As with azulene, the ground-state structure of calicene is aromatically stabilized owing to the push-pull effect between the rings (Figure ). However, while azulene respects Hund's rule in its excited states, calicene does not. In this letter, we explore the potential for controlling Hund's rule violations in calicene derivatives. Through analysis of the charge-transfer (CT) mechanism of its excited states, we show that the frontier MO energetics can be systematically tuned to achieve inversion of the S1 and T1 states. We evaluate the excited state gaps by computing the vertical excitation energies using equations-of-motion coupled cluster with singles and doubles (EOM-CCSD) and the cc-pVDZ basis. Structures are optimized in the ground state at the ωB97X-D/def2-TZVP level and are identified as energy minima with no imaginary frequencies (see Supporting Information for full computational details). EOM-CCSD provides a conservative assessment of excited-state singlet-triplet gaps in organic molecules, and we compare with several other approximated CC methods with larger basis sets in Table of the Supporting Information. Furthermore, our results for calicene are consistent with previously reported results at the CASPT2 level. Calicene exhibits a Hund's rule violation between the S3 and T4 states, which involve the same electron configuration and exhibit a robustly negative energy gap of E(S3-T4)=-98 meV at the EOM-CCSD/cc-pVDZ level (Figure ). A closer look at the orbitals of calicene reveals two quasi-degenerate highest occupied and lowest unoccupied MOs (HOMOs and LUMOs, Figure ). The first four singlet and triplet excited states of calicene are each described predominantly by a single-particle transition between these four possible MO pairs (Fig ).