ROLE OF COHERENT PHENOMENA IN ULTRAFAST BIOLOGICAL PROCESSES

相干现象在超快生物过程中的作用

• 批准号: 6480852
• 负责人: ROBIN Main HOCHSTRASSER
• 金额: $ 15.58万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-01 至 2002-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6480852
• 关键词: biological products; biomedical equipment development; biomedical resource

An important question is whether the coherence introduced by optical excitation in the initial step of a light driven reaction is maintained during the primary process or not Do the dynamics of the initially formed wavepacket on the reactive surface involve coherent motion? The observations of coherent wavepacket propagation provides an additional probe of the nature of the potential energy surface upon which the primary dynamical processes are occurring. The photophysical properties of a series of ethynyl-bridged (porphinato)zinc(II) oligomers have been investigated over the femtosecond and picosecond time scales using ultrafast magic angle and polarized pump-probe spectroscopy. They exhibit rapid (less than or equal to 50 fs) formation of the emitting state following Soret photoexcitation, nearly an order of magnitude faster than the similar to 1 ps S2 ??S1 internal conversion observed for a monomeric (porphinato)zinc(II) complex that bears an ethyne moiety fused directly to its macrocycle carbon framework [(5-trimethylsilylethynyl-10,20-diphenylporphinato)zinc (II)]. The femtosecond and picosecond dynamics are strongly influenced by the porphyrin-to-porphyrin linkage topology: if a beta-to-beta ethyne bridge links the two (porphinato)zinc(II) moieties, this maintains the x-y degeneracy of the emitting state, the dynamics of which are consistent with energy equilibration within a weakly coupled porphyrin pair. In contrast, systems whi ch feature a meso-to-meso ethynyl-bridged linkage topology between (porphinato)zinc(II) units exhibit properties consistent with significant inter-ring conjugation and loss of x-y degeneracy for the (pi, pi*) excited states. Collectively, the steady-state and time-resolved results for these meso-to-meso bridged systems suggest some degree of conformational heterogeneity for the ground state structures in solution, which differ with respect to the degree of conjugation of porphyrin rings; these conformers interconvert in the S1 excited state on a similar to 30 ps time scale to produce a conformationally uniform, coplanar emitting state.

一个重要的问题是， 在光驱动反应的初始步骤中的光激发是 保持在主要过程中或不做的动态 在反应表面上最初形成的波包涉及相干的 动议？ 相干波包传播的观测结果提供了 一个额外的探测势能面的性质， 主要的动力学过程正在发生。 的 一系列乙炔桥连的聚乙炔的物理化学性质 （卟啉合）锌（II）低聚物已经研究了超过 飞秒和皮秒时间尺度使用超快魔角和 偏振泵浦探测光谱学 他们表现出快速（小于或 等于50 fs）在Soret之后形成发射态 光激发，几乎比类似的快一个数量级。 1 ps S2？S1内转化观察到的单体 带有乙炔部分稠合的（卟啉基）锌（II）络合物 直接影响到其大循环碳框架 [（5-三甲基甲硅烷基乙炔基-10，20-二苯基卟啉）锌（II）]。 的 飞秒和皮秒动力学受到 卟啉-卟啉连接拓扑：如果β-至-β-乙炔 桥连接两个（卟啉）锌（II）部分，这保持了 发射态的x-y简并度，其动力学为 与弱耦合卟啉内的能量平衡一致 汇率 相比之下，具有中-中尺度特征的系统 （卟啉基）锌（II）单元之间的乙炔桥连拓扑结构 表现出与显著的环间共轭一致的性质 以及（pi，pi*）激发态的x-y简并性的损失。 总的来说，稳态和时间分辨的结果，这些 meso-to-meso桥接系统表明了一定程度的构象 溶液中基态结构的不均匀性， 卟啉环的共轭程度不同; 这些构象在S1激发态中在类似于 30 ps的时间尺度，以产生构象均匀的共面 发射态