High-spin ground states via electron delocalization in mixed-valence imidazolate-bridged divanadium
Author: ["Bettina Bechlars","Deanna M. D'Alessandro","David M. Jenkins","Anthony T. Iavarone","Starla D. Glover","Clifford P. Kubiak","Jeffrey R. Long"]
Publication: Nature Chemistry
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Abstract
The field of molecular magnetism has grown tremendously since the discovery of single-molecule magnets, but it remains centred around the superexchange mechanism. The possibility of instead using a double-exchange mechanism (based on electron delocalization rather than Heisenberg exchange through a non-magnetic bridge) presents a tantalizing prospect for synthesizing molecules with high-spin ground states that are well isolated in energy. We now demonstrate that magnetic double exchange can be sustained by simple imidazolate bridging ligands, known to be well suited for the construction of coordination clusters and solids. A series of mixed-valence molecules of the type [(PY5Me2)VII(µ-Lbr) VIII(PY5Me2)]4+ were synthesized and their electron delocalization probed through cyclic voltammetry and spectroelectrochemistry. Magnetic susceptibility data reveal a well-isolated S = 5/2 ground state arising from double exchange for [(PY5Me2)2V2(µ-5,6-dimethylbenzimidazolate)]4+. Combined modelling of the magnetic data and spectral analysis leads to an estimate of the double-exchange parameter of B = 220 cm−1 when vibronic coupling is taken into account. Single-molecule magnets are clusters of metal ions linked together by organic bridges, with properties typically arising from exchange coupling of unpaired metal electrons. In mixed-valence systems, another magnetic mechanism involving itinerant electrons can also occur and induce a high-spin ground state. Now, such electron delocalization has been observed through an imidazolate bridge — a common linker in metal-organic architectures — which may enable the construction of higher spin clusters or three-dimensional magnets.
Cite this article
Bechlars, B., D'Alessandro, D., Jenkins, D. et al. High-spin ground states via electron delocalization in mixed-valence imidazolate-bridged divanadium complexes. Nature Chem 2, 362–368 (2010). https://doi.org/10.1038/nchem.585
