The strong electron correlation potentially present in organic radicals complicates the calculation of their excited state properties. Consequently, employing quantum chemistry methods that can effectively handle the multiconfigurational nature of these electronic states becomes highly desirable. Among them, we mention multiconfigurational self-consistent field (MCSCF), complete active space self-consistent field (CASSCF) together with second-order perturbation theory (either CASPT2 or NEVPT2 ), state-specific multireference perturbation theory (SSMRPT), configuration interaction singles and doubles (CISD), coupled cluster, spin-flip restricted active space configuration interaction (SF-RASCI), and complete active space configuration interaction density functional theory (CASCI-DFT). However, the application of these methods has been confined to rather small systems. As a result, conventional ground-state DFT and excited-state time-dependent DFT (TDDFT) methods remain attractive for studying organic radicals, despite the previously mentioned theoretical difficulties. Due to the possible spin-contamination issues in the unrestricted version of TDDFT for open-shell molecules, explicitly spin-adapted TDDFT (X-TDDFT) is typically employed. Additionally, spin-polarized DFT calculations incorporating many-body perturbative corrections at the G 0 W 0 level have also been utilized. We employ an alternative approach by conducting a comprehensive study of various phenalenyl radicals using the Pariser-Parr-Pople (PPP) model Hamiltonian to account for electron correlation in π-conjugated molecules. Developed in the 1950s, this model has been successful in accurately describing the ground state and excited state properties of various small organic molecules. The PPP model has recently made a comeback to address singlet-triplet (ST) inversion in some OLED emitters, as well as doublet emission in both planar and non-planar organic radicals. Although the PPP model was originally designed for π-conjugated hydrocarbons, it can be adapted to accommodate non-planar systems by incorporating additional terms that account for deviations from planarity. Moreover, the model can be extended to systems containing heteroatoms by adjusting its key parameters against experimental data. 17,82-86 These adaptations significantly broaden the applicability of the PPP model, enabling its use in the study of strong radical emitters that are both non-planar and contain heteroatoms. An important symmetry inherent to the PPP model, but only approximately followed by more advanced (all-electron) Hamiltonians, is the so-called particle-hole (ph) symmetry. Alternant hydrocarbons provide a real molecular framework where this symmetry is closely approximated. In such hydrocarbons, the carbon atoms can be divided into two distinct sets through a specific marking process: every other carbon atom is marked with a star, ensuring that no two starred carbons share a direct covalent bond. As a result, starred carbons only bond with unstarred carbons, and vice versa. Rings composed of an even number of atoms satisfy this condition, while rings with an odd number of atoms do not (see SI Section S3 for examples of alternant and non-alternant hydrocarbons). The PPP particle-hole symmetry in alternant hydrocarbons is reflected in the unique arrangement of their orbital energy levels and the specific structure of the molecular orbitals (MOs). In alternant systems, MOs come in pairs with corresponding positive and negative energies. If the alternant system has an even number of atoms, the negative energy levels are fully occupied in the ground state, while the positive levels remain empty; thus, bonding and antibonding MOs appear as occupied-virtual pairs. Alternant hydrocarbons with an odd number of atoms have an additional feature, namely a singly occupied non-bonding orbital at zero energy (see SI Section S3). Finally, the particle-hole symmetry in the PPP model assumes the absence of heteroatoms. Therefore, when heteroatoms are introduced into the structure of an alternant hydrocarbon, they alter the energies of the bonding and antibonding molecular orbitals, resulting in an asymmetry among the energy levels.