Tuning the Photochromic Properties of Molybdenum Bisphosphonate Polyoxometalates
Tuning the Photochromic Properties of Molybdenum Bisphosphonate Polyoxometalates
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DOI：
10.1021/ic202299d
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发表时间：
2012-02-20
影响因子：
4.6
通讯作者：
Mialane, Pierre
中科院分区：
文献类型：
--
作者：
El Moll, Hani;Dolbecq, Anne;Mialane, Pierre
通式为[(Mo3O8)(4)(O3Pc(CmH2mNRR‘R’‘)(O)PO3)(4)](8-)(m=3；R，R’，R‘’=H或CH3)和[(Mo3O8)(2)(O)-(O3PC(CmH2mNRR‘r’‘))(O)PO3(2)(6-)(m=3或4；R，R‘和R’‘=H或CH3)，并用单晶X射线衍射法测定了它们的结构。这些化合物是由不同的烷基双膦酸铵功能化的{Mo-12}或{Mo-6}无机核组成的，这些配体的烷基链长度和N原子上接枝的甲基数量不同。组成这些材料的反阳离子(Na+、K+、Rb+、Cs+和/或NH4+)的性质也受到了调节。水介质中的P-31核磁共振波谱研究表明，所报道的所有十二核化合物在溶液中都是稳定的，而对于六核化合物，证明了两个异构体之间的动态平衡，并确定了其中一个的标准热力学参数。研究了具有代表性的六种化合物的电化学性质。研究发现，所有被研究的多金属氧酸盐的Mo6+/Mo5+还原电位都是相似的。此外，研究还表明，电化学循环是一种将这些化合物沉积到表面的有效方法。本文报道的所有配合物的光致变色性质都在固态下进行了研究。在近紫外光(UV)照射下，{MON}体系由白色转变为红棕色，而{Mo-6}化合物呈紫色。系统地定量了变色动力学，测定了光学带隙、显著变色动力学参数和变色动力学半衰期。这证明了其中几种材料在紫外线诱导下会产生非常强烈和快速的颜色变化，具有显著的颜色对比度。最后，从POM的拓扑结构、接枝的双膦配体的性质以及有机-无机界面的氢键网络的设计等几个重要参数讨论了这些体系的光学性质。
Seven hybrid organic inorganic bisphosphonate molybdenum(VI) polyoxometalate complexes with the general formula [(Mo3O8)(4)(O3PC(CmH2mNRR'R '')(O)PO3)(4)](8-) (m = 3; R, R', and R '' = H or CH3) and [(Mo3O8)(2)(O)-(O3PC(CmH2mNRR'R '')(O)PO3)(2)](6-) (m = 3 or 4; R, R', and R '' = H or CH3) have been synthesized and their structures solved using single-crystal X-ray diffraction. These compounds are made of a {Mo-12} or a {Mo-6} inorganic core functionalized by various alkylammonium bisphosphonates, with these ligands differing by the length of their alkyl chains and the number of methyl groups grafted on the N atom. The nature of the counter-cations (Na+ K+, Rb+, Cs+, and/or NH4+) constituting these materials has also been modulated. P-31 NMR spectroscopic studies in aqueous media have shown that all the dodecanuclear complexes reported here are stable in solution, whereas for the hexanuclear compounds, a dynamic equilibrium between two isomers has been evidenced, and the corresponding standard thermodynamic parameters determined for one of them. The electrochemical properties of six representative compounds of this family have been investigated. It has been found that the Mo6+/Mo5+ reduction potential is similar for all the polyoxometalates studied. Besides, it is shown that electrochemical cycling is an efficient method for the deposition of these compounds on a surface. The photochromic properties of all the complexes reported herein have been studied in the solid state. Under irradiation in the near ultraviolet (UV), the {Mon} systems shift from white to reddish-brown, while the {Mo-6} compounds develop a purple coloration. The coloration kinetics has been systematically quantified and the optical band gaps, the salient coloration kinetic parameters and the coloration kinetic half-life times have been determined. This has evidenced that several of these materials develop very strong and rapid UV-induced color changes, with remarkable coloration contrasts. Finally, the optical properties of these systems are discussed in light of several salient parameters as the POM topology, the nature of the grafted bisphosphonate ligand, and the design of the hydrogen-bonding network at the organic-inorganic interface.