title: Ambivalent binding between a radical-based pincer ligand and iron.
abstract: A complex exhibiting valence delocalization was prepared from 3,5-bis(2-pyridyl)-1,2,4,6-thiatriazinyl (), an inherently redox active pincer-type ligand, coordinated to iron ( ()). Complex can be prepared via two routes, either from the reaction of the neutral radical with FeCl2 or by treatment of the anionic ligand () with FeCl3, demonstrating its unique redox behaviour. Electrochemical studies, solution absorption and solid-state diffuse reflectance measurements along with X-ray crystallography were carried out to elucidate the molecular and solid-state properties. Temperature- and field-dependent Mössbauer spectroscopy coupled with magnetic measurements revealed that exhibits an isolated S = 5/2 ground spin state for which the low-temperature magnetic behaviour is dominated by exchange interactions between neighbouring molecules. This ground state is rationalized on the basis of DFT calculations that predict the presence of strong electronic interactions between the redox active ligand and metal. This interaction leads to the delocalization of β electron density over the two redox active centres and highlights the difficulty in assigning formal charges to .
authors.affiliation: Department of Chemistry, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada. jbrusso@uottawa.ca m.murugesu@uottawa.ca.
authors.forename: Katie L M
authors.initials: KL
authors.lastname: Harriman
authors.forename: Alicea A
authors.initials: AA
authors.lastname: Leitch
authors.forename: Sebastian A
authors.initials: SA
authors.lastname: Stoian
authors.forename: Fatemah
authors.initials: F
authors.lastname: Habib
authors.forename: Jared L
authors.initials: JL
authors.lastname: Kneebone
authors.forename: Serge I
authors.initials: SI
authors.lastname: Gorelsky
authors.forename: Ilia
authors.initials: I
authors.lastname: Korobkov
authors.forename: Serge
authors.initials: S
authors.lastname: Desgreniers
authors.forename: Michael L
authors.initials: ML
authors.lastname: Neidig
authors.forename: Stephen
authors.initials: S
authors.lastname: Hill
authors.forename: Muralee
authors.initials: M
authors.lastname: Murugesu
authors.forename: Jaclyn L
authors.initials: JL
authors.lastname: Brusso