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Reaction of a rare and well‐characterized MnIII‐superoxo species, Mn(BDPBrP)(O2⋅) (1, H2BDPBrP=2,6‐bis((2‐(S)‐di(4‐bromo)phenylhydroxylmethyl‐1‐pyrrolidinyl)methyl)pyridine), with 4‐dimethylaminophenol at −80 °C proceeds via concerted proton electron transfer (CPET) to produce a MnIII‐hydroperoxo complex, Mn(BDPBrP)(OOH) (2), alongside 4‐dimethylaminophenoxy radical; whereas, upon treatment with 4‐nitrophenol, complex 1 undergoes a proton transfer process to afford a MnIV‐hydroperoxo complex, [Mn(BDPBrP)(OOH)]+ (3). Intriguingly, the reactions of 1 with 4‐chlorophenol and 4‐methoxyphenol follow two routes of CPET and sequential proton and electron transfer to furnish complex 2 in the end. UV‐vis and EPR spectroscopic studies coupled with DFT calculations provided support for this wide mechanistic spectrum of activating various phenol O−H bonds by a single MnIII‐superoxo complex, 1. [ABSTRACT FROM AUTHOR]

Here, we combined magnetometry, multi‐frequency electronic paramagnetic resonance, and wave function based ab initio calculations to investigate magnetic properties of two high spin Co(II) complexes Co(BDPRP) (BDPRP=2,6‐bis((2‐(S)‐di(4‐R)phenylhydroxylmethyl‐1‐pyrrolidi‐nyl)methyl)pyridine, R=H for 8; R=tBu for 9). Complexes 8 and 9 featuring effective D3h symmetry were found to possess D=24.0 and 32.0 cm−1, respectively, in their S=3/2 ground states of 1e''dxz/yz41e'dxy/x2-y221a1'dz21 ${{\left(1{{\rm e}}^{{\rm { {^\prime}}}{\rm { {^\prime}}}}\right({d}_{xz/yz}\left)\right)}^{4}{\left(1{{\rm e}}^{{\rm { {^\prime}}}}\right({d}_{{xy/{x}^{2}-y}^{2}}\left)\right)}^{2}{\left(1{{\rm a}}_{1}^{{\rm { {^\prime}}}}\right({d}_{{z}^{2}}\left)\right)}^{1}}$. Ligand field analyses revealed that the low‐lying d‐d excited states make either positive or vanishing contributions to D. Hence, total positive D values were measured for 8 and 9, as well as related D3h high spin Co(II) complexes. In contrast, negative D values are usually observed for C3v congeners. In‐depth analyses suggested that lowering symmetry from D3h to C3v induces orbital mixing between 1edxz/yz ${1{\rm e}\left({d}_{xz/yz}\right)}$ and 2edxy/x2-y2 ${2{\rm e}\left({d}_{{xy/{x}^{2}-y}^{2}}\right)}$ and admixes excited state 4A21e→2e ${{}^{4}{{\rm A}}_{2}\left(1e\to 2e\right)}$ into the ground state. Both factors turn the total D value progressively negative with the increasing distance (δ) of the Co(II) center out of the equatorial plane. Therefore, δ determines the sign and magnitude of final D values of five‐coordinate trigonal bipyramidal S=3/2 Co(II) complexes as measured for a series of such species with varying δ. [ABSTRACT FROM AUTHOR]