Effect of ancillary ligand on electronic structure as probed by 51V solid-state NMR spectroscopy for vanadium–o-dioxolene complexes

Abstract

A series of vanadium(V) complexes with o-dioxolene (catecholato) ligands and an ancillary ligand, (N-(salicylideneaminato)ethylenediamine) (hensal), were investigated using 51V solid-state magic angle spinning NMR spectroscopy (51V MAS NMR) to assess the local environment of the vanadium(V). The solid-state 51V NMR parameters of vanadium(V) complexes with a related potentially tetradentate ancillary ligand (N-salicylidene-N′-(2-hydroxyethyl)ethylenediamine) (h2shed) were previously shown to be associated with the size of the HOMO-LUMO gap in the complex, and as such provide insights on the interaction between metal ion and ligand (P. B. Chatterjee, et al., Inorg. Chem 50 (2011) 9794). Our results show that the modification of the ancillary ligand does not impact the observed trend between complexes ranging from catechols with electron rich to electron poor substituents. However, the ancillary ligand does impact the size of the HOMO-LUMO separation in the parent complex and thus the solid-state vanadium NMR chemical shift of the unsubstituted vanadium complex. For these complexes significant changes observed in the isotropic shifts and more modest changes detected in the CQ reflect the electronic changes in the complex as the catechol is varied. However, no obvious trend was observed in the chemical shift anisotropies (δσ and ησ) with the variation in the catechol. The electronic changes in the coordination environment of the vanadium can be described using solid-state 51V NMR spectroscopy.

51V NMR Crystallography of Vanadium Chloroperoxidase and Its Directed Evolution P395D/L241V/T343A Mutant: Protonation Environments of the Active Site

“…51 V MAS NMR spectra yield information on the anisotropic quadrupolar and chemical shift interactions, which are exquisitely sensitive to the coordination environment of the metal center, as others and we have previously demonstrated . Indeed, 51 V MAS NMR spectroscopy has been used to characterize a broad range of vanadium inorganic complexes in the past decade. , As we have demonstrated in multiple studies, 51 V NMR parameters are not only sensitive to the first coordination sphere, but they are also affected by the distal substituents, , and to the presence of redox active ligands. , 51 V MAS NMR can thus yield reliable information about the chemical nature of the vanadium center and the detailed ligand environments. This approach is particularly powerful when coupled with Density Functional Theory (DFT). ,,, NMR crystallography is another emerging technique that allows structural analysis of diamagnetic solids .…”

A Short‐Lived but Highly Cytotoxic Vanadium(V) Complex as a Potential Drug Lead for Brain Cancer Treatment by Intratumoral Injections

“…A non-innocent mixed-ligand monooxido V V complex (that is, containing a redox active ligand; 1 in Scheme 1) [10] with a tridentate Schiff base (N-(salicylideneaminato)-N'-(2hydroxyethyl)ethane-1,2-diamine) and 3,5-di-tert-butylcatecholato ligands was recently shown to remain intact long enough in cell culture medium and cell membrane models to cause high cytotoxicity in cultured human bone cancer cells. [11] Decomposition of 1 under biologically relevant conditions released monomeric and oligomeric V V oxido complexes ( 51 V NMR spectroscopy data) [11] that reacted further with cell culture medium.…”

Characterization of V–Mo–W Mixed Oxide Catalyst Surface Species by 51V Solid-State Dynamic Nuclear Polarization NMR

“…Solid-state NMR (ssNMR) provides structural information on the local environments of NMR active nuclei, which makes it extremely useful for characterizing complex or disordered systems. As example, solid-state 51 V NMR spectroscopy has been used to determine the electronic structure and active sites of vanadium containing systems like metallo proteins, bioinorganic solids − and inorganic catalysts. − Nowadays, the main focus of 51 V NMR spectroscopy is the study of vanadates having catalytic properties, and of supported vanadium oxide catalysts. − Since ssNMR spectroscopy is appropriate to characterize the molecular structure and dynamics of metal oxides, its application for the analysis of the vanadium oxide phases is the focus of the present study.…”