CuBr2 complexes with 3,5-disubstituted pyridine ligands

Landee, C.P.; Dickie, D.A.; Turnbull, M.M.

doi:10.1107/S2056989025001343

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Volume 81| Part 3| March 2025|

https://doi.org/10.1107/S2056989025001343

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CuBr₂ complexes with 3,5-disubstituted pyridine ligands

Christopher P. Landee,^a Diane A. Dickie ^b and Mark M. Turnbull ^c ^*

^aDept. of Physics, Clark University, 950 Main St., Worcester, MA 01610, USA, ^bDept. of Chemistry, University of Virginia, McCormack Rdl., Charlottesville, VA 22904, USA, and ^cCarlson School of Chemistry and Biochemistry, Clark University, 950 Main St., Worcester, MA 01610, USA
^*Correspondence e-mail: mturnbull@clarku.edu

Edited by M. Weil, Vienna University of Technology, Austria (Received 30 January 2025; accepted 13 February 2025; online 18 February 2025)

Reaction of copper(II) bromide with 3,5-dichloropyridine (3,5-Cl₂py) or 3,5-dimethylpyridine (3,5-Me₂py) led to the isolation of the coordination polymers catena-poly[[bis(3,5-dichloropyridine)copper(II)]-di-μ-bromido], [CuBr₂(C₅H₃Cl₂N)₂]_n or [CuBr₂(3,5-Cl₂py)₂]_n (1), and catena-poly[[bis(3,5-dimethylpyridine)copper(II)]-di-μ-bromido], [CuBr₂(C₇H₉N)₂]_n or [CuBr₂(3,5-Me₂py)₂]_n (2), respectively. The structures are characterized by bibromide-bridged chains [d(av.)_Cu⋯Cu = 3.93 (9) Å]. In 1, the chains are linked perpendicular to the a axis by non-classical hydrogen bonds and halogen bonds, while in 2, only non-classical hydrogen bonds are observed.

Keywords: crystal structure; copper(II) bromide; 3,5-dichloropyridine; 3,5-dimethylpyridine.

CCDC references: 2423676; 2423675

1. Chemical context

The introduction of random features in a structure may have significant and unique effects on the physical properties of materials. As such, attempts have been made to introduce randomness into the structures of solids by chemists and physicists through modification of the crystal structure (Anderson, 1958 ; Mackenzie, 1964 ) with particular interest in its applications for quantum information (Khrennikov, 2016 ; Feng et al., 2025 ) and band theory (Coey et al., 2005 ; Murugesan et al., 2025 ). Specific to the field of magnetism, the effects of randomness on valence-bond solids (Kimchi et al., 2018 ) and spin glasses (Toulouse, 1986 ) have been areas of focus.

We have been studying the mechanism of magnetic superexchange for some time through the production of families of complexes of transition metal ions, in particular those containing substituted pyridine species as ligands (Graci et al., 2024a ,b ; Monroe et al., 2024 ; Atkinson et al., 2024 ) or charge-balancing cations (Graci et al., 2024a; Bellesis et al., 2024 ). In the hope of introducing randomness into such compounds, we have examined systems where we hoped that structurally similar compounds with subtly different ligands would allow the production of solid solutions of low-dimensional coordination polymers. One such possible paring included Cu^II bibromide-bridged chains with ancillary pyridine ligands of different, but similar, substitution. Here we report the preparation and structures of the CuBr₂L₂ complexes with L = 3,5-dichloropyridine (1) or 3,5-dimethylpyridine (2).

2. Structural commentary

The asymmetric unit of [CuBr₂(3,5-Cl₂py)₂]_n (1) [3,5-Cl₂py = 3,5-dichloropyridine) is composed of one 3,5-Cl₂py molecule, one bromide ion and one Cu^II ion, which is located on an inversion center rendering all trans-bonds 180° as required by symmetry. The molecular unit is shown in Fig. 1. Selected bond lengths and angles are provided in Table 1. The coordination environment around the Cu^II ion is nearly square-planar [∠_{Br1—Cu1—N1} = 89.66 (10)°]. The copper coordination sphere is planar, also as required by symmetry, and the plane of the pyridine ring (mean deviation of constituent atoms = 0.0086 Å) is inclined by 58.1 (1)° relative to that plane. The chlorine atoms are displaced slightly (∼0.05 Å) to opposite faces of the pyridine ring.

Table 1
Selected geometric parameters (Å, °) for 1

Cu1—N1	2.039 (3)	Cu1—Br1	2.4246 (4)

N1—Cu1—Br1	89.66 (10)

Figure 1
The molecular unit of 1 showing displacement ellipsoids at the 50% probability level (hydrogen atoms are shown as spheres of arbitrary size). Only the asymmetric unit and Cu coordination sphere are labeled. [Symmetry code: (A) 1 − x, 1 − y, 2 − z.]

[CuBr₂(3,5-Me₂py)₂]_n (2) [3,5-Me₂py = 3,5-dimthylpyridine) is structurally very similar to 1, with one 3,5-Me₂py molecule, one bromide ion and one Cu^II ion comprising the asymmetric unit (Fig. 2). Selected bond lengths and angles are provided in Table 2. The coordination environment around the Cu^II ion is again nearly square-planar [∠_{Br1—Cu1—N1} = 90.27 (12)°]with the plane of the pyridine ring (mean deviation of the constituent atoms = 0.0095 Å) inclined by 60.8 (1)° relative to the Cu coordination plane. The carbon atoms of the methyl groups are displaced slightly to opposite faces of the plane of the pyridine ring (C7, ∼0.02 Å; C8, ∼0.01 Å).

Table 2
Selected geometric parameters (Å, °) for 2

Cu1—N1	2.007 (4)	Cu1—Br1	2.4350 (5)

N1—Cu1—Br1	90.27 (12)

Figure 2
The molecular unit of 2 showing displacement ellipsoids at the 50% probability level (hydrogen atoms are shown as spheres of arbitrary size). Only the asymmetric unit and Cu coordination sphere are labeled. [Symmetry code: (A) 1 − x, 1 − y, 2 − z.]

3. Supramolecular features

Molecules of 1 are linked into chains parallel to the a axis via non-symmetrically bridging bromide ions (Fig. 3). Each bromide ion exhibits a long Br1⋯Cu1A contact of 3.031 (5) Å with a corresponding Cu1—Br1⋯Cu1^A angle of 89.6 (2)° and a Br1—Cu1⋯Br1^C angle of 90.4 (2) (supplementary as required by symmetry; symmetry codes refer to Fig. 3). The chains are further stabilized by weak, non-classical hydrogen bonds between the hydrogen atoms ortho to the pyridine nitrogen atoms and bromide ions of adjacent molecules in the chain (Table 3). Interchain interactions occur via non-classical hydrogen bonds (Table 3, Fig. 4) between the C4—H4 group and a bromide ion of a neighboring chain related by a 2₁-screw axis. Additional interchain stabilization is provided by Type II halogen bonds between chlorine atoms of adjacent chains [d_Cl3⋯Cl5A = 3.601 (3) Å, ∠_{C3—Cl3⋯Cl5B} = 104.6 (2)°, ∠_{Cl3⋯Cl5B—C5B} = 151.0 (2)°].

Table 3
Hydrogen-bond geometry (Å, °) for 1

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯Br1ⁱ	0.95	2.83	3.472 (4)	126
C4—H4⋯Br1ⁱⁱ	0.95	2.86	3.622 (4)	138
C6—H6⋯Br1ⁱⁱⁱ	0.95	2.82	3.441 (4)	124
Symmetry codes: (i) ; (ii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (iii) .

Figure 3
The chain structure of 1 viewed parallel to the bc face diagonal (a axis horizontal). [Symmetry codes: (A) x − 1, y, z; (C) −x, 1 − y, 2 − z.]

Figure 4
The crystal structure of 1 viewed parallel to the a axis (chain axis). Dashed lines represent hydrogen bonds.

Compound 2 is structurally similar to 1. The semi-coordinate bridging bromide ions make contacts of 3.213 (5) Å between unit-cell translated molecules, again parallel to the a axis. These are significantly longer (∼0.2 Å) than observed in 1 as a result of the larger methyl substituents. The corresponding angles are ∠_{Cu1—Br1⋯Cu1A} = 88.8 (2)° and ∠_{Br1—Cu1⋯Br1C} = 91.2 (2)°, showing a larger deviation from 90° compared with 1. Further intrachain stabilization is again provided via non-classical hydrogen bonds (Table 4). Unsurprisingly, again the bulk of the methyl groups forces increased separations and an equivalent non-classical hydrogen bond between C4—H4 and a neighboring chain bromide ion becomes significantly weaker [d = 3.742 (5) Å] compared to 1, although the overall interchain geometry is maintained. The absence of the chlorine atoms, and hence the halogen bonds, is likely also partially responsible for the increased separation between chains. The structurally similar nature of the asymmetric units is clearly seen in the overlay of the two structures (Fig. 5).

Table 4
Hydrogen-bond geometry (Å, °) for 2

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2⋯Br1ⁱ	0.95	3.12	3.406 (5)	100
C6—H6⋯Br1ⁱⁱ	0.95	2.83	3.515 (5)	130
Symmetry codes: (i) ; (ii) .

Figure 5
An overlay of the asymmetric units of 1 (solid bonds) and 2 (dashed bonds). The overlay was created using the best fit of the species Cu1, Br1 and N1 from the two structures.

The structure of 2 has previously been reported based on film data (Ooijen et al., 1979 ) with a reliability factor R = 13.0 at 295 K. In the prior study, the positions of hydrogen atoms were not included in the final refinement. The Cu—Br and Cu—N bond lengths and Cu⋯Br contact distances are all somewhat longer (3.286 Å) as would be expected at the higher temperature. The reported Br—Cu—N angle deviates slightly more from 90° (∼0.6 °) while the Cu—Br⋯Cu bridging angle is significantly closer to 90° (89.96°) compared to the refined crystal structure model of 2.

Regretably, attempts to prepare crystals with mixed 3,5-dichloropyridine and 3,5-dimethylpyridine were unsuccessful in spite of the structurally similar nature of the individual complexes.

4. Database survey

A significant number of complexes of the general formula CuX₂(s-py)₂ has been reported (where s-py represents a substituted pyridine ligand) based upon a survey of the Cambridge Structure Database (CSD, version 5.46, update November 2024; Groom et al., 2016 ). With s = H, both the chloride and bromide complexes are known (Morosin, 1975 ). Those compounds and compounds with substituents in the 4-position tend to form bi-bridged chains similar to 1 and 2 with substituents including alkyl groups (Laing & Carr, 1971 ; Marsh et al., 1981 ; Matshwele et al., 2022 ), alkoxy groups (Gungor, 2021 ), halogens (Vitorica-Yrezabel et al., 2011 ) and carboxylate derivatives (Fellows & Prior, 2017 ; Ahadi et al., 2015 ; Zhang et al., 1997 ; Hearne et al., 2019 ; Heine et al., 2020a ; Ma et al., 2010 ). The same is generally true for substituents in the 3/5 positions (with or without a substituent also in the 4-position), with substituents such as hydroxy (Segedin et al., 2008 ), amino (Lah & Leban, 2005 ), alkyl (Bondarenko et al., 2021 ; Awwadi, 2013 ), aryl (Richardson et al., 2018 ), halogens (Awwadi et al., 2006 , 2011 ; Mínguez Espallargas et al., 2006 ; Puttreddy et al., 2018 ) and carboxylate derivatives (Fellows & Prior, 2017; Chen et al., 2011 ). However, this can be disrupted by the presence of substituents that can coordinate to the open coordination sites at the Cu^II ion (Li et al., 2004 ; Zhang et al., 2004 ), which may result in polymorphs (Heine et al., 2020b ). Bulky substituents in the 2-position may result in the formation of dimers (Forman et al., 2015 ; Huynh et al., 2023 ; Herringer et al., 2011 ) rather than extended chains, or simply isolated complexes (Lennartson et al., 2007 ; Vural & İdil, 2019 ; Aguirrechu-Comerón et al., 2015 ). The effects of multiple substituents has been recently described (Dubois et al., 2018 , 2019 ).

5. Synthesis and crystallization

Compound 1: CuBr₂ (0.221 g, 0.99 mmol) and 3,5-dichloropyridine (0.298 g, 2.01 mmol) were dissolved in 25 ml of acetonitrile, covered with parafilm with a few holes introduced and left to crystallize at room temperature. After ∼3 weeks, green needles were isolated by filtration, washed quickly with cold acetonitrile and allowed to air-dry to give 0.189 g (37%).

Compound 2: CuBr₂ (0.225 g, 1.01 mmol) and 3,5-dimethylpyridine (0.221 g, 2.06 mmol) were dissolved in 20 ml of acetonitrile with gentle warming, covered with parafilm with a few holes introduced and left to crystallize at room temperature. After ∼3 weeks, green needles were isolated by filtration, washed quickly with cold acetonitrile and allowed to air-dry to give 0.146 g (33%).

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 5. Hydrogen atoms bonded to carbon atoms were placed geometrically and refined with a riding model with U_iso(H) = 1.2(C). The crystal of 2 under investigation was a four-component twin with refined fractional volume contributions of 0.5063, 0.4350, 0.0381 and 0.0206.

Table 5
Experimental details

	1	2
Crystal data
Chemical formula	[CuBr₂(C₅H₃Cl₂N)₂]	[CuBr₂(C₇H₉N)₂]
M_r	519.33	437.66
Crystal system, space group	Monoclinic, P2₁/c	Monoclinic, P2₁/c
Temperature (K)	120	100
a, b, c (Å)	3.86683 (17), 14.1943 (6), 13.7347 (6)	3.9901 (2), 14.2902 (9), 13.8338 (8)
β (°)	91.453 (4)	93.638 (2)
V (Å³)	753.62 (5)	787.20 (8)
Z	2	2
Radiation type	Cu Kα	Mo Kα
μ (mm⁻¹)	14.67	6.45
Crystal size (mm)	0.20 × 0.04 × 0.04	0.46 × 0.03 × 0.03

Data collection
Diffractometer	SuperNova, Dual, Cu at zero, Atlas	Bruker APEXII CCD
Absorption correction	Multi-scan (CrysAlis PRO; Agilent Technologies, 2011	Multi-scan (TWINABS; Sheldrick, 2012 )
T_min, T_max	0.531, 1.000	0.650, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	8288, 1513, 1406	3775, 3775, 3425
R_int	0.052	0.058
(sin θ/λ)_max (Å⁻¹)	0.623	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.102, 1.05	0.044, 0.087, 1.05
No. of reflections	1513	3775
No. of parameters	88	91
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.15, −0.85	0.69, −0.64
Computer programs: CrysAlis PRO (Agilent Technologies, 2011), APEX4 and SAINT (Bruker, 2022 ), SHELXS (Sheldrick, 2008 ), SHELXL (Sheldrick, 2015 ), SHELXTL (Sheldrick, 2008) and publCIF (Westrip, 2010 ).

Supporting information

CCDC references: 2423676; 2423675

Crystal structure: contains datablocks 1, 2. DOI: https://doi.org/10.1107/S2056989025001343/wm5752sup1.cif

Structure factors: contains datablock 1. DOI: https://doi.org/10.1107/S2056989025001343/wm57521sup2.hkl

Structure factors: contains datablock 2. DOI: https://doi.org/10.1107/S2056989025001343/wm57522sup3.hkl

checkCIF report

Computing details top

catena-Poly[[bis(3,5-dichloropyridine)copper(II)]-di-µ-bromido] (1) top

Crystal data top

[CuBr₂(C₅H₃Cl₂N)₂]	F(000) = 494
M_r = 519.33	D_x = 2.289 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54184 Å
a = 3.86683 (17) Å	Cell parameters from 4275 reflections
b = 14.1943 (6) Å	θ = 3.1–73.6°
c = 13.7347 (6) Å	µ = 14.67 mm⁻¹
β = 91.453 (4)°	T = 120 K
V = 753.62 (5) Å³	Rod, green
Z = 2	0.20 × 0.04 × 0.04 mm

Data collection top

SuperNova, Dual, Cu at zero, Atlas diffractometer	1513 independent reflections
Radiation source: SuperNova (Cu) X-ray Source	1406 reflections with I > 2σ(I)
Mirror monochromator	R_int = 0.052
Detector resolution: 10.6501 pixels mm^-1	θ_max = 73.8°, θ_min = 4.5°
ω scans	h = −4→4
Absorption correction: multi-scan (CrysAlisPro; Agilent Technologies, 2011	k = −17→17
T_min = 0.531, T_max = 1.000	l = −16→17
8288 measured reflections

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)] = 0.039	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.102	H-atom parameters constrained
S = 1.05	w = 1/[σ²(F_o²) + (0.0663P)² + 1.7392P] where P = (F_o² + 2F_c²)/3
1513 reflections	(Δ/σ)_max = 0.001
88 parameters	Δρ_max = 1.15 e Å⁻³
0 restraints	Δρ_min = −0.85 e Å⁻³

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
Cu1	0.500000	0.500000	1.000000	0.0193 (2)
Br1	0.10173 (9)	0.59337 (3)	0.90079 (3)	0.01846 (17)
N1	0.4871 (9)	0.3973 (2)	0.8962 (3)	0.0201 (7)
C2	0.5726 (10)	0.4173 (3)	0.8042 (3)	0.0200 (8)
H2	0.642863	0.479406	0.788200	0.024*
C3	0.5596 (10)	0.3483 (3)	0.7321 (3)	0.0207 (8)
Cl3	0.6854 (3)	0.37701 (8)	0.61594 (7)	0.0291 (3)
C4	0.4493 (11)	0.2585 (3)	0.7523 (3)	0.0223 (8)
H4	0.435302	0.211395	0.703291	0.027*
C5	0.3592 (10)	0.2398 (3)	0.8477 (3)	0.0206 (8)
Cl5	0.2163 (3)	0.12924 (7)	0.87993 (7)	0.0275 (2)
C6	0.3861 (10)	0.3095 (3)	0.9187 (3)	0.0209 (8)
H6	0.332306	0.294833	0.984100	0.025*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0232 (4)	0.0167 (4)	0.0179 (4)	0.0033 (3)	−0.0022 (3)	−0.0031 (3)
Br1	0.0173 (3)	0.0187 (3)	0.0194 (3)	0.00076 (13)	0.00064 (16)	0.00106 (13)
N1	0.0199 (17)	0.0185 (16)	0.0220 (17)	0.0025 (12)	−0.0007 (13)	−0.0013 (12)
C2	0.0199 (19)	0.0204 (19)	0.0197 (19)	−0.0002 (14)	−0.0007 (14)	−0.0011 (14)
C3	0.0199 (19)	0.0241 (19)	0.0184 (18)	−0.0007 (15)	0.0032 (14)	−0.0022 (14)
Cl3	0.0386 (6)	0.0286 (5)	0.0204 (5)	−0.0038 (4)	0.0073 (4)	−0.0028 (4)
C4	0.026 (2)	0.0204 (19)	0.0207 (19)	0.0015 (16)	−0.0001 (15)	−0.0038 (15)
C5	0.0196 (18)	0.0190 (18)	0.023 (2)	0.0016 (15)	−0.0009 (14)	−0.0013 (15)
Cl5	0.0346 (5)	0.0199 (5)	0.0281 (5)	−0.0047 (4)	0.0021 (4)	−0.0015 (4)
C6	0.0198 (18)	0.0193 (19)	0.0237 (19)	0.0030 (15)	0.0004 (15)	−0.0009 (15)

Geometric parameters (Å, º) top

Cu1—N1ⁱ	2.039 (3)	C3—C4	1.373 (6)
Cu1—N1	2.039 (3)	C3—Cl3	1.729 (4)
Cu1—Br1	2.4246 (4)	C4—C5	1.390 (6)
Cu1—Br1ⁱ	2.4246 (4)	C4—H4	0.9500
N1—C2	1.344 (5)	C5—C6	1.391 (6)
N1—C6	1.344 (5)	C5—Cl5	1.725 (4)
C2—C3	1.394 (6)	C6—H6	0.9500
C2—H2	0.9500

N1ⁱ—Cu1—N1	180.0	C4—C3—C2	120.9 (4)
N1ⁱ—Cu1—Br1	90.34 (10)	C4—C3—Cl3	120.1 (3)
N1—Cu1—Br1	89.66 (10)	C2—C3—Cl3	119.0 (3)
N1ⁱ—Cu1—Br1ⁱ	89.66 (10)	C3—C4—C5	117.0 (4)
N1—Cu1—Br1ⁱ	90.34 (10)	C3—C4—H4	121.5
Br1—Cu1—Br1ⁱ	179.999 (15)	C5—C4—H4	121.5
C2—N1—C6	119.5 (3)	C4—C5—C6	120.6 (4)
C2—N1—Cu1	120.2 (3)	C4—C5—Cl5	120.3 (3)
C6—N1—Cu1	120.2 (3)	C6—C5—Cl5	119.1 (3)
N1—C2—C3	120.9 (4)	N1—C6—C5	121.0 (4)
N1—C2—H2	119.5	N1—C6—H6	119.5
C3—C2—H2	119.5	C5—C6—H6	119.5

C6—N1—C2—C3	−0.3 (6)	C3—C4—C5—C6	−0.9 (6)
Cu1—N1—C2—C3	−178.9 (3)	C3—C4—C5—Cl5	179.8 (3)
N1—C2—C3—C4	1.9 (6)	C2—N1—C6—C5	−1.9 (6)
N1—C2—C3—Cl3	−178.0 (3)	Cu1—N1—C6—C5	176.7 (3)
C2—C3—C4—C5	−1.3 (6)	C4—C5—C6—N1	2.5 (6)
Cl3—C3—C4—C5	178.7 (3)	Cl5—C5—C6—N1	−178.2 (3)

Symmetry code: (i) −x+1, −y+1, −z+2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···Br1ⁱⁱ	0.95	2.83	3.472 (4)	126
C4—H4···Br1ⁱⁱⁱ	0.95	2.86	3.622 (4)	138
C6—H6···Br1^iv	0.95	2.82	3.441 (4)	124

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

catena-Poly[[bis(3,5-dimethylpyridine)copper(II)]-di-µ-bromido] (2) top

Crystal data top

[CuBr₂(C₇H₉N)₂]	F(000) = 430
M_r = 437.66	D_x = 1.846 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 3.9901 (2) Å	Cell parameters from 3415 reflections
b = 14.2902 (9) Å	θ = 2.9–28.2°
c = 13.8338 (8) Å	µ = 6.45 mm⁻¹
β = 93.638 (2)°	T = 100 K
V = 787.20 (8) Å³	Needle, green
Z = 2	0.46 × 0.03 × 0.03 mm

Data collection top

Bruker APEXII CCD diffractometer	3425 reflections with I > 2σ(I)
φ and ω scans	R_int = 0.058
Absorption correction: multi-scan (TWINABS; Sheldrick, 2012)	θ_max = 28.3°, θ_min = 2.9°
T_min = 0.650, T_max = 0.746	h = −5→5
3775 measured reflections	k = 0→19
3775 independent reflections	l = 0→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)] = 0.044	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.087	H-atom parameters constrained
S = 1.05	w = 1/[σ²(F_o²) + (0.0241P)² + 1.7185P] where P = (F_o² + 2F_c²)/3
3775 reflections	(Δ/σ)_max = 0.001
91 parameters	Δρ_max = 0.69 e Å⁻³
0 restraints	Δρ_min = −0.64 e Å⁻³

Special details top

Refinement. Refined as a 4-component twin.

Rint = 0.0762 for all 26103 observations and Rint = 0.0577 for all 8044 observations with I > 3sigma(I). Rint is based on agreement between observed single and composite intensities and those calculated from refined unique intensities and twin fractions. 2022 corrected reflections were written to file a HKLF 4-type file. Reflections were merged according to point-group 2/m. Minimum and maximum apparent transmission: 0.649678 0.745686. Additional spherical absorption correction were applied with µ*r = 0.2000. The HKLF 5 dataset was constructed from all observations involving domain 1. 10695 corrected reflections written to HKLF 5-type file. Reflections were merged according to point-group 2/m. Single reflections that also occurred in composites were omitted. Minimum and maximum apparent transmission: 0.649545 0.745686. Additional spherical absorption correction applied with µ*r = 0.2000

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

	x	y	z	U_iso*/U_eq
Cu1	0.500000	0.500000	0.500000	0.0159 (2)
Br1	0.88458 (12)	0.40484 (3)	0.60226 (4)	0.01099 (12)
N1	0.4753 (11)	0.3991 (3)	0.3989 (3)	0.0148 (8)
C2	0.5684 (13)	0.4157 (4)	0.3100 (4)	0.0151 (11)
H2	0.644319	0.476702	0.295266	0.018*
C3	0.5605 (13)	0.3482 (4)	0.2376 (4)	0.0134 (11)
C4	0.4344 (13)	0.2605 (4)	0.2590 (4)	0.0144 (10)
H4	0.419115	0.213034	0.210788	0.017*
C5	0.3306 (13)	0.2424 (4)	0.3513 (4)	0.0147 (11)
C6	0.3613 (13)	0.3133 (4)	0.4192 (4)	0.0148 (10)
H6	0.298962	0.300820	0.483049	0.018*
C7	0.6748 (16)	0.3708 (4)	0.1379 (4)	0.0210 (12)
H7A	0.651403	0.315085	0.096682	0.025*
H7B	0.536313	0.421464	0.109048	0.025*
H7C	0.910514	0.390453	0.143358	0.025*
C8	0.1978 (15)	0.1474 (4)	0.3771 (4)	0.0205 (12)
H8A	0.194168	0.106560	0.320159	0.025*
H8B	0.343355	0.120063	0.429397	0.025*
H8C	−0.030447	0.153981	0.398525	0.025*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0231 (4)	0.0114 (4)	0.0122 (4)	0.0079 (4)	−0.0074 (4)	−0.0055 (3)
Br1	0.01092 (18)	0.0107 (2)	0.0112 (2)	0.0017 (2)	−0.00078 (16)	0.0002 (2)
N1	0.0191 (19)	0.012 (2)	0.013 (2)	0.0028 (18)	−0.0045 (18)	−0.0028 (16)
C2	0.016 (2)	0.012 (2)	0.016 (2)	0.002 (2)	−0.003 (2)	−0.003 (2)
C3	0.014 (3)	0.015 (2)	0.011 (2)	0.003 (2)	0.001 (2)	−0.002 (2)
C4	0.012 (2)	0.014 (2)	0.017 (3)	0.002 (2)	−0.004 (2)	−0.0072 (19)
C5	0.013 (3)	0.014 (2)	0.017 (3)	0.002 (2)	0.000 (2)	−0.004 (2)
C6	0.014 (2)	0.016 (2)	0.014 (2)	0.001 (2)	0.000 (2)	0.001 (2)
C7	0.023 (3)	0.022 (3)	0.019 (3)	−0.001 (2)	0.005 (2)	−0.001 (2)
C8	0.020 (3)	0.020 (3)	0.022 (3)	−0.005 (2)	0.001 (2)	−0.001 (2)

Geometric parameters (Å, º) top

Cu1—N1	2.007 (4)	C4—H4	0.9500
Cu1—N1ⁱ	2.007 (4)	C5—C6	1.382 (7)
Cu1—Br1	2.4350 (5)	C5—C8	1.507 (7)
Cu1—Br1ⁱ	2.4350 (5)	C6—H6	0.9500
N1—C2	1.328 (7)	C7—H7A	0.9800
N1—C6	1.343 (7)	C7—H7B	0.9800
C2—C3	1.389 (7)	C7—H7C	0.9800
C2—H2	0.9500	C8—H8A	0.9800
C3—C4	1.390 (7)	C8—H8B	0.9800
C3—C7	1.515 (7)	C8—H8C	0.9800
C4—C5	1.391 (8)

N1—Cu1—N1ⁱ	180.0 (2)	C6—C5—C4	117.9 (5)
N1—Cu1—Br1	90.27 (12)	C6—C5—C8	121.1 (5)
N1ⁱ—Cu1—Br1	89.73 (12)	C4—C5—C8	121.0 (5)
N1—Cu1—Br1ⁱ	89.73 (12)	N1—C6—C5	123.0 (5)
N1ⁱ—Cu1—Br1ⁱ	90.27 (12)	N1—C6—H6	118.5
Br1—Cu1—Br1ⁱ	180.0	C5—C6—H6	118.5
C2—N1—C6	118.3 (4)	C3—C7—H7A	109.5
C2—N1—Cu1	120.9 (4)	C3—C7—H7B	109.5
C6—N1—Cu1	120.9 (3)	H7A—C7—H7B	109.5
N1—C2—C3	123.3 (5)	C3—C7—H7C	109.5
N1—C2—H2	118.3	H7A—C7—H7C	109.5
C3—C2—H2	118.3	H7B—C7—H7C	109.5
C2—C3—C4	117.6 (5)	C5—C8—H8A	109.5
C2—C3—C7	121.0 (5)	C5—C8—H8B	109.5
C4—C3—C7	121.3 (5)	H8A—C8—H8B	109.5
C3—C4—C5	119.8 (4)	C5—C8—H8C	109.5
C3—C4—H4	120.1	H8A—C8—H8C	109.5
C5—C4—H4	120.1	H8B—C8—H8C	109.5

C6—N1—C2—C3	−1.4 (8)	C3—C4—C5—C6	−0.7 (8)
Cu1—N1—C2—C3	179.2 (4)	C3—C4—C5—C8	−179.1 (5)
N1—C2—C3—C4	2.9 (8)	C2—N1—C6—C5	−1.3 (8)
N1—C2—C3—C7	−179.1 (5)	Cu1—N1—C6—C5	178.1 (4)
C2—C3—C4—C5	−1.7 (8)	C4—C5—C6—N1	2.3 (8)
C7—C3—C4—C5	−179.8 (5)	C8—C5—C6—N1	−179.3 (5)

Symmetry code: (i) −x+1, −y+1, −z+1.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2···Br1ⁱ	0.95	3.12	3.406 (5)	100
C6—H6···Br1ⁱⁱ	0.95	2.83	3.515 (5)	130

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

Funding information

Funding for Open Access publication by the Gustaf H. Carlson Fund is gratefully acknowledged.

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