School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
Dalton Trans. 2012 Oct 21;41(39):12185-91. doi: 10.1039/c2dt31474f.
A novel pyrene covalently-attached polyoxometalate (POM) hybrid has been synthesized and fully characterized. The attractive electronic and photophysical properties of pyrene derivatives make the hybrid promising for studying and understanding electron transfer mechanisms in organic-functionalized POMs. The hybrid has an electronic absorption at 450 nm, indicating that there is a strong electronic interaction between the organic pyreneimido group and inorganic hexamolybdate cluster. The electron transfer mechanism of the as-prepared hybrid is illuminated via the combined studies of theoretical calculations and transient absorption spectroscopy. Time-dependent density functional theory studies revealed that the strong electronic absorption at the visible region mainly comes from the optically allowed π-π* transitions of the pyreneimido component (S(0) to S(2) transition). The electron transfer process from the excited pyreneimido moiety to the inorganic POM cluster is at the time scale of ~700 fs, which could be ascribed to the internal conversion of singlet excited states from S(2) state to S(1) state. This study provided a clear understanding of the mechanism governing the electron transfer process in organoimido derivatives of POMs. This result might offer a new route for the design of new charge transfer hybrid clusters of organic functionalized POMs and crucial guidance for their applications in optical and electrical devices.
一种新型的芘共价连接的多金属氧酸盐（POM）杂化物已经被合成并进行了全面的表征。芘衍生物具有吸引人的电子和光物理性质，使得该杂化物有望用于研究和理解有机功能化 POMs 中的电子转移机制。该杂化物在 450nm 处具有电子吸收，表明有机芘亚胺基团和无机六钼酸盐簇之间存在强烈的电子相互作用。通过理论计算和瞬态吸收光谱的综合研究，阐明了所制备的杂化物的电子转移机制。含时密度泛函理论研究表明，可见光区的强电子吸收主要来自于芘亚胺组分的光允许π-π*跃迁（S(0)到 S(2)跃迁）。电子从激发的芘亚胺部分向无机 POM 簇的转移过程在 ~700fs 的时间尺度内发生，这可以归因于从 S(2)态到 S(1)态的单重激发态的内转换。这项研究提供了对 POMs 中有机亚胺衍生物中电子转移过程的机制的清晰理解。这一结果可能为设计新型有机功能化 POMs 的电荷转移杂化簇提供新途径，并为其在光学和电子器件中的应用提供关键指导。
