{"title":"Separating an overlapped 1H peak and identifying its 1H-1H correlations with the use of single-channel 1H solid-state NMR at fast MAS","authors":"Nghia Tuan Duong , Vipin Agarwal , Yusuke Nishiyama","doi":"10.1016/j.ssnmr.2022.101774","DOIUrl":null,"url":null,"abstract":"<div><p>Fast magic-angle spinning (≥60 kHz) technique has enabled the acquisition of high-resolution <sup>1</sup>H NMR spectra of solid materials. However, the spectral interpretation is still difficult because the <sup>1</sup><span>H peaks are overlapped due to the narrow chemical shift range and broad linewidths. An additional </span><sup>13</sup>C or <sup>14</sup>N or <sup>1</sup>H dimension possibly addresses the issues of overlapped proton resonances, but it leads to the elongated experimental time. Herein, we introduce a single-channel <sup>1</sup>H experiment to separate the overlapped <sup>1</sup>H peak and identify its spatially proximal <sup>1</sup>H–<sup>1</sup><span>H correlations. This sequence combines selective excitation, selective </span><sup>1</sup>H–<sup>1</sup><span>H polarization transfer by selective recoupling of protons (SERP), and broadband </span><sup>1</sup>H recoupling by back-to-back (BABA) recoupling sequences. The concept for <sup>1</sup>H separation is based on (i) the selective excitation of a well-resolved <sup>1</sup>H peak and (ii) the selective dipolar polarization transfer from this isolated <sup>1</sup>H peak to one of the <sup>1</sup>H peaks in the overlapped/poor resolution region by SERP and (iii) the detection of <sup>1</sup>H–<sup>1</sup>H correlations from these two <sup>1</sup>H peaks to other neighboring <sup>1</sup>Hs by BABA. We demonstrated the applicability of this approach to identify overlapped peaks on two molecules, β-L-aspartyl-<span>l</span><span>-alanine and Pioglitazone.HCl. The sequence allows the clear observation of </span><sup>1</sup>H–<sup>1</sup>H correlations from an overlapped <sup>1</sup>H peak without an additional heteronuclear dimension and ensures efficient polarization transfers that leads to twelve fold reduction in experimental time compared to <sup>14</sup>N edited experiments. The limitation and the conditions of applicability for this approach are discussed in detail.</p></div>","PeriodicalId":21937,"journal":{"name":"Solid state nuclear magnetic resonance","volume":null,"pages":null},"PeriodicalIF":1.8000,"publicationDate":"2022-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Solid state nuclear magnetic resonance","FirstCategoryId":"92","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0926204022000030","RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
引用次数: 1
Abstract
Fast magic-angle spinning (≥60 kHz) technique has enabled the acquisition of high-resolution 1H NMR spectra of solid materials. However, the spectral interpretation is still difficult because the 1H peaks are overlapped due to the narrow chemical shift range and broad linewidths. An additional 13C or 14N or 1H dimension possibly addresses the issues of overlapped proton resonances, but it leads to the elongated experimental time. Herein, we introduce a single-channel 1H experiment to separate the overlapped 1H peak and identify its spatially proximal 1H–1H correlations. This sequence combines selective excitation, selective 1H–1H polarization transfer by selective recoupling of protons (SERP), and broadband 1H recoupling by back-to-back (BABA) recoupling sequences. The concept for 1H separation is based on (i) the selective excitation of a well-resolved 1H peak and (ii) the selective dipolar polarization transfer from this isolated 1H peak to one of the 1H peaks in the overlapped/poor resolution region by SERP and (iii) the detection of 1H–1H correlations from these two 1H peaks to other neighboring 1Hs by BABA. We demonstrated the applicability of this approach to identify overlapped peaks on two molecules, β-L-aspartyl-l-alanine and Pioglitazone.HCl. The sequence allows the clear observation of 1H–1H correlations from an overlapped 1H peak without an additional heteronuclear dimension and ensures efficient polarization transfers that leads to twelve fold reduction in experimental time compared to 14N edited experiments. The limitation and the conditions of applicability for this approach are discussed in detail.
期刊介绍:
The journal Solid State Nuclear Magnetic Resonance publishes original manuscripts of high scientific quality dealing with all experimental and theoretical aspects of solid state NMR. This includes advances in instrumentation, development of new experimental techniques and methodology, new theoretical insights, new data processing and simulation methods, and original applications of established or novel methods to scientific problems.