Affiliation:
1. Department of Chemistry Center for Biophysics and Quantitative Biology Materials Research Laboratory University of Illinois Urbana-Champaign Urbana Illinois, 61801 USA
2. George L. Clark X-Ray Facility and 3 M Materials Laboratory University of Illinois, Urbana-Champaign Urbana Illinois, 61801 USA
Abstract
AbstractMononuclear monodioxolene valence tautomeric (VT) cobalt complexes typically exist in their low spin (l.s.) CoIII(cat2−) and high spin (h.s.) CoII(sq⋅−) forms (cat2−=catecholato, and sq⋅−=seminquinonato forms of 3,5−di−tBu‐1,2‐dioxolene), which reversibly interconvert via temperature‐dependent intramolecular electron transfer. Typically, the remaining four coordination sites on cobalt are supported by a tetradentate ligand whose properties influence the temperature at which VT occurs. We report that replacing one chelating pyridyl arm of tris(2‐pyridylmethyl)amine (tpa) with a weaker field ortho‐anisole moiety facilitates access to a third magnetic state, and examine a series of related complexes. Variable temperature crystallographic, magnetic, calorimetric, and spectroscopic studies support that this third state is consistent with l.s. CoII(sq⋅−). Thus, our ligand modifications not only provide access to the VT transition from l.s. CoIII(cat2−) to l.s. CoII(sq⋅−), but at higher temperatures, the complex undergoes spin crossover from l.s. CoII(sq⋅−) to h.s. CoII(sq⋅−), representing the first example of two‐step magnetic switching in a mononuclear monodioxolene cobalt complex. We hypothesize that ligand dynamicity may facilitate access to the rarely observed l.s. CoII(sq⋅−) intermediate state, suggesting a new design criterion in the development of stimulus‐responsive multi‐state molecular switches.
Funder
National Institutes of Health
Subject
General Chemistry,Catalysis
Cited by
8 articles.
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