Lennart Kruse, Angel Mary Chiramel Tony, Dietmar Paschek, Peter Stange, Ralf Ludwig* and Anne Strate*,
{"title":"从核磁共振场循环弛豫测量法看离子液体中阳离子和阴离子的转换动力学:突出异核贡献的重要性","authors":"Lennart Kruse, Angel Mary Chiramel Tony, Dietmar Paschek, Peter Stange, Ralf Ludwig* and Anne Strate*, ","doi":"10.1021/acs.jpclett.4c0224510.1021/acs.jpclett.4c02245","DOIUrl":null,"url":null,"abstract":"<p >NMR field cycling relaxometry is a powerful method for determining the rotational and translational dynamics of ions, molecules, and dissolved particles. This is in particular true for ionic liquids (ILs) in which both ions carry NMR sensitive nuclei. In the IL triethylammonium bis(trifluoromethanesulfonyl)imide ([TEA][NTf<sub>2</sub>]), there are <sup>1</sup>H nuclei at the [TEA]<sup>+</sup> cations and <sup>19</sup>F nuclei at the [NTf<sub>2</sub>]<sup>−</sup> anions. Moreover, the high viscosity of this IL leads to frequency-dependent relaxation rates, leaving the so-called extreme narrowing regime. Both the rotational and the translational dynamics of the constituents of ILs can be obtained by separating the contributions of intra- and intermolecular relaxation rates. In particular, the translational dynamics can be obtained separately by applying the so-called “low-frequency approach” (LFA), utilizing the fact that the change in the total relaxation rates at low frequencies results solely from translational motions. However, for systems containing multiple NMR active nuclei, heteronuclear interactions can also affect their relaxation rates. For [TEA][NTf<sub>2</sub>], the intermolecular relaxation rate is either the sum of <sup>1</sup>H–<sup>1</sup>H cation–cation and <sup>1</sup>H–<sup>19</sup>F cation–anion interactions or the sum of <sup>19</sup>F–<sup>19</sup>F anion–anion and <sup>19</sup>F–<sup>1</sup>H anion–cation interactions. Due to the lack of available experimental information, the <sup>1</sup>H–<sup>19</sup>F heteronuclear intermolecular contribution has often been neglected in the past, assuming it to be negligible. Employing a suitable set of ILs and by making use of isotopic H/D substitution, we show that the <sup>1</sup>H–<sup>19</sup>F heteronuclear intermolecular contribution in fact cannot be neglected and that the LFA cannot be applied to the total <sup>1</sup>H and total <sup>19</sup>F relaxation rates.</p>","PeriodicalId":62,"journal":{"name":"The Journal of Physical Chemistry Letters","volume":null,"pages":null},"PeriodicalIF":4.8000,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Translational Dynamics of Cations and Anions in Ionic Liquids from NMR Field Cycling Relaxometry: Highlighting the Importance of Heteronuclear Contributions\",\"authors\":\"Lennart Kruse, Angel Mary Chiramel Tony, Dietmar Paschek, Peter Stange, Ralf Ludwig* and Anne Strate*, \",\"doi\":\"10.1021/acs.jpclett.4c0224510.1021/acs.jpclett.4c02245\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p >NMR field cycling relaxometry is a powerful method for determining the rotational and translational dynamics of ions, molecules, and dissolved particles. This is in particular true for ionic liquids (ILs) in which both ions carry NMR sensitive nuclei. In the IL triethylammonium bis(trifluoromethanesulfonyl)imide ([TEA][NTf<sub>2</sub>]), there are <sup>1</sup>H nuclei at the [TEA]<sup>+</sup> cations and <sup>19</sup>F nuclei at the [NTf<sub>2</sub>]<sup>−</sup> anions. Moreover, the high viscosity of this IL leads to frequency-dependent relaxation rates, leaving the so-called extreme narrowing regime. Both the rotational and the translational dynamics of the constituents of ILs can be obtained by separating the contributions of intra- and intermolecular relaxation rates. In particular, the translational dynamics can be obtained separately by applying the so-called “low-frequency approach” (LFA), utilizing the fact that the change in the total relaxation rates at low frequencies results solely from translational motions. However, for systems containing multiple NMR active nuclei, heteronuclear interactions can also affect their relaxation rates. For [TEA][NTf<sub>2</sub>], the intermolecular relaxation rate is either the sum of <sup>1</sup>H–<sup>1</sup>H cation–cation and <sup>1</sup>H–<sup>19</sup>F cation–anion interactions or the sum of <sup>19</sup>F–<sup>19</sup>F anion–anion and <sup>19</sup>F–<sup>1</sup>H anion–cation interactions. Due to the lack of available experimental information, the <sup>1</sup>H–<sup>19</sup>F heteronuclear intermolecular contribution has often been neglected in the past, assuming it to be negligible. Employing a suitable set of ILs and by making use of isotopic H/D substitution, we show that the <sup>1</sup>H–<sup>19</sup>F heteronuclear intermolecular contribution in fact cannot be neglected and that the LFA cannot be applied to the total <sup>1</sup>H and total <sup>19</sup>F relaxation rates.</p>\",\"PeriodicalId\":62,\"journal\":{\"name\":\"The Journal of Physical Chemistry Letters\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":4.8000,\"publicationDate\":\"2024-10-10\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"The Journal of Physical Chemistry Letters\",\"FirstCategoryId\":\"1\",\"ListUrlMain\":\"https://pubs.acs.org/doi/10.1021/acs.jpclett.4c02245\",\"RegionNum\":2,\"RegionCategory\":\"化学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"The Journal of Physical Chemistry Letters","FirstCategoryId":"1","ListUrlMain":"https://pubs.acs.org/doi/10.1021/acs.jpclett.4c02245","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
Translational Dynamics of Cations and Anions in Ionic Liquids from NMR Field Cycling Relaxometry: Highlighting the Importance of Heteronuclear Contributions
NMR field cycling relaxometry is a powerful method for determining the rotational and translational dynamics of ions, molecules, and dissolved particles. This is in particular true for ionic liquids (ILs) in which both ions carry NMR sensitive nuclei. In the IL triethylammonium bis(trifluoromethanesulfonyl)imide ([TEA][NTf2]), there are 1H nuclei at the [TEA]+ cations and 19F nuclei at the [NTf2]− anions. Moreover, the high viscosity of this IL leads to frequency-dependent relaxation rates, leaving the so-called extreme narrowing regime. Both the rotational and the translational dynamics of the constituents of ILs can be obtained by separating the contributions of intra- and intermolecular relaxation rates. In particular, the translational dynamics can be obtained separately by applying the so-called “low-frequency approach” (LFA), utilizing the fact that the change in the total relaxation rates at low frequencies results solely from translational motions. However, for systems containing multiple NMR active nuclei, heteronuclear interactions can also affect their relaxation rates. For [TEA][NTf2], the intermolecular relaxation rate is either the sum of 1H–1H cation–cation and 1H–19F cation–anion interactions or the sum of 19F–19F anion–anion and 19F–1H anion–cation interactions. Due to the lack of available experimental information, the 1H–19F heteronuclear intermolecular contribution has often been neglected in the past, assuming it to be negligible. Employing a suitable set of ILs and by making use of isotopic H/D substitution, we show that the 1H–19F heteronuclear intermolecular contribution in fact cannot be neglected and that the LFA cannot be applied to the total 1H and total 19F relaxation rates.
期刊介绍:
The Journal of Physical Chemistry (JPC) Letters is devoted to reporting new and original experimental and theoretical basic research of interest to physical chemists, biophysical chemists, chemical physicists, physicists, material scientists, and engineers. An important criterion for acceptance is that the paper reports a significant scientific advance and/or physical insight such that rapid publication is essential. Two issues of JPC Letters are published each month.