Centro Química Estrutural, Instituto Superior Técnico, TU Lisbon, Av. Rovísco Pais, 1049-001 Lisbon, Portugal.
Phys Chem Chem Phys. 2011 Sep 7;13(33):15094-102. doi: 10.1039/c1cp20800d. Epub 2011 Jul 25.
We report the structural characterization of vanadyl acetylacetonate in imidazolium room temperature ionic liquids--bbimNTf(2), bmimNTf(2), C(3)OmimNTf(2), bm(2)imNTf(2), bmimPF(6), bmimOTf, bmimBF(4), bmimMeCO(2), bmimMeSO(4), bmimMe(2)PO(4) and bmimN(CN)(2)--and organic solvents. The complex was characterized by visible electronic (Vis) and EPR spectroscopies. VO(acac)(2) shows solvatochromism in the selected ionic liquids and behaves as in organic solvents, evidencing coordination of the ionic liquid anion in the solvents with higher coordinating ability. The Lewis basicity order obtained for the IL anions was: PF(6)(-) < NTf(2)(-) < OTf(-)≈ MeCO(2)(-) < MeSO(4)(-) < BF(4)(-)≈ N(CN)(2)(-) < Me(2)PO(4)(-). The solvent effect on the spectroscopic data was tentatively examined using linear solvation energy relationships based on the Kamlet-Taft solvent scale (α, β and π*), however no suitable correlation was found with all data. The EPR characterization showed the presence of two isomers in bmimOTf, bmimMeCO(2) and bmimMe(2)PO(4), suggesting coordination of the ionic liquid anions in both equatorial and axial positions. The full geometry optimization of cis-/trans-VO(acac)(2)(OTf)(-) and cis-/trans-VO(acac)(2)(OTf)(mmim) structures was done at the B3P86/6-31G* level of theory. The calculations confirm that the anion OTf(-) is able to coordinate to VO(acac)(2) with the trans isomer being more stable than the cis by 4.8 kcal mol(-1).
我们报告了乙酰丙酮氧钒在咪唑室温离子液体--bbimNTf(2)、bmimNTf(2)、C(3)OmimNTf(2)、bm(2)imNTf(2)、bmimPF(6)、bmimOTf、bmimBF(4)、bmimMeCO(2)、bmimMeSO(4)、bmimMe(2)PO(4)和 bmimN(CN)(2)--和有机溶剂中的结构特征。该配合物通过可见电子（Vis）和 EPR 光谱进行了表征。VO(acac)(2)在所选离子液体中表现出溶剂变色性，并且在有机溶剂中表现出与有机溶剂相似的行为，这表明离子液体阴离子在具有更高配位能力的溶剂中配位。根据 IL 阴离子获得的路易斯碱性顺序为：PF(6)(-) < NTf(2)(-) < OTf(-)≈ MeCO(2)(-) < MeSO(4)(-) < BF(4)(-)≈ N(CN)(2)(-) < Me(2)PO(4)(-)。使用基于 Kamlet-Taft 溶剂标度（α、β 和 π*）的线性溶剂化能量关系，初步考察了溶剂对光谱数据的影响，但没有找到与所有数据都合适的相关性。EPR 表征表明，bmimOTf、bmimMeCO(2)和 bmimMe(2)PO(4)中存在两种异构体，表明离子液体阴离子在赤道和轴向位置都发生了配位。cis-/trans-VO(acac)(2)(OTf)(-)和 cis-/trans-VO(acac)(2)(OTf)(mmim)结构的全几何优化在 B3P86/6-31G*理论水平上进行。计算结果证实，OTf(-)阴离子能够与 VO(acac)(2)配位，反式异构体比顺式异构体稳定，稳定常数相差 4.8 kcal mol(-1)。
