Uncovering a Hydrogen-Bond-Enabled Pathway to Dinitrosyl Iron Complexes
Abstract
Dinitrosyl iron complexes (DNICs) are prevalent NO-derived iron species; yet the factors that govern their formation at non-heme iron centers remain poorly understood. Here, we show that secondary-sphere hydrogen bonding interaction, together with steric accessibility of the Fe center enables quantitative formation of a {Fe(NO)2}9 (1-DNIC) complex through a previously unrecognized NO-driven redox pathway. Reaction of [Fe(DIG2dien)]2+ (DIG2dien = N-methyl-bis[2-(N,N′-diisopropylguanidino)ethyl]amine) with NO gas affords [Fe(DIG2dien)(NO)2]+ (1-DNIC) as the sole detectable iron-containing product. Spectroscopic and computational characterization by Mössbauer, EPR, SQUID, IR, X-ray absorption spectroscopy and DFT calculation establish an S = 1/2 ground state and a hydrogen-bond-supported {Fe(NO)2}9 unit. Mechanistic studies support a self-sustaining pathway in which NO functions as both a nitrosylating agent and a reductant, thereby circumventing the stoichiometric constraints of the previously reported disproportionation mechanisms. Notably, the sterically hindered analogue [Fe(DIG3tren)]2+ (2, DIG3tren = tris(N’,N”-diisopropylguanidinyl-2-ethyl)amine) reacts with NO gas to form the linear, hydrogen-bonded {FeNO}7 complex [Fe(DIG3tren)(NO)]2+ (2-NO) rather than a DNIC. Furthermore, 1-DNIC transfers NO to the ferrous precursor 2, generating 2-NO with concomitant formation of trace N2O. These findings establish secondary-sphere hydrogen bonding as a key determinant of DNIC assembly and reveal a hydrogen-bond-mediated, NO-driven mechanism for quantitative DNIC formation at a non-heme iron center.
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BibTeX
@misc{jux2026uncovering,
title = {{Uncovering a Hydrogen-Bond-Enabled Pathway to Dinitrosyl Iron Complexes}},
author = {Matthias Jux and Maximilian Schütze and Munir Mardini and Konstantin Krause and Michael Haumann and Yong Wang and Kallol Ray},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008233/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008233/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Uncovering a Hydrogen-Bond-Enabled Pathway to Dinitrosyl Iron Complexes
AU - Matthias Jux
AU - Maximilian Schütze
AU - Munir Mardini
AU - Konstantin Krause
AU - Michael Haumann
AU - Yong Wang
AU - Kallol Ray
PY - 2026
DA - 2026/09/03
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008233/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008233/v1
AB - Dinitrosyl iron complexes (DNICs) are prevalent NO-derived iron species; yet the factors that govern their formation at non-heme iron centers remain poorly understood. Here, we show that secondary-sphere hydrogen bonding interaction, together with steric accessibility of the Fe center enables quantitative formation of a {Fe(NO)2}9 (1-DNIC) complex through a previously unrecognized NO-driven redox pathway. Reaction of [Fe(DIG2dien)]2+ (DIG2dien = N-methyl-bis[2-(N,N′-diisopropylguanidino)ethyl]amine) with NO gas affords [Fe(DIG2dien)(NO)2]+ (1-DNIC) as the sole detectable iron-containing product. Spectroscopic and computational characterization by Mössbauer, EPR, SQUID, IR, X-ray absorption spectroscopy and DFT calculation establish an S = 1/2 ground state and a hydrogen-bond-supported {Fe(NO)2}9 unit. Mechanistic studies support a self-sustaining pathway in which NO functions as both a nitrosylating agent and a reductant, thereby circumventing the stoichiometric constraints of the previously reported disproportionation mechanisms. Notably, the sterically hindered analogue [Fe(DIG3tren)]2+ (2, DIG3tren = tris(N’,N”-diisopropylguanidinyl-2-ethyl)amine) reacts with NO gas to form the linear, hydrogen-bonded {FeNO}7 complex [Fe(DIG3tren)(NO)]2+ (2-NO) rather than a DNIC. Furthermore, 1-DNIC transfers NO to the ferrous precursor 2, generating 2-NO with concomitant formation of trace N2O. These findings establish secondary-sphere hydrogen bonding as a key determinant of DNIC assembly and reveal a hydrogen-bond-mediated, NO-driven mechanism for quantitative DNIC formation at a non-heme iron center.
ER -