Seungwoo Hong

A mononuclear non-heme manganese(V)-oxo complex, [Mn(V)(O)(TAML)](-) (1), was synthesized by activating dioxygen in the presence of olefins with weak allylic C-H bonds and characterized structurally and spectroscopically. In mechanistic studies, the formation rate of 1 was found to depend on the allylic C-H bond dissociation energies (BDEs) of olefins, and a kinetic isotope effect (KIE) value of 16 was obtained in the reactions of cyclohexene and cyclohexene-d10. These results suggest that a hyd

One primary goal in biomimetic research is to understand mechanisms of dioxygen activation, structures of reactive intermediates, and reactivities of the intermediates involved in catalytic oxidation reactions by metalloenzymes, such as heme and nonheme iron oxygenases. In this communication, we have reported the first example of generating nonheme iron(III)-hydroperoxo and iron(IV)-oxo complexes by activating O(2) with a biologically important electron donor, an NADH analogue, and an acid. The

Mononuclear nonheme iron(IV)-oxo complexes with two different topologies, cis-α-[Fe(IV)(O)(BQCN)](2+) and cis-β-[Fe(IV)(O)(BQCN)](2+), were synthesized and characterized with various spectroscopic methods. The effect of ligand topology on the reactivities of nonheme iron(IV)-oxo complexes was investigated in C-H bond activation and oxygen atom-transfer reactions; cis-α-[Fe(IV)(O)(BQCN)](2+) was more reactive than cis-β-[Fe(IV)(O)(BQCN)](2+) in the oxidation reactions. The reactivity difference b

There are mechanistic dichotomies with regard to the formation, electronic structures and reaction mechanisms of metal-oxygen intermediates, since these metal-oxygen species could be composed of different resonance structures or canonical structures of the oxidation states of metals and ligands, which may undergo different reaction pathways. Even the same metal-oxygen intermediates, such as metal-oxo species, may undergo an electron-transfer pathway or a direct hydrogen or oxygen atom transfer p

Mononuclear nonheme iron(V)-oxo complexes have been reported previously. Herein, we report the first example of a mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [(TAML)Fe^V(NTs)]^- (1). The spectroscopic characterization of 1 revealed an S = 1/2 Fe(V) oxidation state, an Fe-N bond length of 1.65(4) Å, and an Fe-N vibration at 817 cm^-1. The reactivity of 1 was demonstrated in C-H bond functionalization and nitrene transfer

The ring size effect of macrocyclic TMC ligands in nonheme iron(IV)-oxo complexes has been examined in hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactions; an iron(IV)-oxo complex bearing a smaller TMC ligand is more reactive in both HAT and OAT reactions, resulting from its high Fe(IV/III) redox potential.

We report for the first time electron-transfer (ET) properties of mononuclear nonheme iron-oxo and -imido complexes with the formal oxidation states of five and six, such as an iron(V)-imido TAML cation radical complex, which is formally an iron(VI)-imido complex [Fe^V(NTs)(TAML^+•)] (<b>1</b>; NTs = tosylimido), an iron(V)-imido complex [Fe^V(NTs)(TAML)]^- (<b>2</b>), and an iron(V)-oxo complex [Fe^V(O)(TAML)]^- (<b>3</b>). The one-ele

High-spin iron(III) iodosylarene complexes bearing an N-methylated cyclam ligand are synthesized and characterized using various spectroscopic methods. The nonheme high-spin iron(III) iodosylarene intermediates are highly reactive oxidants capable of activating strong C-H bonds of alkanes; the reactivity of the iron(III) iodosylarene intermediates is much greater than that of the corresponding iron(IV) oxo complex. The electrophilic character of the iron(III) iodosylarene complexes is demonstrat

A mononuclear nonheme iron(V)-imido complex bearing a tetraamido macrocyclic ligand (TAML), [Fe^V(NTs)(TAML)]^- (1), was oxidized by one-electron oxidants, affording formation of an iron(V)-imido TAML cation radical species, [Fe^V(NTs)(TAML^+•)] (2); 2 is a diamagnetic (S = 0) complex, resulting from the antiferromagnetic coupling of the low-spin iron(V) ion (S = 1/2) with the one-electron oxidized ligand (TAML^+•). 2 is a competent oxidant in C-

Members of the RAF family (ARAF, BRAF, and CRAF/RAF-1) are involved in a variety of cellular activities, including growth, survival, differentiation, and transformation. An oncogene encodes BRAF, the function of which is linked to MEK activation. BRAF is the most effective RAF kinase in terms of induction of MEK/ERK activity. However, the mechanisms involved in BRAF regulation remain unclear. In the present work, we used a tandem affinity purification approach to show that RNF149 (RING finger pr

The mechanism of the alkylperoxo O–O bond cleavage of low-spin iron(III)–alkylperoxo species has been well established in nonheme iron models. In contrast, the alkylperoxo O–O bond cleavage in nonheme high-spin iron(III)–alkylperoxo species binding an axial ligand has yet to be elucidated. Herein, we report the synthesis and characterization of mononuclear nonheme high-spin iron(III)–alkylperoxo complexes each bearing an N-tetramethylated 13-membered macrocyclic ligand (13-TMC), [FeIII(OOC(CH3)3

Abstract High‐valent cobalt‐oxo intermediates are proposed as reactive intermediates in a number of cobalt‐complex‐mediated oxidation reactions. Herein we report the spectroscopic capture of low‐spin ( S =1/2) Co IV ‐oxo species in the presence of redox‐inactive metal ions, such as Sc 3+ , Ce 3+ , Y 3+ , and Zn 2+ , and the investigation of their reactivity in CH bond activation and sulfoxidation reactions. Theoretical calculations predict that the binding of Lewis acidic metal ions to the coba