logo

SCIENCE CHINA Chemistry, Volume 60, Issue 7: 970-978(2017) https://doi.org/10.1007/s11426-016-0389-4

Hydrogen bonding mediated ion pairs of some aprotic ionic liquids and their structural transition in aqueous solution

More info
  • ReceivedSep 24, 2016
  • AcceptedDec 26, 2016
  • PublishedMar 2, 2017

Abstract

Ion pair speciation of ionic liquids (ILs) has an important effect on the physical and chemical properties of ILs and recognition of the structure of ion pairs in solution is essential. It has been reported that ion pairs of some ILs can be formed by hydrogen bonding interactions between cations and anions of them. Considering the fact that far-IR (FIR) spectroscopy is a powerful tool in indicating the intermolecular and intramolecular hydrogen bonding, in this work, this spectroscopic technique has been combined with molecular dynamic (MD) simulation and nuclear magnetic resonance hydrogen spectroscopy (1H NMR) to investigate ion pairs of aprotic ILs [Bmim][NO3], [BuPy][NO3], [Pyr14][NO3], [PP14][NO3] and [Bu-choline][NO3] in aqueous IL mixtures. The FIR spectra have been assigned with the aid of density functional theory (DFT) calculations, and the results are used to understand the effect of cationic nature on the structure of ion pairs. It is found that contact ion pairs formed in the neat aprotic ILs by hydrogen bonding interactions between cation and anion, were still maintained in aqueous solutions up to high water mole fraction (say 0.80 for [BuPy][NO3]). When water content was increased to a critical mole fraction of water (say 0.83 for [BuPy][NO3]), the contact ion pairs could be transformed into solvent-separated ion pairs due to the formation of the hydrogen bonding between ions and water. With the further dilution of the aqueous ILs solution, the solvent-separated ion pairs was finally turned into free cations and free anions (fully hydrated cations or anions). The concentrations of the ILs at which the contact ion pairs were transformed into solvent-separated ion pairs and solvent-separated ion pairs were transformed into free ions (fully hydrated ion) were dependent on the cationic structures. These information provides direct spectral evidence for ion pair structures of the aprotic ILs in aqueous solution. MD simulation and 1H NMR results support the conclusion drawn from FIR spectra investigations.


Funded by

National Natural Science Foundation of China(21573060,21673068)

Program for Innovative Research Team in Science and Technology in University of Henan Province(16IRTSTHN002)

Plan for Scientific Innovation Talent of Henan Province(144200510004)


Acknowledgment

This work was supported by the National Natural Science Foundation of China (21573060, 21673068), Program for Innovative Research Team in Science and Technology in University of Henan Province (16IRTSTHN002), Plan for Scientific Innovation Talent of Henan Province (144200510004) and The High Performance Computing Center of Henan Normal University.


Interest statement

The authors declare that they have no conflict of interest.


Supplement

The supporting information is available online at http://chem.scichina.com and http://link.springer.com/journal/11426. The supporting materials are published as submitted, without typesetting or editing. The responsibility for scientific accuracy and content remains entirely with the authors.


References

[1] Zhang S, Sun J, Zhang X, Xin J, Miao Q, Wang J, Zhang L, Dong K, Chen S, Zhang S. Chem Soc Rev, 2014, 43: 7838-7869 CrossRef PubMed Google Scholar

[2] Chen S, Zhang S, Liu X, Wang J, Wang J, Dong K, Sun J, Xu B, Zhu Q, Ma J, Kang X, Sun X, Hu J, Yang G, Han B. Phys Chem Chem Phys, 2014, 16: 5893-5906 CrossRef PubMed ADS Google Scholar

[3] Hayes R, Warr GG, Atkin R. Chem Rev, 2015, 115: 6357-6426 CrossRef PubMed Google Scholar

[4] Dupont J. Acc Chem Res, 2011, 44: 1223-1231 CrossRef PubMed Google Scholar

[5] Neto BAD, Meurer EC, Galaverna R, Bythell BJ, Dupont J, Cooks RG, Eberlin MN. J Phys Chem Lett, 2012, 3: 3435-3441 CrossRef PubMed Google Scholar

[6] Marcus Y, Hefter G. Chem Rev, 2006, 106: 4585-4621 CrossRef PubMed Google Scholar

[7] Dupont J. J Braz Chem Soc, 2004, 15: 341-350 CrossRef Google Scholar

[8] Zahn S, Uhlig F, Thar J, Spickermann C, Kirchner B. Angew Chem Int Ed, 2008, 47: 3639-3641 CrossRef PubMed Google Scholar

[9] Tsuzuki S, Tokuda H, Hayamizu K, Watanabe M. J Phys Chem B, 2005, 109: 16474-16481 CrossRef PubMed Google Scholar

[10] Fumino K, Reimann S, Ludwig R. Phys Chem Chem Phys, 2014, 16: 21903-21929 CrossRef PubMed ADS Google Scholar

[11] Fumino K, Ludwig R. J Mol Liq, 2014, 192: 94-102 CrossRef Google Scholar

[12] Consorti CS, Suarez PAZ, de Souza RF, Burrow RA, Farrar DH, Lough AJ, Loh W, da Silva LHM, Dupont J. J Phys Chem B, 2005, 109: 4341-4349 CrossRef PubMed Google Scholar

[13] Sadeghi R, Ebrahimi N. J Phys Chem B, 2011, 115: 13227-13240 CrossRef PubMed Google Scholar

[14] Li W, Zhang Z, Han B, Hu S, Xie Y, Yang G. J Phys Chem B, 2007, 111: 6452-6456 CrossRef PubMed Google Scholar

[15] Katsuta S, Imai K, Kudo Y, Takeda Y, Seki H, Nakakoshi M. J Chem Eng Data, 2008, 53: 1528-1532 CrossRef Google Scholar

[16] Dorbritz S, Ruth W, Kragl U. Adv Synth Catal, 2005, 347: 1273-1279 CrossRef Google Scholar

[17] Gozzo FC, Santos LS, Augusti R, Consorti CS, Dupont J, Eberlin MN. Chem Eur J, 2004, 10: 6187-6193 CrossRef PubMed Google Scholar

[18] Bini R, Bortolini O, Chiappe C, Pieraccini D, Siciliano T. J Phys Chem B, 2007, 111: 598-604 CrossRef PubMed Google Scholar

[19] Neto B, Ebeling G, Goncalves R, Gozzo F, Eberlin M, Dupont J. Synthesis, 2004: 1155–1158. Google Scholar

[20] Avent AG, Chaloner PA, Day MP, Seddon KR, Welton T. J Chem Soc Dalton Trans, 1994: 3405-3413 CrossRef Google Scholar

[21] Mele A, Tran CD, De Paoli Lacerda SH. Angew Chem Int Ed, 2003, 42: 4364-4366 CrossRef PubMed Google Scholar

[22] Scharf NT, Stark A, Hoffmann MM. J Solution Chem, 2013, 42: 2034-2056 CrossRef Google Scholar

[23] Zheng YZ, Wang NN, Luo JJ, Zhou Y, Yu ZW. Phys Chem Chem Phys, 2013, 15: 18055-18064 CrossRef PubMed Google Scholar

[24] Bešter-Rogač M, Stoppa A, Hunger J, Hefter G, Buchner R. Phys Chem Chem Phys, 2011, 13: 17588-17598 CrossRef PubMed Google Scholar

[25] Stoppa A, Hunger J, Hefter G, Buchner R. J Phys Chem B, 2012, 116: 7509-7521 CrossRef PubMed Google Scholar

[26] Batista MLS, Kurnia KA, Pinho SP, Gomes JRB, Coutinho JAP. J Phys Chem B, 2015, 119: 1567-1578 CrossRef PubMed Google Scholar

[27] Roohi H, Khyrkhah S. Comp Theor Chem, 2014, 1037: 70-79 CrossRef Google Scholar

[28] Zhang L, Xu Z, Wang Y, Li H. J Phys Chem B, 2008, 112: 6411-6419 CrossRef PubMed Google Scholar

[29] Zanatta M, Girard AL, Simon NM, Ebeling G, Stassen HK, Livotto PR, dos Santos FP, Dupont J. Angew Chem Int Ed, 2014, 53: 12817-12821 CrossRef PubMed Google Scholar

[30] Yaghini N, Pitawala J, Matic A, Martinelli A. J Phys Chem B, 2015, 119: 1611-1622 CrossRef PubMed Google Scholar

[31] Yaghini N, Nordstierna L, Martinelli A. Phys Chem Chem Phys, 2014, 16: 9266-9275 CrossRef PubMed ADS Google Scholar

[32] Ren Z, Brinzer T, Dutta S, Garrett-Roe S. J Phys Chem B, 2015, 119: 4699-4712 CrossRef PubMed Google Scholar

[33] Strauch M, Roth C, Kubatzki F, Ludwig R. ChemPhysChem, 2014, 15: 265-270 CrossRef PubMed Google Scholar

[34] Fumino K, Stange P, Fossog V, Hempelmann R, Ludwig R. Angew Chem Int Ed, 2013, 52: 12439-12442 CrossRef PubMed Google Scholar

[35] Pierola IF, Agzenai Y. J Phys Chem B, 2012, 116: 3973-3981 CrossRef PubMed Google Scholar

[36] Fumino K, Wulf A, Ludwig R. Angew Chem Int Ed, 2008, 47: 8731-8734 CrossRef PubMed Google Scholar

[37] Wulf A, Fumino K, Ludwig R. Angew Chem Int Ed, 2010, 49: 449-453 CrossRef PubMed Google Scholar

[38] Fumino K, Reichert E, Wittler K, Hempelmann R, Ludwig R. Angew Chem Int Ed, 2012, 51: 6236-6240 CrossRef PubMed Google Scholar

[39] Fumino K, Wulf A, Ludwig R. Angew Chem Int Ed, 2009, 48: 3184-3186 CrossRef PubMed Google Scholar

[40] Fumino K, Wulf A, Ludwig R. Angew Chem Int Ed, 2008, 47: 3830-3834 CrossRef PubMed Google Scholar

[41] Roth C, Peppel T, Fumino K, Köckerling M, Ludwig R. Angew Chem Int Ed, 2010, 49: 10221-10224 CrossRef PubMed Google Scholar

[42] Stassen HK, Ludwig R, Wulf A, Dupont J. Chem Eur J, 2015, 21: 8324-8335 CrossRef PubMed Google Scholar

[43] Stange P, Fumino K, Ludwig R. Angew Chem Int Ed, 2013, 52: 2990-2994 CrossRef PubMed Google Scholar

[44] Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA, Cheeseman JR, Scalmani G, Barone V, Mennucci B, Petersson GA, et al. Gaussian 09. Revision D.01. Wallingford, CT: Gaussian, Inc., 2009. Google Scholar

[45] Boys SF, Bernardi F. Mol Phys, 1970, 19: 553-566 CrossRef Google Scholar

[46] Liu X, Zhou G, Zhang S, Wu G, Yu G. J Phys Chem B, 2007, 111: 5658-5668 CrossRef PubMed Google Scholar

[47] Freire MG, Neves CMSS, Shimizu K, Bernardes CES, Marrucho IM, Coutinho JAP, Canongia Lopes JN, Rebelo LPN. J Phys Chem B, 2010, 114: 15925-15934 CrossRef PubMed Google Scholar

[48] Wu Y, Tepper HL, Voth GA. J Chem Phys, 2006, 124: 024503-024503 CrossRef PubMed ADS Google Scholar

[49] Lyubartsev AP, Laaksonen A. Comp Phys Commun, 2000, 128: 565-589 CrossRef ADS Google Scholar

[50] Tuckerman M, Berne BJ, Martyna GJ. J Chem Phys, 1992, 97: 1990-2001 CrossRef ADS Google Scholar

[51] Leeuw SWD, Perram JW, Smith ER. Proc R Soc A-Math Phys Eng Sci, 1983, 388: 177-193 CrossRef Google Scholar

[52] Martyna GJ, Tuckerman ME, Tobias DJ, Klein ML. Mol Phys, 1996, 87: 1117-1157 CrossRef Google Scholar

[53] Köddermann T, Klembt S, Klasen D, Paschek D, Kragl U, Ludwig R. ChemPhysChem, 2012, 13: 1748-1752 CrossRef PubMed Google Scholar

[54] Zhao Y, Wang J, Wang H, Li Z, Liu X, Zhang S. J Phys Chem B, 2015, 119: 6686-6695 CrossRef PubMed Google Scholar

[55] Koch W, Holthausen MC. A Chemist’s Guide to Density Functional Theory. 2nd Ed. Weinheim: Wiley-VCH Verlag GmbH, 2001. Google Scholar

[56] Zhao Y, Gao S, Wang J, Tang J. J Phys Chem B, 2008, 112: 2031-2039 CrossRef PubMed Google Scholar

[57] Karve L, Dutt GB. J Phys Chem B, 2012, 116: 1824-1830 CrossRef PubMed Google Scholar

[58] Remsing RC, Liu Z, Sergeyev I, Moyna G. J Phys Chem B, 2008, 112: 7363-7369 CrossRef PubMed Google Scholar

[59] Singh T, Kumar A. J Phys Chem B, 2007, 111: 7843-7851 CrossRef PubMed Google Scholar

  • Scheme 1

    The simplified 2D representation for the structures of contact ion pair, solvent-separated ion pair and free ion of ionic liquids. Black spot: solvent molecule (color online).

  • Figure 1

    FIR spectra of neat [BuPy][NO3] in the range of 50–450 cm−1.

  • Figure 2

    FIR spectra of the IL in [BuPy][NO3]/H2O mixture in the range of 50–450 cm−1 as a function of mole fraction of water (χ H 2O ) (color online).

  • Scheme 2

    The chemical structures and H atom numbering of the ILs.

  • Figure 3

    The variation of average hydrogen bonding number between cation and anion of the ILs with mole fraction of water (χH2 O ) at 298 K (color online).

  • Figure 4

    Radial distribution function of O atom of [NO3] around H2 atom of the cations in neat ILs and ILs-H2O systems. (a) [Bmim][NO3]; (b) [BuPy][NO3] (color online).

  • Figure 5

    The variety of Δδobsd of the protons for [BuPy][NO3] with mole fraction of water in the [BuPy][NO3]-H2O mixtures. In this system, Δδobsd is defined as the difference between its chemical shifts in the mixtures and that in the neat ILs (color online).

  • Figure 6

    The change of Δδobsd for protons of the cations in ILs-H2O systems as a function of χH2 O , where Δδobsd values were obtained with reference to the chemical shift of the protons at χH2O =0.67 (color online).

  • Table 1   The optimized stable geometries for ion pairs of the ILs and the corresponding energies

    IL

    Optimized geometry

    Eion-pair (hartree)

    Ecation (hartree)

    ΔEint (kJ mol−1)

    [BuPy][NO3]

    −686.616199

    −406.025743

    −348.92

    [Pyr14][NO3]

    −690.230173

    −409.642460

    −341.72

    [PP14][NO3]

    −690.227403

    −409.638616

    −344.54

    [Bu-choline][NO3]

    −727.361494

    −446.765533

    −363.38

    [Bmim][NO3]

    −703.882485

    −423.287870

    −359.84

  • Table 2   The molecule number of ILs and water for each simulated systems

    System

    IL

    H2O

    IL-H2O

    128

    0

    128

    128

    128

    256

    128

    384

    128

    512

    128

    640

    128

    768

    128

    896

    128

    1024

    128

    1280

  • Table 3   Wavenumber of neat [BuPy][NO] at 298 K and the related assignments

    Experimental value (cm−1)

    Calculated value (cm−1)

    Assignment

    112.3

    136.7

    stretching vibration of hydrogen bonding between H2, H3, H4 atoms and O atom in [NO3]

    95.4

    105.5

    stretching vibration of cation

    402.8

    387.8/405.1

    bending vibration of cation

  • Table 4   The mole fraction of water () and the number of water moleculars () needed for the transition of contact ion pair to solvent-sepratered ion pair

    IL

    [Bmim][NO3]

    [BuPy][NO3]

    [Pyr14][NO3]

    [PP14][NO3]

    [Bu-choline][NO3]

    χH2O

    0.86

    0.83

    0.83

    0.86

    0.80

    n

    6

    5

    5

    6

    4

Copyright 2019 Science China Press Co., Ltd. 《中国科学》杂志社有限责任公司 版权所有

京ICP备18024590号-1