Liu Chun-Guang, Guan Wei, Song Ping, Su Zhong-Min, Yao Chan, Wang En-Bo
Institute of Functional Material Chemistry, Northeast Normal University, Changchun 130024, PR China.
Inorg Chem. 2009 Sep 7;48(17):8115-9. doi: 10.1021/ic900829z.
The donor-conjugated bridge-acceptor (D-A) model, as a simple molecular scheme, has been successfully used in the development of second-order organic compound, organometallic compound, and metal complex nonlinear optical (NLO) materials. However, for the totally inorganic molecules, the use of this model is still prohibitive. In the present paper, time-dependent density functional theory (TDDFT) was used to investigate the second-order NLO properties of vanadium- and molybdenum-trisubstituted Keggin and Wells-Dawson polyoxometalates (POMs). The results show that these POM clusters possess D-A structures. The oxygen atoms in the cap region and metal (vanadium and molybdenum) atoms in another cap region in these POM clusters can be viewed as the electron donor and acceptor, respectively. The vanadium ion derivatives possess larger second-order NLO responses and dipole moment than molybdenum ions derivatives; thus, the three vanadium atoms in the cap region act as a strong acceptor related to the three molybdenum atoms in cap region in our D-A scheme. The vanadomolybdate with Wells-Dawson structure displays the good second-order NLO response because of the relevant long conjugated bridge and strong acceptor. This D-A model may be an effective approach for optimizing the first hyperpolarizabilities of inorganic POM clusters.
供体-共轭桥-受体（D-A）模型作为一种简单的分子体系，已成功应用于二阶有机化合物、有机金属化合物和金属配合物非线性光学（NLO）材料的开发。然而，对于全无机分子，该模型的应用仍然受限。在本文中，采用含时密度泛函理论（TDDFT）研究了钒和钼三取代的Keggin型和Wells-Dawson型多金属氧酸盐（POMs）的二阶NLO性质。结果表明，这些POM簇具有D-A结构。这些POM簇帽区的氧原子和另一个帽区的金属（钒和钼）原子可分别视为电子供体和受体。钒离子衍生物比钼离子衍生物具有更大的二阶NLO响应和偶极矩；因此，在我们的D-A体系中，帽区的三个钒原子作为一个比帽区的三个钼原子更强的受体。具有Wells-Dawson结构的钒钼酸盐由于其相关的长共轭桥和强受体而表现出良好的二阶NLO响应。这种D-A模型可能是优化无机POM簇第一超极化率的有效方法。
