A series of organic hybrid polyoxovanadate clusters incorporating tris(hydroxymethyl)methane derivatives.

A series of new organic hybrid polyoxovanadate clusters [VO(μ-OH)(acac)(Htri)] (1, Htri = tris(hydroxymethyl) aminomethane, acac = acetylacetone), [VO(acac)(Htri)(L)] {HL = methanol (2), ethanol (3a and 3b), ethylene glycol (4) and benzyl alcohol (5)}, {VO(HO)(tri-acetamide)(CHCOO)} (6, Htri-acetamide = -(2-hydroxy-1,1-bis-hydroxymethyl-ethyl)-acetamide), [VO(μ-OH)(Htri)]·6HO (7) and [VO(tri)(Htri)(HCOO)(CHCOO)]·2HO (8) were prepared by hydro(solvo)thermal methods and characterized structurally. 1 contains [VO(OH)(acac)] and [VO(Htri)] units, which are further interconnected common edges to build a tetravanadyl cluster [VO(OH)(acac)(Htri)] with the double-deficient cube [VO]. The tetravanadyl cluster frameworks of 2-5 can be derived from the tetravanadyl cluster of 1 by replacing two -OH groups with two deprotonated organic alcohol ligands, namely, CHO (2), CHCHO (3a and 3b), HO(CH)O (4) and CHCHO (5). Interestingly, both 3a and 3b have the same chemical structure, but they exhibit different conformational polymorphisms [denoted as α-type (3a) and β-type (3b)]. Such conformational polymorphisms within the polyoxovanadate clusters incorporating tris(hydroxymethyl)methane derivatives emerged for the first time. 6 displays another tetravanadyl cluster {VO(HO)(tri-acetamide)(CHCOO)} with a [VO] fragment, where the tri-acetamide unit comes from the amidation reaction of Htri and acetic acid and caps the tetrahedral void of the tetravanadyl cluster. The polyoxovanadate cluster of 7 can originate from the Lindqvist-type hexavanadyl cluster [VO] by replacing nine μ-oxides with nine alkoxides of three tri-acetamide ligands. 8 exhibits a fully reduced tetradecavanadyl cluster based on the linkage of two heptavanadyl clusters two O bridges. The magnetic properties of 1-8 show typical antiferromagnetic interactions.