Of particular interest is a detailed comparative understanding of the cationic hyperporphyrin {H4[TAPP]} 2+ and the anionic hyperporphyrin {H2[TOPP]} 4-. In the case of {H4[TAPP]} 2+ , electron density is transferred from the strongly electron-donating mesoaminophenyl substituents to the protonated porphyrin core. In {H2[TOPP]} 4-, the porphyrin core is formally neutral, but the meso positions carry strongly electron-donating phenoxide substituents. In spite of the obvious difference in the overall charge situation, the direction of charge transfer is inward in both systems, from the meso-aryl groups to the porphyrin core. In a recent Perspective article, we noted that hyperporphyrins exhibiting charge transfer in the opposite direction, i.e., from the porphyrin core to the meso-aryl groups, were unknown. Subsequently such outward charge transfer has been established in anionic metallotriarylcorroles -so-called inverse hypercorroles. Experimentally, the UV-vis spectra of deprotonated H2[THPP] vary substantially with solvent. Thus, the lowest-energy hyperporphyrin band maximum of {H2[TOPP]} 4-has been reported at a variety of wavelengths between 660 and 705 nm. The influence of structural perturbation of the meso-aryl groups on the porphyrin macrocycle can be readily appreciated from a set of comparative (CAMY-B3LYP) MO energy level diagrams of the four species studied (Figure ). As expected, unadorned H2[TPP] conforms to Gouterman's four-orbital model, i.e., the two HOMOs and the two LUMOs are energetically well-separated from all other occupied and unoccupied MOs. Also, as expected for porphyrins with electron-donating meso substituents, all three neutral porphyrins studied exhibit a2u HOMOs with large amplitudes at the meso carbons and the central nitrogens. With increasing electrondonating character of the meso aryl group, from H2[TPP] through H2[THPP] to H2[TOLiPP], aryl character mixes into the a2u HOMO, elevating its orbital energy relative to the Gouterman a1u MO and the two LUMOs (Figure ). This orbital mixing leads to shrinking HOMO-LUMO gaps along the series of compounds studied and for the hyperporphyrin spectra of interest. Not entirely unexpectedly, an extreme scenario arises for the H2[TOPP]} 4-tetraanion: for the CAMY-B3LYP functional, the HOMO is essentially entirely localized on the phenoxide substituents, with the Gouterman a1u and a2u MOs appearing as HOMO-1 and HOMO-4, respectively (Figure ). The dramatic difference in HOMO energy levels between H2[TOLiPP] and H2[TOPP]} underscores the importance of solvation and counterions in determining the HOMO-LUMO gap of peripherally deprotonated H2[THPP] under basic conditions, which is consistent with experimental findings. TDDFT calculations allow a more detailed appreciation of the optical spectra of H2[THPP] and its O-deprotonated counterpart (Table ). Unless otherwise mentioned, the discussion below will focus on CAMY-B3LYP results. For H2[TPP], the two Q transitions (ignoring vibrationally excited states that are also observed experimentally) have approximately 2/3 HOMO (generally a2u) character and 1/3 HOMO-1 (a1u) character. In more detail, the lowerenergy Q transition is approximately 2/3 HOMO-to-LUMO and 1/3 HOMO-1-to-LUMO+1, while the higher energy Q band is approximately 2/3 HOMO-to-LUMO+1 and 1/3 HOMO-1-to-LUMO. In H2[THPP] and H2[TOLiPP], the HOMO (a2u) character of the Q transitions is significantly higher, approximately 80% and about 85-90%, respectively. It is this increased HOMO character that accounts for the redshifted Q bands of H2[THPP] and H2[TOLiPP] relative to H2 [TPP]. For the three charge-neutral tetrarylporphyrin systems studied here, the Soret transitions entail a much lower proportion of HOMO character relative to the Q transitions so it makes sense that the spectral redshifts are more muted for the Soret transitions.