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The Original CoII Heteroscorpionates Revisited: On the EPR of Pseudotetrahedral CoII
Author(s) -
Baum Robert R.,
Myers William K.,
Greer Samuel M.,
Breece Robert M.,
Tierney David L.
Publication year - 2016
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.201501356
Subject(s) - chemistry , electron paramagnetic resonance , hyperfine structure , crystallography , zero field splitting , spectroscopy , nuclear magnetic resonance , electron , atomic physics , physics , quantum mechanics , spin polarization
An examination of the solution spectroscopy of a series of tetrahedral bis‐bispyrazolylborate complexes of Co II is presented. This includes a re‐examination of the UV/Vis‐NIR of the three stable derivatives, Bp 2 Co, Bp 3,5Me 2 Co and (Ph 2 Bp) 2 Co, which showed two transitions previously unobserved, one arising from splitting of the near‐infrared d ‐ d transition and one arising from a ligand‐based or charge‐transfer mechanism; a reevaluation of Δ and B led to values more in line with similar complexes. Frozen solution EPR of the series of complexes suggests all are under the influence of a non‐negligible, negative zero‐field splitting. This is in contrast to previous powder measurements, which we show observed only a subset of the available transitions, leading to a mis‐assignment of the parent complex's electronic structure. We present a proposal, based on the EPR of this closely related set of complexes, that the 59 Co hyperfine coupling that is only sometimes observed in the EPR of pseudotetrahedral Co II at X‐band is in fact indicative of an M S = ± 3/2 ground level ( D < 0), with the hyperfine coupling originating in the nominally forbidden Δ M S = 3 transition along g ∥ .