Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University, Ren Min Street No. 5268, Changchun, Jilin 130024, P.R. China.
Dalton Trans. 2012 Sep 7;41(33):10097-104. doi: 10.1039/c2dt30449j. Epub 2012 Jul 5.
We theoretically investigate a novel switching phenomenon based on the divacant Keggin-type polyoxotungstate bearing chiral organophosphonate {NH(2)CH(CH(3))PO}(2)(γ-SiW(10)O(36)), that is the synchronous chiroptical and nonlinear optical (NLO) switch triggered by redox. The ECD calculations on the Boltzmann weighted conformations of the three oxidation states of this chiral polyoxometalate (POM) clearly present a chiroptical switching process. The electronic transition and the bond-length alternation studies show that the chirality transfer from chiral carbon atom to POM cage increases as the polyanion is reduced. Simultaneously, the static first hyperpolarizability of studied chiral POM quadrupled from the oxidized state to the 1e-reduced state, and is further doubled to the 2e-reduced state, which is mainly due to the increasing electronic-dipole-allowed d-d charge transfer transitions in the POM cage. This work firstly reproduces the ECD spectrum of chiral POM with high accuracy and proves the possibility for confirming the molecular conformations of flexible chiral POMs in solution by the aid of ECD calculations. Most importantly, a sensitive diplex switch based on a chiral POM is predicted in theory, which may aid the design of novel POM-based switches.
我们从理论上研究了一种基于具有手性有机膦酸的空缺 Keggin 型多钨酸盐{NH(2)CH(CH(3))PO}(2)(γ-SiW(10)O(36))的新型开关现象，即氧化还原触发的手性和非线性光学（NLO）同步开关。该手性多金属氧酸盐（POM）三种氧化态的玻尔兹曼加权构象的 ECD 计算清楚地呈现出手性开关过程。电子跃迁和键长交替研究表明，手性碳原子与 POM 笼之间的手性转移随着多阴离子的还原而增加。同时，研究的手性 POM 的静态第一超极化率从氧化态增加到 1e-还原态时增加了四倍，进一步增加到 2e-还原态时增加了一倍，这主要是由于 POM 笼中允许的电子偶极子-d-d 电荷转移跃迁增加。这项工作首次以高精度再现了手性 POM 的 ECD 光谱，并通过 ECD 计算证明了在溶液中确认柔性手性 POM 分子构象的可能性。最重要的是，理论上预测了基于手性 POM 的灵敏双频开关，这可能有助于设计新型基于 POM 的开关。
