Vanadium(V)-protein model studies: solid-state and solution structure

Abstract

The structures of oxovanadium(V) triethanolaminate, 1, and oxovanadium(V) tri-2-propanolaminate, 2, have been determined. In each case the V(V) atom exhibits distorted trigonal bipyramidal coordination with the nitrogen atom and the oxo group in the axial positions. The distortion is observed because the vanadium atom is displaced out of the plane of the triethanolaminate oxygens in the direction of the doubly-bonded oxygen. Compound 1 crystallizes in the monoclinic space group P21 with a = 7.051 (2) A, b = 7.429(2) A, c = 7.980(2) A, @ = 93.46(3)O, V = 417.2(2) A', and 2 = 2. The discrete complex exhibits a V-N bond length of 2.276(1) A and an average VO(C) bond length of 1.794(3) A. Compound 2 crystallizes in the hexagonal space group P63 with a = 9.465(2) A, c = 7.493(2) A, V = 581.3(2) A, and 2 = 2. The discrete complex exhibits a V-N bond length of 2.297(15) A and a VO(C) bond length of 1.794 (5) A. The multinuclear solution NMR parameters of 1 and 2 were determined and compared to the parameters for aqueous complexes of vanadate and triethanolamine and vanadate and tri-2-propanolamine, respectively. The results and analyses of these systems lead to structural characterization of the aqueous complexes. 13C NMR and multinuclear NMR studies of related vanadium(V)-peptide complexes should assist in characterizing the coordination chemistry about the vanadium in complexes that resist structural analysis by X-ray diffraction.

Fifteen Years of Dancing with Vanadium

“…By 13 C and 1 H NMR spectroscopy and coordination-induced shifts (CISs), it was established that the species in aqueous solution had one ethanolamine/propanolamine arm free and two coordinated to the vanadium atom. This structure (1) was different from the structure in organic solvents and in the solid state ([VO(tpa)]) [60]. The two possible structures in aqueous solution are one with the cis-dioxo group in the same plane as the tripropanolamine nitrogen atom, 2, and one with the two oxo groups trans to the tripropanolamine nitrogen and oxygen atoms, 3, respectively.…”

“…The reaction of vanadate with ethanol [20] was the first of a series of organic systems that included numerous coordinating functionalities such as hydroxyl [20,21], carboxyl [35,48,49], amino [35,38,50,51], amido [52][53][54], phospho [22,55], and bi- [21,35,38,49,56] and multidentate [34,37,39,51,[53][54][55][57][58][59][60][61][62] ies mapped out what types of complexes formed, the pH dependence of complex formation, and the stoichiometry of the systems. This approach was followed in most subsequent studies.…”

“…The Crans group was the first group probing the solution structure of systems by generating the solid-state data upon which a framework could be built [17,60,72]. The 51 V NMR studies are necessary to document the stoichiometry and the number of different types of species that exist in solution.…”

“…However, detailed structural analysis requires multiple approaches including X-ray crystallography of solid-state materials as well as additional spectroscopic studies in solution probing connectivity and ligand coordination. An early and particularly pleasing example of these types of studies is the investigation of the vanadate-triethanolamine and vanadate-tripropanolamine systems [34,44,60]. The initial 51 V NMR studies on this system [34,44] was followed by the synthesis of the complex in both organic and aqueous solvent, X-ray crystallographic characterization of the solid material in addition to multinuclear NMR studies in aqueous solution [60].…”

“…An early and particularly pleasing example of these types of studies is the investigation of the vanadate-triethanolamine and vanadate-tripropanolamine systems [34,44,60]. The initial 51 V NMR studies on this system [34,44] was followed by the synthesis of the complex in both organic and aqueous solvent, X-ray crystallographic characterization of the solid material in addition to multinuclear NMR studies in aqueous solution [60]. By 13 C and 1 H NMR spectroscopy and coordination-induced shifts (CISs), it was established that the species in aqueous solution had one ethanolamine/propanolamine arm free and two coordinated to the vanadium atom.…”