Schnappinger Thomas, Kölle Patrick, Marazzi Marco, Monari Antonio, González Leticia, de Vivie-Riedle Regina
Department of Chemistry, Ludwig-Maximilians-Universität München, Butenandtstraße 5-13, 81377 Munich, Germany.
Phys Chem Chem Phys. 2017 Sep 27;19(37):25662-25670. doi: 10.1039/c7cp05061e.
The fast and slow components of the relaxation of photoexcited thiophene have been investigated by means of SHARC (surface hopping including arbitrary couplings) molecular dynamics based on multiconfiguration electronic structure calculations. Triplet states are included to ascertain their role in the relaxation process. After thiophene is excited to the S state, ultrafast dynamics (τ = 96 fs) initiates a ring opening due to cleavage of a carbon sulfur bond and simultaneous ring puckering. This time constant is in agreement with previous experimental and theoretical studies. The subsequent dynamics of the open-ring structures is characterized by the interplay of internal conversion and intersystem crossing. For the open-ring structures, the S, S, T and T states are nearly degenerate and the spin-orbit couplings are large. The underlying potential energy surface is flat and long-lived open-ring structures in the singlet as well as in the triplet states are formed. Both the participation of triplet states and the shape of the energy surface explain the experimentally observed slow ring closure in the ground state.
通过基于多组态电子结构计算的SHARC（包括任意耦合的表面跳跃）分子动力学方法，研究了光激发噻吩弛豫的快、慢成分。考虑了三重态以确定它们在弛豫过程中的作用。噻吩被激发到S态后，超快动力学（τ = 96 fs）由于碳硫键的断裂和同时发生的环褶皱而引发开环。这个时间常数与先前的实验和理论研究一致。开环结构随后的动力学特征是内转换和系间窜越的相互作用。对于开环结构，S、S、T和T态几乎简并，自旋轨道耦合很大。潜在的势能面是平坦的，在单重态和三重态中都形成了长寿命的开环结构。三重态的参与和能量表面的形状都解释了实验观察到的基态下缓慢的闭环现象。
