Crystal structure and Hirshfeld surface analysis of 2-bromo­ethyl­ammonium bromide – a possible side product upon synthesis of hybrid perovskites

Semenikhin, O.A.; Shova, S.; Golenya, I.A.; Naumova, D.D.; Gural'skiy, I.A.

doi:10.1107/S2056989024005619

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Volume 80| Part 7| July 2024| Pages 738-741

https://doi.org/10.1107/S2056989024005619

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Crystal structure and Hirshfeld surface analysis of 2-bromoethylammonium bromide – a possible side product upon synthesis of hybrid perovskites

Oleksandr A. Semenikhin,^a ^* Sergiu Shova,^b Irina A. Golenya,^a Dina D. Naumova ^a and Il'ya A. Gural'skiy ^a

^aDepartment of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska St. 64, Kyiv 01601, Ukraine, and ^bDepartment of Inorganic Polymers, Petru Poni Institute of Macromolecular Chemistry, Aleea Grigore Ghica Voda 41-A, Iasi 700487, Romania
^*Correspondence e-mail: alex.semenikhin@knu.ua

Edited by M. Weil, Vienna University of Technology, Austria (Received 24 May 2024; accepted 11 June 2024; online 18 June 2024)

This study presents the synthesis, characterization and Hirshfeld surface analysis of a small organic ammonium salt, C₂H₇BrN⁺·Br⁻. Small cations like the one in the title compound are considered promising components of hybrid perovskites, crucial for optoelectronic and photovoltaic applications. While the incorporation of this organic cation into various hybrid perovskite structures has been explored, its halide salt counterpart remains largely uninvestigated. The obtained structural results are valuable for the synthesis and phase analysis of hybrid perovskites. The title compound crystallizes in the solvent-free form in the centrosymmetric monoclinic space group P2₁/c, featuring one organic cation and one bromide anion in its asymmetric unit, with a torsion angle of −64.8 (2)° between the ammonium group and the bromine substituent, positioned in a gauche conformation. The crystal packing is predominantly governed by Br⋯H interactions, which constitute 62.6% of the overall close atom contacts.

Keywords: crystal structure; Hirshfeld surface analysis; 2-bromoethylamine hydrobromide; hybrid perovskite.

CCDC reference: 2362029

1. Chemical context

Hybrid perovskites have emerged as a class of highly promising compounds for a wide array of applications in optoelectronics and photovoltaics due to their semiconducting properties. Among these, perovskites with a tri-periodic arrangement have garnered significant attention owing to their optimal bandgap width (Dey et al., 2021 ; Liu et al., 2021 ; Hassan et al., 2021 ; Yoo et al., 2021 ). Notably, the aziridinium cation (AzrH) has recently been shown to support such perovskite structures. In the form (AzrH)BX₃ (B = Pb, Sn; X = Br, I; Petrosova et al., 2022 ; Kucheriv et al., 2023 ), these perovskites display promising physical properties (Mączka et al., 2023 ; Stefańska et al., 2022 ), and nanomaterials based on them offer potential for various applications (Semenikhin et al., 2023 ; Bodnarchuk et al., 2024 ).

The high reactivity of aziridine poses a synthetic challenge as it can undergo ring-opening in acidic environments, leading to the formation of perovskites with low periodicity such as (X(CH₂)₂NH₃)_2n(BX)_4n (B = Pb, Sn; X = Br, I; Skorokhod et al., 2023 ; Song et al., 2022 ; Sourisseau et al., 2007 ; Lemmerer & Billing, 2010 ) and 2-bromoethylammonium bromide as a side product. However, these perovskite materials also often manifest physical properties that are as well worth exploring.

In this study, we present the crystal structure analysis and Hirshfeld surface analysis of an organic–inorganic hybrid salt, C₂H₇BrN⁺Br⁻. While this organic cation has previously been incorporated into various hybrid perovskite structures, its halide salt counterpart remains unexplored, representing a significant gap in analysis of these materials. Knowledge of its structure is also important for the phase analysis of studied aziridinium-based materials.

2. Structural commentary

The title compound crystallizes in a solvent-free form and consists of one organic cation and one bromide anion in the asymmetric unit (Fig. 1). The backbone of the cation, N1, C2, C1, Br1, has a torsion angle of −64.8 (2)°, with the atoms positioned in a gauche conformation. The N1—C2 and C1—C2 bonds have lengths of 1.480 (3) and 1.513 (4) Å, respectively. These values are typical for protonated alkylamines and consistent with previous reports (Ishida, 2000 ). The C1—Br1 length is 1.953 (3) Å, which is also a typical value for C—X length in alkyl halides (Allen et al., 1987 ).

Figure 1
The asymmetric unit of 2-bromoethylammonium bromide with displacement ellipsoids drawn at the 50% probability level. The dotted line represents the hydrogen bond between the cation and anion.

3. Intermolecular features

Fig. 2 shows a view of the structure along the b axis, which illustrates the intermolecular organization through N—H⋯Br hydrogen bonds, revealing that each bromide anion is the acceptor of four contacts with NH₃⁺ groups. Corresponding numerical data are given in Table 1. Our analysis uncovered different patterns of hydrogen-bonding interactions. Specifically, N1—H1A⋯Br2 and N1—H1B⋯Br2ⁱ [symmetry code: (i) −x + 1, −y + 1, −z + 1] interactions demonstrate typical classical behavior, with angles of 156.1° and 156.2°, and D⋯A distances of 3.3010 (19) Å and 3.381 (2) Å, respectively. In contrast, N1—H1C⋯Br2ⁱⁱ and N1—H1C⋯Br2ⁱⁱⁱ [symmetry codes: (ii) x, −y + $[{1\over 2}]$ , z + $[{1\over 2}]$ ; (iii) −x + 1, y + $[{1\over 2}]$ , −z + $[{3\over 2}]$ ] contacts exhibit weaker interactions, with longer D⋯A distances of 3.3904 (19) and 3.4292 (18) Å, and angles of 125.1° and 140.3°. Fig. 3 shows that the arrangement of cations and anions leads to the formation of double layers.

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯Br2	0.85	2.51	3.3010 (19)	156
N1—H1B⋯Br2ⁱ	0.85	2.59	3.381 (2)	156
N1—H1C⋯Br2ⁱⁱ	0.85	2.83	3.3904 (19)	125
N1—H1C⋯Br2ⁱⁱⁱ	0.85	2.73	3.4292 (18)	140
Symmetry codes: (i) ; (ii) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (iii) $[-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Figure 2
Projection of the crystal structure along the b axis, showing the hydrogen-bonding interactions with the anion being an acceptor of four N—H⋯Br hydrogen bonds.

Figure 3
Space-filling model of the title compound showing the organization into double layers extending parallel to (100).

4. Hirshfeld analysis

The intermolecular interactions in 2-bromoethylammonium bromide were analyzed using Hirshfeld surface calculations, employing CrystalExplorer (Spackman et al., 2021 ). Results are plotted over the d_norm range between −0.4077 and +1.2052 a.u. (Spackman & Jayatilaka, 2009 ). A three-dimensional model of the Hirshfeld surface (Fig. 4) highlights strong Br⋯H/H⋯Br contacts, exhibiting a cation volume of 103.45 Å, a surface area of 119.7 Å, a globularity of 0.890, and an asphericity of 0.059. Additionally, two-dimensional fingerprint plots were generated, illustrating all specific intermolecular contacts (McKinnon et al., 2007 ). Fig. 5 shows Br⋯H/H⋯Br, Br⋯Br interactions, and all interactions present in the structure with meaningful intermolecular contacts. In the crystal packing, Br⋯H interactions predominate, constituting 62.6% of the overall close atom contacts, while Br⋯Br interactions contribute with 2.6%, and H⋯H contacts account for 34.8%, indicating no additional interactions involving the heteroatoms.

Figure 4
Three-dimensional model of the Hirshfeld surface for 2-bromoethylammonium bromide mapped over d_norm, representing strong intermolecular interactions. [Symmetry codes: (i) −x + 1, −y + 1, −z + 1; (ii) x, −y + $[{1\over 2}]$ , z + $[{1\over 2}]$ ; (iii) −x + 1, y + $[{1\over 2}]$ , −z + $[{3\over 2}]$ .]

Figure 5
Two-dimensional fingerprint plots of 2-bromoethylammonium bromide showing (a) all interactions, (b) Br⋯H/H⋯Br and (c) Br⋯Br interactions (d_i and d_e are the closest internal and external distances in Å on the Hirshfeld surface) and (d) their percentage contributions.

5. Synthesis and crystallization

All chemicals were purchased from Enamine Ltd (Kyiv, Ukraine) and used without any further purification. Aziridine (258.4 µl, 5 mmol) was added dropwise under stirring to 2 ml of conc. HBr, gradually heated to 353 K until water evaporation occurred and colorless crystals formed. The obtained crystals were left under Paratone(R) oil until the X-ray measurement.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms were placed at calculated positions with U_iso(H) = 1.2U_eq(C,N). Hydrogens atom of CH₂ group were included in idealized positions (C—H = 0.99 Å).

Table 2
Experimental details

Crystal data
Chemical formula	C₂H₇BrN⁺·Br⁻
M_r	204.91
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	200
a, b, c (Å)	7.8966 (4), 8.3394 (4), 9.0089 (4)
β (°)	100.546 (5)
V (Å³)	583.24 (5)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	13.75
Crystal size (mm)	0.15 × 0.05 × 0.02

Data collection
Diffractometer	XtaLAB Synergy, Dualflex, HyPix
Absorption correction	Multi-scan (CrysAlis PRO; Rigaku OD, 2024 $[Rigaku OD (2024). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ )
T_min, T_max	0.451, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	4504, 1453, 1242
R_int	0.024
(sin θ/λ)_max (Å⁻¹)	0.709

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.024, 0.054, 1.04
No. of reflections	1453
No. of parameters	49
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.56, −0.47
Computer programs: CrysAlis PRO (Rigaku OD, 2024 $[Rigaku OD (2024). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England.]$ ), SHELXT (Sheldrick, 2015a ), SHELXL (Sheldrick, 2015b ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2362029

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989024005619/wm5723sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989024005619/wm5723Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989024005619/wm5723Isup3.cml

checkCIF report

Computing details top

2-Bromoethylammonium bromide top

Crystal data top

C₂H₇BrN⁺·Br⁻	F(000) = 384
M_r = 204.91	D_x = 2.334 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.8966 (4) Å	Cell parameters from 2526 reflections
b = 8.3394 (4) Å	θ = 2.6–30.0°
c = 9.0089 (4) Å	µ = 13.75 mm⁻¹
β = 100.546 (5)°	T = 200 K
V = 583.24 (5) Å³	Plate, clear intense colourless
Z = 4	0.15 × 0.05 × 0.02 mm

Data collection top

XtaLAB Synergy, Dualflex, HyPix diffractometer	1453 independent reflections
Radiation source: micro-focus sealed X-ray tube, PhotonJet (Mo) X-ray Source	1242 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.024
Detector resolution: 10.0000 pixels mm^-1	θ_max = 30.3°, θ_min = 2.6°
ω scans	h = −10→10
Absorption correction: multi-scan (CrysAlisPro; Rigaku OD, 2024)	k = −10→11
T_min = 0.451, T_max = 1.000	l = −12→12
4504 measured reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H atoms treated by a mixture of independent and constrained refinement
R[F² > 2σ(F²)] = 0.024	w = 1/[σ²(F_o²) + (0.028P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.054	(Δ/σ)_max = 0.001
S = 1.04	Δρ_max = 0.56 e Å⁻³
1453 reflections	Δρ_min = −0.47 e Å⁻³
49 parameters	Extinction correction: SHELXL (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0055 (7)
Primary atom site location: dual

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Br2	0.62288 (3)	0.21658 (3)	0.52611 (2)	0.02586 (10)
Br1	0.80287 (4)	0.89002 (3)	0.82138 (3)	0.03709 (11)
N1	0.6130 (3)	0.5414 (2)	0.7338 (2)	0.0252 (4)
H1A	0.5825 (5)	0.4579 (15)	0.6819 (15)	0.030*
H1B	0.5747 (6)	0.6239 (14)	0.6835 (16)	0.030*
H1C	0.5728 (7)	0.5380 (17)	0.8149 (12)	0.030*
C2	0.8034 (3)	0.5490 (3)	0.7706 (3)	0.0265 (5)
H2A	0.848456	0.575438	0.678011	0.032*
H2B	0.848904	0.442408	0.806124	0.032*
C1	0.8670 (4)	0.6727 (3)	0.8908 (3)	0.0333 (6)
H1D	0.993935	0.665423	0.918954	0.040*
H1E	0.817760	0.649328	0.981906	0.040*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br2	0.03128 (17)	0.02218 (16)	0.02435 (15)	0.00045 (10)	0.00574 (11)	−0.00179 (9)
Br1	0.02685 (18)	0.03231 (18)	0.0526 (2)	−0.00574 (11)	0.00868 (13)	−0.00512 (11)
N1	0.0289 (12)	0.0227 (10)	0.0238 (10)	0.0008 (9)	0.0048 (9)	0.0001 (8)
C2	0.0235 (14)	0.0286 (13)	0.0286 (12)	0.0067 (11)	0.0076 (10)	0.0059 (10)
C1	0.0256 (15)	0.0420 (15)	0.0294 (13)	−0.0019 (13)	−0.0023 (11)	0.0071 (11)

Geometric parameters (Å, º) top

Br1—C1	1.953 (3)	C2—H2A	0.9900
N1—H1A	0.849 (12)	C2—H2B	0.9900
N1—H1B	0.849 (12)	C2—C1	1.513 (4)
N1—H1C	0.849 (12)	C1—H1D	0.9900
N1—C2	1.480 (3)	C1—H1E	0.9900

H1A—N1—H1B	109.5	H2A—C2—H2B	107.9
H1A—N1—H1C	109.5	C1—C2—H2A	109.1
H1B—N1—H1C	109.5	C1—C2—H2B	109.1
C2—N1—H1A	109.5	Br1—C1—H1D	109.3
C2—N1—H1B	109.5	Br1—C1—H1E	109.3
C2—N1—H1C	109.5	C2—C1—Br1	111.77 (17)
N1—C2—H2A	109.1	C2—C1—H1D	109.3
N1—C2—H2B	109.1	C2—C1—H1E	109.3
N1—C2—C1	112.4 (2)	H1D—C1—H1E	107.9

N1—C2—C1—Br1	−64.8 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Br2	0.85	2.51	3.3010 (19)	156
N1—H1B···Br2ⁱ	0.85	2.59	3.381 (2)	156
N1—H1C···Br2ⁱⁱ	0.85	2.83	3.3904 (19)	125
N1—H1C···Br2ⁱⁱⁱ	0.85	2.73	3.4292 (18)	140

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x, −y+1/2, z+1/2; (iii) −x+1, y+1/2, −z+3/2.

Funding information

Funding for this research was provided by the EURIZON project, which is funded by the European Union (grant No. 871072).

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Tailor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. 1–19. CrossRef Google Scholar
Bodnarchuk, M. I., Feld, L. G., Zhu, C., Boehme, S. C., Bertolotti, F., Avaro, J., Aebli, M., Mir, S. H., Masciocchi, N., Erni, R., Chakraborty, S., Guagliardi, A., Rainò, G. & Kovalenko, M. V. (2024). ACS Nano, 18, 5684–5697. CAS PubMed Google Scholar
Dey, A., Ye, J., De, A., Debroye, E., Ha, S. K., Bladt, E., Kshirsagar, A. S., Wang, Z., Yin, J., Wang, Y., Quan, L. N., Yan, F., Gao, M., Li, X., Shamsi, J., Debnath, T., Cao, M., Scheel, M. A., Kumar, S., Steele, J. A., Gerhard, M., Chouhan, L., Xu, K., Wu, X. G., Li, Y., Zhang, Y., Dutta, A., Han, C., Vincon, I., Rogach, A. L., Nag, A., Samanta, A., Korgel, B. A., Shih, C. J., Gamelin, D. R., Son, D. H., Zeng, H., Zhong, H., Sun, H., Demir, H. V., Scheblykin, I. G., Mora-Seró, I., Stolarczyk, J. K., Zhang, J. Z., Feldmann, J., Hofkens, J., Luther, J. M., Pérez-Prieto, J., Li, L., Manna, L., Bodnarchuk, M. I., Kovalenko, M. V., Roeffaers, M. B. J., Pradhan, N., Mohammed, O. F., Bakr, O. M., Yang, P., Müller-Buschbaum, P., Kamat, P. V., Bao, Q., Zhang, Q., Krahne, R., Galian, R. E., Stranks, S. D., Bals, S., Biju, V., Tisdale, W. A., Yan, Y., Hoye, R. L. Z. & Polavarapu, L. (2021). ACS Nano, 15, 10775–10981. Web of Science CrossRef CAS PubMed Google Scholar
Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K. & Puschmann, H. (2009). J. Appl. Cryst. 42, 339–341. Web of Science CrossRef CAS IUCr Journals Google Scholar
Hassan, Y., Park, J. H., Crawford, M. L., Sadhanala, A., Lee, J., Sadighian, J. C., Mosconi, E., Shivanna, R., Radicchi, E., Jeong, M., Yang, C., Choi, H., Park, S. H., Song, M. H., De Angelis, F., Wong, C. Y., Friend, R. H., Lee, B. R. & Snaith, H. J. (2021). Nature, 591, 72–77. CrossRef CAS PubMed Google Scholar
Ishida, H. (2000). Z. Naturforsch. Teil A, 55, 769–771. CAS Google Scholar
Kucheriv, O. I., Sirenko, V. Y., Petrosova, H. R., Pavlenko, V. A., Shova, S. & Gural'skiy, I. A. (2023). Inorg. Chem. Front. 10, 6953–6963. CSD CrossRef CAS Google Scholar
Lemmerer, A. & Billing, D. G. (2010). CrystEngComm, 12, 1290–1301. Web of Science CSD CrossRef CAS Google Scholar
Liu, X.-K., Xu, W., Bai, S., Jin, Y., Wang, J., Friend, R. H. & Gao, F. (2021). Nat. Mater. 20, 10–21. CrossRef CAS PubMed Google Scholar
Mączka, M., Ptak, M., Gągor, A., Zaręba, J. K., Liang, X., Balčiūnas, S., Semenikhin, O. A., Kucheriv, O. I., Gural'skiy, I. A., Shova, S., Walsh, A., Banys, J. & Šimėnas, M. (2023). Chem. Mater. 35, 9725–9738. PubMed Google Scholar
McKinnon, J. J., Jayatilaka, D. & Spackman, M. A. (2007). Chem. Commun. pp. 3814–3816. Web of Science CrossRef Google Scholar
Petrosova, H. R., Kucheriv, O. I., Shova, S. & Gural'skiy, I. A. (2022). Chem. Commun. 58, 5745–5748. CSD CrossRef CAS Google Scholar
Rigaku OD (2024). CrysAlis PRO. Rigaku Oxford Diffraction, Yarnton, England. Google Scholar
Semenikhin, O. A., Kucheriv, O. I., Sacarescu, L., Shova, S. & Gural'skiy, I. A. (2023). Chem. Commun. 59, 3566–3569. CrossRef CAS Google Scholar
Sheldrick, G. M. (2015a). Acta Cryst. A71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Sheldrick, G. M. (2015b). Acta Cryst. C71, 3–8. Web of Science CrossRef IUCr Journals Google Scholar
Skorokhod, A., Quarti, C., Abhervé, A., Allain, M., Even, J., Katan, C. & Mercier, N. (2023). Chem. Mater. 35, 2873–2883. CSD CrossRef CAS Google Scholar
Song, Z., Yu, B., Wei, J., Li, C., Liu, G. & Dang, Y. (2022). Inorg. Chem. 61, 6943–6952. CSD CrossRef ICSD CAS PubMed Google Scholar
Sourisseau, S., Louvain, N., Bi, W., Mercier, N., Rondeau, D., Buzaré, J.-Y. & Legein, C. (2007). Inorg. Chem. 46, 6148–6154. CSD CrossRef PubMed CAS Google Scholar
Spackman, M. A. & Jayatilaka, D. (2009). CrystEngComm, 11, 19–32. Web of Science CrossRef CAS Google Scholar
Spackman, P. R., Turner, M. J., McKinnon, J. J., Wolff, S. K., Grimwood, D. J., Jayatilaka, D. & Spackman, M. A. (2021). J. Appl. Cryst. 54, 1006–1011. Web of Science CrossRef CAS IUCr Journals Google Scholar
Stefańska, D., Ptak, M. & Mączka, M. (2022). Molecules, 27, 7949–7960. PubMed Google Scholar
Yoo, J. J., Seo, G., Chua, M. R., Park, T. G., Lu, Y., Rotermund, F., Kim, Y.-K., Moon, C. S., Jeon, N. J., Correa-Baena, J.-P., Bulović, V., Shin, S. S., Bawendi, M. G. & Seo, J. (2021). Nature, 590, 587–593. CrossRef CAS PubMed Google Scholar

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