Hedegård, E. D.; Jensen, F.; Kongsted, J. J. Chem. Theory Comput. 2012, 8, 4425
Contributed by Steven Bachrach.
Reposted from Computational Organic Chemistry with permission
This work is licensed under a Creative Commons AttributionNoDerivs 3.0 Unported License.
Contributed by Steven Bachrach.
Reposted from Computational Organic Chemistry with permission
What is the appropriate basis set to use for computing optical rotations? Hedgård, Jensen, and Kongsted examined the optical rotation of 16 using B3LYP and CAMB3LYP at two different wavelengths.^{1} They examined a series of different basis sets, including the augpCS sets^{2} (developed for NMR computations), the augccpVXZ series and 6311++G(3df,3pd). They compared the computed optical rotation with the different basis sets with the value obtained from an extrapolated basis set computation. The mean absolute deviation using either B3LYP or CAMB3LYP at the two different basis sets are listed in Table 1. The bottom line is that augpcS2 is the preferred method, but this basis set is rather large and computations of big molecules will be difficult. The augpcS1 set is the best choice for large molecules. Errors with the extensive Pople basis set and the augccpVXZ sets are quite sizable and of concern (especially at the shorter wavelength). It should also be mentioned that even with the largest augpcS basis sets extrapolated to the CBS limit, the computed value of the optical rotation of 3 has the wrong sign! Clearly, basis set choice is not the only issue of concern. We remain in need of a robust methodology for computing optical activity.
Table 1. Mean absolute deviation of the optical activities of 16 evaluated at two wavelengths.
589.3 nm

355.0 nm
 
Basis set

B3LYP

CAMB3LYP

B3LYP

CAMB3LYP

augpcS1

4.5

2.2

20.8

15.3

augpcS2

1.4

1.1

4.0

1.5

augccpVDZ

15.6

13.6

62.2

144.1

augccpVTZ

3.9

6.3

9.2

37.0

6311++G(3df,3pd)

6.4

10.3

20.5

40.7

References
(1) Hedegård, E. D.; Jensen, F.; Kongsted, J. "Basis Set Recommendations for DFT Calculations of GasPhase Optical Rotation at Different Wavelengths," J. Chem. Theory Comput. 2012, 8, 44254433, DOI:10.1021/ct300359s
(2) Jensen, F. "Basis Set Convergence of Nuclear Magnetic Shielding Constants Calculated by Density Functional Methods," J. Chem. Theory Comput. 2008, 4, 719727, DOI: 10.1021/ct800013z
This work is licensed under a Creative Commons AttributionNoDerivs 3.0 Unported License.