Solvent-assisted conformational isomerization (SACI) of meta-substituted phenols: Tuning relative stability, isomerization barrier, and IVR rate

Solvent-assisted conformational isomerization (SACI) in meta-substituted phenols with substituents of varying electron-donating/withdrawing properties was studied in the gas phase. SACI of m-anisidine (m-methoxyaniline) occurs when the binding energy of solvent is higher than isomerization barrier, very similarly to the previously reported case of m-aminophenol. Two conformers of m-chlorophenol have similar relative energy, and SACI does not occur because forward/reverse isomerization rates are similar. While SACI does not occur with m-cyanophenol–H2O though the binding energy is higher than the barrier, D2O can induce SACI of m-cyanophenol because of increased intermolecular vibrational relaxation rate. In m-cyanophenol-d1, SACI yield with D2O becomes even greater due to faster intramolecular vibrational energy redistribution.