磺酸功能化的离子液体型多金属氧酸盐的光色性能

发现磺酸功能化离子液体型多金属氧酸盐(IL-POM)具有可逆光色性质,并在紫外光激发下,详细考察了PyPS]_nH_3-nPW₁₂(n=1,3)(PyPs:吡啶丙磺酸盐)、PyPS]₄SiW₁₂、TEAPS]₃PW₁₂(TEAPS:3-(三乙胺基)丙磺酸盐)等样品的光致变色行为。 结果表明,磺酸化的IL-POM是一类弱的电荷转移多金属氧酸盐,但在紫外光激发下有机阳离子和POM阴离子间可以发生电子相互作用,实现W⁶⁺→W⁵⁺的还原,并形成稳定的电荷转移复合物,导致样品显色。 钨磷酸盐的光色性大大强于钨硅酸盐,且空气中避光放置可以消色。 但样品容易疲劳,着色-褪色重复性不好。 对光色机理的研究显示,有机阳离子中的-SO₃H基团作为电子供体参与了变色过程。 揭示了磺酸基团的电子供体作用,为设计电荷转移多金属氧酸盐和POM基光色材料提供了新的思路。

Photochromism of Ionic Liquid-like Polyoxometalates Functionalized by Sulfonic Acid

It was found that ionic liquid-like polyoxometalates(IL-POM) functionalized by sulfonic acid possess reversible photochromic properties. Detailed photochromism of PyPS]_nH_3-nPW₁₂(n=1,3), PyPS]₄SiW₁₂ and TEAPS]₃PW₁₂ samples were investigated. IL-POMs functionalized by sulfonic acid are a class of salts with weak charge-transfer effect. Under UV irradiation, however, electron interaction between organic cations and POM anions results in the reduction of W⁶⁺ to W⁵⁺. The formation of a stable charge-transfer complex leads to the coloration. The photochromic ability of tungstophosphate is stronger than that of tungstosilicate. The decoloration occurred in air when the colored sample was placed in dark. But the sample is easily fatigued and a coloration-decoloration cycle with poor reproducibility is observed. A study on photochromic mechanism shows that -SO₃H group in organic cation is involved in photochromic process as an electron donor. This reveals the donor property of sulfonic acid and provides a new strategy for designing charge-transfer polyoxometalates and POM-based photochromic materials.