n the Unexpected Accuracy of the M06L Functional in the Calculation of (1)J(FC) Spin-Spin Coupling Constant

Author(s)

de Giovanetti, Marinella ^[1] ; Ferraz Bitencourt, Luis Felipe ^[2] ; Cormanich, Rodrigo ^[2] ; Sauer, Stephan P. A. ^[1]

Affiliation

^[1] Univ Copenhagen, Dept Chem, DK-2100 Copenhagen O - Denmark

^[2] Univ Estadual Campinas, Chem Inst, BR-13083970 Campinas, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF CHEMICAL THEORY AND COMPUTATION; v. 17, n. 12, p. 7712-7723, DEC 14 2021.
• Web of Science Citations: 0

Abstract

One-bond spin-spin coupling constants (SSCCs) between F and C are computed with density functional theory (DFT). Surprisingly, M06L stands out for its striking accuracy, outperforming any other investigated functional, including PBE0, otherwise considered one of the most reliable for couplings involving F. Although the computation of nuclear magnetic resonance (NMR) parameters involving F is known to be a challenging task, even with a rather small basis set as pcJ-1, M06L provides results with a MAD = 11.7 Hz, whereas the average deviation gets as much as 5 times larger for PBE0 (MAD = 60.0 Hz). In the context of SSCCs on the order of 300 Hz, this is particularly remarkable. We find that the accuracy of M06L/pcJ-1 in predicting (1)J(FC) constants does not stem from a well-suited exchange or correlation part of the functional. Instead, it is believed to arise from a fortuitous cancellation of errors, as revealed by investigating the convergence of the basis set. Our findings also indicate that (1)J(FC) constants are highly dependent on the amount of exact exchange included in the expression of the functional, with large fractions being critically important to achieving satisfactory results. Studying the effects of the geometry on (1)J(FC), we find that optimizing the geometry at the level of theory used to calculate SSCCs generally improves the quality of the results, although the combination of a M06-2X/aug-cc-pVTZ geometry with M06L/pcJ-1 (1)J(FC) constants best reproduces the experimental data for organofluorine compounds (with the exception of fluoroalkenes). (AU)

• FAPESP's process: 18/03910-1 - Physicochemical studies of fluorinated organic compounds: experimental and theoretical approaches
• Grantee: Rodrigo Antonio Cormanich
• Support Opportunities: Research Grants - Young Investigators Grants
• FAPESP's process: 19/24788-2 - Theoretical studies of organofluorinated compounds: benchmarking theoretical calculations for nJCF coupling constants
• Grantee: Luis Felipe Ferraz Bitencourt
• Support Opportunities: Scholarships in Brazil - Scientific Initiation