title: Magneto-Structural Correlations in Pseudotetrahedral Forms of the [Co(SPh)4]2-Complex Probed by Magnetometry, MCD Spectroscopy, Advanced EPR Techniques, and ab Initio Electronic Structure Calculations.
abstract: The magnetic properties of pseudotetrahedral Co(II) complexes spawned intense interest after (PPh4)2[Co(SPh)4] was shown to be the first mononuclear transition-metal complex displaying slow relaxation of the magnetization in the absence of a direct current magnetic field. However, there are differing reports on its fundamental magnetic spin Hamiltonian (SH) parameters, which arise from inherent experimental challenges in detecting large zero-field splittings. There are also remarkable changes in the SH parameters of [Co(SPh)4]2-upon structural variations, depending on the counterion and crystallization conditions. In this work, four complementary experimental techniques are utilized to unambiguously determine the SH parameters for two different salts of [Co(SPh)4]2-: (PPh4)2[Co(SPh)4] (1) and (NEt4)2[Co(SPh)4] (2). The characterization methods employed include multifield SQUID magnetometry, high-field/high-frequency electron paramagnetic resonance (HF-EPR), variable-field variable-temperature magnetic circular dichroism (VTVH-MCD), and frequency domain Fourier transform THz-EPR (FD-FT THz-EPR). Notably, the paramagnetic Co(II) complex [Co(SPh)4]2-shows strong axial magnetic anisotropy in 1, with D = -55(1) cm-1and E/D = 0.00(3), but rhombic anisotropy is seen for 2, with D = +11(1) cm-1and E/D = 0.18(3). Multireference ab initio CASSCF/NEVPT2 calculations enable interpretation of the remarkable variation of D and its dependence on the electronic structure and geometry.
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany.|Novosibirsk State University , Pirogova 2, 630090 Novosibirsk, Russia.
authors.forename: Elizaveta A
authors.identifier: http://orcid.org/0000-0003-4407-1882
authors.initials: EA
authors.lastname: Suturina
authors.affiliation: Berlin Joint EPR Lab, Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie , Kekuléstraße 5, 12489 Berlin, Germany.
authors.forename: Joscha
authors.initials: J
authors.lastname: Nehrkorn
authors.affiliation: Department of Chemistry, University of California Berkeley , Berkeley, California 94720, United States.|Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Zadrozny
authors.affiliation: National High Magnetic Field Laboratory , Tallahassee, Florida 32310, United States.|Department of Physics, Clarendon Laboratory, University of Oxford , Parks Road, Oxford OX1 3PU, United Kingdom.
authors.forename: Junjie
authors.initials: J
authors.lastname: Liu
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany.|Bulgarian Academy of Sciences , Institute of General and Inorganic Chemistry, Akad. Georgi Bontchev Street 11, 1113 Sofia, Bulgaria.
authors.forename: Mihail
authors.initials: M
authors.lastname: Atanasov
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany.
authors.forename: Thomas
authors.identifier: http://orcid.org/0000-0002-0399-7999
authors.initials: T
authors.lastname: Weyhermüller
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Maganas
authors.affiliation: National High Magnetic Field Laboratory , Tallahassee, Florida 32310, United States.|Department of Physics, Florida State University , Tallahassee, Florida 32306, United States.
authors.forename: Stephen
authors.initials: S
authors.lastname: Hill
authors.affiliation: Berlin Joint EPR Lab, Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin für Materialien und Energie , Kekuléstraße 5, 12489 Berlin, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schnegg
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany.
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.affiliation: Department of Chemistry, University of California Berkeley , Berkeley, California 94720, United States.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Long
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, Mülheim an der Ruhr 45470, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Neese