Matrix isolation and computational study of isodifluorodibromomethane $(F2CBr–Br)$⁠: A route to $Br2$ formation in $CF2Br2$ photolysis Available to Purchase

The photolysis products of dibromodifluoromethane $(CF2Br2)$ were characterized by matrix isolation infrared and UV/Visible spectroscopy, supported by ab initio calculations. Photolysis at wavelengths of 240 and 266 nm of $CF2Br2:Ar$ samples $(∼1:5000)$ held at $∼5K$ yielded iso-$CF2Br2$ $(F2CBrBr)$⁠, a weakly bound isomer of $CF2Br2$⁠, which is characterized here for the first time. The observed infrared and UV/Visible absorptions of iso-$CF2Br2$ are in excellent agreement with computational predictions at the B3LYP/aug-cc-pVTZ level. Single point energy calculations at the CCSD(T)/aug-cc-pVDZ level on the B3LYP optimized geometries suggest that the isoform is a minimum on the $CF2Br2$ potential energy surface, lying some 55 kcal/mol above the $CF2Br2$ ground state. The energies of various stationary points on the $CF2Br2$ potential energy surface were characterized computationally; taken with our experimental results, these show that iso-$CF2Br2$ is an intermediate in the $Br+CF2Br→CF2+Br2$ reaction. The photochemistry of the isoform was also investigated; excitation into the intense 359 nm absorption band resulted in isomerization to $CF2Br2$⁠. Our results are discussed in view of the rich literature on the gas-phase photochemistry of $CF2Br2$⁠, particularly with respect to the existence of a roaming atom pathway leading to molecular products.