Investigating the Vanadium Environments in Hydroxylamido V(V) Dipicolinate Complexes Using ⁵¹V NMR Spectroscopy and Density Functional Theory

Abstract

Using 51 V magic angle spinning solid-state NMR, SSNMR, spectroscopy and quantum chemical DFT calculations we have characterized the chemical shift and quadrupolar coupling parameters of a series of 8 hydroxylamido vanadium(V) dipicolinate complexes of the general formula VO(dipic)(ONR 1 R 2 )(H 2 O) where R 1 and R 2 can be H, CH 3 , or CH 2 CH 3 . This class of vanadium compounds was chosen for investigation because of their seven coordinate vanadium atom, a geometry for which there is limited 51 V SSNMR data. Furthermore, a systematic series of compounds with different electronic properties are available and allows for the effects of ligand substitution on the NMR parameters to be studied. The quadrupolar coupling constants, C Q , are small, 3.0 to 3.9 MHz, but exhibit variations as a function of the ligand substitution. The chemical shift tensors in the solid state are sensitive to changes in both the hydroxylamide substituent and the dipic ligand, a sensitivity which is not observed for isotropic chemical shifts in solution. The chemical shift tensors span approximately 1000 ppm, and are nearly axially symmetric. Based on DFT calculations of the chemical shift tensors, one of the largest contributors to the magnetic shielding anisotropy is an occupied molecular orbital with significant vanadium d z 2 character along the V=O bond.

Anti-diabetic effects of vanadium(III, IV, V)–chlorodipicolinate complexes in streptozotocin-induced diabetic rats

“…The H 2 dipic-Cl ligand and the K[V V O 2 (dipic-Cl)] (V 5 dipic-Cl) complex were prepared as previously described (Ooms et al 2007). The synthesis of H[V III (dipic-Cl) 2 ] Á 5H 2 O (V 3 dipic-Cl) was modified from the preparation of a similar complex (Chatterjee et al 1998).…”

Mixed‐Ligand Oxidovanadium(V) Complexes with N′‐Salicylidenehydrazides: Synthesis, Structure, and 51V Solid‐State MAS NMR Investigation

“…As can be seen from Table 2 this second-order correction is found to be within -3 and -5 ppm. This is because of the comparatively small values of the nuclear quadrupolar coupling constant in the order of about 4 MHz, which is at the lower end of the usually observed range for oxidovanadium(V) [42,43] and dioxidovanadium(V) [44] complexes going up to about 7 MHz. Nevertheless, the spectra are characterized by a considerable asymmetry of the EFG tensor with values between 0.4 and 0.8.…”

Evaluating the accuracy of density functional theory for calculating 1H and 13C NMR chemical shifts in drug molecules

“…[3][4][5] Detailed expositions of the various theories that underpin the calculation of magnetic properties have been the subject of several excellent articles. [6][7][8][9][10] Examples of diverse chemical problems which have been addressed using NMR calculations include: analysis of rotational barriers in neutral and protonated furfurylidenanilines, [11] studies on vanadium(V) dipicolinate complexes, [12,13] work on proton exchange reactions in porphyrins, [14] intramolecular hydrogen bonding, [15] studies on the 1 H and 13 C NMR chemical shifts in transition metal hydrides, [16] substituted hydrocarbons [17] and fullerenes, [18,19] configurational assignments in cellulose, [20] 6β-hydroxyhyoscyamine diastereoisomers, [21] lactones [22] and lactams, [23] and chemical shift assignment in natural products [24] and in drug molecules like Taxol. [25] Early efforts using quantum chemistry to predict NMR chemical shifts and spin-spin coupling constants employed the Individual Gauges for Localized Orbitals (IGLO) method.…”