Control of the entatic state by targeted optical excitation of the ligand sphere

吸能态的概念描述了电荷转移和伴随的结构重排的矛盾关系。这就提出了一个基本问题，即电荷转移是否受到结构性前组织的影响。这个问题对于化学中的许多催化活性体系是必不可少的，其中过渡金属络合物的催化性质由其定制的配体球控制。在生物无机化学中，有几个小组已经报道了熵模型系统。这些模型系统具有结构上预先组织的配体球。一个系统的研究是阻碍了一个可调的preorganisation系统不容易化学合成的事实。我们已经表明，光激发的电荷转移导致的状态，这对应于一个完整的过渡金属的电荷转移到配体system.This项目的重点，因此，有针对性的光学操纵的配体系统的一个稳定的模型系统的一个entatic状态，以激发配体的preorganisation。因此，我们通过中红外泵浦光束激发适合的配体振动，将一个熵态调谐到另一个。这个过程在振动激发的发射下进行。泵浦光束的功率现在允许振动激发的精确控制。不同红外激活模式的激发使得能够有针对性地选择预组织系统的不同激发模式。相比之下，在可见光或紫外光谱范围内的常规激发通过激发成高度激发的电子态而触发高度复杂的过程级联，其最终以光活化的熵态结束。这些状态的研究应在本项目中通过UV/维斯-或IR-泵浦拉曼探针实验进行补充，并通过瞬态吸收测量和时间分辨荧光进行补充。 在这项研究中，我们将回答如何的熵态的动力学区分电子激发到电荷转移过渡和结构激发的配体系统在中红外范围。详细地说，我们的目标是澄清，如果定制的激发到配体系统的本征模，并促进吸能态之间的过渡。这将最终导致一个答案的问题，在多大程度上可以控制和操纵的光的熵状态。

The concept of the entatic state describes the ambivalent relation of a charge transfer and an accompanying structural rearrangement. It poses the fundamental question if the charge transfer is favoured by a structural pre-organisation. This question is essential for many catalytically active systems in chemistry where the catalytic properties of transition metal complexes are controlled by their tailored ligand sphere. In bioinorganic chemistry, several groups have reported entatic model systems. These model systems possess structurally preorganised ligand spheres. A systematic study is impeded by the fact that systems with a tunable preorganisation are not easily chemically synthesised. We have shown earlier that the optically excited charge transfer leads to a state, which corresponds to a complete transfer of charge from the transition metal to the ligand system.This project focuses, thus, on the targeted optical manipulation of the ligand systems of a stable model system for an entatic state in order to excite the preorganisation of the ligands. Therefore, we excite via a mid-infrared pump beam suited ligand vibrations, which tune an entatic state into another one. This process proceeds under emission of vibrational excitations. The power of the pump beam allows now the exact control of the vibrational excitation. The excitation of different infrared-active modes enables the targeted selection of different excitation patterns of preorganised systems. In contrast, the conventional excitation in the visible or ultraviolet spectral range triggers a highly complex process cascade by the excitation into highly ecited electronic states, which finally ends up in a photoactivated entatic state. The investigation of these states shall be realised in this project complementary by UV/VIS- or IR-pump Raman-probe experiments, which are complemented by transient absorption measurements and time-resolved fluorescence. We will answer in this study how the dynamics of the entatic state differentiates between the electronic excitation into the charge transfer transition and the structural excitation of the ligand systems in the mid IR range. In detail, we target to clarify if the tailored excitation into eigenmodes of the ligand system and facilitate the transition between entatic states. This would finally lead to an answer of the question how far entatic states can be controlled and manipulated by light.