Theoretical study of the C3Cl radical and its cation

A theoretical study of C₃Cl and C₃Cl⁺ isomers has been carried out. The global minimum for C₃Cl is a cyclic C_2V species (a three-membered ring with an exocyclic chlorine atom). However, a quasi-linear CCCCl structure is predicted to lie only 3-5 kcal mol⁻¹ higher. This quasi-linear structure is floppy, since the linear arrangement lies only 2-3 kcal mol⁻¹ higher in energy. The cyclic and open-chain isomers have dipole moments of 1.986 and 3.363 D, respectively. In C₃Cl⁺ the global minimum is a linear singlet species, the singlet cyclic isomer lying about 19 kcal mol⁻¹ higher. The ionization potentials of cyclic and open-chain C₃Cl are estimated to be 9.17 and 8.21 eV, respectively, suggesting that these species should be easily ionized if present in the interstellar medium.