W-band EPR studies of high-spin nitrenes with large spin-orbit contribution to zero-field splitting
- Institute of Problems of Chemical Physics RAS, Chernogolovka (Russian Federation)
- Max-Planck Institute for Chemical Energy Conversion, Mulheim/Ruhr (Germany)
First W-band 94 GHz EPR spectra of randomly oriented triplet, quintet, and septet nitrenes formed during the photolysis of 1,3,5-triazido-2,4,6-tribromobenzene in cryogenic matrices are reported. In comparison with conventional X-band 9 GHz electron paramagnetic resonance (EPR) spectroscopy, W-band EPR spectroscopy allows the detection and complete spectroscopic characterization of all paramagnetic species formed at different stages of the photolysis of aromatic polyazides. This type of spectroscopy is of paramount importance for experimental determination of the sign of the zero-field splitting (ZFS) parameters of high-spin molecules with large spin-orbit contribution to the ZFS, caused by the effect of heavy atoms. The study shows that triplet 1,3-diazido-2,4,6-tribromo-5-nitrenobenzene (T1) has D{sub T} = 1.369 cm{sup −1}, E{sub T} = 0.093 cm{sup −1}, and g = 2.0033, quintet 1-azido-2,4,6-tribromo-3,5-dinitrenobenzene (Q1) shows D{sub Q} = − 0.306 cm{sup −1}, E{sub Q} = 0.0137 cm{sup −1}, and g = 2.0070, and septet 2,4,6-tribromo-1,3,5-trinitrenobenzene (S1) has D{sub S} = − 0.203 cm{sup −1}, E{sub S} = 0, and g = 2.0073. The experimental ZFS parameters agree well with the results of density functional theory calculations at the PBE/Ahlrichs-DZ level of theory, showing that such calculations adequately describe the magnetic properties of bromine-containing high-spin nitrenes. Both experimental and theoretical data indicate that, in contrast to all known to date quintet dinitrenes, dinitrene Q1 has the negative sign of magnetic anisotropy due to the “heavy atom effect.” This dinitrene along with septet trinitrene S1 possess the largest negative value of D among all known quintet and septet organic polyradicals.
- OSTI ID:
- 22493581
- Journal Information:
- Journal of Chemical Physics, Vol. 143, Issue 8; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Studies on monomers and dimers of Y(III) and La(III) porphyrin complexes by time-resolved electron paramagnetic resonance
Spectroscopic and Computational Studies of Spin States of Iron(IV) Nitrido and Imido Complexes
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTRA
ABSORPTION SPECTROSCOPY
ANISOTROPY
ATOMS
AZIDES
BROMINE
COMPARATIVE EVALUATIONS
DENSITY FUNCTIONAL METHOD
ELECTRON SPIN RESONANCE
GHZ RANGE
L-S COUPLING
MAGNETIC PROPERTIES
MATRICES
MOLECULES
NITROGEN
ORGANIC POLYMERS
PARAMAGNETISM
PHOTOLYSIS
TRIPLETS