title: Spectroscopic and Computational Studies of Spin States of Iron(IV) Nitrido and Imido Complexes.
abstract: High-oxidation-state metal complexes with multiply bonded ligands are of great interest for both their reactivity as well as their fundamental bonding properties. This paper reports a combined spectroscopic and theoretical investigation into the effect of the apical multiply bonded ligand on the spin-state preferences of threefold symmetric iron(IV) complexes with tris(carbene) donor ligands. Specifically, singlet (S = 0) nitrido [{PhB(ImR)3}FeN], R =tBu (1), Mes (mesityl, 2) and the related triplet (S = 1) imido complexes, [{PhB(ImR)3}Fe(NR')]+, R = Mes, R' = 1-adamantyl (3),tBu (4), were investigated by electronic absorption and Mössbauer effect spectroscopies. For comparison, two other Fe(IV) nitrido complexes, [(TIMENAr)FeN]+(TIMENAr= tris[2-(3-aryl-imidazol-2-ylidene)ethyl]amine; Ar = Xyl (xylyl), Mes), were investigated by57Fe Mössbauer spectroscopy, including applied-field measurements. The paramagnetic imido complexes 3 and 4 were also studied by magnetic susceptibility measurements (for 3) and paramagnetic resonance spectroscopy: high-frequency and -field electron paramagnetic resonance (for 3 and 4) and frequency-domain Fourier-transform (FD-FT) terahertz electron paramagnetic resonance (for 3), which reveal their zero-field splitting parameters. Experimentally correlated theoretical studies comprising ligand-field theory and quantum chemical theory, the latter including both density functional theory and ab initio methods, reveal the key role played by the Fe 3dz2(a1) orbital in these systems: the nature of its interaction with the nitrido or imido ligand dictates the spin-state preference of the complex. The ability to tune the spin state through the energy and nature of a single orbital has general relevance to the factors controlling spin states in complexes with applicability as single molecule devices.
authors.affiliation: Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology , Radlinského 9, SK-81237 Bratislava, Slovakia.
authors.forename: Lukas
authors.initials: L
authors.lastname: Bucinsky
authors.affiliation: Institute of Physical Chemistry and Chemical Physics, Faculty of Chemical and Food Technology, Slovak University of Technology , Radlinského 9, SK-81237 Bratislava, Slovakia.
authors.forename: Martin
authors.initials: M
authors.lastname: Breza
authors.affiliation: Department of Chemistry, Indiana University , 800 E. Kirkwood Avenue, Bloomington, Indiana 47401, United States.|Department of Chemistry and Biochemistry, New Mexico State University , Las Cruces, New Mexico 88003, United States.
authors.forename: Wei-Tsung
authors.initials: WT
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Indiana University , 800 E. Kirkwood Avenue, Bloomington, Indiana 47401, United States.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Hickey
authors.affiliation: Department of Chemistry and Chemical Biology, The University of New Mexico , Albuquerque, New Mexico 87131, United States.
authors.forename: Diane A
authors.identifier: http://orcid.org/0000-0003-0939-3309
authors.initials: DA
authors.lastname: Dickie
authors.affiliation: Department of Chemistry and Biochemistry, New Mexico State University , Las Cruces, New Mexico 88003, United States.
authors.forename: Ismael
authors.initials: I
authors.lastname: Nieto
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Jordan A
authors.initials: JA
authors.lastname: DeGayner
authors.affiliation: Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: T David
authors.identifier: http://orcid.org/0000-0003-4144-900X
authors.initials: TD
authors.lastname: Harris
authors.affiliation: Department of Chemistry and Pharmacy, Friedrich-Alexander-University Erlangen-Nürnberg , Egerlandstraße 1, D-91058 Erlangen, Germany.
authors.forename: Karsten
authors.identifier: http://orcid.org/0000-0002-7844-2998
authors.initials: K
authors.lastname: Meyer
authors.affiliation: National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States.
authors.forename: J
authors.initials: J
authors.lastname: Krzystek
authors.affiliation: National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States.
authors.forename: Andrew
authors.identifier: http://orcid.org/0000-0001-6225-9796
authors.initials: A
authors.lastname: Ozarowski
authors.affiliation: Department of Chemistry, University of Washington , Seattle, Washington 98195, United States.
authors.forename: Joscha
authors.initials: J
authors.lastname: Nehrkorn
authors.forename: Alexander
authors.initials: A
authors.lastname: Schnegg
authors.forename: Karsten
authors.initials: K
authors.lastname: Holldack
authors.affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem , 91904 Jerusalem, Israel.
authors.forename: Rolfe H
authors.initials: RH
authors.lastname: Herber
authors.affiliation: Department of Biological, Chemical and Physical Sciences, Roosevelt University , Chicago, Illinois 60605, United States.
authors.forename: Joshua
authors.identifier: http://orcid.org/0000-0003-3307-2556
authors.initials: J
authors.lastname: Telser
authors.affiliation: Department of Chemistry, Indiana University , 800 E. Kirkwood Avenue, Bloomington, Indiana 47401, United States.|Department of Chemistry and Biochemistry, New Mexico State University , Las Cruces, New Mexico 88003, United States.
authors.forename: Jeremy M
authors.identifier: http://orcid.org/0000-0002-3206-4725
authors.initials: JM
authors.lastname: Smith