Activation of order-disorder dynamics in crystalline Buckybowls

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

M. Gaboardi et al. Carbon 183, 196 (2021)


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. 
In this newly found high-temperature state, corannulene molecules still preserve their crystalline arrangement and average orientations, characterized by onion-like clusters composed by four molecules (cfr. synchrotron powder diffraction data and structure in Fig. 1a),

whilst their activated dynamics hints to the fast rotation around the pentagonal axis. Furthermore, upon cooling from the melt, an unexpectedly large supercooling hysteresis was measured, unlike any other polycyclic aromatic system similar to corannulene studied at this level of detail.  

The speed-up of intra and intermolecular dynamics seen in the higher-temperature solid phase, an energy storage density of ca.70 J/g associated with corannulene re-crystallization, comparable to those achieved in by far-more-complex multicomponent systems, and the very strong hysteresis observed by calorimetry advice for the capitalization of this type of disorder in practical applications, particularly those relating to the storage of thermal energy.

Retrieve article
Emergence of Dynamical Disorder and Phase Metastability in Carbon Nanobowls
Gaboardi Mattia, Silverwood Ian, Braunewell B., Siegel Jay, Fernandez-Alonso F.
Carbon, Vol. 183, pp. 196-204 (2021)
doi: 10.1016/j.carbon.2021.07.003


Last Updated on Friday, 24 June 2022 15:21