Institut Lavoisier de Versailles, UMR 8180, Université de Versailles Saint-Quentin en Yvelines, 45 Avenue des Etats-Unis, 78035 Versailles cedex, France.
Inorg Chem. 2012 Feb 20;51(4):2291-302. doi: 10.1021/ic202299d. Epub 2012 Jan 27.
Seven hybrid organic-inorganic bisphosphonate molybdenum(VI) polyoxometalate complexes with the general formula (Mo(3)O(8))(4)(O(3)PC(C(m)H(2m)NRR'R″)(O)PO(3))(4) (m = 3; R, R', and R″ = H or CH(3)) and (Mo(3)O(8))(2)(O)(O(3)PC(C(m)H(2m)NRR'R″)(O)PO(3))(2) (m = 3 or 4; R, R', and R″ = H or CH(3)) 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 NH(4)(+)) constituting these materials has also been modulated. (31)P 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 Mo(6+)/Mo(5+) 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 {Mo(12)} 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.
七种杂化有机-无机双膦酸钼(VI)多金属氧酸盐配合物，具有通式 (Mo(3)O(8))(4)(O(3)PC(C(m)H(2m)NRR'R″)(O)PO(3))(4)（m = 3；R、R' 和 R″ = H 或 CH(3)) 和 (Mo(3)O(8))(2)(O)(O(3)PC(C(m)H(2m)NRR'R″)(O)PO(3))(2)（m = 3 或 4；R、R' 和 R″ = H 或 CH(3))，已经通过单晶 X 射线衍射法合成并解析了它们的结构。这些化合物由各种烷基铵双膦酸功能化的{Mo(12)}或{Mo(6)}无机核组成，这些配体的区别在于其烷基链的长度和氮原子上接枝的甲基数。构成这些材料的抗衡阳离子（Na(+)、K(+)、Rb(+)、Cs(+)和/或 NH(4)(+)）的性质也进行了调制。在水介质中的 (31)P NMR 光谱研究表明，这里报道的所有十二核配合物在溶液中都是稳定的，而对于六核化合物，已经证明存在两种异构体之间的动态平衡，并确定了其中一种异构体的相应标准热力学参数。对该系列的六个代表性化合物的电化学性质进行了研究。结果表明，所有研究的多金属氧酸盐的 Mo(6+)/Mo(5+)还原电位相似。此外，还表明电化学循环是在表面上沉积这些化合物的有效方法。所有报道的配合物的光致变色性质在固态下进行了研究。在近紫外 (UV) 照射下，{Mo(12)}体系从白色变为红棕色，而{Mo(6)}化合物呈现紫色。系统地量化了着色动力学，并确定了光学带隙、显著的着色动力学参数和着色动力学半衰期。这表明，这些材料中的几种具有非常强和快速的 UV 诱导的颜色变化，具有显著的颜色对比度。最后，根据多金属氧酸盐拓扑、接枝双膦酸配体的性质以及有机-无机界面氢键网络的设计等几个显著参数，讨论了这些体系的光学性质。
