Institute of Functional Material Chemistry, Key Laboratory of Polyoxometalate Science of Ministry of Education, Faculty of Chemistry, Northeast Normal University, Changchun, People's Republic of China.
J Mol Graph Model. 2010 Aug 24;29(1):13-20. doi: 10.1016/j.jmgm.2010.04.006. Epub 2010 Apr 24.
The Lambda-shaped phenanthroline-hexamolybdate compounds that are based on the reversible Mo-centered redox process were investigated. The attachment of hexamolybdate terminals to phenanthroline by a pi-conjugated phenylamine bridge generated the organic ligand-centered or Ni-centered HOMO and the transition metal Mo-centered LUMO. The population in HOMO and LUMO predicted the reversible Mo(VI/V) redox process and the ligand-to-metal charge transfer (LMCT) to a polyanion acceptor, which consequently evoked a significant second-order nonlinear optical (NLO) response. Moreover, the electron transition of these compounds exhibited a large beta(zyy) tensor along the y-axis, which confirms a promising two-dimensional (2D) character with sizable anisotropy values. Interestingly, the addition of electrons into the high-valence Mo atom in the hexamolybdate acceptor evoked dramatic enhancements in the NLO response for the reduction states in contrast to the response of the corresponding oxidation states. The reduction states in system I exhibited second-order NLO responses about 200 times larger than the oxidation states. In addition, the attachment of the Ni atom in compound IIa(red) enhanced the NLO response to nearly 1019 times greater than the response of the corresponding oxidation state compound IIa. The Ni atom as the electron donor plays an important role in the major electron transition for the reduction states in system II. Therefore, the NLO response of such compounds can be reversibly switched through the transition metal Mo(VI/V) redox that is effectively coupled with the LMCT transition. Thus, the NLO activity can be controlled by a one-electron redox process, and the redox-active phenanthroline-hexamolybdate compounds are promising candidates for 2D redox-switching NLO materials in novel optoelectronic applications.
研究了基于可逆 Mo 中心氧化还原过程的 Lambda 形菲咯啉-六钼酸盐化合物。通过一个π共轭苯基亚胺桥将六钼酸盐末端连接到菲咯啉上，生成有机配体中心或 Ni 中心 HOMO 和过渡金属 Mo 中心 LUMO。HOMO 和 LUMO 中的电子占据预测了可逆 Mo(VI/V)氧化还原过程和配体到金属的电荷转移 (LMCT) 到多阴离子受体，从而引发了显著的二阶非线性光学 (NLO) 响应。此外，这些化合物的电子跃迁在 y 轴上表现出较大的 beta(zyy)张量，这证实了具有可观各向异性值的二维 (2D) 特征。有趣的是，在六钼酸盐受体中高价 Mo 原子中添加电子会引起 NLO 响应的显著增强，特别是在还原态与相应氧化态相比时。在体系 I 中，还原态的二阶 NLO 响应大约是氧化态的 200 倍。此外，化合物 IIa(red)中 Ni 原子的附加增强了 NLO 响应，使其接近氧化态化合物 IIa 的 1019 倍。作为电子供体的 Ni 原子在体系 II 中还原态的主要电子跃迁中起着重要作用。因此，这种化合物的 NLO 响应可以通过与 LMCT 跃迁有效耦合的过渡金属 Mo(VI/V) 氧化还原可逆切换。因此，NLO 活性可以通过单电子氧化还原过程来控制，并且具有氧化还原活性的菲咯啉-六钼酸盐化合物是新型光电应用中 2D 氧化还原切换 NLO 材料的有前途的候选者。
