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7024422 
Journal Article 
Elucidating the Electronic Structure of High-Spin [Mn-III(TPP)Cl] Using Magnetic Circular Dichroism Spectroscopy 
Galinato, MGI; Brocious, EP; Paulat, F; Martin, S; Skodack, J; Harland, JB; Lehnert, N; , 
2020 
Yes 
Inorganic Chemistry
ISSN: 0020-1669
EISSN: 1520-510X 
AMER CHEMICAL SOC 
WASHINGTON 
59 
4 
2144-2162 
English 
32030987 
WOS:000514488400006 
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 = F, Cl, I, Br) complexes with emphasis on the spectroscopic properties of [Mn-III(TPP)Cl], using variable-temperature 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(pi)(CT ((Cl,pi))), Q band, and overlap-forbidden Cl(p(x/y))_d(pi)-> d(x)2-(y)2 transitions that gain intensity from the strongly allowed pi -> pi*((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(pi), CT(cl,pi/sigma), and symmetry-forbidden CT character, mixed with the pi -> pi*((0)) transition. The strong d(x2-y2)_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)(pi)< 81 > and the Cl(p(z))_d(z2) orbitals. Through this direct orbital pathway, the pi ->pi* (0) transition acquires intrinsic metal-d -> porphyrin CT character, where the pi ->pi* (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.