular
parameters, we were able to uncover the roots of property differences.
Altogether, our results provide comprehensive molecular and crystal
level insight into the effect of positional isomerism, which may be
useful for new molecular design.