<p>Tight-binding molecular dynamics simulations are carried out to analyse the thermal stability of the carbon [<i>n</i>,5] prismanes with <i>n</i> = 2–4 over a wide temperature range. The results obtained demonstrate that the isomerisation activation energy as well as the frequency factor in the Arrhenius equation of these metastable nanostructures rapidly decreases with an increase of <i>n</i>. Therefore, the increase in the effective length of [<i>n</i>,5] prismane leads to the decrease in its lifetime up to the moment of its isomerisation. Nevertheless, the stability of [<i>n</i>,5] prismanes is confirmed to be sufficient for their existence at the liquid-nitrogen temperature. The main identified mechanism of [<i>n</i>,5] prismanes isomerisation is the interlayer C–C bond breaking leading to their transformation to the hypostrophene-based molecular systems.</p
