## Abstract

The electronic spectrum of thiophenol was simulated by a normal-mode sampling approach combined with TDDFT in the Tamm-Dancoff approximation (TDA). The vertical excitation energies were compared with electronic structure calculations by completely renormalized equation-of-motion coupled cluster theory with single and double excitations and noniterative inclusion of connected triples (CR-EOM-CCSD(T)) and by multi-reference perturbation theory. The spectrum was computed both with and without solvation effects, and these spectra are compared to each other and to experiment. Using multireference-perturbation-theory adiabatic wave functions and model-space diabatization by the fourfold way, diabatic potential energy surfaces of the lowest three singlet states (^{1}ππ, ^{1}ππ∗, and ^{1}n_{π}σ∗) were constructed along the S-H stretching coordinate, the C-C-S-H torsion coordinate, and the v_{16a} and v_{16b} normal coordinates. The first two of these two are primary coordinates for the photodissociation, and the diabatic crossing seams of the three states were calculated and plotted as functions of the two coordinates. The other two coordinates are out-of-plane ring distortion modes studied to assess the extent of their role in coupling the states near the first conical intersection, and the v_{16a} mode was shown to be an important coupling mode there. The current study is the first step toward a detailed mechanistic analysis of the photoinduced S-H fission process of thiophenol, a test system to understand ^{1}n_{π}σ∗-mediated reactions, at the same time already providing a better understanding of the thiophenol electronic excitations by clarifying the assignment of the experimental results.

Original language | English (US) |
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Pages (from-to) | 28144-28154 |

Number of pages | 11 |

Journal | Physical Chemistry Chemical Physics |

Volume | 20 |

Issue number | 44 |

DOIs | |

State | Published - 2018 |

### Bibliographical note

Funding Information:This work was supported in part by the U. S. Department of Energy, Office of Basic Energy Sciences, under grant no. DE-SC0008666, by National Natural Science Foundation of China (No. 51536002), and Linyao Zhang was also supported by a scholarship from China Scholarship Council (201706120185).