Manganese porphyrins are used as catalysts in the oxidation of olefins and nonactivated hydrocarbons. Key to these reactions are high-valent Mn−(di)oxo species, for which [Mn(Porph)(X)] serve as precursors. To elucidate their properties, it is crucial to understand the interaction of the Mn center with the porphyrin ligand. Our study focuses on simple high-spin [Mn III (TPP)X] (X = F, Cl, I, Br) complexes with emphasis on the spectroscopic properties of [Mn III (TPP)Cl], using variabletemperature variable-field magnetic circular dichroism spectroscopy and time-dependent density functional theory to help with band assignments. The optical properties of [Mn III (TPP)Cl] are complicated and unusual, with a Soret band showing a high-intensity feature at 21050 cm −1 and a broad band that spans 23200−31700 cm −1 . The 15000−18500 cm −1 region shows the Cl(p x/y ) → d π (CT (Cl,π) ), Q band, and overlap-forbidden Cl(p x/y )_d π → d x 2 −y 2 transitions that gain intensity from the strongly allowed π → π* (0) transition. The 20000−21000 cm −1 region displays the prominent pseudo A-type signal of the Soret band. The strongly absorbing features at 22500−28000 cm −1 exhibit A 1u ⟨79⟩/A 2u ⟨81⟩ → d π , CT (Cl,π/σ) , and symmetry-forbidden CT character, mixed with the π → π* (0) transition. The strong d x 2 −y 2 _B 1g ⟨80⟩ orbital interaction drives the ground-state MO mixing. Importantly, the splitting of the Soret band is explained by strong mixing of the porphyrin A 2u (π)⟨81⟩ and the Cl(p z )_d z 2 orbitals. Through this direct orbital pathway, the π → π* (0) transition acquires intrinsic metal-d → porphyrin CT character, where the π → π* (0) intensity is then transferred into the high-energy CT region of the optical spectrum. The heavier halide complexes support this conclusion and show enhanced orbital mixing and drastically increased Soret band splittings, where the 21050 cm −1 band shifts to lower energy and the high-energy features in the 23200−31700 cm −1 range increase further in intensity, compared to the chloro complex.

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