High-frequency and -field electron paramagnetic resonance of vanadium(IV, III, and II) complexes

In this review, we discuss the advantages of performing electron paramagnetic resonance (EPR) on coordination and metalloorganic complexes containing various oxidation states of vanadium, from +4 to +2, using the high-frequency and -field version of this technique, known as HFEPR. Thus, HFEPR is advantageous in investigating (S = 1/2) V(IV) species due to its higher g-factor resolution over conventional EPR, albeit at the price of losing the hyperfine structure resolution due to g-strain. It is very much desirable in characterizing (S = 3/2) V(II) complexes since it is capable of precisely and accurately measuring the zero-field splitting present in these species. Finally, HFEPR is indispensable in investigating (S = 1)V(III) species, which in conventional conditions are often EPR-silent due to the combination of their large zero-field splitting and integer spin number. The use of HFEPR thus can provide additional information regarding the oxidation state of the metal and the coordination geometry. (C) 2014 Elsevier B.V. All rights reserved.