pH-responsive switching of near-infrared absorption of a diradical complex of PtII and 3,4-diaminobenzoate formed in aqueous solutions
pH-responsive switching of near-infrared absorption of a diradical complex of PtII and 3,4-diaminobenzoate formed in aqueous solutions
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DOI：
10.1016/j.ica.2011.08.018
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发表时间：
2011-11-30
影响因子：
2.8
通讯作者：
Hoshino, Hitoshi
中科院分区：
文献类型：
--
作者：
Tamura, Kousaku;Masuya, Atsuko;Hoshino, Hitoshi
在碱性水溶液中，3，4-二氨基苯甲酸酯（H-2（L-2（PDA）与Pt-II反应形成1：2（Pt：L）络合物，其强烈吸收713 nm处的近红外（NIR）光（λ = 8.0 x 10（4）M（1）cm（1））。吸收在pH < 3（在DMSO中）时消失，显示NIR吸收的pH响应性切换。通过比较该配合物与含有类似的苯二胺配体[（L-1（ISQ））（2）= o-二亚氨基苯并半醌自由基]的配合物[Pt-II（L-1（ISQ））（2）]（2）的近红外吸收行为，该配合物可以用公式表示为[Pt-II（L-2（ISQ））（2）]（2）。实体的归属与氧化还原和光谱电化学行为以及电子自旋共振（ESR）光谱一致。首先，[Pt-II（L-2（ISQ））（2）]（2）的单电子氧化形成ESR沉默络合物，该ESR沉默络合物可归属于二聚络合物[{Pt-II（L-2（ISQ））（L-2（IBQ））}（2）]（2）[（L-2（IBQ））=邻亚氨基苯醌形式]，其中（L-2（ISQ））（2）（-）处的两个自由基中心反铁磁耦合。其次，[Pt-II（L-2（ISQ））（2）]（2）的单电子还原络合物显示出归因于[Pt-II（L-2（ISQ））（L-2（PDA））]（3）的ESR信号; 34%的电子自旋位于Pt-II中心而不是（L-2（ISQ））（2）（-）部分。因此，NIR吸收的pH响应性关闭通过在较低pH区域中溶液的静止电位的增加而将[Pt-II（L-2（ISQ））（2）]（2）氧化为[{Pt-II（L-2（ISQ））（L-2（IBQ））}（2）]（2）来合理地解释。(C)2011 Elsevier B. V.保留所有权利。
In alkaline aqueous solutions, 3,4-diaminobenzoate (H-2(L-2(PDA))) reacts with Pt-II to form a 1:2 (Pt:L) complex that intensely absorbs near-infrared (NIR) light at 713 nm (epsilon = 8.0 x 10(4) M (1) cm (1)). The absorption disappeared at pH < 3 (in DMSO), showing pH-responsive switching of the NIR absorption. By comparing the NIR-absorbing behavior of this complex to that of a complex, [Pt-II(L-1(ISQ))(2)](2), containing the analogous phenylenediamine ligand [(L-1(ISQ))(2) = o-diiminobenzosemiquinonate radical], the complex can be formulated as [Pt-II(L-2(ISQ))(2)](2). The assignment of the entity was consistent with the redox and spectro-electrochemical behaviors and electronic spin resonance (ESR) spectroscopy. First, one-electron oxidation of [Pt-II(L-2(ISQ))(2)](2) formed an ESR-silent complex assignable to the dimeric complex [{Pt-II(L-2(ISQ))(L-2(IBQ))}(2)](2) [(L-2(IBQ)) = o-iminobenzoquinone form] in which the two radical centers at (L-2(ISQ))(2)(-) were antiferromagnetically coupled. Second, the one-electron reduced complex of [Pt-II(L-2(ISQ))(2)](2) exhibited an ESR signal attributed to [Pt-II(L-2(ISQ))(L-2(PDA))](3) ; 34% of the electronic spin was located at the Pt-II center rather than on the (L-2(ISQ))(2)(-) moiety. The pH-responsive switching-off of the NIR absorption was thus rationally explained by oxidation of [Pt-II(L-2(ISQ))(2)](2) to [{Pt-II(L-2(ISQ))(L-2(IBQ))}(2)](2) by the increase of the rest potential of the solution in the lower pH region. (C) 2011 Elsevier B.V. All rights reserved.