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<p>Nitrocubanes and their extended derivatives constitute a distinctive class of high-energy materials in which extreme structural strain is combined with dense functionalization and rich chemical reactivity. While successive incorporation of nitro groups enhances energetic performance, it simultaneously introduces pronounced electronic and structural destabilization. In this work, we present a systematic density functional theory (DFT) investigation of mono- to octanitrocubanes and nitro-substituted biscubane frameworks to quantitatively unravel the molecular origin of this instability. Using a homodesmotic reaction approach, we define and evaluate the nitro-group-induced destabilization energy (E<sub>d–NO₂</sub>) as a cumulative energetic descriptor that isolates and measures the incremental destabilizing contribution of each additional nitro substituent. Concurrently, molecular electrostatic potential (MESP) analysis reveals a progressive attenuation of the negative electrostatic potential at the nitro oxygen atoms with increasing substitution, manifested as a monotonic decrease in the minimum potential value (<i>V</i><sub>min</sub>). This electrostatic depletion correlates strongly with both E<sub>d–NO₂</sub> and the C–NO₂ bond dissociation energies, and is consistent with the gradual development of NO₂ radical-like character and an enhanced propensity for homolytic C–N bond cleavage. Stepwise bond dissociation analysis further shows that the first C–NO₂ rupture acts as a molecular trigger, substantially lowering the energetic barrier for subsequent dissociation and establishing a cascade-type decomposition mechanism. Topological electron-density analysis and principal component analysis reveal that destabilization energy, trigger-bond activation, electrostatic depletion, and electron-density redistribution evolve cooperatively along a common nitration-induced perturbation pathway. Extension of this framework to corner-, edge-, and face-shared biscubanes reveals dramatically amplified destabilization and strain energies, highlighting the combined impact of extreme geometric confinement and nitro-induced electronic perturbation. Overall, this study establishes a unified, mechanism-oriented picture of nitrocubane sensitivity and identifies <i>V</i><sub>min</sub> as a highly sensitive electronic descriptor correlated with trigger sensitivity and energetic material design.</p>

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Quantifying nitro group destabilization in polynitrocubanes: homodesmotic energetics, MESP topology, and bond activation

  • 期刊论文

  • 发表日期：

    2026年6月20日

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  • Devarajan Dilu,
  • Cherumuttathu H. Suresh,
  • Sasidharan Nimesh,
  • Kuttan Prabhakaran,
  • Kunduchi Periya Vijayalakshmi

摘要

Nitrocubanes and their extended derivatives constitute a distinctive class of high-energy materials in which extreme structural strain is combined with dense functionalization and rich chemical reactivity. While successive incorporation of nitro groups enhances energetic performance, it simultaneously introduces pronounced electronic and structural destabilization. In this work, we present a systematic density functional theory (DFT) investigation of mono- to octanitrocubanes and nitro-substituted biscubane frameworks to quantitatively unravel the molecular origin of this instability. Using a homodesmotic reaction approach, we define and evaluate the nitro-group-induced destabilization energy (Ed–NO₂) as a cumulative energetic descriptor that isolates and measures the incremental destabilizing contribution of each additional nitro substituent. Concurrently, molecular electrostatic potential (MESP) analysis reveals a progressive attenuation of the negative electrostatic potential at the nitro oxygen atoms with increasing substitution, manifested as a monotonic decrease in the minimum potential value (Vmin). This electrostatic depletion correlates strongly with both Ed–NO₂ and the C–NO₂ bond dissociation energies, and is consistent with the gradual development of NO₂ radical-like character and an enhanced propensity for homolytic C–N bond cleavage. Stepwise bond dissociation analysis further shows that the first C–NO₂ rupture acts as a molecular trigger, substantially lowering the energetic barrier for subsequent dissociation and establishing a cascade-type decomposition mechanism. Topological electron-density analysis and principal component analysis reveal that destabilization energy, trigger-bond activation, electrostatic depletion, and electron-density redistribution evolve cooperatively along a common nitration-induced perturbation pathway. Extension of this framework to corner-, edge-, and face-shared biscubanes reveals dramatically amplified destabilization and strain energies, highlighting the combined impact of extreme geometric confinement and nitro-induced electronic perturbation. Overall, this study establishes a unified, mechanism-oriented picture of nitrocubane sensitivity and identifies Vmin as a highly sensitive electronic descriptor correlated with trigger sensitivity and energetic material design.