Photoionization Spectroscopic and Theoretical Study on the Molecular Structures of cis- and trans- 3-Chlorothioanisole.

Resonance-enhanced two-photon ionization (R2PI) and mass-analyzed threshold ionization (MATI) spectra are measured for the cis- and trans- 3-chlorothioanisole (3ClTA). The first electronic excitation energy ( E 1 ) and the adiabatic ionization energy (IE) of the cis- rotamer are determined to be 33 959±3 and 65 326±5 cm -1 , respectively, and those of the trans- rotamer are determined to be 34102±3 and 65 471±5 cm -1 , respectively. Density functional theory (DFT) calculations confirm that both the cis- and trans- rotamers of 3ClTA are stable and coexist in their respective S 0 , S 1 , and D 0 states. Both rotamers adopt planar structures with cis- being slightly more stable than trans- in the respective S 0 , S 1 , and D 0 states. The conformation, substitution, and isotope effects on the molecular structure, active vibrations, and electronic transition and ionization energies of 3ClTA are analyzed.