Highly efficient visible-light driven photochromism: developments towards a solid-state molecular switch operating through a triplet-sensitised pathway.
Highly efficient visible-light driven photochromism: developments towards a solid-state molecular switch operating through a triplet-sensitised pathway.
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DOI：
10.1002/chem.201003487
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发表时间：
2011-04
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通讯作者：
S. Brayshaw;Stephanie Schiffers;A. J. Stevenson;S. Teat;M. Warren;R. Bennett;I. Sazanovich;A. Buckley;J. Weinstein;P. Raithby
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作者：
S. Brayshaw;Stephanie Schiffers;A. J. Stevenson;S. Teat;M. Warren;R. Bennett;I. Sazanovich;A. Buckley;J. Weinstein;P. Raithby
介绍了一种新型的高效光致变色金属有机二噻吩基乙烯（DTE）配合物，它是由两个Pt（II）发色团对称修饰的DTE核[Pt（PEt（3））（2）（C C）（DTE）（C C）Pt（PEt（3））（2）Ph]（1）的第一个实例，在不同极性的溶剂中，在薄膜中，甚至在固态下，当被可见光激活时，它会发生闭环。配合物1已被合成，并通过（共振）拉曼光谱和瞬态吸收光谱计算补充，充分电子化学特征。1的单晶中的闭环光转换已经被X射线晶体学跟踪。该工艺具有80%的极高产率-大大优于其他DTE衍生物。值得注意的是，1的光环化甚至在可见光（>400 nm）下发生，其不被非金属化的DTE核HC = C（DTE）C = CH（2）本身吸收。这种不寻常的行为和在溶液中的高光环化产率归因于1中的重原子的存在，其能够通过瞬态吸收光谱和DFT计算阐明三重态敏化的光环化途径。共振拉曼研究的结果证实，在光环化过程中的1的封闭和开放形式的前线轨道中的炔基单元的参与。环化后拉曼光谱的变化允许识别拉曼标记带，其包括乙炔伸缩振动。重要的是，这些带出现在不受其他振动阻碍的光谱区域中，并且可以用于光环化/光致回复过程的非破坏性监测，以及用于这种类型的有效光致变色热稳定系统中的光学读出。这项研究表明了一种策略，用于产生高效的固态光开关，其中修改的Pt（II）的单位有可能调整吸收特性，因此在整个可见光范围内的工作波长。
We introduce a new highly efficient photochromic organometallic dithienylethene (DTE) complex, the first instance of a DTE core symmetrically modified by two Pt(II) chromophores [Pt(PEt(3))(2)(C≡C)(DTE)(C≡C)Pt(PEt(3))(2)Ph] (1), which undergoes ring-closure when activated by visible light in solvents of different polarity, in thin films and even in the solid state. Complex 1 has been synthesised and fully photophysically characterised by (resonance) Raman and transient absorption spectroscopy complemented by calculations. The ring-closing photoconversion in a single crystal of 1 has been followed by X-ray crystallography. This process occurs with the extremely high yield of 80%--considerably outperforming the other DTE derivatives. Remarkably, the photocyclisation of 1 occurs even under visible light (>400 nm), which is not absorbed by the non-metallated DTE core HC≡C(DTE)C≡CH (2) itself. This unusual behaviour and the high photocyclisation yields in solution are attributed to the presence of a heavy atom in 1 that enables a triplet-sensitised photocyclisation pathway, elucidated by transient absorption spectroscopy and DFT calculations. The results of resonance Raman investigation confirm the involvement of the alkynyl unit in the frontier orbitals of both closed and open forms of 1 in the photocyclisation process. The changes in the Raman spectra upon cyclisation have permitted the identification of Raman marker bands, which include the acetylide stretching vibration. Importantly, these bands occur in the spectral region unobstructed by other vibrations and can be used for non-destructive monitoring of photocyclisation/photoreversion processes and for optical readout in this type of efficiently photochromic thermally stable systems. This study indicates a strategy for generating efficient solid-state photoswitches in which modification of the Pt(II) units has the potential to tune absorption properties and hence operational wavelength across the visible range.