Savolainen Janne, Dijkhuizen Niels, Fanciulli Riccardo, Liddell Paul A, Gust Devens, Moore Thomas A, Moore Ana L, Hauer Jürgen, Buckup Tiago, Motzkus Marcus, Herek Jennifer L
FOM Institute for Atomic and Molecular Physics (AMOLF), Kruislaan 407, 1098 SJ Amsterdam, The Netherlands.
J Phys Chem B. 2008 Mar 6;112(9):2678-85. doi: 10.1021/jp0757199. Epub 2008 Feb 9.
A caroteno-purpurin dyad molecule was studied by steady-state and pump-probe spectroscopies to resolve the excited-state deactivation dynamics of the different energy levels as well as the connecting energy flow pathways and corresponding rate constants. The data were analyzed with a two-step multi-parameter global fitting procedure that makes use of an evolutionary algorithm. We found that following ultrafast excitation of the donor (carotenoid) chromophore to its S2 state, the energy flows via two channels: energy transfer (70%) and internal conversion (30%) with time constants of 54 and 110 fs, respectively. Additionally, some of the initial excitation is found to populate the hot ground state, revealing another limitation to the functional efficiency. At later times, a back transfer occurs from the purpurin to the carotenoid triplet state in nanosecond timescales. Details of the energy flow within the dyad as well as species associated spectra are disentangled for all excited-state and ground-state species for the first time. We also observe oscillations with the most pronounced peak on the Fourier transform spectrum having a frequency of 530 cm(-1). The dyad mimics the dynamics of the natural light-harvesting complex LH2 from Rhodopseudomonas acidophila and is hence a good model system to be used in studies aimed to further explain previous work in which the branching ratio between the competing pathways of energy loss and energy transfer could be manipulated by adaptive femtosecond pulse shaping.
通过稳态光谱和泵浦-探测光谱对一种胡萝卜素-紫红素二元分子进行了研究，以解析不同能级的激发态失活动力学以及连接的能量流途径和相应的速率常数。利用一种进化算法，通过两步多参数全局拟合程序对数据进行了分析。我们发现，在供体（类胡萝卜素）发色团超快激发到其S2态后，能量通过两个通道流动：能量转移（70%）和内转换（30%），时间常数分别为54和110飞秒。此外，发现一些初始激发会填充热基态，这揭示了功能效率的另一个限制。在稍后的时间，在纳秒时间尺度上发生了从紫红素到类胡萝卜素三重态的反向转移。首次解析了二元分子内能量流的细节以及所有激发态和基态物种的相关光谱。我们还观察到振荡，傅里叶变换光谱上最明显的峰值频率为530厘米-1。该二元分子模拟了嗜酸红假单胞菌天然光捕获复合物LH2的动力学，因此是一个很好的模型系统，可用于旨在进一步解释先前工作的研究，在先前的工作中，能量损失和能量转移竞争途径之间的分支比可通过自适应飞秒脉冲整形进行调控。
