Herein, we demonstrate the correlation of 51V NMR chemical shifts with redox potentials for a series of non-innocent vanadium(V) catecholate complexes. Several of the synthesized complexes shown here were characterized previously by both solid state and solution 51V NMR spectroscopy. Illustrated is an observed linear correlation between solution and solid state 51V NMR chemical shifts, which is consistent with the solution structure being similar to that observed in the solid state. Since the solid state 51V NMR chemical shift describes the electronic structure of the vanadium complexes, there exists the potential for the use of the 51V NMR chemical shift to characterize the properties of these complexes. The vanadium(V) catecholate complexes used in this study are, in fact, redox active and the chemical shifts fall outside the normal populated isotropic 51V NMR chemical shift range (-300 to -700 ppm), which is anticipated for complexes with non-innocent redox active ligands. The series of catecholate complexes are therefore well suited for examination of the hypothesis that the 51V NMR chemical shifts of the vanadium(V) catechol complexes correlate with the redox potential of these compounds. Cyclic Voltammetry studies were completed to determine the redox potential of each complex in solution. The 51V NMR chemical shifts were then plotted as a function of the redox potential. A linear correlation was observed for the 51V NMR isotropic chemical shift versus redox potential for the three known and three novel VO(HSHED) compounds containing a non-innocent catecholate ligand. These studies show that substitution of the non-innocent catechol ligand with electron-donating groups results in a downfield shift in 51V NMR spectra and a decrease in redox potential. However, in contrast, substitution of the catecholate ligand with electron-withdrawing groups results in an up field shift in 51V NMR and an increase in redox potential. Together, these studies demonstrate for the first time that 51V NMR chemical shifts correlate with the redox potential of the vanadium(V) catecholates and could potentially be a useful method for characterization of the redox properties of these vanadium (V) catecholate complexes.

Correlating redox potential with 51V NMR chemical shifts for vanadium (V) catecholates

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.