Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Hydrogen Bond Donor or trans Donor: Spectroscopic Characterization and Reactivity Studies of Ferryl-oxo Intermediates Bearing a Pendant Alcohol Moiety (#575)

Dibya Jyoti MSc Barman 1 , Kallol Prof. Dr. Ray 1 , Dibya Jyoti Barman 1
  1. Institute of Chemistry, Humboldt-Universität zu Berlin, Berlin, Germany

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Increasing interest in the microenvironment1, 2 surrounding the active sites of different enzymes has recently led to many crucial structure-function-oriented discoveries3, 4. In light of this extensive research, high-valent ferryl-oxo species are frequently broached as the key reactive oxidants5-7. With the motivation to stabilize and understand the fundamental properties of such an iron(IV)-oxo center in trans tyrosine bound enzymes, catalases8, 9, vastly known for catalytic disproportionation reaction of hydrogen peroxide, we have investigated the effect of a pendant neutral alcohol moiety in the N-alkylated cyclam (1,4,8,11-tetraazacyclotetradecane) ligand backbone10. The oxo group binds to the site syn (1-syn) or anti (1-anti) (Figure 1) to the three methyl and –CH2CH2OH groups (TMC-HOR = 2-(4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecan1-yl)ethan-1-ol). Unlike in the previously reported [FeIV(Oanti)(TMC-SR)]+ (TMC-SR = 1-mercaptoethyl-4,8,11-trimethyl-1,4,8,11 tetraazacyclotetradecane) intermediate11, bearing an axial mono-anionic thiolate ligand trans to the oxo unit, the pendant alcohol moiety in 1-syn and 1-anti remains protonated as a prerequisite for the stabilization of the iron(IV)-oxo core in TMC-HOR ligand systems. It serves as a H-bonding donor to the iron(IV)-oxo unit in 1-syn, and stays bound trans to the iron(IV)-oxo moiety in 1-anti. Comparative reactivity study reveals 1-syn to be a stronger hydrogen atom abstraction and oxygen atom transfer agent relative to 1-anti. The different orientations of the oxo group, as well as the H-Bonding and trans effect, jointly contribute to the different spectroscopic and reactivity properties of 1-syn and 1-anti.

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