Benchmarking study on calculation of specific optical rotation of rigid chiral molecules in solution: 1:1 solute-solvent complex with PCM solvation model

Abstract

We carried out DFT calculations of the specific optical rotation (OR) of six rigid chiral molecules in gas and solution phases. To examine the explicit solvent effect, multiple conformers of a 1:1 solute–solvent complex were considered. The most accurate results in the gas phase were obtained using cam-B3LYP/aug-cc-PVTZ. The specific ORs of chiral solutes were computed using cam-B3LYP/aug-cc-PVTZ in conjunction with the PCM solvation model. The calculated ORs of the six chiral molecules in hexane at 633 nm agreed overall with experimental measurements, but the explicit addition of hexane produced more accurate results. Applying the PCM model alone to (R)-methyloxirane did not reproduce experimentally observed distinct OR values for three different nonpolar solvents with similar dielectric constants. Using a 1:1 solute–solvent complex with the PCM model produced OR values for (R)-methyloxirane in cyclohexane, carbon tetrachloride, and benzene that were in considerably better agreement with the experimental solution values.