A theoretical study of singly occupied molecular bands and their magnetic character in one-dimensional trioxotriangulene chains

Abstract Further theoretical insights into solid-state electronics of organic crystals are necessary to enable material applications for open-shell molecules. However, the effects of exchange repulsion and the overlap of magnetic orbitals in their crystals have yet to be investigated. In this study, we examine the Br₃TOT crystal as a model system featuring a one-dimensional structure with antiferromagnetic ordering and unique functional properties. We conducted a detailed investigation of the electronic states and magnetic properties as well as the effects of expansion and compression using approximate spin-projected density functional theory with plane-wave basis (AP-DFT/plane-wave). The dependence of the effective exchange integral (J) on the intraradical distance suggests that compression along the stacking direction induces magnetic reversal from antiferromagnetism (AFM) to ferromagnetism (FM). We found that strong exchange repulsion in the crystal is crucial for switching devices that utilise the AFM–FM transition. Furthermore, our results demonstrate that the molecular symmetry changes that accompany expansion and compression are influenced by the symmetry of the crystal structure. The enhanced qualities are associated with a quinone structure, which is important for battery reactions. Consequently, the AP-DFT/plane-wave method showed the importance of exchange repulsion and crystal structures for in silico design of open-shell molecular devices.