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A Structural Model for the Iron–Nitrosyl Adduct of Gentisate Dioxygenase
Author(s) -
Banerjee Atanu,
Li Jia,
Speelman Amy L.,
White Corey J.,
Pawlak Piotr L.,
Brennessel William W.,
Lehnert Nicolai,
Chavez Ferman A.
Publication year - 2018
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201800992
Subject(s) - chemistry , adduct , hydrogen bond , fourier transform infrared spectroscopy , electron paramagnetic resonance , density functional theory , solvent , phosphine , dichloromethane , crystallography , stereochemistry , computational chemistry , molecule , organic chemistry , nuclear magnetic resonance , catalysis , quantum mechanics , physics
We present the synthesis, properties, and characterization of [Fe(T1Et4iPrIP)(NO)(H 2 O) 2 ](OTf) 2 ( 1 ) {T1Et4iPrIP = Tris(1‐ethyl‐4‐isopropyl‐imidazolyl)phosphine} as a model for the nitrosyl adduct of gentisate 1,2‐dioxygenase (GDO). The further characterization of [Fe(T1Et4iPrIP)(THF)(NO)(OTf)](OTf) ( 2 ) which was previously communicated (Inorg. Chem. 2014 , 53, 5414) is also presented. The weighted average Fe–N–O angle of 162° for 1 is very close to linear (≥ 165°) for these types of complexes. The coordinated water ligands participate in hydrogen bonding interactions. The spectral properties (EPR, UV/Vis, FTIR) for 1 are compared with 2 and found to be quite comparable. Complex 1 closely follows the relationship between the Fe–N–O angle and NO vibrational frequency which was previously identified for six‐coordinate {FeNO} 7 complexes. Liquid FTIR studies on 2 indicate that the ν(NO) vibration position is sensitive to solvent shifting to lower energy (relative to the solid) in donor solvent THF and shifting to higher energy in dichloromethane. The basis for this behavior is discussed. The K eq for NO binding in 2 was calculated in THF and found to be 470 m –1 . Density functional theory (DFT) studies on 1 indicate donation of electron density to the iron center from the π* orbitals of formally NO – . Such a donation accounts for the near linearity of the Fe–N–O bond and the large ν(NO) value of 1791 cm –1 .