A computational investigation on the photo-isomerization of 2,4,6-octatriene and its UV-visible spectrum

作者：Chattopadhyay Anjan^*; Saini Praveen; Hakim Raymond; Komainda Adrian; Koeppel Horst

来源：Chemical Physics, 2018, 509: 98-105.

DOI：10.1016/j.chemphys.2017.12.006

• Photoisomerization
• UV-visible spectrum
• Ab initio
• Dynamics
• Conical intersection

The dynamical processes following photoexcitation of all-trans 2,4,6-octatriene to the two lowest singlet excited states are investigated theoretically, from two different points of view. The S-1-S-0 photoisomerization is characterized with a focus on structural aspects (stationary points and reactive modes), while for the UV-visible spectrum, arising from excitation to the S-2 state, nonadiabatic quantum dynamics calculations with four planar degrees of freedom are performed. The underlying electronic structure data are obtained from CASSCF and MS-CASPT2 ab initio computations, the quantum dynamical calculations rely on the Multiconfiguration Time-Dependent Hartree (MCTDH) method. The observed envelope of the UV-Visible spectrum is well reproduced and the substantial broadness of the spectral features related to a nonradiative S-2-S-1 transition proceeding within few tens of femtoseconds. The vertical excitation energy from the A(g) to the B-u state shows a red-shift (similar to 0.2 eV with the cc-pVTZ basis set) with reference to the all-trans hexatriene system. This affects the S-2-S-1 nonradiative decay, while the methylation of the terminal carbon atoms seems to have a minor influence on the photo-isomerization path.

• 出版日期2018-6-15