¹³C chemical shift predictions for bakuchiol ‒ A recently discovered agent against organ damage
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
58
02(45) (2021) 58-64
13C chemical shift predictions for bakuchiol‒a recently discovered agent
against organ damage
Tính toán độ dịch chuyển hóa học 13C của bakuchiol‒tác nhân mới điều trị tổn thương
các cơ quan
Nguyen Thi Nhu Ya, Nguyen Trong Thiena,b*
Nguyễn Thị Như Ý a, Nguyễn Trọng Thiệna,b*
aFaculty of Pharmacy, College of Medicine and Pharmacy Duy Tan University, Da Nang 550000, Vietnam
bKhoa Dược, Trường Y- Dược, Đại học Duy Tân, Đà Nẵng, Việt Nam
bInstitute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
bViện Nghiên cứu và Phát triển Công nghệ Cao, Đại học Duy Tân, Đà Nẵng, Việt Nam
(Ngày nhận bài: 03/12/2020, ngày phản biện xong: 07/01/2021, ngày chấp nhận đăng: 13/03/2021)
Abstract
The calculations of 13C NMR chemical shifts for bakuchiol, a promising anti-aging agent, were performed using 11
functionals (B3LYP, B3PW91, BPV86, CAM-B3LYP, HCTH, HSEH1PBE, mPW1PW91, PBEPBE, TPSSTPSS, and
ωB97XD) and 10 common basis sets (3-21G, 6-31G(d,p), 6-31G(d,3p), 6-31G(3d,p) 6-31G++(d,p), DGDZVP,
DGDZVP2, LANL2DZ, LANL2MB) to compare with experimental data. While functionals did not strongly impact the
computed 13C chemical shifts, basis sets showed a significant influence on the results. For those functionals, B3LYP,
B3PW91, CAM-B3LYP, HSEH1PBE, mPW1PW91, and ωB97XD were found to have strong correlations (r2 ≥ 0.9987)
and low errors (CMAEs ≤ 1.96 ppm and CMAEs ≤ 2.49 ppm); among the tested basis sets 3-21G, DGDZVP provided
the best results (r2 ≥ 0.9980, CMAEs ≤ 2.37 ppm and CMAEs ≤ 2.67 ppm). These results would allow meaningful
predictions of 13C chemical shifts for bakuchiol.
Keywords: 13C chemical shifts; NMR; DFT functionals; basis sets; bakuchiol.
Tóm tắt
Phổ 13C của bakuchiol, tác nhân chống lão hóa, được tính toán bằng 11 hàm mật độ (B3LYP, B3PW91, BPV86, CAM-
B3LYP, HCTH, HSEH1PBE, mPW1PW91, PBEPBE, TPSSTPSS, và ωB97XD) và 10 mức lý thuyết (3-21G, 6-
31G(d,p), 6-31G(d,3p), 6-31G(3d,p) 6-31G++(d,p), DGDZVP, DGDZVP2, LANL2DZ, LANL2MB) nhằm so sánh với
dữ liệu thực nghiệm. Trong khi các hàm mật độ thể hiện ảnh hưởng nhỏ lên độ dịch chuyển hóa học 13C, các kết quả
tính toán bằng mức lý thuyết cho thấy sự phân hóa rộng hơn về độ chính xác. B3LYP, B3PW91, CAM-B3LYP,
HSEH1PBE, mPW1PW91, và ωB97XD có độ tương quan cao (r2 ≥ 0.9987) và lỗi thấp (CMAEs ≤ 1.97 ppm và
CMAEs ≤ 2.49 ppm); trong các mức lý thuyết, 3-21G, DGDZVP cho các kết quả với độ chính xác cao (r2 ≥ 0.9980,
CMAEs ≤ 2.37 ppm and CMAEs ≤ 2.67 ppm).
Từ khóa: Phổ 13C; NMR; hàm DFT; mức lý thuyết; bakuchiol.
*Corresponding Author: Nguyen Trong Thien; Faculty of Pharmacy, College of Medicine and Pharmacy Duy Tan
University, Da Nang 550000, Vietnam; Institute of Research and Development, Duy Tan University, Da Nang 550000,
Vietnam
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
59
1. Introduction
proliferation of various cancer cells, including
stomach, breast, and skin cancer cells and
liverfibrosis via promoting myofibroblast
apoptosis. It relieves the hepatotoxic of
multiple toxicants by suppressing oxidative
Bakuchiol (Figure 1), a prenylated phenolic
monoterpene isolated from the fruit of Psoralea
corylifolia, has recently shown a variety of
pharmacological effects such as antioxidant,
anti-bacterial, anti-inflammatory, anti-aging,
and estrogen-like effects[1][2]. It also has
protective effects in the heart, liver skin, and
other organs. In addition, bakuchiol inhibits the
stress
and
inflammatory
changes[3].
Understanding the structure of bakuchiol would
provide insights into its pharmacological
effects.
Figure 1. (A) Bakuchiol and (B) its optimized structure at the IEFPCM(CHCl3)/B3LYP-631G(d,p) level of theory with
numbered carbons (H atoms were omitted for clarity).
The combination of experimental and
computational NMR techniques has been a
strong tool for providing the structural
information of biologically active natural
products, which can support the difficult
assignments and the confirmation of their
structures and provide valuable insights into the
electronic environments of active NMR nucleus
[4][5][6]. The gauge-including atomic orbitals
(GIAO)/density functional theory (DFT)
method are generally accepted as a standard
method in computing shielding constants due to
its reliability and applicability [7][8][9]. The
accuracy of calculated chemical shifts typically
depends on an appropriate combination of
exchange-correlation functionals and basis sets
[10]. Aimed to find suitable methods with high
accuracy, this present study evaluated 11 DFT
functionals and 11 common basis sets in the
calculations of 13C chemical shifts for
bakuchiol.
2. Computational methods
All calculations were performed using the
Gaussian09 [11]. Geometry optimizations of
bakuchiol
were
performed
at
the
IEFPCM(CHCl3)/B3LYP/6-31G(d,p) level[12][13].
Subsequent frequency calculations ensured that
a potential energy surface (PES) local
minimum was attained during the energy
minimization. Cartesian coordinates of the
resulting structures are given in the Supporting
Information.
The following 11 functionals coupled with
6-31G(d,p) [14] and 10 basis set coupled with
B3LYP [15] were evaluated:
- Funtionals: B3LYP (Becke’s 3-parameter
hybrid functional[16] using B exchange[17]
and LYP correlation),[15] B3PW91 (Perdew
and Wang’s 1991 gradient-corrected correlation
functional),[18][19] BPV86 (Perdew’s 1986
functional),[16][20][21] CAM-B3LYP (Handy
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
60
and co-workers’ long-range corrected version
of B3LYP using the Coulomb-attenuating
method),[22] HCTH (Hamprecht-Cohen-Tozer-
13C. Computed results were evaluated using
mean absolute value (│Δδ│/ppm, Equation 4);
corrected mean absolute error (CMAE/ppm,
Equation 5); corrected root mean squared error
(CRMSE/ppm, Equation 6); and the Pearson
correlation coefficient (r2). The smaller values
of CMAE and CRMSE indicate smaller errors
and the larger value of r2 means a stronger
Handy
GGA
functional),[23][24][25]
HSEH1PBE (The exchange part of the screened
Coulomb potential of Heyd, Scuseria, and
Ernzerhof),[26][27] LSDA (Local spin-density
approximation),[28]
mPW1PW91
(mPW
exchange and PW91 correlation),[29][30]
PBEPBE (The functional of Perdew, Burke,
and Ernzerhof),[31] TPSSTPSS (The exchange
component of the Tao-Perdew-Staroverov-
Scuseria),[32][33] and ωB97XD (Head-Gordon
and coworkers’ dispersion corrected long-range
corrected hybrid functional)[34][35].
correlation
between
theoretical
and
experimental data. Error calculations and linear
correlations were performed using Microsoft
Excel 2013.
(1)
(2)
(3)
(4)
- Basis sets: Pople’s 3-21G, 6-31G(d,p), 6-
31G(3d,p), 6-31G(d,3p), 6-31++G(d,p), and 6-
311G;[36][37][14] DGDZVP, DGDZVP2 ;[38]
LANL2MB and LANL2DZ (Los Alamas
ECP).[39][40]
(5)
(6)
Unless specified otherwise, single-point
NMR GIAO calculations were carried out in
gas phase[41]. The GIAO NMR results were
observed and extracted using GaussView06.
Each optimized structure was used for
3. Results and Discussion
3.1. The evaluation of 11 DFT functionals
11 Functionals were evaluated, and the
results were showed in Table 1 and Figure 2.
The functionals were sorted alphabetically by
name. Table 1 shows statistical parameters
using 11 different DFT functionals coupled
with 6-31G(d,p) basis set and Figure 2
illustrates absolute deviations. Overall, the
correlation coefficients and error results
indicate that the calculations provided a
qualitatively accurate description of the 13C
NMR chemical shifts. The CMAE and CRMSE
values were in the ranges of 1.44 to 2.62 ppm
and 1.72 to 3.53 ppm, respectively. The
coefficients of determination (r2) were above
0.9976 for all tested functionals. C3 and C16
were consistently observed with the noticeable
deviations ranged from 2.18 to 6.28 ppm and
2.39 to 4.98 ppm, respectively (Figure 2). The
computing the
shielding constants (
corresponding isotropic
. The chemical shifts
(
) given in the Supporting Information were
obtained using Equation 1. For both 13C NMR
calculations, an average of values of
equivalents atoms was assumed. For example, a
single proton/carbon signal is observed for the
two symmetrically aromatic CH groups of
bakuchiol. To reduce the systematic error of the
calculations, the linear regression analysis of
the calculated chemical shifts versus the
experimental ones (
(Equation 2) were
performed and the scaled chemical shifts (
)
were computed according to Equation 3. As
reference had a negligible impact on the linear
regression analysis, the fix values of 197 ppm
was chosen as TMS shielding constants for
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
61
two best performers with strong correlations
and low errors for C calculations were CAM-
ppm, and r2 = 0.9991), ωB97XD (CMAE =
1.48ppm, CRMSE = 1.80 ppm, and r2 = 0.9990).
13
B3LYP (CMAE = 1.44 ppm, CRMSE = 1.72
Table 1. 13C NMR chemical shifts of bakuchiol calculated using 11 functionals
δ(13C)
Entry
Functional
B3LYP
B3PW91
BPV86
CAM-B3LYP
HCTH
HSEH1PBE
LSDA
mPW1PW91
PBEPBE
TPSSTPSS
ωB97XD
r2
CMAE
1.79
1.97
2.36
1.44
2.23
1.91
2.62
1.91
1.91
2.50
1.48
CRMSE
2.33
2.49
3.17
1.72
2.96
2.34
3.53
2.36
2.34
2.94
1.80
1
2
3
4
5
6
7
8
9
0.9987
0.9988
0.9978
0.9991
0.9981
0.9989
0.9976
0.9989
0.9989
0.9981
0.9990
10
11
Figure 2. Absolute deviations of 13C chemical shift calculations using 11 functionals.
3.2. The evaluation of 11 basis sets
ranged from 1.79 to 4.97 ppm and 2.22 to 5.13
ppm, respectively (Table 3). The largest
deviations were found for C3, C11, and C16
with CMAE and CRMSE values in the ranges
of 1.05 to 6.25 ppm, 0.46 to 6.11 ppm, and 2.13
to 4.47 ppm, respectively (Figure 1).
11 Basic sets were employed for computing
13C chemical shifts of bakuchiol. In general, the
calculated results were observed with low
associated errors and strong linear correlations
(r2 ≥ 0.9958). CMAE and CRMSE values were
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
62
13
Table 2. The calculated C NMR chemical shifts of Bakuchiol in CHCl3 using 10 basic sets.
All chemical shifts, CMAEs, and CRMSEs are in ppm.
δ(13C)
Entry
Basis set
r2
CMAE CRMSE
1
2
3
4
5
6
7
8
10
11
3-21G
0.9981
0.9987
0.9971
0.9975
0.9958
0.9976
0.9985
0.9962
0.9970
0.9970
2.37
1.79
2.62
2.33
3.35
1.93
2.19
4.97
3.13
3.80
2.67
2.33
3.21
2.67
3.43
2.71
2.22
5.13
3.28
3.81
6-31G(d,p)
6-31G(3d,p)
6-31G(d,3p)
6-31++G(d,p)
6-311G
DGDZVP
DGDZVP2
LANL2DZ
LANL2MB
Figure 3. Absolute deviations of 13C chemical shift calculations using 10 basis sets.
4. Conclusion
excellent correlations between theoretical and
experimental data (r2 > 0.9987) were observed.
Given such high degree of accuracy achieved in
calculating 13C chemical shifts of bakuchiol,
this work can be useful for supporting the
assignments of the experimental NMR spectra of
bakuchiol and similar retinoid compounds.
Further studies on the chemical shift calculations
of these compounds are under-investigation.
We have performed the evaluation of 11
DFT functionals and 11 basis sets using GIAO
method on the calculation of 13C chemical
shifts for bakuchiol. Our results showed the two
best performing functionals were CAM-B3LYP
(CMAEs ≤ 1.44 ppm) and ωB97XD (CRMSEs
≤ 1.80 ppm), and the best basis set was 6-
31G(d,p) (CMAEs ≤ 1.79 ppm). In these cases,
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
63
Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M.
Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F.
Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N.
Kudin, V.N. Staroverov, T. Keith, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J.C. Burant,
S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M.
Millam, M. Klene, J.E. Knox, J.B. Cross, V.
Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E.
Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, R.L. Martin, K.
Morokuma, V.G. Zakrzewski, G.A. Voth, P.
Salvador, J.J. Dannenberg, S. Dapprich, A.D.
Daniels, O. Farkas, J.B. Foresman, J. V. Ortiz, J.
Cioslowski, F.D. J., Gaussian 09, Revision D.01,
(2013).
References
[1] S. Dhaliwal, I. Rybak, S.R. Ellis, M. Notay, M.
Trivedi, W. Burney, A.R. Vaughn, M. Nguyen, P.
Reiter, S. Bosanac, H. Yan, N. Foolad, R.K.
Sivamani, Prospective, randomized, double‐blind
assessment of topical bakuchiol and retinol for
facial photoageing, Br. J. Dermatol. 180 (2019)
[2] T. Esumi, C. Yamamoto, Y. Fukuyama, A short
synthesis of (+)-bakuchiol, Synlett. 24 (2013) 1845–
[3] Z. Xin, X. Wu, T. Ji, B. Xu, Y. Han, M. Sun, S.
Jiang, T. Li, W. Hu, C. Deng, Y. Yang, Bakuchiol:
A newly discovered warrior against organ damage,
Pharmacol.
Res.
141
(2019)
208–213.
[12] J. Tomasi, B. Mennucci, R. Cammi, Quantum
mechanical continuum solvation models, Chem.
Rev. 105 (2005) 2999–3093.
[4] H.D. Watts, M.N.A. Mohamed, J.D. Kubicki,
Comparison of multistandard and TMS-standard
calculated NMR shifts for coniferyl alcohol and
application of the multistandard method to lignin
dimers, J. Phys. Chem. B. 115 (2011) 1958–1970.
[13] J. Tomasi, B. Mennucci, E. Cancès, The IEF version
of the PCM solvation method: An overview of a
new method addressed to study molecular solutes at
the QM ab initio level, in: J. Mol. Struct.
THEOCHEM, Elsevier, 1999: pp. 211–226.
[14] M.M. Francl, W.J. Pietro, W.J. Hehre, J.S. Binkley,
M.S. Gordon, D.J. DeFrees, J.A. Pople, Self-
consistent molecular orbital methods. XXIII. A
polarization-type basis set for second-row elements,
J. Chem. Phys. 77 (1982) 3654–3665.
1
[5] J.S. Lomas, H NMR spectra of alcohols and diols
in chloroform: DFT/GIAO calculation of chemical
shifts, Magn. Reson. Chem. 52 (2014) 745–754.
[6] B.G. Diehl, H.D. Watts, J.D. Kubicki, M.R. Regner,
J. Ralph, N.R. Brown, Towards lignin-protein
crosslinking: Amino acid adducts of a lignin model
quinone methide, Cellulose. 21 (2014) 1395–1407.
[7] K. Wolinski, J.F. Hinton, P. Pulay, Efficient
Implementation of the Gauge-Independent Atomic
Orbital Method for NMR Chemical Shift
Calculations, J. Am. Chem. Soc. 112 (1990) 8251–
[15] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J.
Frisch, Ab Initio calculation of vibrational
absorption and circular dichroism spectra using
density functional force fields, J. Phys. Chem. 98
(1994) 11623–11627.
[8] J. Gauss, Effects of electron correlation in the
calculation of nuclear magnetic resonance chemical
shifts, J. Chem. Phys. 99 (1993) 3629–3643.
[16] A.D. Becke, Density-functional thermochemistry.
III. The role of exact exchange, J. Chem. Phys. 98
(1993)
5648–5652.
[9] R. Ditchfield, Self-consistent perturbation theory of
diamagnetism I. A gauge-invariant LCAO method
for N.M.R. Chemical shifts, Mol. Phys. 27 (1974)
789–807.
[17] A.D. Becke, Density-functional exchange-energy
approximation with correct asymptotic behavior,
Phys.
Rev.
A.
38
(1988)
3098–3100.
[10] M.A. Iron, Evaluation of the Factors Impacting the
Accuracy of 13C NMR Chemical Shift Predictions
using Density Functional Theory - The Advantage
of Long-Range Corrected Functionals, J. Chem.
[18] J.P. Perdew, J.A. Chevary, S.H. Vosko, K.A.
Jackson, M.R. Pederson, D.J. Singh, C. Fiolhais,
Atoms,
Applications
molecules,
of the
solids,
and
surfaces:
gradient
generalized
Theory
Comput.
13
(2017)
5798–5819.
approximation for exchange and correlation, Phys.
Rev. B. 46 (1992) 6671–6687.
[11] M.J. Frisch, J.R. Cheeseman, G. Scalmani, V.
Barone, B. Mennucci, G.A. Petersson, H. Nakatsuji,
M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov,
J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M.
[19] J.P. Perdew, J.A. Chevary, S.H. Vosko, K.A.
Jackson, M.R. Pederson, D.J. Singh, C. Fiolhais,
Erratum: Atoms, molecules, solids, and surfaces:
Nguyen Thi Nhu Y, Nguyen Trong Thien / Tạp chí Khoa học và Công nghệ Đại học Duy Tân 02(45) (2021) 58-64
64
Applications
of the
generalized
gradient
approximation for exchange and correlation
(Physical Review B (1993) 48, 7, (4978)), Phys.
Rev. B. 48 (1993) 4978.
[31] J.P. Perdew, K. Burke, M. Ernzerhof, Generalized
gradient approximation made simple, Phys. Rev.
Lett. 77 (1996) 3865–3868.
[32] J. Tao, J.P. Perdew, V.N. Staroverov, G.E. Scuseria,
[20] J.P. Perdew, Density-functional approximation for
the correlation energy of the inhomogeneous
electron gas, Phys. Rev. B. 33 (1986) 8822–8824.
[21] S.H. Vosko, L. Wilk, M. Nusair, Accurate spin-
dependent electron liquid correlation energies for
local spin density calculations: a critical analysis,
Climbing
the
density
functional
ladder:
Nonempirical
meta–generalized
gradient
approximation designed for molecules and solids,
Phys. Rev. Lett. 91 (2003) 146401.
[33] J.P. Perdew, A. Ruzsinszky, G.I. Csonka, L.A.
Constantin, J. Sun, Workhorse semilocal density
functional for condensed matter physics and quantum
chemistry, Phys. Rev. Lett. 103 (2009) 026403.
[34] J. Da Chai, M. Head-Gordon, Systematic
optimization of long-range corrected hybrid density
functionals, J. Chem. Phys. 128 (2008) 084106.
Can.
J.
Phys.
58
(1980)
1200–1211.
[22] T. Yanai, D.P. Tew, N.C. Handy, A new hybrid
exchange-correlation functional using the Coulomb-
attenuating method (CAM-B3LYP), Chem. Phys.
Lett. 393 (2004) 51–57.
[23] F.A. Hamprecht, A.J. Cohen, D.J. Tozer, N.C.
Handy, Development and assessment of new
exchange-correlation functionals, J. Chem. Phys.
109 (1998) 6264–6271.
[35] J. Chai, M. Head-Gordon, Long-range corrected
hybrid density functionals with damped atom–atom
dispersion corrections, Phys. Chem. Chem. Phys. 10
(2008) 6615–6620.
[24] A. Daniel Boese, N.L. Doltsinis, N.C. Handy, M.
Sprik, New generalized gradient approximation
functionals, J. Chem. Phys. 112 (2000) 1670–1678.
https://doi.org/10.1039/B810189B.
[36] J. Stephen Binkley, J. A. Pople, W. J. Hehre, Self-
consistent molecular orbital methods. 21. Small
split-valence basis sets for first-row elements, J.
Am. Chem. Soc. 102 (1980) 939–947.
[25] A.D. Boese, N.C. Handy, A new parametrization of
exchange-correlation
generalized
gradient
approximation functionals, J. Chem. Phys. 114
(2001) 5497–5503.
[37] R. Ditchfield, W.J. Hehre, J.A. Pople, Self-
consistent molecular-orbital methods. IX. An
extended gaussian-type basis for molecular-orbital
studies of organic molecules, J. Chem. Phys. 54
[38] C. Sosa, J. Andzelm, B. C. Elkin, E. Wimmer, K. D.
Dobbs, D. A. Dixon, A local density functional
study of the structure and vibrational frequencies of
molecular transition-metal compounds, J. Phys.
Chem. 96 (1992) 6630–6636.
[26] J. Heyd, G.E. Scuseria, M. Ernzerhof, Hybrid
functionals based on a screened Coulomb potential,
J. Chem. Phys. 118 (2003) 8207–8215.
[27] M. Ernzerhof, J.P. Perdew, Generalized gradient
approximation to the angle- and system-averaged
exchange hole, J. Chem. Phys. 109 (1998) 3313–
[28] J.P. Perdew, Y. Wang, Accurate and simple analytic
representation of the electron-gas correlation
energy, Phys. Rev. B. 45 (1992) 13244–13249.
[29] J.P. Perdew, K. Burke, Generalized gradient
approximation for the exchange-correlation hole of
a many-electron system, Phys. Rev. B - Condens.
Matter Mater. Phys. 54 (1996) 16533–16539.
[30] C. Adamo, V. Barone, Exchange functionals with
improved long-range behavior and adiabatic
connection methods without adjustable parameters:
The mPW and mPW1PW models, J. Chem. Phys.
108 (1998) 664–675.
[39] P.J. Hay, W.R. Wadt, Ab initio effective core
potentials for molecular calculations. Potentials for
the transition metal atoms Sc to Hg, J. Chem. Phys.
82 (1985) 270–283.
[40] W.R. Wadt, P.J. Hay, Ab initio effective core
potentials for molecular calculations. Potentials for
main group elements Na to Bi, J. Chem. Phys. 82
[41] T.T. Nguyen, P.Q. Le, J. Helminen, J. Sipilä, The
1H and 13C chemical shifts of 5–5 lignin model
dimers: An evaluation of DFT functionals, J. Mol.
Struct. 1226 (2021) 129300.
7 trang
16/04/2022
960
Bạn đang xem tài liệu "¹³C chemical shift predictions for bakuchiol ‒ A recently discovered agent against organ damage", để tải tài liệu gốc về máy hãy click vào nút Download ở trên
File đính kèm:
- c_chemical_shift_predictions_for_bakuchiola_recently_discove.pdf
