Basis set dependence of coupled cluster optical rotation computations.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular modeling

Background:

• Accurate computation of specific molecular rotations is crucial for understanding chemical properties.
• Evaluating the performance of different basis sets is essential for optimizing computational efficiency and accuracy.
• Five challenging molecules with known experimental rotations were selected for this study.

Purpose of the Study:

• To compute specific rotations for five difficult molecules using coupled cluster (CC) and density functional theory (DFT).
• To compare the performance of novel LPol basis sets against established correlation-consistent (cc) basis sets.
• To assess the efficiency and accuracy of LPol basis sets at various wavelengths.

Main Methods:

• Density functional theory (DFT) and coupled cluster (CC) computational methods were employed.
• Calculations were performed using the newly developed LPol basis sets and standard Dunning correlation-consistent basis sets.
• Specific rotations were computed for (S)-methyloxirane, (S)-methythiirane, (S)-2-chloropropionitrile, (1S,4S)-norbornenone, and (1R,5R)-β-pinene at 355, 436, 589, and 633 nm.

Main Results:

• The LPol basis sets demonstrated efficiency, often outperforming cc basis sets of comparable size.
• The smallest LPol-ds basis set showed performance close to the basis set limit, rivaling larger sets.
• Despite the LPol sets' performance, high levels of electron correlation, vibrational corrections, and solvent effects remain necessary for accurate experimental rotation reproduction.
• Discrepancies were noted for β-pinene, where DFT and experimental agreement was not achieved as previously suggested.

Conclusions:

• LPol basis sets offer an efficient and effective alternative for computing molecular rotations, particularly for challenging molecules.
• The accuracy of computed rotations is highly dependent on incorporating electron correlation, vibrational effects, and solvent models.
• Further investigation is needed to fully reconcile computational results with experimental data for certain molecules like β-pinene.