Novel peroxosolvates of tetraalkylammonium halides: the first case of layers containing hydrogen-bonded peroxide molecules

Abstract

Novel peroxosolvates of tetraalkylammonium halides Et₄N⁺Cl⁻·2(H₂O₂) (1), Et₄N⁺Br⁻·2(H₂O₂) (2), Me₃(ClCH₂CH₂)N⁺Cl⁻·H₂O₂ (3) and Me₃PhN⁺Cl⁻·H₂O₂ (4) were prepared from concentrated hydrogen peroxide and the corresponding structures were determined by X-ray crystallography. Structures 1 and 2 are formed by globose Et₄N⁺ cations and are the first examples of layers containing H-bonded peroxide molecules. By contrast, 3 and 4 are formed by sufficiently aspherical Me₃(ClCH₂CH₂)N⁺ and Me₃PhN⁺ units and contain infinitely long hydrogen-bonded peroxide–halide chains.

---

Introduction

Peroxosolvates (crystalline adducts of hydrogen peroxide) were first discovered by Tanatar in the early 20th century.¹ Two of these compounds, namely peroxosolvates of urea and sodium carbonate, have become widespread as bleaching and disinfection agents for industrial, housekeeping and pharmaceutical use and current production reaches up to several hundred tons a year.² The main research direction for peroxosolvates during the twentieth century has been the preparation of novel stable hydrogen peroxide carriers.^3–6 It has been proposed that highly stable peroxosolvates could be designed by maximizing the number of hydrogen bonds in structures.⁷ Several quite stable organic peroxosolvates were thus produced in which peroxide molecules form the largest possible number of hydrogen bonds – six (corresponding to 2 donor bonds and 4 acceptor bonds).⁸

Over the last decade several entirely new perspective approaches in peroxosolvate chemistry have been developed. A) Hydrogen peroxide adducts of some organic compounds have been proposed as mild, selective and stoichiometric oxidizing agents for organic synthesis.^9,10 B) Several peroxosolvates of highly energetic materials have been prepared in an attempt to enhance properties like oxygen balance, and detonation velocities and pressures.^11–13 C) Drug–drug cocrystals containing hydrogen peroxide have been developed because H₂O₂ exhibits wide spectrum of antimicrobial activity.¹⁴ Recently, a promising peroxosolvate of antifungal drug miconazole was structurally characterized.¹⁵ D) Particular attention has been given to H₂O₂ cocrystals containing hydrogen-bonded peroxide and peroxide–water clusters⁸ due to the importance of hydrogen peroxide as a signalling biological molecule that undergoes cooperative transport across cellular membranes.^16,17 Recently, large 0D-hydrogen peroxide insular dodecameric and pentameric clusters have been reported in the structures of 2-aminonicotinic acid and lidocaine N-oxide peroxosolvates, and it appears that no special conditions are required for hydrogen peroxide cluster formation.¹⁸ Structures containing 1D-chains of H-bonded peroxide^19–22 and water–peroxide^23,24 have been intensively studied. Peroxide–halide and peroxide–carbonate chains have also been investigated.^25,26 To the best of our knowledge, peroxosolvates with hydrogen-bonded 2D and 3D peroxide motifs have not been reported to date.

Results and discussion

Recently, the usage of organic coformers without donor H-atoms has been suggested for the targeted formation of peroxosolvates with an infinite 1D-hydrogen peroxide clusters.²⁷ It has been shown that hydrogen bonds in Hal⁻⋯HO₂H units can act as templates for the supramolecular organization of tetraphenylphosphonium halide peroxosolvates.²⁵ Thus tetraalkylammonium salts appear to have good prospects due to their availability and multiplicity. Herein we report four novel structures of peroxosolvates of tetraalkylammonium salts.

Structures 1–4 comprise Et₄N⁺ or Me₃RN⁺ cations (R = ClCH₂CH₂–, and Ph), halide counterions and one or two crystallographically independent hydrogen peroxide molecules (Fig. 1–3). The R₄N⁺ cations adopt an ordinary tetrahedral geometry.²⁸ The halide anions and all the peroxide molecules occupy general positions. The O–O distances lie within normal range for solvent H₂O₂ molecules (1.431(2)–1.460(1) Å).²² The torsion H–O–O–H angles (94(2)–159(5)°) are also typical for hydrogen peroxide molecules without imposed crystallographic symmetry.⁸

Fig. 1 Asymmetric unit in structure 1. Displacement ellipsoids are shown at the 50% probability level. Hydrogen bonds are shown by dashed lines.

Fig. 2 Asymmetric unit in structure 3. Displacement ellipsoids are shown at the 50% probability level. Hydrogen bonds are shown by dashed lines.

Fig. 3 Asymmetric unit in structure 4. Displacement ellipsoids are shown at the 50% probability level. Hydrogen bonds are shown by dashed lines.

In structure 1, the peroxide molecule H1–O1–O2–H2 forms two moderate donor hydrogen bonds with chlorine anions and a neighbouring peroxide molecule H3–O3–O4–H4 (Fig. S1 in ESI,†Table 1). H3–O3–O4–H4 forms three almost linear hydrogen bonds (2 donor bonds and 1 acceptor bond) (Fig. S2 in ESI†). As a result, unprecedented 2D-layers containing hydrogen-bonded peroxides are formed (Fig. 4 and 5). Within these layers, chloride anions participate in three hydrogen bonds for a total Cl⁻/H₂O₂ ratio of 1 : 2. Note that only 1D peroxide–halide clusters of ⋯Cl⁻⋯(H₂O₂)_n⋯Cl⁻⋯ (n = 1, 2) are reported to date.²⁵ Of interest, exactly the same 2D clusters of water⋯Cl⁻ are well-known.²⁹ According to Infantes–Motherwell notation, they belong to L8(6) extended motif.³⁰ By contrast to structure 1, these 2D water⋯halogen clusters are usually involved in additional hydrogen bonding with the cation layers.³¹ Moreover, the similar N–H⋯Hal⁻ bonded layers were reported for some simple amine hydrohalides, namely anilinium chloride,³² cyclohexylammonium chloride,³³ and 1-decylammonium bromide.³⁴

Table 1 Hydrogen bond parameters for 1, 2, 3, and 4

		d(O–H), Å	d(H⋯A), Å	d(O⋯A), Å	∠(O–H⋯A), °
O1–H1⋯O4	1	0.86(3)	1.97(3)	2.833(2)	173(3)
	2	0.76(4)	2.07(4)	2.818(3)	168(5)
O2–H2⋯Cl1	1	0.89(3)	2.26(3)	3.1517(15)	172(3)
Br1	2	0.84(4)	2.48(4)	3.2881(19)	161(6)
O3–H3⋯Cl1	1	0.82(3)	2.30(3)	3.1179(13)	170(3)
Br1	2	0.85(4)	2.40(4)	3.238(2)	166(3)
O4–H4⋯Cl1	1	0.89(2)	2.21(2)	3.0951(12)	173(3)
Br1	2	0.81(3)	2.43(3)	3.2353(18)	175(3)
O1–H1⋯Cl3	3	0.826(18)	2.223(19)	3.0438(9)	172.4(17)
O2–H2⋯Cl4		0.868(18)	2.207(18)	3.0659(9)	170.1(14)
O3–H3⋯Cl3		0.810(19)	2.27(2)	3.0710(10)	169.2(17)
O4–H4⋯Cl4		0.803(17)	2.273(18)	3.0768(9)	180(2)
O1–H1⋯Cl1	4	0.873(19)	2.197(19)	3.0548(11)	167.3(16)
O2–H2⋯Cl1		0.87(2)	2.22(2)	3.0733(10)	169.3(18)

---

Fig. 4 Peroxide–halide H-bonded layers in the structure 1 (view along c-axis).

Fig. 5 Peroxide–halide and cationic layers in the structure 1 (view along b-axis).

As expected, Et₄N⁺ cations also form layers perpendicular to the c-axis. The shortest interaction separations (7.24 and 7.31 Å) for these layers are observed along both ab-diagonals (Fig. 6). The globose shape of the Et₄N⁺ cations causes the aforementioned separations to be very close to each other. However, these separations are also very close to the halogen⋯halogen distances along the ab-diagonal within the Cl⁻⋯(H₂O₂)_n⋯Cl⁻ units (both of which are 7.28 Å). The adequate aforementioned bilateral separations appear to be the main cause of peroxide layered crystal packing. Bromide 2 is isomorphous to 1, with very similar H-bond parameters. However, Hal⁻⋯(H₂O₂)_n⋯Hal⁻ units are easily tunable²⁵ due to the low barriers to rotation for peroxide molecules.³⁵

Fig. 6 Cationic layers in the structure 1 (view along c-axis). The shortest interaction separations are shown by red narrows.

The mixed-substituted cation Me₃(ClCH₂CH₂)N⁺ is essentially nonspherical (Fig. 2). Thus, it is highly unlikely that hydrogen-bonded peroxide layers form in the corresponding peroxosolvate structures. In fact, only 1D chains of ⋯Cl⁻⋯H₂O₂⋯Cl⁻⋯ were observed in the crystals of 3 (Fig. 7). Both peroxide molecules and both chlorine anions only form two donor hydrogen bonds. These bonds are somewhat shorter than those in 1, with O⋯Cl⁻ distances in 3.0438(9)–3.0768(9) Å range.

Fig. 7 Peroxide–halide H-bonded chains in the structure 3.

In structure 4, two Me₃PhN⁺ cations combined into elongated centrosymmetric dimers via π⋯π interactions with an interplanar separation of 3.430 Å (Fig. 8). A CSD search showed that the same dimers were recently observed in the structure of 2(Me₃PhN⁺)·(Cl₁₂²⁻).³⁶ H-Bonded 1D chains of ⋯Cl⁻⋯H₂O₂⋯Cl⁻⋯ similar to those in 3 were found for peroxosolvate 4.

Fig. 8 Cationic dimers in the structure 4. π⋯π interactions are shown by dashed lines.

Conclusions

The structures of Et₄N⁺Cl⁻·2(H₂O₂) and Et₄N⁺Br⁻·2(H₂O₂) formed by globose Et₄N⁺ cations are the first examples of peroxosolvates with 2D layers containing H-bonded peroxides. By contrast, the structures Me₃(ClCH₂CH₂)N⁺Cl⁻·H₂O₂ and Me₃PhN⁺Cl⁻·H₂O₂ formed by sufficiently aspherical Me₃(ClCH₂CH₂)N⁺ and Me₃PhN⁺ units contain infinitely long 1D hydrogen-bonded peroxide–halide chains. These compounds appear to be promising for applications because both components, hydrogen peroxide¹⁴ and Et₄N⁺ salts,³⁷ demonstrate high antimicrobial activity.

Experimental

Tetraalkylammonium salts and 50% hydrogen peroxide were purchased from Aldrich. 94% hydrogen peroxide was prepared by an extraction method.³⁸ Handling procedures for concentrated hydrogen peroxide are described in detail (danger of explosion!).^39,40 Colourless crystals of 1–4 were obtained by cooling to −21 °C saturated solutions (rt) of respective anhydrous salts in 94% hydrogen peroxide. Unfortunately, all crystalline samples 1–4 were unstable without mother liquors and completely degrade in a few minutes when exposed to open air. The latter prevented carrying-out powder diffraction and DSC experiments.

Experimental data sets were collected on a Bruker SMART APEX II diffractometer (for 1, 3 and 4) and Bruker D8 Venture machine for 2 using graphite monochromatized Mo-Kα radiation (λ = 0.71073 Å). Absorption corrections based on measurements of equivalent reflections were applied.⁴¹ The structures were solved by direct methods and refined by full matrix least-squares on F² with anisotropic thermal parameters for all non-hydrogen atoms.⁴² All hydrogen atoms were found from difference Fourier synthesis and refined with isotropic thermal parameters. In all structures, partial substitutional disorder of hydrogen peroxide by water molecules^43–46 was not observed since no residual peaks with an intensity more than 0.17 e A⁻³ were seen in the hydrogen peroxide molecule regions. Crystal data and details of X-ray analysis are given in Table S1.† The single crystal X-ray diffraction analysis were performed at the Centre of Shared Equipment of IGIC RAS within the State Assignment on Fundamental Research to the Kurnakov Institute of General and Inorganic Chemistry.

Author contributions

Mger A. Navasardyan – crystallization, data collection; Stanislav I. Bezzubov – data collection, visualization; Alexander G. Medvedev – crystallization, data collection; Petr V. Prikhodchenko – conceptualization, formal analysis; Andrei V. Churakov – funding acquisition; project administration, writing.

Conflicts of interest

There are no conflicts to declare.

Acknowledgements

The authors thank RFBR for financial support (grants 18-29-19119 and 20-03-00449).

Notes and references

1. S. Tanatar, Zh. Russ. Fiz.-Khim. O-va., 1908, 40, 376.
2. H. Jakob, S. Leininger, T. Lehmann, S. Jacobi and S. Gutewort, Peroxo Compounds, Inorganic, Ullmann's encyclopedia of industrial chemistry, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2012, vol. 26.
3. T. Wagner-Jauregg, J. Am. Chem. Soc., 1952, 74, 1358.
4. J. M. Adams, R. G. Pritchard and J. M. Thomas, J. Chem. Soc., Chem. Commun., 1976, 358.
5. D. Thierbach, F. Huber and H. Preut, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem., 1980, 36, 974.
6. A. Adam and M. Mehta, Angew. Chem., Int. Ed., 1998, 37, 1387.
7. J. M. Adams and V. Ramdas, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem., 1978, 34, 2150.
8. A. G. Medvedev, A. V. Churakov, P. V. Prikhodchenko, O. Lev and M. V. Vener, Molecules, 2021, 26, 26.
9. S. H. Ahn, K. J. Cluff, N. Bhuvanesh and J. Blümel, Angew. Chem., Int. Ed., 2015, 54, 13341.
10. G. Chehardoli and M. A. Zolfigol, Phosphorus, Sulfur Silicon Relat. Elem., 2010, 185, 193.
11. J. C. Bennion, N. Chowdhury, J. W. Kampf and A. J. Matzger, Angew. Chem., Int. Ed., 2016, 55, 1.
12. R. A. Wiscons, M. Bellas, J. C. Bennion and A. J. Matzger, Cryst. Growth Des., 2018, 18, 7701.
13. J. Luo, H. Xia, W. Zhang, S. Song and Q. Zhang, J. Mater. Chem. A, 2020, 8, 12334.
14. E. Linley, S. P. Denyer, G. McDonnell, C. Simons and J. Y. Maillard, J. Antimicrob. Chemother., 2012, 67, 1589.
15. K. M. Kersten, M. E. Breen, A. K. Mapp and A. J. Matzger, Chem. Commun., 2018, 54, 9286.
16. O. Rodrigues, G. Reshetnyak, A. Grondin, Y. Saijo, N. Leonhardt, C. Maurel and L. Verdoucq, Proc. Natl. Acad. Sci. U. S. A., 2017, 114, 9200.
17. G. P. Bienert and F. Chaumont, Biochim. Biophys. Acta, Gen. Subj., 2014, 1840, 1596.
18. D. A. Grishanov, M. A. Navasardyan, A. G. Medvedev, O. Lev, P. V. Prikhodchenko and A. V. Churakov, Angew. Chem., Int. Ed., 2017, 56, 15241.
19. M. A. Navasardyan, D. A. Grishanov, P. V. Prikhodchenko and A. V. Churakov, Acta Crystallogr., Sect. E: Crystallogr. Commun., 2020, 76, 1331.
20. M. A. Navasardyan, D. A. Grishanov, T. A. Tripol'skaya, L. G. Kuzmina, P. V. Prikhodchenko and A. V. Churakov, CrystEngComm, 2018, 20, 7413.
21. P. V. Prikhodchenko, A. G. Medvedev, T. A. Tripol'skaya, A. V. Churakov, Y. Wolanov, J. A. K. Howard and O. Lev, CrystEngComm, 2011, 13, 2399.
22. I. Yu. Chernyshov, M. V. Vener, P. V. Prikhodchenko, A. G. Medvedev, O. Lev and A. V. Churakov, Cryst. Growth Des., 2017, 17, 214.
23. A. V. Churakov and J. A. K. Howard, Acta Crystallogr., Sect. E: Struct. Rep. Online, 2007, 63, o4483.
24. G. Laus, V. Kahlenberg, K. Wurst, T. Lörting and H. Schottenberger, CrystEngComm, 2008, 10, 1638.
25. A. V. Churakov, P. V. Prikhodchenko and J. A. K. Howard, CrystEngComm, 2005, 7, 664.
26. A. G. Medvedev, A. A. Mikhaylov, A. V. Churakov, P. V. Prikhodchenko and O. Lev, Acta Crystallogr., Sect. C: Cryst. Struct. Commun., 2012, 68, i20.
27. M. A. Navasardyan, S. I. Bezzubov, L. G. Kuz'mina, P. V. Prikhodchenko and A. V. Churakov, Acta Crystallogr., Sect. E: Crystallogr. Commun., 2017, 73, 1793.
28. C. R. Groom, I. J. Bruno, M. P. Lightfoot and S. C. Ward, Acta Crystallogr., Sect. B: Struct. Sci., Cryst. Eng. Mater., 2016, 72, 171.
29. L. Infantes, J. Chisholm and S. Motherwell, CrystEngComm, 2003, 5, 480.
30. L. Infantes and S. Motherwell, CrystEngComm, 2002, 4, 454.
31. H. Bock, H. Schödel, T. T. H. Van, R. Dienelt and M. Gluth, J. Prakt. Chem./Chem.-Ztg., 1998, 340, 722.
32. E. López-Duplá, P. G. Jones and F. Vancea, Z. Naturforsch., B: J. Chem. Sci., 2003, 58, 191.
33. S. T. Rao and M. Sundaralingam, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem., 1969, 25, 2509.
34. L.-J. Zhang, Y.-Y. Di and D.-F. Lu, J. Chem. Thermodyn., 2011, 43, 1591.
35. R. H. Hunt, R. A. Leacock, W. Peters and K. T. Hecht, J. Chem. Phys., 1965, 42, 1931.
36. K. Sonnenberg, P. Pröhm, N. Schwarze, C. Müller, H. Beckers and S. Riedel, Angew. Chem., Int. Ed., 2018, 57, 9136.
37. F. M. Dolgushin, A. S. Goloveshkin, I. V. Ananyev, S. V. Osintseva, Yu. V. Torubaev, S. S. Krylov and A. S. Golub, Acta Crystallogr., Sect. C: Struct. Chem., 2019, 75, 402.
38. Y. Wolanov, O. Lev, A. V. Churakov, A. G. Medvedev, V. M. Novotortsev and P. V. Prikhodchenko, Tetrahedron, 2010, 66, 5130.
39. W. C. Schumb, C. N. Satterfield and R. P. Wentworth, Hydrogen peroxide, Reinhold publishing corp., New York, 1955.
40. O. Maass and W. H. Hatcher, J. Am. Chem. Soc., 1920, 42, 2569.
41. G. M. Sheldrick, SADABS. Program for scaling and correction of area detector data, University of Göttingen, Germany, 1997.
42. G. M. Sheldrick, Acta Crystallogr., Sect. A: Found. Crystallogr., 2008, 64, 112.
43. B. F. Pedersen, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem., 1972, 28, 746.
44. B. F. Pedersen, Acta Crystallogr., Sect. B: Struct. Crystallogr. Cryst. Chem., 1972, 28, 1014.
45. G. Laus, V. Kahlenberg, K. Wurst, T. Lörting and H. Schottenberger, CrystEngComm, 2008, 10, 1638.
46. A. V. Churakov, P. V. Prikhodchenko and J. A. K. Howard, CrystEngComm, 2005, 7, 664.

---

Footnote

† Electronic supplementary information (ESI) available: Table S1. Crystal data, data collection and refinement parameters for 1–4. Fig. S1 and S2. CCDC 2116891 (1), 2116893 (2), 2116892 (3) and 2116894 (4). For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/d1ce01476e

---