Dibenzo[ghi,mno]Fluoranthene, akacorannulene (C20H10), is a peculiar bowl-shaped molecule displaying unusual pentagonal symmetry and building block of the most celebrated Buckminster Fullerene – C60.
Its nanostructured arrangement together with the eminent dipole moment of 2.1 Debye and a high electron affinity, make this system largely appealing for its use in energy-related applications, such as in hydrogen storage, ion-batteries, or super-capacitors. Additionally, this molecule has been suggested to be a component of interstellar dusts.
In this work, published in Carbon, an international group including researchers from Italy, United Kingdom, Spain, and China has brought to the fore the unexpectedly rich thermophysical behaviour of this system in the thermal range 200 – 600 K, not anticipated on the basis of previous studies.
Combining state-of-the-art synchrotron (MCX beamline, Elettra) and neutron (IRIS beamline, ISIS) scattering techniques, together with differential scanning calorimetry (DSC), for the first time a well defined pre-melting transition has been clearly identified starting at about 382 K, well below the melting point of 540 K, resulting in the progressive suppression of molecular and supramolecular order and associated to the emergence of rotor-like states, as highlighted by the decrease in the elastic intensity and the sizeable increase in the quasi-elastic scattering (see Fig 1b– showing a marked separation in temperature between the two regimes).
Read more on the Elettra website
Image: Figure 1. (a) Synchrotron powder diffraction and Rietveld refinement of the room temperature average structure of Corannulene. (b) Temperature dependent quasi-elastic (IQE) and elastic (Iel) fractions, highlighting the transition to the dynamic state.