The vast majority of closed-shell organic molecules obey Hund's rule, which predicts that each triplet state will be of lower energy than the singlet state with the same electron configuration. Hund's rule thus provides a state ordering where the singlet and triplet manifolds are paired as illustrated with the non-alternant hydrocarbon azupyrene in Figure . Molecules that violate this rule are rare and of fundamental interest. While violations in open-shell ground-state configurations attracted much early attention, excited-state violations in closed-shell molecules have recently seen a revival due to their potential use for design of molecular emitters., In such molecules, there are low-lying singlet states that have lower energy than the equivalent triplet state, for example in isopyrene where E(S 1 -T 1 ) is negative, as shown in Figure . Ideally, it is the gap between the lowest excited singlet (S 1 ) and triplet (T 1 ) states that is inverted, which is the case in isopyrene. However, it is often the case that the singlet and triplet manifolds do not follow the same order, for example the B 2u and B 3u states in azupyrene and isopyrene (Figure ). Consequently, there are often lower energy triplet states with a different electron configuration than the S 1 state. The mechanism responsible for Hund's rule violations is still being explored. It is clear that the molecular orbitals (MOs) involved in the excitation, typically the highest occupied and lowest unoccupied MO (HOMO and LUMO), must have minimal overlap. A symmetric molecular core is essential for achieving this, which is seen in the azaphenalene class. Similarly, we have recently explored a class of non-alternant hydrocarbons with high-symmetry pentalenic or heptalenic cores that are achieved through aromatic stabilization, e.g. isopyrene, or by appropriate substituent patterns. It is imperative to build a fundamental understanding of the structural and electronic mechanisms responsible for excited-state Hund's rule violations by further exploring molecules with inverted singlet-triplet gaps.