In this study, we investigate the effects of nitrogen and boron dopants on the properties of phenalene/phenalenyl systems based on the Hückel theory by using the Hueckel Molecular Orbital software. The dopants configurations are graphitic, pyridinic, and pyrrolic. The electronic configuration of bare phenalene confirms the delocalization of π electrons and the radical properties of the molecule, which is in good agreement with the results of previous studies. Dopant types and positions strongly affect the number of π electrons in the system, molecular orbital energy, total energy, average π-electron energy, and gap energy. The molecular energy level degeneracy strongly depends on the rotational symmetry of the system, in the order of graphitic, pyridinic, and pyrrolic. A preserved radical behavior and the number of π electrons are found for the pyridinic dopant type, while closed electronic configuration is observed for graphitic and pyrrolic types. A lower gap energy is typically found for B-doped phenalene compared to that for N-doped phenalene; this opens the possibility for the enhancement of photoluminescence intensity. This study, although qualitative, confirms the effects of dopants on the chemical and physical properties of phenalene/phenalenyl systems.

Abstract Freezing of cobalt nitrate hexahydrate (CoNHH) under a static magnetic field was studied at three different magnetic field intensities. The results show that the magnetic field has a significant effect when the sample enters the solid phase and reduces the stochastic behaviour of the nucleation. Thermal properties investigated using thermogravimetric and differential thermal analysis revealed the shift to a lower temperature for the onset of decomposition and melting temperature after the freeze-thaw in a magnetic field. Besides that, we observed a significant change in the FT-IR peaks that might indicate the emergence of cobalt nitrate with a lower hydrate number, a phase separation effect, and the evaporation of NO3- ions. Refinement of the XRD spectra shows a single phase of CoNHH with a slight lattice parameter change after the freezing-thawing in a magnetic field. The freezing behaviour of CoNHH was compared to that observed previously for water, a salt solution, and an ethylene glycol solution. We investigated the relationship of the freezing behaviour with hydrogen bonding and magnetic properties and its impact on the change in the Gibbs free energy. The results of this study are important to optimise the performance of CoNHH as latent thermal energy storage.