Photoinduced Formation of H-Bonded Ion Pair in HCFC-133a.

High-level multireference electronic structure calculations have been performed to study the Cl- yield from photoexcited CF3CH2Cl (HCFC-133a). The analysis of this process tells that it relates to an electron transfer from the carbon to the Cl atom, forming a highly polar contact ion-pair complex, CF3HCH+···Cl-, in the excited (S3) state. This complex has a strong binding energy of 3.53 eV, from which 0.47 eV is due to an underlying hydrogen bond. Through comparison with the results obtained for the prototype CH3Cl system, where a similar ion-pair state associated with Cl- formation has also been observed, it is suggested that photodissociation of HCFC-133a can also yield Cl- through an analogous process. This hypothesis is further supported by nonadiabatic dynamics simulations, which shows formation of the ion-pair complex in the subpicosecond time scale.