Initial structures for substrates, intermediate radicals, fluorinated products, and the Mn(TMP) catalyst used in prior experimental studies were built in Avogadro v1.2.0 104 . These structures were then force-field optimized in Avogadro using UFF force field . Besides isolated complexes, geometries were also built for intermediates formed during the catalytic cycle 1 (see Section 2). Unconstrained geometry optimizations were carried out with TeraChem 106 using hybrid B3LYP 107-109 density functional theory (DFT) where semi-empirical D3 110 dispersion with Becke-Johnson 111 damping was incorporated. The multibasis feature of TeraChem was employed, with the LANL2DZ 112-113 effective core potential (ECP) used for Mn and Cl, and 6-31G* 114 basis set for all other atoms. All optimization calculations were carried out in Cartesian coordinates using L-BFGS algorithm implemented in DL-FIND 115 with the default thresholds of 4.5 x 10 -4 hartree per bohr for the maximum gradient and 1 x 10 -6 hartree for selfconsistent field (SCF) convergence. Level-shifting 116 values of 0.25 hartree were applied for both occupied and virtual orbitals for open-shell calculations which were carried out in a spinunrestricted formalism. Closed-shell singlet calculations were carried out in a spin-restricted formalism.