Crystal structures and Hirshfeld surface comparison of fumarate and bromide salts of the etoxazole metabolite designated R7 (aminium ions)

Mohan Kumar, T.M.; Sowbhagya, C.; Bhavya, P.; Yathirajan, H.S.; Parkin, S.

doi:10.1107/S2056989026002197

research communications

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 82| Part 4| April 2026| Pages 326-330

https://doi.org/10.1107/S2056989026002197

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Crystal structures and Hirshfeld surface comparison of fumarate and bromide salts of the etoxazole metabolite designated R7 (aminium ions)

Thaluru M. Mohan Kumar,^a Chaluvarangaiah Sowbhagya,^a Papegowda Bhavya,^b Hemmige S. Yathirajan ^c ^* and Sean Parkin ^d

^aDepartment of Physical Sciences, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Bengaluru-560 035, India, ^bDepartment of Applied Sciences, New Horizon College of Engineering, Bengaluru-560 103, India, ^cDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysuru-570 006, India, and ^dDepartment of Chemistry, University of Kentucky, Lexington, KY, 40506-0055, USA
^*Correspondence e-mail: [email protected]

Edited by X. Hao, Institute of Chemistry, Chinese Academy of Sciences (Received 23 February 2026; accepted 27 February 2026; online 5 March 2026)

Etoxazole (C₂₁H₂₃F₂NO₂) is a fluorinated insecticide/acaricide that acts as an inhibitor of chitin biosynthesis. Its degradation products include several persistent environmental contaminants, including a metabolite designated ‘R7’ (C₁₉H₂₅F₂NO₃), which has a readily protonated amine group, to give the R7H⁺ cation, namely, 2-azaniumyl-2-(4-tert-butyl-2-ethoxyphenyl)ethyl 2,6-difluorobenzoate. This paper reports the crystal structures of two salts of R7H⁺: the bromide (I: C₂₁H₂₆F₂NO₃⁺·Br⁻) and the 3-carboxyprop-2-enoate (hereafter fumarate) (II: C₂₁H₂₆F₂NO₃⁺·C₄H₃O₄⁻). Although the R7H⁺ cations in I and II are chemically identical, the salts crystallize in substantially different structures. Crystals of I are tetragonal, space-group type P42₁c, whereas those of II are monoclinic, space-group type P2₁/n, each containing one cation–anion pair in their respective asymmetric units (Z′ = 1). The R7H⁺ cation in both structures feature a central 2-azaniumyl linker connecting 4-tert-butyl-2-ethoxyphenyl and 2,6-difluorobenzoate rings. Cation conformation is primarily governed by different torsional degrees of freedom, leading to distinct overall conformations. The crystal packing in I is driven by N—H⋯Br hydrogen bonds, π–π and C—H⋯π interactions, which arrange the cations into columns parallel to the crystallographic c-axis. In contrast, the packing in II consists of N—H⋯O hydrogen bonds to adjacent fumarate anions, forming extended hydrogen-bonded chains. The fumarate anions are sandwiched between R7H⁺ cations, placing the fumarate double bond between aromatic rings. Hirshfeld-surface analysis shows that intermolecular contacts in both structures are dominated by interactions involving hydrogen (93.4% in I, 92.2% in II).

Keywords: crystal structure; Hirshfeld surface; etoxazole metabolite R7; acaricide; insecticide.

CCDC references: 2533698; 2533697

1. Chemical context

Etoxazole [C₂₁H₂₃F₂NO₂, systematic name 4-(4-tert-butyl-2-ethoxyphenyl)-2-(2,6-difluorophenyl)-4,5-dihydro-1,3-oxazole], is an oxazoline-based fluorinated insecticide/acaricide, which acts as an inhibitor of chitin biosynthesis. It was developed as a new-generation pesticide to address the growing resistance of spider mites to traditional acaricides, and was selected for development in 1990, achieving registration in 1998 (Suzuki et al., 2002 ). This classification reflects its superior bioactivity and novel target compared to established chitin synthesis inhibitors, pyrethroids, and organophosphate (Li et al., 2014 ) and has been deployed globally since 1998 (Park et al., 2020 ). The synthesis and activity of various 2,4-diphenyl-1,3-oxazolines with acaricidal/insecticidal properties were reported by Suzuki et al. (2002). Metabolic studies of etoxazole by Sun et al. (2019 ), Macar et al. (2022 ) and others, have revealed several distinct metabolites resulting from oxidative degradation, especially of its oxazoline ring. These environmental contaminants have been found in plants, earthworms, and soil (Sun et al., 2019), as well as in rats (Yilmaz et al., 2017 ). In view of the agricultural and environmental significance of etoxazole and its metabolites, we have recently reported the crystal structures of etoxazole itself (Sowbhagya et al., 2025a ), as well as the etoxazole metabolites designated R13 (Mohan Kumar et al., 2024 ) and R4 (Sowbhagya et al., 2025b ). Another related degradation product of etoxazole is the R7 metabolite [C₁₉H₂₅F₂NO₃, systematic name: 2-amino-2-(4-tert-butyl-2-ethoxyphenyl)ethyl 2,6-difluorobenzoate], which has an amino group that readily protonates to form an aminium ion, R7H⁺. This paper reports crystal structures of the bromide (I: C₂₁H₂₆BrF₂NO₃) and fumarate (II: C₂₅H₂₉F₂NO₇) salts of R7H⁺.

2. Structural commentary

In spite of having chemically identical cations, the crystal structures of I and II are substantially different. Crystals of I are tetragonal, space-group type P $[\overline{4}]$ 2₁c, whereas those of II are monoclinic, space-group type P2₁/n, though both have one molecule in their respective asymmetric units (Z′ = 1).

The R7H⁺ cation in each salt is comprised of a central 2-azaniumyl (CH₂CHNH₃⁺) linker flanked by 4-tert-butyl-2-ethoxyphenyl and 2,6-difluorobenzoate substituted rings, as shown in Figs. 1 and 2. No unusual bond lengths or angles are found in either structure. The conformations of the R7H⁺ cations are governed primarily by torsional degrees of freedom about the C3—C4, C2—C3, O1—C2, and C1—C16 bonds. These are shown qualitatively in a least-squares overlay plot (Fig. 3) and quantified in Table 1. In the central 2-azaniumyl moiety, atom C3 is stereogenic , but both structures are strictly racemic (I is non-centrosymmetric but possesses a c-glide). The chosen asymmetric units for I and II both had C3 assigned as R. A least-squares fit overlay of all 27 non-H cation atoms, however, yields a smaller r.m.s. deviation (1.1328 Å vs 1.5544 Å) when one structure is inverted relative to the other. Thus, the R enantiomer of R7H⁺ in I has a better overall fit to the S enantiomer of II and vice versa, which emphasizes the distinct conformations of the two structures.

Table 1
Conformation-defining torsion angles (°) in I and II

Torsion angle	I	II
C5—C4—C3—C2	98.7 (3)	−117.45 (12)
C4—C3—C2—O1	178.0 (2)	160.96 (9)
C3—C2—O1—C1	−120.5 (3)	170.25 (9)
C2—O1—C1—C16	175.2 (2)	175.71 (10)
O1—C1—C16—C21	−144.0 (3)	134.09 (12)
N1—C3—C2—O1	−58.2 (3)	−73.64 (10)
N1—C3—C4—C9	155.1 (3)	−61.61 (13)
C9—O2—C10—C11	67.6 (4)	164.55 (11)
C4—C9—O2—C10	−161.5 (3)	−168.79 (10)
C8—C7—C13—C14	165.0 (2)	123.99 (12)

Figure 1
An ellipsoid plot (50% probability) of I. Hydrogen atoms are drawn as small arbitrary circles.

Figure 2
An ellipsoid plot (50% probability) of II. Hydrogen atoms are drawn as small arbitrary circles.

Figure 3
A least-squares-fit overlay of R7H⁺ cations from I and II.

3. Supramolecular features

In I, the only conventional hydrogen-bond donor is the ammonium nitrogen atom, N1, which forms hydrogen bonds to three symmetry-related Br⁻ anions. These are: N1—H1A⋯Br1ⁱ, N1—H1B⋯Br1ⁱⁱ, and N1—H1C⋯Br1 (symmcodes and distances are given in Table 2). In addition, the contact N1—H1A⋯F1ⁱⁱ and three weak contacts with C—H as donor are flagged as ‘potential hydrogen bonds' by SHELXL (details in Table 2). There are also π–π and C—H⋯π contacts in I. Difluorobenzene ring C16–C21 π-stacks with its counterpart at (1 − x, 2 − y, z) D_Cg⋯Cg = 3.814 (2) Å, while ring C4–C9 is in close contact with H18ⁱⁱ, D_Cg_⋯H = 2.73 Å. Each type of interaction is shown in Fig. 4a. In combination, these contacts connect the R7H⁺ cations into columns parallel to the c-axis, which pack in a square array to give the overall tetragonal packing symmetry, as shown in Fig. 4b.

Table 2
Hydrogen-bond geometry (Å, °) for I

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯Br1ⁱ	0.88	2.57	3.337 (2)	147
N1—H1A⋯F1ⁱⁱ	0.88	2.52	3.073 (3)	122
N1—H1B⋯Br1ⁱⁱ	0.88	2.39	3.259 (2)	170
N1—H1C⋯Br1	0.88	2.38	3.252 (2)	175
C10—H10A⋯Br1ⁱⁱⁱ	0.99	2.75	3.650 (3)	152
C2—H2B⋯O2	0.99	2.62	3.116 (4)	111
C8—H8⋯Br1ⁱⁱⁱ	0.95	3.10	4.040 (3)	170
Symmetry codes: (i) ; (ii) ; (iii) $[x-{\script{1\over 2}}, -y+{\script{3\over 2}}, -z+{\script{1\over 2}}]$ .

Figure 4
(a) A partial packing plot of I. Hydrogen bonds are shown as thick dotted lines, N—H⋯F contacts as open dashed lines, π–π stacked rings by thin dashed lines, and C—H⋯π contacts as dotted lines. (b) A view down the crystallographic c-axis showing the fourfold symmetry.

In II, the R7H⁺ ammonium group also forms three conventional hydrogen bonds. Two of these are to O4 of adjacent fumarate anions, namely N1—H1C⋯O4 and N1—H1A⋯O4ⁱ (distances, angles and symmcodes are given in Table 3). The remaining hydrogen bond is intramolecular, N1—H1B⋯O2, within the R7H⁺ cation. Atom H1B is also in close contact with a symmetry-related fumarate O7, i.e., N1—H1B⋯O7ⁱⁱ, but the angle is small (111.5°, Table 3). In addition, the fumarate anions form extended O6—H6A⋯O5^iv hydrogen-bonded chains. As in I, there are also weaker contacts with C—H as donor, which are also given in Table 3. There is no π–π stacking of rings in I, but the central double bond of the fumarate anion sits sandwiched between the planes of ring C4–C9 and C16–C19ⁱ at a distances of 3.512 and 3.636, Å, respectively between ring and double-bond centroids. These interactions are shown in Fig. 5.

Table 3
Hydrogen-bond geometry (Å, °) for II

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O4ⁱ	0.89	1.89	2.7160 (12)	152
N1—H1B⋯O2	0.89	2.30	2.8889 (12)	123
N1—H1B⋯O7ⁱⁱ	0.89	2.36	2.8103 (13)	112
N1—H1C⋯O4	0.89	1.84	2.6915 (12)	158
C2—H2A⋯O7ⁱⁱ	0.99	2.53	3.1832 (15)	123
C2—H2B⋯O3ⁱⁱⁱ	0.99	2.48	3.1727 (15)	127
O6—H6A⋯O5^iv	0.92	1.62	2.5184 (11)	165
Symmetry codes: (i) ; (ii) $[-x+{\script{3\over 2}}, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iii) ; (iv) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

Figure 5
A partial packing plot of II. Hydrogen bonds are shown as thick dotted lines and overlap of the fumarate double bond with aromatic rings as thin dashed lines.

A Hirshfeld surface analysis using CrystalExplorer (Spackman et al., 2021 ) shows that the most important intermolecular contacts for the R7H⁺ cation in I and II involve hydrogen (93.4% in I, 92.2% in II), with over 50% being H⋯H in both structures. These are summarized pairwise for ease of comparison in Fig. 6.

Figure 6
Hirshfeld-surface fingerprint plots of the most abundant types of atom-atom contacts in I and II. (a),(b) H⋯H contacts, (c),(d) H⋯F, (e),(f) H⋯C, (g),(h) H⋯O/Br and H⋯O contacts. For ease of comparison of the hydrogen-bonding contacts of the ammonium cation, panel (g) is a composite of H⋯O and H⋯Br contacts.

4. Database survey

A search of the Cambridge Structural Database (CSD v6.0, April 2025: Groom et al., 2016 ) using a search fragment consisting of the R7 backbone but with the tert-butyl, ethoxy, and fluoride substituents set to ‘any group' and the carbon–nitrogen and carbonyl–group bonds set to ‘any type' returned 64 hits. Of these, none includes either unsubstituted amino (–NH₂) or ammonium (–NH₃⁺) groups. Furthermore, only three structures include fluorine substituents: CSD refcodes AFABUE (Maligres et al., 2002 ) and CIBKUT (Seiler et al., 1999 ) have –CF₃ groups, while LEZRIU (Xing et al., 2018 ) has a single fluorine atom at the 4-position of the benzoate ring, but otherwise have little in common with R7. Other related structures include the parent molecule etoxazole (DULGUQ: Sowbhagya et al., 2025a) and its R4 (ULOVAW: Sowbhagya et al., 2025b) and R13 (UGUQUM: Mohan Kumar et al., 2024) metabolites.

5. Synthesis and crystallization

Solutions of the etoxazole metabolite R7 (100 mg, 0.265 mmol) in methanol (5 ml) were mixed with either equimolar quantities of a methanolic solution of fumaric acid (31 mg) or 2 ml of HBr (48% aqueous solution) in 10 ml of methanol and stirred for an hour at 313 K. The mixtures were set aside for slow evaporation for 24 h. The resulting crystals, suitable for X-ray diffraction analysis, were collected by filtration and air dried.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 4. All hydrogen atoms were found in difference-Fourier maps, but subsequently included in the refinement using riding models. Carbon-bound hydrogen atoms were affixed with constrained distances set to 0.95 Å (Csp²—H), 0.98 Å (RCH₃), 0.99 Å (R₂CH₂) and 1.00 Å (R₃CH). Hydrogen atoms bound to nitrogen and oxygen used riding models that allowed their bond distances to refine. U_iso(H) parameters were set to values of either 1.2U_eq or 1.5U_eq (RCH₃, RNH₃, OH) of the attached atom.

Table 4
Experimental details

	I	II
Crystal data
Chemical formula	C₂₁H₂₆F₂NO₃⁺·Br⁻	C₂₁H₂₆F₂NO₃⁺·C₄H₃O₄⁻
M_r	458.34	493.49
Crystal system, space group	Tetragonal, P $[\overline{4}]$ 2₁c	Monoclinic, P2₁/n
Temperature (K)	100	100
a, b, c (Å)	15.2984 (2), 15.2984 (2), 17.8818 (3)	12.0615 (2), 15.3673 (3), 14.0141 (3)
α, β, γ (°)	90, 90, 90	90, 110.506 (1), 90
V (Å³)	4185.07 (13)	2432.96 (8)
Z	8	4
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	2.00	0.11
Crystal size (mm)	0.21 × 0.19 × 0.18	0.19 × 0.18 × 0.12

Data collection
Diffractometer	Bruker D8 Venture dual source	Bruker D8 Venture dual source
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )	Multi-scan (SADABS; Krause et al., 2015)
T_min, T_max	0.830, 0.928	0.917, 0.971
No. of measured, independent and observed [I > 2σ(I)] reflections	75181, 4795, 4496	42339, 5576, 4976
R_int	0.049	0.031
(sin θ/λ)_max (Å⁻¹)	0.650	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.024, 0.058, 1.03	0.036, 0.101, 1.03
No. of reflections	4795	5576
No. of parameters	259	324
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.80, −0.44	0.34, −0.21
Absolute structure	Flack x determined using 1911 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013 )	–
Absolute structure parameter	0.018 (3)	–
Computer programs: APEX5 (Bruker, 2023 ), SHELXT (Sheldrick, 2015a ), SHELXL2025/1 (Sheldrick, 2015b ), XP in SHELXTL (Sheldrick, 2008 ), over-lay (Parkin, 2025 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC references: 2533698; 2533697

Crystal structure: contains datablocks I, II, global. DOI: https://doi.org/10.1107/S2056989026002197/nx2032sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989026002197/nx2032Isup2.hkl

Structure factors: contains datablock II. DOI: https://doi.org/10.1107/S2056989026002197/nx2032IIsup3.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989026002197/nx2032Isup4.cml

Supporting information file. DOI: https://doi.org/10.1107/S2056989026002197/nx2032IIsup5.cml

checkCIF report

Computing details top

2-Azaniumyl-2-(4-tert-butyl-2-ethoxyphenyl)ethyl 2,6-difluorobenzoate bromide (I) top

Crystal data top

C₂₁H₂₆F₂NO₃⁺·Br⁻	D_x = 1.455 Mg m⁻³
M_r = 458.34	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P42₁c	Cell parameters from 9610 reflections
a = 15.2984 (2) Å	θ = 2.6–27.5°
c = 17.8818 (3) Å	µ = 2.00 mm⁻¹
V = 4185.07 (13) Å³	T = 100 K
Z = 8	Irregular block, colourless
F(000) = 1888	0.21 × 0.19 × 0.18 mm

Data collection top

Bruker D8 Venture dual source diffractometer	4795 independent reflections
Radiation source: microsource	4496 reflections with I > 2σ(I)
Detector resolution: 7.41 pixels mm^-1	R_int = 0.049
φ and ω scans	θ_max = 27.5°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −19→19
T_min = 0.830, T_max = 0.928	k = −19→16
75181 measured reflections	l = −23→23

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.024	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.058	w = 1/[σ²(F_o²) + (0.0243P)² + 2.4223P] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max = 0.002
4795 reflections	Δρ_max = 0.80 e Å⁻³
259 parameters	Δρ_min = −0.44 e Å⁻³
0 restraints	Absolute structure: Flack x determined using 1911 quotients [(I⁺)-(I^-)]/[(I⁺)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.018 (3)

Special details top

Experimental. The crystal was mounted using polyisobutene oil on the tip of a fine glass fibre, which was fastened in a copper mounting pin with electrical solder. It was placed directly into the cold gas stream of a liquid-nitrogen based cryostat (Hope, 1994; Parkin & Hope, 1998).

Diffraction data were collected with the crystal at 100K.

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.

Refinement. Refinement progress was checked using Platon (Spek, 2020) and by an R-tensor (Parkin, 2000). The final model was further checked with the IUCr utility checkCIF.

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

	x	y	z	U_iso*/U_eq
Br1	0.62255 (2)	0.58962 (2)	0.39254 (2)	0.01946 (8)
F1	0.57938 (12)	0.78020 (12)	0.58387 (9)	0.0244 (4)
F2	0.34194 (13)	0.97753 (13)	0.58768 (10)	0.0315 (5)
O1	0.46509 (15)	0.79073 (13)	0.47217 (11)	0.0210 (5)
O2	0.27044 (14)	0.80263 (14)	0.31527 (11)	0.0218 (4)
O3	0.4237 (2)	0.93037 (16)	0.45861 (13)	0.0469 (8)
N1	0.41590 (16)	0.62168 (16)	0.42530 (12)	0.0179 (4)
H1A	0.3844 (11)	0.5764 (10)	0.4118 (9)	0.027*
H1B	0.4117 (13)	0.6290 (6)	0.4739 (10)	0.027*
H1C	0.4708 (12)	0.6127 (8)	0.4132 (9)	0.027*
C1	0.4477 (2)	0.8717 (2)	0.49735 (16)	0.0212 (6)
C2	0.45015 (19)	0.77420 (19)	0.39362 (18)	0.0209 (6)
H2A	0.505536	0.756944	0.369078	0.025*
H2B	0.428066	0.827752	0.368948	0.025*
C3	0.38341 (18)	0.70115 (18)	0.38652 (15)	0.0173 (5)
H3	0.328393	0.720397	0.411841	0.021*
C4	0.36260 (19)	0.68309 (19)	0.30538 (15)	0.0170 (6)
C5	0.39957 (18)	0.61581 (19)	0.26437 (14)	0.0188 (6)
H5	0.441988	0.579018	0.287063	0.023*
C6	0.3753 (2)	0.60129 (19)	0.19004 (15)	0.0201 (6)
H6	0.401034	0.554458	0.162943	0.024*
C7	0.31381 (19)	0.65487 (19)	0.15526 (15)	0.0170 (6)
C8	0.27756 (19)	0.7236 (2)	0.19644 (16)	0.0175 (6)
H8	0.236174	0.761410	0.173554	0.021*
C9	0.30155 (19)	0.73723 (19)	0.27069 (15)	0.0171 (6)
C10	0.1902 (2)	0.8458 (2)	0.29526 (18)	0.0290 (7)
H10A	0.194533	0.867321	0.243186	0.035*
H10B	0.181494	0.896979	0.328314	0.035*
C11	0.1127 (2)	0.7860 (3)	0.30182 (19)	0.0391 (9)
H11A	0.058984	0.819086	0.292220	0.059*
H11B	0.110555	0.761248	0.352339	0.059*
H11C	0.117919	0.738644	0.265185	0.059*
C12	0.2838 (2)	0.64002 (19)	0.07426 (15)	0.0195 (6)
C13	0.1847 (2)	0.6239 (3)	0.07394 (19)	0.0356 (8)
H13A	0.165704	0.609215	0.023144	0.053*
H13B	0.154416	0.676820	0.090753	0.053*
H13C	0.170823	0.575431	0.107730	0.053*
C14	0.3291 (3)	0.5618 (2)	0.03807 (17)	0.0317 (8)
H14A	0.309098	0.555738	−0.013747	0.048*
H14B	0.314701	0.508575	0.065992	0.048*
H14C	0.392483	0.570840	0.038724	0.048*
C15	0.3045 (2)	0.7211 (2)	0.02736 (17)	0.0266 (7)
H15A	0.284634	0.711835	−0.024144	0.040*
H15B	0.367679	0.731538	0.027601	0.040*
H15C	0.274350	0.771924	0.048583	0.040*
C16	0.45887 (19)	0.87692 (19)	0.58045 (16)	0.0184 (6)
C17	0.52045 (19)	0.82971 (19)	0.62108 (16)	0.0197 (6)
C18	0.5267 (2)	0.8323 (2)	0.69799 (16)	0.0220 (6)
H18	0.570311	0.799695	0.723517	0.026*
C19	0.4672 (2)	0.8839 (2)	0.73735 (17)	0.0244 (7)
H19	0.469349	0.885533	0.790432	0.029*
C20	0.4056 (2)	0.9324 (2)	0.69972 (17)	0.0234 (6)
H20	0.365103	0.967676	0.726479	0.028*
C21	0.4032 (2)	0.92928 (19)	0.62289 (17)	0.0220 (6)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.01987 (14)	0.02421 (15)	0.01431 (11)	0.00078 (11)	0.00101 (12)	0.00146 (12)
F1	0.0237 (9)	0.0264 (9)	0.0230 (9)	0.0065 (8)	−0.0018 (7)	−0.0009 (7)
F2	0.0326 (10)	0.0308 (10)	0.0312 (11)	0.0145 (8)	−0.0093 (8)	−0.0051 (8)
O1	0.0334 (12)	0.0155 (10)	0.0140 (9)	−0.0006 (9)	−0.0079 (8)	−0.0011 (8)
O2	0.0258 (11)	0.0241 (11)	0.0154 (9)	0.0063 (9)	−0.0050 (8)	−0.0046 (8)
O3	0.089 (2)	0.0268 (13)	0.0252 (11)	0.0228 (14)	−0.0070 (14)	0.003 (1)
N1	0.0205 (12)	0.0193 (12)	0.014 (1)	−0.0003 (12)	−0.0012 (9)	0.0008 (9)
C1	0.0248 (15)	0.0183 (14)	0.0205 (14)	0.0000 (13)	−0.0014 (11)	0.0000 (12)
C2	0.0263 (15)	0.0237 (14)	0.0127 (11)	−0.0035 (11)	−0.0033 (13)	−0.0004 (13)
C3	0.0195 (13)	0.0193 (13)	0.0130 (12)	0.0013 (11)	−0.0013 (12)	0.0018 (11)
C4	0.0188 (14)	0.0188 (14)	0.0135 (13)	−0.0028 (11)	−0.0015 (10)	0.0009 (10)
C5	0.0182 (14)	0.0214 (15)	0.0170 (12)	0.0033 (12)	−0.0017 (10)	0.0013 (11)
C6	0.0246 (15)	0.0191 (15)	0.0167 (12)	0.0030 (13)	−0.0005 (12)	−0.0009 (10)
C7	0.0185 (14)	0.0199 (14)	0.0127 (12)	−0.0046 (12)	−0.0014 (11)	0.0027 (11)
C8	0.0178 (14)	0.0185 (14)	0.0161 (13)	−0.0009 (11)	−0.0023 (11)	0.0020 (11)
C9	0.0179 (14)	0.0190 (14)	0.0145 (13)	−0.0020 (11)	0.0014 (11)	−0.0002 (11)
C10	0.0338 (18)	0.0326 (18)	0.0206 (15)	0.0144 (15)	−0.0054 (13)	−0.0057 (13)
C11	0.0228 (18)	0.067 (3)	0.0278 (18)	0.0075 (18)	0.0006 (14)	−0.0051 (17)
C12	0.0276 (16)	0.0190 (15)	0.0118 (12)	0.0013 (12)	−0.0031 (11)	−0.0007 (11)
C13	0.0316 (18)	0.053 (2)	0.0224 (15)	−0.0098 (18)	−0.0063 (14)	−0.0077 (16)
C14	0.054 (2)	0.0239 (17)	0.0171 (14)	0.0089 (16)	−0.0062 (14)	−0.0036 (12)
C15	0.041 (2)	0.0237 (16)	0.0150 (14)	−0.0003 (15)	−0.0021 (13)	0.0007 (12)
C16	0.0206 (14)	0.0142 (13)	0.0203 (13)	−0.0025 (12)	−0.0029 (11)	−0.0005 (11)
C17	0.0210 (14)	0.0147 (14)	0.0235 (15)	−0.0017 (11)	−0.0008 (11)	−0.0017 (11)
C18	0.0227 (16)	0.0217 (16)	0.0216 (15)	−0.0008 (13)	−0.0044 (12)	0.0011 (12)
C19	0.0284 (16)	0.0243 (16)	0.0205 (14)	−0.0049 (13)	−0.0023 (12)	−0.0018 (13)
C20	0.0237 (15)	0.0227 (16)	0.0239 (14)	−0.0010 (13)	0.0008 (12)	−0.0065 (12)
C21	0.0208 (14)	0.0180 (14)	0.0273 (16)	0.0008 (11)	−0.0050 (11)	−0.0009 (11)

Geometric parameters (Å, º) top

F1—C17	1.353 (3)	C10—C11	1.502 (5)
F2—C21	1.349 (3)	C10—H10A	0.9900
O1—C1	1.345 (4)	C10—H10B	0.9900
O1—C2	1.445 (4)	C11—H11A	0.9800
O2—C9	1.365 (3)	C11—H11B	0.9800
O2—C10	1.439 (4)	C11—H11C	0.9800
O3—C1	1.192 (4)	C12—C14	1.527 (4)
N1—C3	1.485 (3)	C12—C15	1.531 (4)
N1—H1A	0.878 (18)	C12—C13	1.535 (5)
N1—H1B	0.878 (18)	C13—H13A	0.9800
N1—H1C	0.878 (18)	C13—H13B	0.9800
C1—C16	1.498 (4)	C13—H13C	0.9800
C2—C3	1.519 (4)	C14—H14A	0.9800
C2—H2A	0.9900	C14—H14B	0.9800
C2—H2B	0.9900	C14—H14C	0.9800
C3—C4	1.511 (4)	C15—H15A	0.9800
C3—H3	1.0000	C15—H15B	0.9800
C4—C5	1.385 (4)	C15—H15C	0.9800
C4—C9	1.394 (4)	C16—C17	1.392 (4)
C5—C6	1.398 (4)	C16—C21	1.393 (4)
C5—H5	0.9500	C17—C18	1.379 (4)
C6—C7	1.395 (4)	C18—C19	1.395 (4)
C6—H6	0.9500	C18—H18	0.9500
C7—C8	1.399 (4)	C19—C20	1.377 (5)
C7—C12	1.536 (4)	C19—H19	0.9500
C8—C9	1.393 (4)	C20—C21	1.375 (4)
C8—H8	0.9500	C20—H20	0.9500

C1—O1—C2	117.1 (2)	C10—C11—H11B	109.5
C9—O2—C10	119.2 (2)	H11A—C11—H11B	109.5
C3—N1—H1A	109.5	C10—C11—H11C	109.5
C3—N1—H1B	109.5	H11A—C11—H11C	109.5
H1A—N1—H1B	109.5	H11B—C11—H11C	109.5
C3—N1—H1C	109.5	C14—C12—C15	108.0 (3)
H1A—N1—H1C	109.5	C14—C12—C13	108.7 (3)
H1B—N1—H1C	109.5	C15—C12—C13	109.4 (3)
O3—C1—O1	124.1 (3)	C14—C12—C7	112.3 (3)
O3—C1—C16	124.9 (3)	C15—C12—C7	109.6 (2)
O1—C1—C16	111.0 (3)	C13—C12—C7	108.8 (2)
O1—C2—C3	108.4 (2)	C12—C13—H13A	109.5
O1—C2—H2A	110.0	C12—C13—H13B	109.5
C3—C2—H2A	110.0	H13A—C13—H13B	109.5
O1—C2—H2B	110.0	C12—C13—H13C	109.5
C3—C2—H2B	110.0	H13A—C13—H13C	109.5
H2A—C2—H2B	108.4	H13B—C13—H13C	109.5
N1—C3—C4	111.7 (2)	C12—C14—H14A	109.5
N1—C3—C2	109.8 (2)	C12—C14—H14B	109.5
C4—C3—C2	110.9 (2)	H14A—C14—H14B	109.5
N1—C3—H3	108.1	C12—C14—H14C	109.5
C4—C3—H3	108.1	H14A—C14—H14C	109.5
C2—C3—H3	108.1	H14B—C14—H14C	109.5
C5—C4—C9	118.7 (2)	C12—C15—H15A	109.5
C5—C4—C3	124.0 (3)	C12—C15—H15B	109.5
C9—C4—C3	117.4 (3)	H15A—C15—H15B	109.5
C4—C5—C6	120.9 (3)	C12—C15—H15C	109.5
C4—C5—H5	119.6	H15A—C15—H15C	109.5
C6—C5—H5	119.6	H15B—C15—H15C	109.5
C7—C6—C5	120.6 (3)	C17—C16—C21	115.3 (3)
C7—C6—H6	119.7	C17—C16—C1	124.6 (3)
C5—C6—H6	119.7	C21—C16—C1	120.1 (3)
C6—C7—C8	118.4 (3)	F1—C17—C18	117.4 (3)
C6—C7—C12	122.4 (3)	F1—C17—C16	119.0 (3)
C8—C7—C12	119.3 (3)	C18—C17—C16	123.5 (3)
C9—C8—C7	120.6 (3)	C17—C18—C19	118.3 (3)
C9—C8—H8	119.7	C17—C18—H18	120.8
C7—C8—H8	119.7	C19—C18—H18	120.8
O2—C9—C8	125.1 (3)	C20—C19—C18	120.4 (3)
O2—C9—C4	114.2 (2)	C20—C19—H19	119.8
C8—C9—C4	120.8 (3)	C18—C19—H19	119.8
O2—C10—C11	112.0 (3)	C21—C20—C19	119.1 (3)
O2—C10—H10A	109.2	C21—C20—H20	120.4
C11—C10—H10A	109.2	C19—C20—H20	120.4
O2—C10—H10B	109.2	F2—C21—C20	117.7 (3)
C11—C10—H10B	109.2	F2—C21—C16	119.0 (3)
H10A—C10—H10B	107.9	C20—C21—C16	123.3 (3)
C10—C11—H11A	109.5

C2—O1—C1—O3	−2.5 (5)	C6—C7—C12—C14	−0.3 (4)
C2—O1—C1—C16	175.2 (2)	C8—C7—C12—C14	−179.3 (3)
C1—O1—C2—C3	−120.5 (3)	C6—C7—C12—C15	−120.3 (3)
O1—C2—C3—N1	−58.2 (3)	C8—C7—C12—C15	60.6 (4)
O1—C2—C3—C4	177.9 (2)	C6—C7—C12—C13	120.1 (3)
N1—C3—C4—C5	−24.0 (4)	C8—C7—C12—C13	−58.9 (4)
C2—C3—C4—C5	98.7 (3)	O3—C1—C16—C17	−148.9 (4)
N1—C3—C4—C9	155.1 (2)	O1—C1—C16—C17	33.5 (4)
C2—C3—C4—C9	−82.2 (3)	O3—C1—C16—C21	33.7 (5)
C9—C4—C5—C6	−1.0 (4)	O1—C1—C16—C21	−144.0 (3)
C3—C4—C5—C6	178.1 (3)	C21—C16—C17—F1	−177.2 (3)
C4—C5—C6—C7	0.6 (5)	C1—C16—C17—F1	5.3 (4)
C5—C6—C7—C8	0.4 (4)	C21—C16—C17—C18	0.9 (5)
C5—C6—C7—C12	−178.6 (3)	C1—C16—C17—C18	−176.6 (3)
C6—C7—C8—C9	−0.9 (4)	F1—C17—C18—C19	179.1 (3)
C12—C7—C8—C9	178.1 (3)	C16—C17—C18—C19	1.0 (5)
C10—O2—C9—C8	19.4 (4)	C17—C18—C19—C20	−1.5 (5)
C10—O2—C9—C4	−161.5 (3)	C18—C19—C20—C21	0.1 (5)
C7—C8—C9—O2	179.5 (3)	C19—C20—C21—F2	179.9 (3)
C7—C8—C9—C4	0.5 (4)	C19—C20—C21—C16	2.1 (5)
C5—C4—C9—O2	−178.6 (3)	C17—C16—C21—F2	179.7 (3)
C3—C4—C9—O2	2.2 (4)	C1—C16—C21—F2	−2.7 (4)
C5—C4—C9—C8	0.5 (4)	C17—C16—C21—C20	−2.5 (4)
C3—C4—C9—C8	−178.7 (3)	C1—C16—C21—C20	175.2 (3)
C9—O2—C10—C11	67.6 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Br1ⁱ	0.88	2.57	3.337 (2)	147
N1—H1A···F1ⁱⁱ	0.88	2.52	3.073 (3)	122
N1—H1B···Br1ⁱⁱ	0.88	2.39	3.259 (2)	170
N1—H1C···Br1	0.88	2.38	3.252 (2)	175
C10—H10A···Br1ⁱⁱⁱ	0.99	2.75	3.650 (3)	152
C2—H2B···O2	0.99	2.62	3.116 (4)	111
C8—H8···Br1ⁱⁱⁱ	0.95	3.10	4.040 (3)	170

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

2-Azaniumyl-2-(4-tert-butyl-2-ethoxyphenyl)ethyl 2,6-difluorobenzoate 3-carboxyprop-2-enoate (II) top

Crystal data top

C₂₁H₂₆F₂NO₃⁺·C₄H₃O₄⁻	F(000) = 1040
M_r = 493.49	D_x = 1.347 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 12.0615 (2) Å	Cell parameters from 9544 reflections
b = 15.3673 (3) Å	θ = 2.2–27.4°
c = 14.0141 (3) Å	µ = 0.11 mm⁻¹
β = 110.506 (1)°	T = 100 K
V = 2432.96 (8) Å³	Irregular block, colourless
Z = 4	0.19 × 0.18 × 0.12 mm

Data collection top

Bruker D8 Venture dual source diffractometer	5576 independent reflections
Radiation source: microsource	4976 reflections with I > 2σ(I)
Detector resolution: 7.41 pixels mm^-1	R_int = 0.031
φ and ω scans	θ_max = 27.5°, θ_min = 1.9°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −15→14
T_min = 0.917, T_max = 0.971	k = −19→19
42339 measured reflections	l = −18→18

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.036	Hydrogen site location: difference Fourier map
wR(F²) = 0.101	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ²(F_o²) + (0.0478P)² + 0.9503P] where P = (F_o² + 2F_c²)/3
5576 reflections	(Δ/σ)_max = 0.001
324 parameters	Δρ_max = 0.34 e Å⁻³
0 restraints	Δρ_min = −0.21 e Å⁻³

Special details top

Diffraction data were collected with the crystal at 100K.

Refinement. Refinement progress was checked using Platon (Spek, 2020) and by an R-tensor (Parkin, 2000). The final model was further checked with the IUCr utility checkCIF.

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

	x	y	z	U_iso*/U_eq
F1	0.67039 (8)	0.57077 (6)	0.21102 (6)	0.0434 (2)
F2	0.85345 (9)	0.79866 (6)	0.43330 (9)	0.0529 (3)
O1	0.76401 (7)	0.55478 (5)	0.41727 (6)	0.02341 (18)
O2	0.88984 (7)	0.39851 (5)	0.69176 (6)	0.02211 (18)
O3	0.93824 (8)	0.62310 (6)	0.45018 (8)	0.0378 (2)
N1	0.67234 (8)	0.48113 (6)	0.56665 (7)	0.01848 (19)
H1A	0.6474 (7)	0.5332 (5)	0.5391 (4)	0.028*
H1B	0.7273 (5)	0.4881 (5)	0.6284 (6)	0.028*
H1C	0.6112 (8)	0.4514 (4)	0.5722 (5)	0.028*
C1	0.83341 (10)	0.61834 (8)	0.40508 (9)	0.0249 (2)
C2	0.82292 (10)	0.48524 (7)	0.48618 (9)	0.0231 (2)
H2A	0.875467	0.509055	0.552164	0.028*
H2B	0.870751	0.449240	0.456488	0.028*
C3	0.72419 (10)	0.43206 (7)	0.50020 (8)	0.0193 (2)
H3	0.660726	0.426428	0.431710	0.023*
C4	0.75887 (9)	0.34111 (7)	0.54008 (8)	0.0185 (2)
C5	0.70565 (10)	0.26951 (7)	0.48146 (8)	0.0221 (2)
H5	0.645992	0.278477	0.416717	0.026*
C6	0.73754 (10)	0.18537 (7)	0.51519 (9)	0.0230 (2)
H6	0.699717	0.137722	0.473208	0.028*
C7	0.82469 (10)	0.16949 (7)	0.61028 (8)	0.0198 (2)
C8	0.87624 (10)	0.24084 (7)	0.67047 (8)	0.0195 (2)
H8	0.934267	0.231802	0.736020	0.023*
C9	0.84405 (9)	0.32533 (7)	0.63609 (8)	0.0185 (2)
C10	0.99214 (10)	0.38980 (8)	0.78240 (9)	0.0252 (2)
H10A	1.051536	0.351424	0.769867	0.030*
H10B	0.969971	0.364617	0.838243	0.030*
C11	1.04123 (13)	0.48013 (9)	0.80978 (12)	0.0401 (4)
H11A	1.057683	0.505607	0.752027	0.060*
H11B	1.114639	0.477314	0.869048	0.060*
H11C	0.983333	0.516271	0.826106	0.060*
C12	0.86045 (11)	0.07546 (7)	0.64402 (9)	0.0231 (2)
C13	0.90985 (13)	0.03290 (9)	0.56848 (10)	0.0325 (3)
H13A	0.849949	0.034849	0.499884	0.049*
H13B	0.930531	−0.027790	0.588232	0.049*
H13C	0.980690	0.064420	0.568981	0.049*
C14	0.75153 (12)	0.02405 (8)	0.64565 (10)	0.0304 (3)
H14A	0.689378	0.026624	0.578204	0.046*
H14B	0.722055	0.049559	0.696287	0.046*
H14C	0.773838	−0.036733	0.663484	0.046*
C15	0.95581 (12)	0.07098 (8)	0.75090 (9)	0.0282 (3)
H15A	0.975912	0.010015	0.769547	0.042*
H15B	0.925608	0.097883	0.800339	0.042*
H15C	1.026686	0.102185	0.750946	0.042*
C16	0.76319 (11)	0.68173 (8)	0.32678 (10)	0.0262 (3)
C17	0.68208 (12)	0.65686 (10)	0.2331 (1)	0.0333 (3)
C18	0.61531 (13)	0.71439 (12)	0.16093 (12)	0.0452 (4)
H18	0.560383	0.694544	0.097881	0.054*
C19	0.63056 (15)	0.80174 (12)	0.18290 (15)	0.0521 (5)
H19	0.583635	0.842656	0.134830	0.062*
C20	0.71214 (15)	0.83136 (11)	0.27283 (16)	0.0509 (4)
H20	0.723916	0.891948	0.285955	0.061*
C21	0.77655 (13)	0.77084 (9)	0.34364 (12)	0.0375 (3)
O4	0.47353 (7)	0.38720 (5)	0.53105 (6)	0.02278 (18)
O5	0.40305 (8)	0.25232 (6)	0.53032 (6)	0.0292 (2)
O6	0.74564 (8)	0.26663 (5)	0.85732 (6)	0.0274 (2)
H6A	0.8000 (14)	0.2498 (4)	0.9192 (13)	0.041*
O7	0.68739 (8)	0.12803 (6)	0.85259 (7)	0.0313 (2)
C22	0.47330 (9)	0.31260 (7)	0.56934 (8)	0.0192 (2)
C23	0.56755 (9)	0.29645 (7)	0.67107 (8)	0.0197 (2)
H23	0.615376	0.343869	0.705630	0.024*
C24	0.58657 (10)	0.21927 (7)	0.71429 (8)	0.0217 (2)
H24	0.538305	0.172432	0.678666	0.026*
C25	0.67817 (10)	0.20027 (7)	0.81480 (8)	0.0213 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
F1	0.0488 (5)	0.0455 (5)	0.0311 (4)	−0.0028 (4)	0.0082 (4)	−0.0020 (4)
F2	0.0510 (6)	0.0265 (4)	0.0756 (7)	−0.0040 (4)	0.0153 (5)	−0.0059 (4)
O1	0.0237 (4)	0.0208 (4)	0.0242 (4)	0.0011 (3)	0.0066 (3)	0.0057 (3)
O2	0.0215 (4)	0.0164 (4)	0.0205 (4)	0.0018 (3)	−0.0026 (3)	−0.0011 (3)
O3	0.0224 (4)	0.0356 (5)	0.0520 (6)	0.0002 (4)	0.0089 (4)	0.0142 (5)
N1	0.0176 (4)	0.0158 (4)	0.0195 (4)	0.0016 (3)	0.0033 (3)	0.0016 (3)
C1	0.0246 (6)	0.0222 (6)	0.0295 (6)	0.0015 (4)	0.0116 (5)	0.0033 (5)
C2	0.0226 (5)	0.0202 (5)	0.0256 (6)	0.0035 (4)	0.0072 (4)	0.0048 (4)
C3	0.0214 (5)	0.0167 (5)	0.0173 (5)	0.0015 (4)	0.0037 (4)	0.0002 (4)
C4	0.0193 (5)	0.0166 (5)	0.0182 (5)	0.0018 (4)	0.0049 (4)	0.0011 (4)
C5	0.0244 (5)	0.0196 (5)	0.0175 (5)	0.0012 (4)	0.0015 (4)	0.0001 (4)
C6	0.0281 (6)	0.0170 (5)	0.0198 (5)	−0.0003 (4)	0.0031 (4)	−0.0019 (4)
C7	0.0216 (5)	0.0175 (5)	0.0199 (5)	0.0021 (4)	0.0069 (4)	0.0006 (4)
C8	0.0191 (5)	0.0194 (5)	0.0178 (5)	0.0025 (4)	0.0038 (4)	0.0012 (4)
C9	0.0179 (5)	0.0171 (5)	0.0191 (5)	0.0002 (4)	0.0049 (4)	−0.0015 (4)
C10	0.0219 (5)	0.0206 (5)	0.0233 (5)	0.0013 (4)	−0.0043 (4)	0.0003 (4)
C11	0.0325 (7)	0.0236 (6)	0.0436 (8)	−0.0011 (5)	−0.0123 (6)	0.0007 (6)
C12	0.0288 (6)	0.0166 (5)	0.0215 (5)	0.0038 (4)	0.0057 (4)	0.0006 (4)
C13	0.0413 (7)	0.0276 (6)	0.0283 (6)	0.0116 (5)	0.0119 (5)	0.0006 (5)
C14	0.0354 (7)	0.0228 (6)	0.0299 (6)	−0.0009 (5)	0.0078 (5)	0.0039 (5)
C15	0.0341 (6)	0.0212 (6)	0.0248 (6)	0.0056 (5)	0.0047 (5)	0.0040 (5)
C16	0.0238 (6)	0.0247 (6)	0.0339 (6)	0.0033 (5)	0.0151 (5)	0.0092 (5)
C17	0.0302 (6)	0.0433 (8)	0.0305 (6)	0.0035 (6)	0.0155 (5)	0.0113 (6)
C18	0.0337 (7)	0.0687 (11)	0.0364 (8)	0.0105 (7)	0.0162 (6)	0.0246 (7)
C19	0.0404 (8)	0.0587 (11)	0.0656 (11)	0.0195 (8)	0.0292 (8)	0.0401 (9)
C20	0.0474 (9)	0.0308 (8)	0.0837 (13)	0.0131 (7)	0.0342 (9)	0.0248 (8)
C21	0.0330 (7)	0.0286 (7)	0.0536 (9)	0.0012 (5)	0.0188 (6)	0.0072 (6)
O4	0.0183 (4)	0.0208 (4)	0.0251 (4)	0.0018 (3)	0.0023 (3)	0.0076 (3)
O5	0.0288 (4)	0.0240 (4)	0.0226 (4)	−0.0066 (3)	−0.0063 (3)	0.0042 (3)
O6	0.0294 (4)	0.0214 (4)	0.0199 (4)	−0.0031 (3)	−0.0060 (3)	0.0028 (3)
O7	0.0328 (5)	0.0211 (4)	0.0286 (4)	−0.0010 (4)	−0.0035 (4)	0.0078 (3)
C22	0.0179 (5)	0.0191 (5)	0.0181 (5)	0.0016 (4)	0.0030 (4)	0.0024 (4)
C23	0.0187 (5)	0.0190 (5)	0.0174 (5)	−0.0016 (4)	0.0014 (4)	0.0000 (4)
C24	0.0215 (5)	0.0192 (5)	0.0187 (5)	−0.0021 (4)	0.0002 (4)	0.0007 (4)
C25	0.0216 (5)	0.0203 (5)	0.0188 (5)	0.0006 (4)	0.0032 (4)	0.0017 (4)

Geometric parameters (Å, º) top

F1—C17	1.3547 (17)	C11—H11C	0.9800
F2—C21	1.3436 (19)	C12—C13	1.5314 (17)
O1—C1	1.3357 (14)	C12—C15	1.5376 (16)
O1—C2	1.4488 (13)	C12—C14	1.5400 (17)
O2—C9	1.3698 (13)	C13—H13A	0.9800
O2—C10	1.4338 (13)	C13—H13B	0.9800
O3—C1	1.2015 (15)	C13—H13C	0.9800
N1—C3	1.4950 (14)	C14—H14A	0.9800
N1—H1A	0.893 (8)	C14—H14B	0.9800
N1—H1B	0.893 (8)	C14—H14C	0.9800
N1—H1C	0.893 (8)	C15—H15A	0.9800
C1—C16	1.4898 (16)	C15—H15B	0.9800
C2—C3	1.5127 (16)	C15—H15C	0.9800
C2—H2A	0.9900	C16—C17	1.3881 (19)
C2—H2B	0.9900	C16—C21	1.3894 (19)
C3—C4	1.5089 (15)	C17—C18	1.372 (2)
C3—H3	1.0000	C18—C19	1.375 (3)
C4—C5	1.3886 (15)	C18—H18	0.9500
C4—C9	1.3986 (15)	C19—C20	1.377 (3)
C5—C6	1.3841 (16)	C19—H19	0.9500
C5—H5	0.9500	C20—C21	1.383 (2)
C6—C7	1.3996 (15)	C20—H20	0.9500
C6—H6	0.9500	O4—C22	1.2661 (13)
C7—C8	1.3903 (15)	O5—C22	1.2452 (14)
C7—C12	1.5345 (15)	O6—C25	1.3106 (14)
C8—C9	1.3920 (15)	O6—H6A	0.922 (18)
C8—H8	0.9500	O7—C25	1.2182 (14)
C10—C11	1.5052 (17)	C22—C23	1.5003 (14)
C10—H10A	0.9900	C23—C24	1.3149 (16)
C10—H10B	0.9900	C23—H23	0.9500
C11—H11A	0.9800	C24—C25	1.4831 (15)
C11—H11B	0.9800	C24—H24	0.9500

C1—O1—C2	116.21 (9)	C13—C12—C15	108.35 (10)
C9—O2—C10	118.56 (8)	C7—C12—C15	112.08 (9)
C3—N1—H1A	109.5	C13—C12—C14	109.37 (10)
C3—N1—H1B	109.5	C7—C12—C14	109.78 (10)
H1A—N1—H1B	109.5	C15—C12—C14	108.27 (10)
C3—N1—H1C	109.5	C12—C13—H13A	109.5
H1A—N1—H1C	109.5	C12—C13—H13B	109.5
H1B—N1—H1C	109.5	H13A—C13—H13B	109.5
O3—C1—O1	124.64 (11)	C12—C13—H13C	109.5
O3—C1—C16	124.72 (11)	H13A—C13—H13C	109.5
O1—C1—C16	110.63 (10)	H13B—C13—H13C	109.5
O1—C2—C3	105.09 (9)	C12—C14—H14A	109.5
O1—C2—H2A	110.7	C12—C14—H14B	109.5
C3—C2—H2A	110.7	H14A—C14—H14B	109.5
O1—C2—H2B	110.7	C12—C14—H14C	109.5
C3—C2—H2B	110.7	H14A—C14—H14C	109.5
H2A—C2—H2B	108.8	H14B—C14—H14C	109.5
N1—C3—C4	111.02 (9)	C12—C15—H15A	109.5
N1—C3—C2	109.19 (9)	C12—C15—H15B	109.5
C4—C3—C2	114.82 (9)	H15A—C15—H15B	109.5
N1—C3—H3	107.2	C12—C15—H15C	109.5
C4—C3—H3	107.2	H15A—C15—H15C	109.5
C2—C3—H3	107.2	H15B—C15—H15C	109.5
C5—C4—C9	117.6 (1)	C17—C16—C21	115.70 (12)
C5—C4—C3	120.28 (9)	C17—C16—C1	123.17 (12)
C9—C4—C3	122.13 (10)	C21—C16—C1	121.13 (12)
C6—C5—C4	121.51 (10)	F1—C17—C18	118.27 (14)
C6—C5—H5	119.2	F1—C17—C16	117.86 (12)
C4—C5—H5	119.2	C18—C17—C16	123.85 (15)
C5—C6—C7	120.95 (10)	C17—C18—C19	117.77 (16)
C5—C6—H6	119.5	C17—C18—H18	121.1
C7—C6—H6	119.5	C19—C18—H18	121.1
C8—C7—C6	117.86 (10)	C18—C19—C20	121.64 (14)
C8—C7—C12	122.55 (10)	C18—C19—H19	119.2
C6—C7—C12	119.6 (1)	C20—C19—H19	119.2
C7—C8—C9	120.95 (10)	C19—C20—C21	118.43 (16)
C7—C8—H8	119.5	C19—C20—H20	120.8
C9—C8—H8	119.5	C21—C20—H20	120.8
O2—C9—C8	124.1 (1)	F2—C21—C20	119.16 (14)
O2—C9—C4	114.79 (9)	F2—C21—C16	118.27 (13)
C8—C9—C4	121.1 (1)	C20—C21—C16	122.56 (16)
O2—C10—C11	106.22 (9)	C25—O6—H6A	109.5
O2—C10—H10A	110.5	O5—C22—O4	126.13 (10)
C11—C10—H10A	110.5	O5—C22—C23	117.83 (10)
O2—C10—H10B	110.5	O4—C22—C23	116.04 (10)
C11—C10—H10B	110.5	C24—C23—C22	122.6 (1)
H10A—C10—H10B	108.7	C24—C23—H23	118.7
C10—C11—H11A	109.5	C22—C23—H23	118.7
C10—C11—H11B	109.5	C23—C24—C25	124.52 (10)
H11A—C11—H11B	109.5	C23—C24—H24	117.7
C10—C11—H11C	109.5	C25—C24—H24	117.7
H11A—C11—H11C	109.5	O7—C25—O6	124.32 (10)
H11B—C11—H11C	109.5	O7—C25—C24	121.09 (10)
C13—C12—C7	108.94 (10)	O6—C25—C24	114.58 (10)

C2—O1—C1—O3	−3.44 (18)	C8—C7—C12—C15	1.27 (16)
C2—O1—C1—C16	175.71 (10)	C6—C7—C12—C15	−179.17 (11)
C1—O1—C2—C3	170.25 (9)	C8—C7—C12—C14	121.63 (12)
O1—C2—C3—N1	−73.64 (10)	C6—C7—C12—C14	−58.81 (14)
O1—C2—C3—C4	160.96 (9)	O3—C1—C16—C17	132.61 (14)
N1—C3—C4—C5	118.11 (11)	O1—C1—C16—C17	−46.55 (16)
C2—C3—C4—C5	−117.45 (12)	O3—C1—C16—C21	−46.75 (19)
N1—C3—C4—C9	−61.61 (13)	O1—C1—C16—C21	134.09 (12)
C2—C3—C4—C9	62.83 (14)	C21—C16—C17—F1	176.68 (11)
C9—C4—C5—C6	−1.68 (17)	C1—C16—C17—F1	−2.72 (18)
C3—C4—C5—C6	178.60 (11)	C21—C16—C17—C18	−1.76 (19)
C4—C5—C6—C7	0.26 (18)	C1—C16—C17—C18	178.84 (12)
C5—C6—C7—C8	1.34 (17)	F1—C17—C18—C19	−178.03 (12)
C5—C6—C7—C12	−178.24 (11)	C16—C17—C18—C19	0.4 (2)
C6—C7—C8—C9	−1.49 (16)	C17—C18—C19—C20	1.8 (2)
C12—C7—C8—C9	178.08 (10)	C18—C19—C20—C21	−2.4 (2)
C10—O2—C9—C8	12.17 (16)	C19—C20—C21—F2	−177.63 (14)
C10—O2—C9—C4	−168.79 (10)	C19—C20—C21—C16	0.9 (2)
C7—C8—C9—O2	179.04 (10)	C17—C16—C21—F2	179.64 (12)
C7—C8—C9—C4	0.06 (17)	C1—C16—C21—F2	−0.95 (19)
C5—C4—C9—O2	−177.55 (10)	C17—C16—C21—C20	1.1 (2)
C3—C4—C9—O2	2.17 (15)	C1—C16—C21—C20	−179.53 (13)
C5—C4—C9—C8	1.52 (16)	O5—C22—C23—C24	7.78 (17)
C3—C4—C9—C8	−178.76 (10)	O4—C22—C23—C24	−171.94 (11)
C9—O2—C10—C11	164.55 (11)	C22—C23—C24—C25	−179.7 (1)
C8—C7—C12—C13	−118.63 (12)	C23—C24—C25—O7	176.53 (12)
C6—C7—C12—C13	60.93 (14)	C23—C24—C25—O6	−3.43 (17)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O4ⁱ	0.89	1.89	2.7160 (12)	152
N1—H1B···O2	0.89	2.30	2.8889 (12)	123
N1—H1B···O7ⁱⁱ	0.89	2.36	2.8103 (13)	112
N1—H1C···O4	0.89	1.84	2.6915 (12)	158
C2—H2A···O7ⁱⁱ	0.99	2.53	3.1832 (15)	123
C2—H2B···O3ⁱⁱⁱ	0.99	2.48	3.1727 (15)	127
O6—H6A···O5^iv	0.92	1.62	2.5184 (11)	165

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

Conformation-defining torsion angles (°) in I and II top

Torsion angle	I	II
C5—C4—C3—C2	98.7 (3)	-117.45 (12)
C4—C3—C2—O1	178.0 (2)	160.96 (9)
C3—C2—O1—C1	-120.5 (3)	170.25 (9)
C2—O1—C1—C16	175.2 (2)	175.71 (10)
O1—C1—C16—C21	-144.0 (3)	134.09 (12)
N1—C3—C2—O1	-58.2 (3)	-73.64 (10)
N1—C3—C4—C9	155.1 (3)	-61.61 (13)
C9—O2—C10—C11	67.6 (4)	164.55 (11)
C4—C9—O2—C10	-161.5 (3)	-168.79 (10)
C8—C7—C13—C14	165.0 (2)	123.99 (12)

Acknowledgements

The authors thank Honeychem Pharma Research Pvt. Ltd., Peenya Industrial Area, Bengaluru-560 058, India, for the gift sample of R7.

Funding information

The D8 Venture diffractometer was funded by the NSF (MRI CHE1625732), and by the University of Kentucky.

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Volume 82| Part 4| April 2026| Pages 326-330

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Crystal structures and Hirshfeld surface comparison of fumarate and bromide salts of the etoxazole metabolite designated R7 (aminium ions)

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Database survey

5. Synthesis and crystallization

6. Refinement

Supporting information

Acknowledgements

Funding information

References

research communications

3. Supramolecular features