Reaction dynamics of a photochromic fluorescing dithienylethene
Reaction dynamics of a photochromic fluorescing dithienylethene
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DOI：
10.1021/jp0031956
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发表时间：
2001-03-15
影响因子：
2.9
通讯作者：
Kryschi, C
中科院分区：
文献类型：
--
作者：
Ern, J;Bens, AT;Kryschi, C
通过将蒽作为发色团连接到二噻吩基全氟环戊烯（1,2-双[5-蒽基-2-甲基噻吩-3-基]全氟环戊烯，Ac-BMTFP）上，研究了光致变色和荧光的相互作用。 Ac-BMTFP 开放异构体的蓝色荧光受到闭环反应的抑制。通过测量荧光产率和衰变动力学、光致变色闭环和开环反应的量子产率以及反应中间体的光谱和时间演化，表征了该化合物的光谱性质和反应动力学。根据模型势和单电子密度矩阵对数据进行分析，这些矩阵是使用集体电子振荡器（CEO）方法和 INDO/S 半经验哈密顿量计算的。对于开环反应，确定了光致漂白和吸收瞬变的时间常数为 8 +/- 0.5 ps 的单指数衰减。相反，由于反应和非反应构象异构体的存在，测量的闭环动力学更加复杂。在 S-1 或 S-3 态激发后，开放异构体的两种构象异构体在大约 0.9 ps 的时间尺度上经历快速电子构象弛豫。非反应构象异构体发出荧光，其寿命分布范围从小于 100 ps 到大于 400 ps。反应构象异构体达到寿命为 10 ps 的前体状态，从该状态开始发生闭环反应。开环和闭环反应的速率分别确定为9.5 x 10(9) 和6 x 10(10) s(-1)。样品中不同构象异构体的存在被认为是依赖于荧光有效切换的应用的一个要求，而不是一个缺点。
The interplay of photochromism and fluorescence was studied by attaching anthracene as chromophore to dithienylperfluorocyclopentene (1,2-bis[5-anthryl-2-methylthien-3-yl]perfluorocyclopentene, Ac-BMTFP). The blue fluorescence of the open isomer of Ac-BMTFP is suppressed by the ring-closure reaction.:The spectroscopic properties and the reaction dynamics of this compound were characterized by measurements of the fluorescence yield and decay dynamics, and the quantum yields of the photochromic ring-closure and ring-opening reactions, as well as the spectra and time evolution of reaction intermediates. The data are analyzed in terms of a model potential and single-electron density matrices,which are calculated using the collective electronic oscillator (CEO) approach and the INDO/S semiempirical Hamiltonian. For the ring-opening reaction, single-exponential decays with a time constant of 8 +/- 0.5 ps were determined for the photoinduced bleaching and absorption transients. In contrast, because of the presence of reacting and nonreacting conformers, the dynamics measured for ring closure are more complex. Both conformers of the open isomer undergo a fast electronic-conformational relaxation on a time scale of approximate to0.9 ps after excitation of the S-1 or S-3 state. Nonreacting conformers fluoresce with a distribution of lifetimes ranging from less than 100 ps to more than 400 ps. Reacting conformers reach a precursor state with a lifetime of 10 ps from which the ring-closure reaction takes place. The rates of the ring-opening and ring-closure reactions are determined as 9.5 x 10(9) and 6 x 10(10) s(-1), respectively. Rather than being a drawback, the presence of different conformers in the sample is argued to be a requirement for applications relying on efficient switching of the fluorescence.