Kim Pyosang, Roy Subhangi, Valentine Andrew J S, Liu Xiaolin, Kromer Sarah, Kim Tae Wu, Li Xiaosong, Castellano Felix N, Chen Lin X
Chemical Sciences and Engineering Division, Argonne National Laboratory Lemont IL 60439 USA
Chemistry Department, Northwestern University Evanston IL 60208 USA.
Chem Sci. 2024 Aug 22;15(36):14766-77. doi: 10.1039/d4sc01876a.
Although vibronic coupling phenomena have been recognized in the excite state dynamics of transition metal complexes, its impact on photoinduced electron transfer (PET) remains largely unexplored. This study investigates coherent wavepacket (CWP) dynamics during PET processes in a covalently linked electron donor-acceptor complex featuring a cyclometalated Pt(ii) dimer as the donor and naphthalene diimide (NDI) as the acceptors. Upon photoexciting the Pt(ii) dimer electron donor, ultrafast broadband transient absorption spectroscopy revealed direct modulation of NDI radical anion formation through certain CWP motions and correlated temporal evolutions of the amplitudes for these CWPs with the NDI radical anion formation. These results provide clear evidence that the CWP motions are the vibronic coherences coupled to the PET reaction coordinates. Normal mode analysis identified that the CWP motions originate from vibrational modes associated with the dihedral angles and bond lengths between the planes of the cyclometalating ligand and the NDI, the key modes altering their π-interaction, consequently influencing PET dynamics. The findings highlight the pivotal role of vibrations in shaping the favorable trajectories for the efficient PET processes.
尽管在过渡金属配合物的激发态动力学中已经认识到振转耦合现象，但其对光致电子转移（PET）的影响在很大程度上仍未得到探索。本研究调查了一种共价连接的电子供体-受体配合物在PET过程中的相干波包（CWP）动力学，该配合物以环金属化的Pt（II）二聚体作为供体，萘二酰亚胺（NDI）作为受体。在光激发Pt（II）二聚体电子供体后，超快宽带瞬态吸收光谱揭示了通过某些CWP运动对NDI自由基阴离子形成的直接调制，以及这些CWP的振幅与NDI自由基阴离子形成的相关时间演化。这些结果提供了明确的证据，表明CWP运动是与PET反应坐标耦合的振转相干性。简正模式分析确定，CWP运动源于与环金属化配体平面和NDI之间的二面角和键长相关的振动模式，这些关键模式改变了它们的π相互作用，从而影响PET动力学。这些发现突出了振动在塑造高效PET过程的有利轨迹方面的关键作用。
