Xie Bin-Bin, Xia Shu-Hua, Liu Li-Hong, Cui Ganglong
Key Laboratory of Theoretical and Computational Photochemistry, Ministry of Education, College of Chemistry, Beijing Normal University, Beijing 100875, China.
J Phys Chem A. 2015 Jun 4;119(22):5607-17. doi: 10.1021/acs.jpca.5b02549. Epub 2015 May 22.
Malachite green is a typical triphenylmethane dye widely used in fundamental and industrial research; however, its excited-state relaxation dynamics remains elusive. In this work we simulate its photodynamics from the S2 and S1 states using the fewest-switches surface-hopping scheme. In the S2 photodynamics, the system first relaxes to the S2 minimum, which immediately hops to the S1 state via an S2/S1 conical intersection. In the S1 state, 90% trajectories evolve into a structurally symmetric S1 minimum; the remaining ones proceed toward two propeller-like S1 minima. Two kinds of S1 minima then decay to the S0 state via the S1/S0 conical intersections. The S1 photodynamics is overall similar to the S1 excited-state dynamics as a result of the ultrafast S2 → S1 internal conversion in the S2 photodynamics, but the weights of the trajectories that decay to the S0 state via three different S1/S0 conical intersections are variational. Moreover, the S2 relaxation dynamics mainly happens in a concerted synchronous rotation of three phenyl rings. In comparison, in the S1 relaxation dynamics, the rotations of two aminophenyl rings can proceed in the same and opposite directions. In certain trajectories, only the rotation of an aminophenyl ring is active. On the basis of the results, the S2 and S1 excited-state lifetimes of malachite green in vacuo are calculated to be 424 fs and 1.2 ps, respectively. The present work provides important mechanistic insights for similar triphenylmethane dyes.
孔雀石绿是一种典型的三苯甲烷染料，广泛应用于基础研究和工业研究；然而，其激发态弛豫动力学仍然难以捉摸。在这项工作中，我们使用最少开关表面跳跃方案从S2和S1态模拟其光动力学。在S2光动力学中，系统首先弛豫到S2最低点，然后通过S2/S1锥形交叉点立即跃迁至S1态。在S1态，90%的轨迹演化为结构对称的S1最低点；其余的则朝着两个螺旋桨状的S1最低点发展。然后，两种S1最低点通过S1/S0锥形交叉点衰减到S0态。由于S2光动力学中超快的S2→S1内转换，S1光动力学总体上与S1激发态动力学相似，但通过三个不同的S1/S0锥形交叉点衰减到S0态的轨迹权重是变化的。此外，S2弛豫动力学主要发生在三个苯环的协同同步旋转中。相比之下，在S1弛豫动力学中，两个氨基苯环的旋转可以沿相同和相反的方向进行。在某些轨迹中，只有一个氨基苯环的旋转是活跃的。根据这些结果，计算出真空中孔雀石绿的S2和S1激发态寿命分别为424 fs和1.2 ps。本工作为类似的三苯甲烷染料提供了重要的机理见解。
