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Altheimer BD, Mehta MA. Effects of structural differences on the NMR chemical shifts in isostructural dipeptides. J Phys Chem A 2014; 118:2618-28. [PMID: 24654604 DOI: 10.1021/jp411220y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Porous crystalline dipeptides have gained recent attention for their potential as gas-storage materials. Within this large class is a group of dipeptides containing alanine, valine, and isoleucine with very similar crystal structures. We report the (13)C (carbonyl and Cα) and (15)N (amine and amide) solid-state NMR isotropic chemical shifts in a series of seven such isostructural porous dipeptides as well as shift tensor data for the carbonyl and amide sites. Using their known crystal structures and aided by ab initio quantum chemical calculations for the resonance assignments, we elucidate trends relating local structure, hydrogen-bonding patterns, and chemical shift. We find good correlation between the backbone dihedral angles and the Cα1 and Cα2 shifts. For the C1 shift tensor, the δ11 value shifts downfield as the hydrogen-bond distance increases, δ22 shifts upfield, and δ33 shows little variation. The C2 shift tensor shows no appreciable correlation with structural parameters. For the N2 tensor, δ11 shows little dependence on the hydrogen-bond length, whereas δ22 and δ33 both show a decrease in shielding as the hydrogen bond shortens. Our analysis teases apart some, but not all, structural contributors to the observed differences the solid-state NMR chemical shifts.
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Affiliation(s)
- Benjamin D Altheimer
- Department of Chemistry and Biochemistry, Oberlin College , 119 Woodland Street, Oberlin, Ohio 44074, United States
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Wang WD, Gao X, Strohmeier M, Wang W, Bai S, Dybowski C. Solid-State NMR Studies of Form I of Atorvastatin Calcium. J Phys Chem B 2012; 116:3641-9. [DOI: 10.1021/jp212074a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wei David Wang
- State Key Laboratory of Applied
Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, 730000, China
| | - Xudong Gao
- State Key Laboratory of Applied
Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, 730000, China
| | - Mark Strohmeier
- Product Development, GlaxoSmithKline, Inc., 709 Swedeland Road, King of
Prussia, Pennsylvania 19406, United States
| | - Wei Wang
- State Key Laboratory of Applied
Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, 730000, China
| | - Shi Bai
- State Key Laboratory of Applied
Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, 730000, China
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United
States
| | - Cecil Dybowski
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United
States
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Liu W, Wang WD, Wang W, Bai S, Dybowski C. Influence of Structure on the Spectroscopic Properties of the Polymorphs of Piroxicam. J Phys Chem B 2010; 114:16641-9. [DOI: 10.1021/jp1084444] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- Wei Liu
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, 730000, China, and Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Wei David Wang
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, 730000, China, and Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Wei Wang
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, 730000, China, and Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Shi Bai
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, 730000, China, and Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - Cecil Dybowski
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu, 730000, China, and Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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Liu W, Wang WD, Wang W, Bai S, Dybowski C. Measurement of the principal values of the chemical-shift tensors of overlapping protonated and unprotonated carbons with the 2D-SUPER technique and dipolar dephasing (DD-SUPER). JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2010; 206:177-181. [PMID: 20667754 DOI: 10.1016/j.jmr.2010.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/27/2010] [Accepted: 07/02/2010] [Indexed: 05/29/2023]
Abstract
A modified 2D-SUPER technique is demonstrated to allow independent measurement of the principal values of the chemical-shift tensors of overlapping protonated and unprotonated carbons. The insertion of a dipolar-dephasing period into the sequence causes loss of signal from protonated carbons. The spectrum obtained with this modification allows one to determine the principal values of the unprotonated carbons with high precision. Subsequent fitting of the usual 2D-SUPER spectrum, with the chemical-shift parameters of the unprotonated carbons fixed, gives the parameters of the overlapped resonances of the protonated carbons. As an example, we report the determination of the (13)C chemical-shift parameters of the carbons of form II of piroxicam. The experimental results are compared with those obtained from calculations using the DFT/GIAO method. Potential applications of this method are discussed.
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Affiliation(s)
- Wei Liu
- State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, China
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Affiliation(s)
- Shi Bai
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA
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Salager E, Stein RS, Pickard CJ, Elena B, Emsley L. Powder NMR crystallography of thymol. Phys Chem Chem Phys 2009; 11:2610-21. [PMID: 19421517 DOI: 10.1039/b821018g] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A protocol for the structure determination of powdered solids at natural abundance by NMR is presented and illustrated for the case of the small drug molecule thymol. The procedure uses proton spin-diffusion data from two-dimensional NMR experiments in combination with periodic DFT refinements incorporating (1)H and (13)C NMR chemical shifts. For thymol, the method yields a crystal structure for the powdered sample, which differs by an atomic root-mean-square-deviation (all atoms except methyl group protons) of only 0.07 A from the single crystal X-ray diffraction structure with DFT-optimized proton positions.
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Affiliation(s)
- Elodie Salager
- Université de Lyon, (CNRS/ENS-Lyon/UCB Lyon 1), Centre de RMN à Très Hauts Champs, 5 rue de la Doua, 69100, Villeurbanne, France
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Lesage A. Recent advances in solid-state NMR spectroscopy of spin I = 1/2 nuclei. Phys Chem Chem Phys 2009; 11:6876-91. [DOI: 10.1039/b907733m] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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