Calculation of 15N NMR Chemical Shifts in a ... - ACS Publications

Subscriber access provided by Macquarie University

A: Spectroscopy, Molecular Structure, and Quantum Chemistry

Calculation of 15N NMR Chemical Shifts in a Diversity of Nitrogen-Containing Compounds Using Composite Method Approximation at the DFT, MP2, and CCSD Levels Valentin Semenov, Dmitry Samultsev, and Leonid B. Krivdin J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.9b06780 • Publication Date (Web): 29 Aug 2019 Downloaded from pubs.acs.org on August 30, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Calculation of 15N NMR Chemical Shifts in a Diversity of Nitrogen-Containing Compounds Using Composite Method Approximation at the DFT, MP2, and CCSD Levels Valentin A. Semenov, Dmitry O. Samultsev, and Leonid B. Krivdin* A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, Favorsky St. 1, 664033 Irkutsk, Russia. E-mail: [email protected]

Abstract:

Computation of

15N

NMR chemical shifts in diverse 93 nitrogen-

containing compounds representing almost all known classes, are performed at the DFT, MP2, and CCSD levels using the Composite Method Approximation (CMA) in comparison with experimental results. It is shown that the CMA-DFT and CMACCSD methods provided the best performance characterized by a normalized mean absolute error of 1.1-1.3 % as compared to 2.3 % for the CMA-MP2 results. Taking into account solvent effects within the conductor-like polarizable continuum model, decreased the normalized mean absolute error by 0.4 % for the CMA-DFT and by 0.2 % for the CMA-CCSD calculations.

ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

■

Page 2 of 31

INTRODUCTION

Since the early days of NMR until the present, much attention has been focused on 15N

NMR chemical shifts, both on their experimental and computational aspects.

Indeed, calculation of

15N

NMR chemical shifts provides a powerful tool in the

structural elucidation of nitrogen-containing organic and biological molecules and gives a deeper insight into vitally important biochemical phenomena such as selfassociation, molecular recognition and base-pairing. In continuation of our previous 15N

NMR computational studies,1,2,3,4,5,6,7,8 recently reviewed by one of the authors,9

in this communication we performed a high-level computational study of 15N NMR chemical shifts at the DFT, MP2, and CCSD levels in a broad series of 93 nitrogencontaining compounds representing about 50 different types, namely, amines (1, 2), hydrazines (3, 4), imines (5, 6), hydrazones (7, 8), guanidines (9, 10), diazirines (11), azo compounds (12), carbondiimides (13, 14), triazenes (15, 16), nitriles (17, 18), cyanamides (19, 20), diazo compounds (21), azides (22-24), isonitriles (25, 26), hydroxylamines (27, 28), amides (29, 30), oximes (31, 32), ureates (33, 34), aminoacids (35, 36), carbamates (37, 38), lactams (39, 40), nitroso compounds (41), nitrites (42, 43), isocyanates (44, 45), nitrosoamines (46), esters of cyanic acid (47, 48), nitrones (49, 50), nitroalkanes (51, 52), nitramines (53, 54), nitrates (55, 56), thioamides (57, 58), isothiocyanates (59, 60), sulfinylamines (61, 62), thiocyanides (63, 64), sulphonamides (65, 66), pyrroles (67, 68), pirazoles (69, 70), imidazoles (71, 72), triazoles (73, 74), tetrazoles (75, 76), oxazoles (77, 78), furoxanes (79, 80), ACS Paragon Plus Environment

Page 3 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


thiazoles (81, 82), heterocyclic azines (83, 84), azinoxides (85, 86), diazines (87, 88), triazines (89, 90), and azoloazines (indolizines) (91-93), see Scheme 1 for chemical structures.


The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

Me Et

NH2

Me

Me

Me

1

2

N

NH2

N Me

3 Me

1

2

N

N

N

4

Me N

N

Me

5

Me

Me

N

N

3

2

Me

Me

Me

N

7

8

Et

N

i-Pr

N

N

C

Me

3

1

2

N

N

N

Me

C6H4Me

N

Et

N

C

21

17 1

2

N

N

Me

1

3

N

N

N

Me

N t-Bu

H 2N

Et

3

1

2

N

N

N

1

3

N

N

N

23 ACS Paragon Plus Environment

t-Bu

C

Me

2

1

N

N

C

N

Me

20

2

1

3

N

N

N

24

Ph

Me

19

2

Ph

15 1

18

2

22

C

2

N

Me

10

14

Me

16

2

1

1

13

C

N

3

N

i-Pr

12

N

H

2

N

Et

11

Me

Me

9

i-Pr

N

Me

Me

N 1

6

Me

Me

Me

2

i-Pr

NH

Me

1

Et

Me

HN

N Me

Page 4 of 31

Me

N

25

C

Page 5 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46


OH Et

N

Me

C

N

i-Pr

H

27

Me

Me

1

31

32

Me

O

Me

H 2N H 2N

O

36 N

O

Me

O

1

N

N

NH2

O

Me

Et

O

Me

O

Et

O

O

N

O

Me

43

C

N

Ph

O

N

O

40 C

O

Et

44

C


C

Me N

O

49

O

Me

N

N

48

N

45 Me

Ph

47

NH

39

Me

46

35

H O

OH

34

38 N

H 2C

NH

42

2

H 2N

O

37

41 Me

Et

O

N

N

OH

Ph

O

2

33

O

30

Me

NH2

OH

O

Me

O

N OH

NH2

29

H 2N N

Me

O

28

Me

H

NH2

N

H

26

H

OH

Ph

O

50


O Et

Me

O

N

Pr

N

O

51

O

2

1

N

N

Me

O

52

Page 6 of 31

Me

O

2

1

N

N

H

53

O

O Me

O

O

O

54

Me

Me

Me

N

N

N

N

55

O Et

O

Me

N

Me

Me

Me

Me

N

C

Et

S

N

C

S

O S

56

S

57

58

59

60 O

Me

N

S

O

Et

N

S

O

Me

S

C

N

Et

S

C

N

Me

S

NH2

O

61

62

64

65 Me

O Me

63

H

S

N

N2 N

N

N1

Me

Vi

Me

67

68

69

t-Bu

O

66


Me

N N1 H

70

2

Page 7 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46


N3

N3

N1

N 1

Me

Me

71

N Me

72

N 1

N

N

N2

Me

Me

Me

74

75

73

N O

O

77

78

N1

Me

5

Et

Me

N

N O

79

2

5

O

Et

N 2

N O

80

CHO N

N S

81

S

82

N N

83


3

N2

N1

Me

76

5

N

N 1

N

N 2

N

4

N 2

N3 5

3

N

O

84

85

O


Page 8 of 31

Me N

4

N

N

N2

N

N

N

N

N

N1

N

87

88

89

90

O

86

3

N N

91

N 7a

92

N

N

1

7a

93

Scheme 1. List of compounds.


Page 9 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


■

COMPUTATIONAL DETAILS

Geometry optimizations of all compounds were performed with GAUSSIAN 09 code10 at the MP2/aug-cc-pVTZ level, taking into account solvent effects within the Conductor-like

Polarizable

Continuum Model

(CPCM).11,12,13,14,15

Cartesian

coordinates of all structures optimized at the MP2/aug-cc-pVTZ level are given in the Supporting Information. Calculations of 15N NMR isotropic magnetic shielding constants were carried out at the DFT, MP2, and CCSD levels, taking into account solvent effects within the CPCM scheme. At the DFT level, we used OLYP functional - Handy and Cohen's hybrid functional (OPTX)16 in combination with Lee, Yang and Parr's correlation functional (LYP).17 The DFT and MP2 calculations were performed with GAUSSIAN 09 code,10 while the CCSD calculations were carried out with CFOUR package.18 All calculations of 15N NMR isotropic magnetic shielding constants were performed using the Composite Method Approximation (CMA)19 with Jensen's double and quintuple basis sets, pcSseg-2 and aug-pcS-4.20 Calculated

15N

NMR absolute shielding constants were converted into

15N

NMR

chemical shifts based on the recommendations of the International Union of Pure and Applied Chemistry (IUPAC)21 and chemical shifts of neat nitromethane (used as a standard) calculated at all particular levels of theory applied in this paper. This is described in more detail elsewhere (for references, see the above-mentioned review9). Experimental 15N NMR chemical shifts used as the reference points were taken from different sources.22,23,24



■

Page 10 of 31

RESULTS

Compiled in Table 1 are the

15N

NMR chemical shifts of the whole series of

compounds 1-93, in gas and liquid phases, calculated at the DFT, MP2, and CCSD levels in comparison with experimental data. All DFT, MP2, and CCSD calculations were performed using CMA and denoted, accordingly, as CMA-DFT, CMA-MP2, and CMA-CCSD, which are described by eqns. (1-3). At the DFT level, the OLYP functional was used throughout.

DFT/aug-pcS-4 ≈ HF/aug-pcS-4 + [DFT/pcSseg-2 – HF/pcSseg-2]

(1)

MP2/aug-pcS-4 ≈ HF/aug-pcS-4 + [MP2/pcSseg-2 – HF/pcSseg-2]

(2)

CCSD/aug-pcS-4 ≈ HF/aug-pcS-4 + [CCSD/pcSseg-2 – HF/pcSseg-2]

In this scheme, the DFT, MP2, and CCSD values of

15N

(3)

NMR chemical

shifts were approximated by the sum of uncorrelated HF values, calculated using high-quality, large quintuple (penta-zeta) basis sets with diffuse functions, augpcSseg-4, while the correlation contributions, evaluated as the difference between the DFT, MP2, and CCSD and, on the other hand, HF values, were obtained using a smaller basis set of triple-zeta quality, pcSseg-2. Correlation plots of

15N

NMR

chemical shifts, computed in that way, in gas and liquid phases, in the series of 1-93 (the solvents used for each particular compound are indicated in Table 1), as compared to experiment, are presented in Figures 1-3.


Page 11 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1. 15N NMR chemical shifts (ppm) of 1-93 calculated within the CMA at the DFT, MP2, and CCSD levels in gas phase and taking into account solvent corrections. Cmpd.

Solvent

Nitrogen

Gas phase

CPCM a)

DFT

MP2

CCSD

DFT

MP2

CCSD

Exp. b)

1

Cyclohexane

N

-363.1

-357.5

-367.6

-366.0

-360.1

-369.1

-355.1

2

Cyclohexane

N

-364.1

-361.1

-374.0

-366.0

-363.1

-374.3

-366.9

3

Neat

N

-295.3

-297.1

-312.7

-306.6

4

Neat

N-1

-320.3

-318.8

-334.2

-322.7

N-2

-289.3

-280.6

-297.0

-281.4

5

Neat

N

-64.5

-72.2

-76.7

-76.0

6

Neat

N

-57.9

-64.4

-70.3

-67.4

7

Neat

N-1

-31.2

-35.0

-26.2

-26.6

N-2

-287.5

-287.6

-309.0

-282.0

14.8

1.2

-6.7

-17.2

N-1

-227.6

-224.3

-232.8

-244.2

-239.8

-248.2

-211.1

N-2

-330.9

-329.1

-344.1

-328.0

-326.0

-339.9

-354.1

N-1

-179.2

-179.2

-200.8

-186.8

-187.4

-207.2

-176.5

N-2

-313.0

-313.7

-329.4

-309.6

-311.0

-324.9

-325.2

N-3

-331.7

-330.3

-344.9

-318.2

-317.3

-339.4

-324.2

73.0

1.8

51.5

47.5

8

Neat

9

Chloroform

10

Chloroform

N

11

Diethyl ether

N

71.5

2.0

49.2

12

Neat

N

220.3

153.5

188.3

13

Cyclohexane

N

-278.5

-275.8

-280.6

-279.6

-276.5

-280.8

-276.0

14

Cyclohexane

N-1

-345.5

-265.3

-272.0

-270.3

-265.9

-267.1

-269.0

N-2

-308.9

-272.2

-278.1

-276.3

-273.0

-244.6

-282.0

N-1

50.1

0.4

77.8

49.6

-2.7

78.8

72.0

N-2

-30.9

-50.4

-26.8

-41.9

-58.6

-37.2

-22.0

N-3

-231.7

-231.6

-253.1

-221.7

-222.1

-241.7

-226.0

N-1

57.6

-0.8

87.0

56.8

-4.1

87.6

67.0

N-2

-21.9

-47.6

-15.9

-32.9

-55.1

-26.4

-19.0

N-3

-227.3

-227.3

-248.8

-217.6

-218.0

-237.7

-232.0

15

16

Chloroform

Chloroform

154.0

17

CCl4

N

-117.2

-129.5

-121.2

-129.1

-137.8

-132.6

-127.4

18

CCl4

N

-120.1

-132.9

-122.7

-131.5

-140.7

-133.6

-129.0

19

Neat

N-1

-171.0

-183.6

-172.0


-196.0


20

21

22

23

24

Neat

n-Pentane

n-Hexane

Neat

CCl4

Page 12 of 31

N-2

-378.6

-372.9

-381.9

-366.0

N-1

-170.0

-186.1

-172.8

-164.0

N-2

-358.4

-360.4

-372.3

-374.0

N-1

-99.0

-158.4

-122.4

-102.3

-160.3

-123.9

-112.4

N-2

6.3

-35.9

0.1

4.2

-38.4

-3.4

2.6

N-1

-134.4

-102.6

-122.1

-134.6

-103.5

-120.9

-130.7

N-2

-321.9

-321.0

-326.3

-321.1

-320.2

-325.4

-321.7

N-3

-175.6

-266.7

-158.7

-178.7

-267.5

-161.7

-171.5

N-1

-137.0

-105.4

-125.0

-134.0

N-2

-287.5

-282.1

-290.5

-286.0

N-3

-166.6

-263.0

-149.0

-162.0

N-1

-136.9

-105.5

-124.2

-137.3

-106.6

-123.2

-132.1

N-2

-308.2

-307.5

-314.0

-308.0

-307.3

-313.4

-306.4

N-3

-179.1

-269.8

-161.4

-182.1

-270.7

-164.3

-166.6

25

Neat

N

-232.8

-214.8

-229.3

-219.6

26

Neat

N

-213.7

-197.6

-213.6

-205.1

27

Chloroform

N

-250.2

-253.3

-269.6

-252.9

-255.3

-270.9

-252.0

28

Chloroform

N

-226.3

-226.6

-245.0

-229.6

-229.4

-246.9

-234.0

29

Water

N

-293.1

-286.6

-299.2

-284.1

-278.2

-289.1

-267.8

30

Chloroform

N

-293.8

-284.8

-297.2

-287.6

-279.0

-290.0

-273.5

31

Chloroform

N

9.0

-2.2

-13.8

0.0

-8.4

-22.8

-34.6

32

Chloroform

N

-4.1

-9.8

-25.4

-13.3

-16.1

-34.6

-45.9

33

DMSO

N

-329.3

-318.0

-328.6

-323.2

-312.6

-329.6

-302.8

34

DMFA

N-1

-323.4

-320.7

-334.5

-316.9

-313.6

-335.8

-314.0

N-2

-327.8

-317.7

-328.3

-322.7

-313.0

-329.2

-307.0

35

Water

N

-378.6

-371.2

-380.6

-381.3

-373.2

-383.3

-350.0

36

Water

N

-365.4

-359.7

-370.1

-367.9

-361.8

-372.6

-348.5

37

DMSO

N

-326.5

-316.8

-326.9

-321.5

-312.2

-321.9

-305.3

38

Chloroform

N

-314.0

-312.7

-326.4

-309.2

-308.1

-321.5

-315.7

39

DMSO

N

-275.2

-272.7

-287.4

-266.1

-262.6

-278.3

-265.5

40

DMSO

N

-269.4

-266.5

-282.0

-260.6

-256.8

-273.2

-263.0

41

Acetone

N

638.7

426.5

568.6

580.4

412.0

510.3

529.0

42

Acetonitrile

N

201.0

123.2

215.1

207.6

128.0

221.7

185.0


Page 13 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


43

Neat

N

202.4

126.8

214.8

195.0

44

Neat

N

-371.0

-364.8

-372.6

-365.4

45

Neat

N

-350.7

-345.0

-354.3

-348.6

46

Neat

N-1

-153.2

-157.6

-170.2

-149.2

N-2

147.4

72.3

193.1

157.6

47

Diethyl ether

N

-226.5

-229.9

-224.2

48

Neat

N

-202.1

-212.8

-205.6

49

Acetone

N

-94.7

-81.7

-88.8

-96.8

-74.4

-90.9

-104.0

50

Acetone

N

-100.3

-84.1

-95.2

-102.7

-77.6

-97.6

-109.0

51

CCl4

N

-6.6

-48.0

23.1

-1.6

-41.0

28.1

-4.1

52

CCl4

N

-7.0

-48.1

22.9

-2.2

-41.4

27.7

-3.8

53

Acetone

N-1

-48.4

-64.1

-4.7

-46.2

-59.2

-2.5

-24.0

N-2

-230.0

-236.2

-241.4

-214.0

-219.5

-225.4

-216.0

N-1

-46.0

-61.8

-5.3

-41.5

-53.5

-0.8

-23.0

N-2

-229.5

-234.6

-239.9

-217.8

-223.6

-228.2

-220.0

54

Acetone

-237.4

-237.6

-235.1

-222.1 -211.0

55

Benzene

N

-51.5

-73.3

-24.0

-49.0

-70.4

-21.5

-39.0

56

Diethyl ether

N

-51.8

-72.9

-23.0

-48.3

-68.8

-19.5

-37.0

57

Tetrachloroethane

N

-246.5

-243.8

-261.3

-237.1

-224.4

-244.4

-229.6

58

Tetrachloroethane

N

-295.9

-292.7

-307.5

-294.7

-283.4

-298.6

-287.0

59

Neat

N

-306.1

-298.1

-305.3

-289.9

60

Neat

N

-286.9

-279.6

-288.2

-273.1

61

Diethyl ether

N

-12.3

-92.0

-25.8

-11.5

-91.8

-25.0

-54.8

62

Diethyl ether

N

-26.3

-102.1

-38.8

-23.0

-100.4

-35.5

-37.4

63

Neat

N

-79.2

-114.1

-91.2

-105.0

64

Neat

N

-75.9

-109.9

-88.1

-102.0

65

DMSO

N

-296.9

-285.0

-300.8

-285.3

-285.4

-299.7

-285.3

66

DMSO

N

-262.2

-252.1

-272.1

-285.7

-251.8

-271.8

-285.7

67

Neat

N

-239.1

-219.6

-240.1

68

Acetone

N

-197.3

-190.0

-215.1

-195.4

-187.6

-213.2

-205.6

69

Chloroform

N-1

-177.2

-166.4

-183.0

-173.2

-161.3

-179.0

-180.8

N-2

-66.6

-70.4

-66.7

-74.8

-76.1

-74.9

-76.5

N-1

-187.4

-173.3

-192.7

-186.2

-170.7

-191.5

-187.0

N-2

-84.4

-79.7

-85.2

-94.1

-86.6

-94.9

-111.0

70

Chloroform


-231.6


71

72

73

74

75

76

Chloroform

DMSO

Acetone

Chloroform

Chloroform

Chloroform

Page 14 of 31

N-1

-223.5

-211.4

-233.2

-215.5

-203.2

-225.2

-221.3

N-3

-99.1

-99.2

-105.0

-113.7

-112.2

-119.6

-125.5

N-1

-227.0

-213.3

-236.0

-217.4

-203.3

-226.4

-221.8

N-3

-104.5

-100.2

-111.1

-122.1

-116.2

-128.7

-120.6

N-1

-148.6

-142.3

-151.6

-144.5

-133.7

-142.3

-144.5

N-2

-3.8

-33.4

4.3

-27.9

-42.7

-6.4

-27.9

N-3

-8.0

-33.2

-2.3

-14.7

-50.4

-19.2

-14.7

N-1

-128.7

-127.7

-129.0

-132.8

-125.1

-126.1

-132.8

N-2, 5

-47.1

-65.0

-42.9

-51.0

-69.3

-48.0

-51.0

N-1

-158.4

-146.4

-164.8

-154.6

-137.7

-156.2

-154.6

N-2

-1.9

-26.2

2.5

-9.9

-30.1

0.1

-9.9

N-3

39.3

3.2

46.5

14.6

-9.9

33.2

14.6

N-4

-35.0

-34.5

-42.0

-49.7

-42.7

-51.4

-49.7

N-1

-104.0

-107.6

-103.1

-98.4

-103.1

-97.1

-98.4

N-2

7.4

-32.9

16.8

4.4

-38.6

11.6

4.4

N-3

-30.8

-40.6

-31.5

-42.9

-48.9

-41.1

-42.9

N-5

-70.0

-76.2

-70.6

-68.7

-77.0

-72.7

-68.7

77

DMSO

N

16.0

20.0

11.2

-1.0

10.1

-5.8

4.3

78

DMSO

N

-115.2

-115.0

-120.2

-125.6

-123.5

-130.6

-123.7

79

Diethyl ether

N-2

-20.1

-26.4

1.2

-22.5

-17.9

-1.2

-25.0

N-5

-16.2

-12.9

-9.4

-21.2

-18.3

-14.4

-13.2

N-2

-18.7

-26.9

3.5

-19.4

-18.7

2.8

-22.0

80

Diethyl ether

81

Acetone

N

-72.4

-71.1

-68.1

-85.8

-78.0

-81.5

-81.5

82

Acetone

N

-48.7

-50.3

-50.5

-61.1

-61.8

-62.9

-55.0

83

Chloroform

N

-50.9

-49.1

-53.8

-62.6

-59.4

-65.5

-68.7

84

DMSO

N

-27.1

-39.0

-37.3

-40.2

-51.4

-50.4

-47.8

85

Chloroform

N

-76.7

-57.6

-62.9

-81.6

-59.7

-67.8

-84.0

86

DMSO

N

-81.9

-56.4

-69.6

-90.2

-64.1

-77.9

-94.3

87

DMSO

N

60.6

30.9

47.7

33.4

7.7

20.5

20.4

88

DMSO

N

-75.4

-64.7

-81.3

-85.6

-73.2

-91.5

-84.8

89

Acetone

N-1

77.4

29.3

65.3

57.2

11.5

45.1

42.0

N-2

34.6

20.7

16.0

14.1

4.3

-4.5

-2.0

N-4

-85.2

-72.5

-78.4

-86.6

-73.4

-79.8

-82.0

N

-91.0

-77.6

-99.6

-97.7

-83.1

-106.3

-97.0

90

Acetone


Page 15 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


91

Acetone

N

-184.2

-169.2

-191.0

-182.8

-167.5

-189.6

-189.8

92

Acetone

N-1

-89.0

-83.4

-91.5

-100.7

-92.8

-103.2

-93.9

N-7a

-140.4

-123.9

-142.1

-140.5

-122.7

-142.2

-144.9

N-3

-125.5

-119.5

-131.5

-142.1

-134.5

-148.1

-140.0

N-7a

-174.6

-158.1

-181.0

-173.1

-155.6

-179.5

-179.5

93

Acetone

a) CPCM b)

calculations were not performed in the cases of neat samples. Experimental values were taken from different sources, see Computational Details for references.



Page 16 of 31

Figure 1. Correlation plots of 15N NMR chemical shifts in gas and liquid (CPCM) phases in the series of 1-93 calculated at the CMADFT(OLYP)/aug-pcS-4 level versus experiment.


Page 17 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46


Figure 2. Correlation plots of 15N NMR chemical shifts in gas and liquid (CPCM) phases in the series of 1-93 calculated at the CMAMP2/aug-pcS-4 level versus experiment.



Page 18 of 31

Figure 3. Correlation plots of 15N NMR chemical shifts in gas and liquid (CPCM) phases in the series of 1-93 calculated at the CMACCSD/aug-pcS-4 level versus experiment.


Page 19 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


It is seen in Figure 4 that CMA-DFT (MAE 9.8 ppm) and CMA-CCSD (MAE 11.9 ppm) results for the liquid CPCM phase are essentially better than those of CMA-MP2 (MAE 20.5 ppm) calculations. Generally, these results are very much encouraging if the whole range of 15N NMR chemical shifts for these series (about 900 ppm) is taken into account. Indeed, the normalized MAE (NMAE) is only about 1.1-1.6 % for CMA-DFT and CMA-CCSD and 2.2 % for CMA-MP2 methods when solvent effects are taken into account. It follows that CMA-DFT and CMA-CCSD methods provide almost the same accuracy as experiment for the computation of 15N NMR chemical shifts for the series of almost 100 of very different nitrogencontaining compounds with the former method being much less computationally demanding.



Page 20 of 31

Figure 4. Mean Absolute Errors (MAE) and Normalized Mean Absolute Errors (NMAE) of the 15N NMR chemical shifts in the series of 1-93 calculated by using "pure" DFT, MP2, and CCSD methods in gas and liquid phases as compared to the "hybrid" ones by using the CMA scheme. For the CCSD level, no CPCM data are available (by the virtue of the performed calculations).


Page 21 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The 15N NMR chemical shifts of about 50 different types of nitrogen atoms in a series of investigated nitrogen-containing compounds were calculated at the CMA-CCSD level, taking into account solvent effects within the CPCM scheme, which is generalized in Figure 5. First, it should be noted that a whole range of 15N NMR calculated chemical shifts is almost 900 parts per million, from ca. -500 ppm for isocyanates to ca. +400 ppm for nitroso compounds, with the largest interval of about 250 ppm caused by substitution effects for imines. This is a prime indication of the fact that configurational assignment of imines can be determined based on

15N

NMR

chemical shifts. However, this is a specific stereochemical aspect to be discussed elsewhere. Secondly, data presented in Figure 5 could serve as a guiding thread in the structural and stereochemical assignment of diverse nitrogen-containing compounds based on their 15N NMR chemical shifts.



Page 22 of 31

Figure 5. 15N NMR chemical shifts in the nitromethane scale of different types of nitrogen atoms calculated at the CMA-CCSD level. ACS Paragon Plus Environment

Page 23 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Special attention in this study was given to solvent effects, considerably increasing the accuracy of chemical shift calculations. This is most obvious for results obtained at the DFT level, both for the pure methods and the CMA-hybrid scheme. Indeed, taking into account solvent effects within the conductor-like polarizable continuum model, within the CMA scheme, decreased the NMAE by 0.4 % for the CMA-DFT and by 0.2 % for the CMA-CCSD calculations. Herewith, solvent corrections were evaluated within the CPCM approximation (see Computational Details for references) when the solute molecule is embedded in a cavity surrounded by a dielectric continuum characterized by dielectric constant ε. The accuracy of this model depends on several factors. The most important one is the use of proper boundary conditions on the surface of the cavity containing the solute. CPCM defines the cavities as envelopes of spheres centered on atoms or atomic groups. Inside the cavity, the dielectric constant is the same as in vacuum; outside the cavity, it takes the value of the particular solvent. Once the cavity has been defined, the surface is smoothly mapped by small regions, which are characterized by the position of its center, its area, and the electrostatic vector normal to the surface passing through its center. Calculated in this manner, solvent corrections to 15N NMR chemical shifts of the representative types of nitrogen-containing compounds are presented in Figure 6. It is seen that solvent corrections are rather essential, falling into a range of about 50 ppm (within the whole range of about 900 ppm) and being positive in the range of about +(0 to 30) ppm or negative in the range of about -(0 to 20) ppm. ACS Paragon Plus Environment


Page 24 of 31

As an example, they are positive for diazoles, oxazoles (and isoxazoles), thiazoles, and pyridines, while they are negative for pyrroles, diazoles, and nitramines. For imines, nitriles, azides, and azaindilizines, solvent corrections may be either positive or negative, depending on the particular chemical environment of nitrogens under consideration. Detalization of these effects can be retrieved from the data presented in Figure 6.


Page 25 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 6. Solvent corrections to the 15N NMR chemical shifts of the representative types of the nitrogen containing compounds calculated within the CPCM scheme. ACS Paragon Plus Environment


Page 26 of 31

■ GENERAL CONCLUSIONS In the present study, we computed

15N

NMR chemical shifts in comparison with

experiment for 93 different nitrogen containing compounds, representing almost all known classes and considering performance versus computational cost. These calculations were performed at the DFT, MP2, and CCSD levels using the Composite Method Approximation (CMA), with the former using Handy and Cohen's OLYP functional in combination with Jensen's double and quintuple basis sets, pcSseg-2 and aug-pcS-4. It was shown that CMA-DFT and CMA-CCSD methods provided the best performance characterized by the normalized mean absolute error of 1.1-1.6 % as compared to 2.2 % for the CMA-MP2 results. Taking into account solvent effects, within the conductor-like polarizable continuum model, decreased the normalized mean absolute error by 0.4 % for the CMA-DFT and by 0.2 % for the CMA-CCSD calculations. As a result of the present study, calculation of

15N

NMR chemical shifts at the DFT level with Jensen's basis sets is highly

recommended in most cases while, for more accurate results at much higher computational cost, the CCSD level is preferable. Computation of

15N

NMR

chemical shifts performed in this way could serve as a guiding thread in structural and stereochemical assignments of the diverse nitrogen containing compounds.

■

ASSOCIATED CONTENT ACS Paragon Plus Environment

Page 27 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Supporting information The Supporting Information is available free of charge on the ACS Publications website: Optimized geometries of 1-93 (PDF).

■

AUTHOR INFORMATION

Corresponding Author *E-mail: [email protected]

ORCID Leonid B. Krivdin: 0000-0003-2941-1084

Notes The authors declare no competing financial interests.

■

ACKNOWLEDGMENT

All calculations were performed at A.E. Favorsky Irkutsk Institute of Chemistry of the Siberian Branch of the Russian Academy of Sciences using computational facilities of Baikal Analytical Center. Authors are grateful to Dr. Y.Y. Rusakov for numerous stimulating discussions. This paper is written in memory of Kirill Chernyshev who inspired our interest in computational 15N NMR.

TOC Graphic ACS Paragon Plus Environment



Page 28 of 31

Page 29 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


■

REFERENCES

[1] Semenov V. A.; Samultsev D. O.; Krivdin L.B. Quantum-chemical calculations of NMR chemical shifts of organic molecules: XIII. Accuracy of the calculation of 15N NMR chemical shifts of azines with account taken of solvation effects. Russ. J. Org. Chem. 2014, 50, 381-388. [2] Samultsev D. O.; Semenov V. A.; Krivdin L. B. On the accuracy of the GIAODFT calculation of

15N

NMR chemical shifts of the nitrogen-containing

heterocycles - a gateway to better agreement with experiment at lower computational cost. Magn. Reson. Chem. 2014, 52, 222-230. [3] Semenov V. A.; Samultsev D. O.; Krivdin L.B. Solvent effects in the GIAODFT calculations of the 15N NMR chemical shifts of azoles and azines. Magn. Reson. Chem. 2014, 52, 686-693. [4] Semenov V. A.; Samultsev D. O.; Krivdin L.B. Theoretical and experimental study of 15N NMR protonation shifts. Magn. Reson. Chem. 2015, 53, 433-441. [5] Semenov, V. A.; Samultsev, D. O.; Rulev, A. Y.; Krivdin, L. B. Theoretical and experimental

15N

NMR study of enamine-imine tautomerism of 4-

trifluoromethyl[b]benzo-1,4-diazepine system. Magn. Reson. Chem. 2015, 53, 1031-1034. [6] Samultsev D. O.; Semenov V. A.; Krivdin L. B. On the accuracy factors and computational cost of the GIAO-DFT calculation of 15N NMR chemical shifts of amides. Magn. Reson. Chem. 2017, 54, 1015-1021. [7] Samultsev, D. O.; Rusakov, Y. Y.; Krivdin, L. B. On the long‐range relativistic effects in the 15N NMR chemical shifts of halogenated azines. Magn. Reson. Chem. 2017, 54, 990-995. [8] Rusakov, Y. Y.; Rusakova, I. L.; Semenov, V. A.; Samultsev, D. O.; Fedorov, S. V.; Krivdin, L. B. Calculation of 15N and 31P NMR chemical shifts of azoles, phospholes, and phosphazoles: a gateway to higher accuracy at less computational cost. J. Phys. Chem. A 2018, 122, 6746-6759.



Page 30 of 31

[9] Krivdin, L. B. Calculation of 15N NMR chemical shifts: Recent advances and perspectives. Prog. NMR Spectrosc. 2017, 102-103, 98-119. [10] Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; et

al.

GAUSSIAN

09,

Revision

C.01,

Gaussian,

Inc.,

see

http://www.gaussian.com. [11] Klamt, A.; Schüürmann, G. COSMO: a new approach to dielectric screening in solvents with explicit expressions for the screening energy and its gradient. J. Chem. Soc., Perkin Trans. 2 1993, 799-805. [12] Andzelm, J.; Kölmel, C.; Klamt, A. Incorporation of solvent effects into density functional calculations of molecular energies and geometries. J. Chem. Phys. 1995, 103, 9312-9320. [13] Barone, V.; Cossi, M. Quantum calculation of molecular energies and energy gradients in solution by a conductor solvent model. J. Phys. Chem. A 1998, 102, 1995-2001. [14] Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. Energies, structures, and electronic properties of molecules in solution with the C‐PCM solvation model. J. Comput. Chem. 2003, 24, 669-681. [15] Takano, Y.; Houk, K. N. Benchmarking the conductor-like polarizable continuum model (CPCM) for aqueous solvation free energies of neutral and ionic organic molecules. J. Chem. Theory Comput. 2005, 1, 70-77. [16] Handy, N. C.; Cohen, A. J. Left-right correlation energy. Mol. Phys. 2001, 99, 403-412. [17] Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti correlationenergy formula into a functional of the electron density. Phys. Rev. B 1988, 37, 785-789. [18] J. F. Stanton, J. Gauss, M. E. Harding, P. G. Szalay with contributions from A. A. Auer, R. J. Bartlett, U. Benedikt, C. Berger, D. E. Bernholdt, Y. J. Bomble, et al. CFOUR, a quantum chemical program package, see http://www.cfour.de. ACS Paragon Plus Environment

Page 31 of 31 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


[19] Reid, D. M.; Collins, M. A. Approximating CCSD(T) nuclear magnetic shielding calculations using composite methods. J. Chem. Theor. Comput. 2015, 11, 5177-5181. [20] Jensen, F. Segmented contracted basis sets optimized for nuclear magnetic shielding. J. Chem. Theory Comp. 2015, 11, 132-138. [21] Harris, R. K.; Becker, E. D.; Cabral de Menezes, S. M.; Granger, P.; Hoffman, R. E.; Zilm, K. W. Further conventions for NMR shielding and chemical shifts. Pure Appl. Chem. 2008, 80, 59-84. [22] Witanowski, M.; Stefaniak, L.; Webb, G. A., in Annual Reports on NMR Spectroscopy, (Ed: G. A. Webb), Vol. 11B, Academic Press, London, 1981. [23]Witanowski, M.; Stefaniak, L.; Webb, G. A., in Annual Reports on NMR Spectroscopy, (Ed: G.A. Webb), Vol. 18, Academic Press, London, 1986. [24] Wiley Spectra Lab Database. See https://sciencesolutions.wiley.com/solutions/wiley-spectra-lab.


Calculation of 15N NMR Chemical Shifts in a ... - ACS Publications

Recommend Documents