Ionothermal synthesis and crystal structure of a new organic–inorganic hybrid compound: catena-poly[bis­(1-ethyl-3-methyl­imidazolium) [hepta-μ-bromido-penta­cuprate(I)]]

A new organic–inorganic hybrid compound, catena-poly[bis­(1-ethyl-3-methyl­imidazolium) [μ₅-bromido-tri-μ₃-brom­ido-tri-μ₂-bromido-penta­cuprate(I)]], {(C₆H₁₁N₂)₂[Cu₅Br₇]}_n, has been obtained under ionothermal conditions from a reaction mixture containing Ba(OH)₂·8H₂O, Cu(OH)₂·2H₂O, As₂O₅, 1-ethyl-3-methyl­imidazolium bromide and distilled water. The crystal structure consists of complex [Cu₅Br₇]²⁻ anions arranged in sinusoidal {[Cu₅Br₇]²⁻}_n chains running along the a axis, which are surrounded by 1-ethyl-3-methyl­imidazolium cations. Three of the five unique Br atoms and one of the three Cu^I atoms occupy special positions with half-occupancy (a mirror plane perpendicular to the b axis, site symmetry m). The Cu^I ions are in a distorted tetra­hedral coordination environment, with four Br atoms at distances ranging from 2.3667 (10) to 2.6197 (13) Å, and an outlier at 3.0283 (12) Å, exceptionally elongated and with a small contribution to the bond-valence sum of only 6.7%. Short C—H...Br contacts build up a three-dimensional network. The Cu...Cu distances within the chain range from 2.8390 (12) to 3.0805 (17) Å, indicating the existence of weak Cu^I...Cu^I cuprophilic inter­actions.

S1. Introduction

The increasing attention paid to the organic–inorganic hybrid materials originates from their fascinating magnetic, electrical, optical and porous properties, as well as from their variety and diversity of structures and topologies (Zhang & Xiong, 2012; Zhou et al., 2012). Among hybrid compounds reported so far, copper(I) halides with different organic templates have been widely investigated due to their rich photoluminescent properties and intriguing topology (Graham et al., 2000; Wang et al., 2002; Peng, et al., 2010; Xin, et al., 2013; Liu et al., 2014). Copper(I) tends to form a variety of coordination compounds with halides, ranging from zero-dimensional complexes to three-dimensional frameworks (Subramanian & Hoffmann, 1992; Peng et al., 2010; Gao et al., 2010; Liu et al., 2014). The introduction of organic molecules in the synthesis of polynuclear copper(I) halides is the most extensively and effectively employed strategy to modulate the copper(I) halide structures (Xin et al., 2013). Only a few reports of the solid-state structures of imidazolium salts containing transition metals and halide anions have been published (Zeller et al. 2005; Chen et al., 2011; Ji et al., 2011; Hu et al., 2011; Shao & Yu, 2014). They all show short contacts between the halide atoms of the cuprate(I) anion and H atoms of the 1-ethyl-3-methyl­imidazolium (emim) cation.

Although the title compound, catena-poly[bis­(1-ethyl-3-methyl­imidazolium) [µ₅-bromido-tri-µ₃-bromido-tri-µ₂-bromido-penta­cuprate(I)]], {(emim)₂[Cu₅Br₇]}_n, (I), was obtained unintentionally, it fits perfectly into our research concerning the iono- and hydro­thermal synthesis, crystallography and properties of organic–inorganic hybrid compounds (Karanović et al., 2011). We report here the details of the ionothermal synthesis and structural characterization of the new organically templated copper(I) bromide (I).

S2. Experimental

S2.1. Synthesis and crystallization

While working on the preparation of inorganic arsenites and arsenates using ionic liquids as a medium, the title compound was obtained by reaction of an 2.00 g of an equimolar mixture of Ba(OH)₂·8H₂O (Fluka), Cu(OH)₂·2H₂O (Alfa Products) and As₂O₅ (AlfaAesar) in a Teflon vessel (V ~8 cm^-1) with a 4:1 mixture of emim bromide and distilled water as the medium. The Teflon vessel was enclosed in a stainless steel autoclave and heated for 4 h under autogenous pressure to 493 K, held at this temperature for 72 h, and cooled to room temperature in another 72 h. Colourless prismatic crystals of (emim)₂[Cu₅Br₇] (yield 20%) were obtained together with blue prismatic crystals of BaCuAs₂O₇ (yield 80%) (Chen & Wang, 1996). The crystals were washed with ethanol and dried in air.

S2.2. Refinement

A complete sphere of reciprocal space (ϕ and ω scans) was measured during data collection at room temperature. Crystal data, data collection and structure refinement details are summarized in Table 1. All non-H atoms were refined with anisotropic displacement parameters. H atoms attached to C atoms were located in geometrically calculated positions and refined using the riding model, with C—H = 0.96 Å and U_iso(H) = 1.5U_eq(C) for methyl H atoms, C—H = 0.97 Å and U_iso(H) = 1.2U_eq(C) for methyl­ene H atoms, and C—H = 0.93 Å and U_iso(H) = 1.2U_eq(C) for imidazolium ring H atoms.

S3. Results and discussion

The co-existence of (emim)₂[Cu₅Br₇] and BaCuAs₂O₇ as the reaction products showed that a partial reduction of Cu^II to Cu^I ions occurred during the synthesis. At first sight, this seems surprising, but reduction of Cu^II or oxidation of Cu^I ions in the course of hydro­thermal reactions has already been observed. For example, in the preparation of Cu complexes with ethyl­enedi­amine, Hammond et al. (2001) started with CuBr or a CuBr/CuBr₂ mixture, and in both cases mixed-valence complexes were obtained. Liu et al. (2014) also prepared mixed-valence Cu^I,II or pure Cu^I complexes using CuBr₂ as a rea­ctant in the presence of isonicotinic acid. All mentioned compounds belong to the group of bromidocuprates(I). In our case, the reduction can be explained by the high reaction temperature of 493 K. According to Chambreau et al. (2012), decomposition of emimBr should occur at 585 K, but the process slowly starts at 473 K with CH₃Br and C₂H₅Br as the main products. Very likely these organic bromides act as in situ reducing agents. Chemically and thermodynamically, the appearance of (emim)₂[Cu₅Br₇] demonstrates a high stability of bromidocuprates(I) if Cu^I and Br^- ions are found in the same reaction mixture.

In the asymmetric unit of (emim)₂[Cu₅Br₇], there are three crystallographically distinct Cu^I atoms, five crystallographically unique Br atoms and two emim cations. The structure is based on penta­nuclear structural units, where five Cu^I atoms (one Cu1 in a special position with half-occupancy, two Cu2 and two Cu3) are tetra­hedrally coordinated, sharing tetra­hedron edges (Fig. 1).

Similar to Cu1, three of the five unique Br atoms (Br1, Br2 and Br3) also occupy special positions with half-occupancy and all are located on the mirror plane perpendicular to the b axis (site symmetry .m.). The penta­nuclear structural units are further joined in the sinusoidal {[Cu₅Br₇]^2-}_n chains running parallel to the crystallographic a axis. These chains can be inter­preted as the polymerization product of the [Cu₅Br₇]^2- unit, where Br atoms are located at the vertices of a very distorted penta­gonal bipyramid, forming a cage containing Cu^I ions in tetra­hedral holes (Fig. 2).

The {[Cu₅Br₇]^2-}_n chains show structural similarities to the three-dimensional [Cu₅Br₇]^2- framework of (C₅H₅NH₂)[Cu₅Br₇] (Chan et al., 1978) and the [Cu₅Br₇]^2- anions found in [(NCH₃)(C₄H₉)₃]₂[Cu₅Br₇] (Andersson & Jagner, 1988), as well as to the sinusoidal [Cu₅Br₇]^2- chain found in [Cu(H₂NCH₂CH₂NH₂)₂][Cu₅Br₇] (Hammond et al., 2001). In the {[Cu₅Br₇]^2-}_n chains found in [Cu(en)₂][Cu₅Br₇] (Hammond et al., 2001) and in the three-dimensional [Cu₅Br₇]^2- framework reported by Chan et al. (1978), the bipyramids were connected by additional face-sharing tetra­hedra formed by Br atoms. Subramanian & Hoffmann (1992) have examined the bonding between the bridging Br and Cu atoms in planar and nonplanar model systems and found an extraordinary structural richness in these halidocuprates(I) consisting of molecular or polymeric [Cu_xBr_y]^n- anions and various, often organic, counter-ions. The idealized polymeric [Cu₅Br₇]^2- anion is constructed from two µ₅-Br at the apices of a penta­gonal bipyramid and five µ₂-Br in its basis with tetra­hedral coordination around all five Cu atoms. They have found that Cu—Br distances increase from 2.227 to 2.421, 2.600 and 2.912 Å, as the Br goes from terminal to bridging two, four and five Cu atoms, respectively.

Although in (emim)₂[Cu₅Br₇] all Cu^I atoms are coordinated by four Br atoms in a distorted CuBr₄ tatrahedra, only one Br atom (Br2) is linked to all five Cu^I atoms (Fig. 2). Br3 is moved from another apex of the penta­gonal bipyramid and consequently linked to only two Cu3 atoms at distances of 2.3667 (10) Å, while another three Cu^I atoms are at the distances longer than 4 Å. Cu1 is coordinated by three µ₃-Br atoms (Br1 and two symmetry equivalents of Br4) and one µ₅-Br (Br2) atom. The coordination polyhedron of the Cu2 site is formed by two µ₂-Br atoms (Br3 and Br5), one µ₃-Br (Br4) and one µ₅-Br (Br2) atom. The geometry of the Cu3 site is completed by two µ₃-Br (Br1 and Br4) atoms, one µ₃-Br (Br4) and one µ₅-Br (Br2). The Cu—Br bond distances range from 2.3667 (10) to 2.6197 (13) Å, while the Br—Cu—Br angles vary from 94.65 (3) to 126.63 (4)° (Table 2). There is a very long Cu—Br outlier [Cu2—Br2 = 3.0283 (12) Å] whose contribution to the sum of the bond valances is only 6.7%. The described distortions convert ideal di-µ₅-bromido-penta-µ₂-bromido-penta­cuprate(I) into deformed m₅-bromido-tri-µ₃-bromido-tri-µ₂-bromido-πentacuprate(I).

The {[Cu₅Br₇]^2-}_n chains are crosslinked into a three-dimensional network by C—H···Br inter­actions, or hydrogen-like bonds, involving the emim cations (Fig. 3). They are established by imidazolium ring H atoms (H1 and H2), as well as by H atoms of the methyl­ene (H5A) and a methyl (H4B) group (Table 3).

Bond-valence calculations (Wills, 2010; Brown, 1996) show that the Cu—Br bond lengths are consistent with the presence of Cu^I and Br^-. The bond-valence sums for Cu^I are in the range 1.1–1.2 v.u. [1.155 (16) for Cu1, 1.083 (8) for Cu2 and 1.103 (10) for Cu3] and for Br are slightly undersaturated (Σν_ij are in the range 0.73–0.84 v.u.), indicating that all Br atoms act as hydrogen-bond acceptors.

Within the {[Cu₅Br₇]^2-}_n chains there are weak Cu^I···Cu^I inter­actions (Table 2), with Cu···Cu distances close to or slightly longer than the sum of the van der Waals radii (2.80 Å; Bondi, 1964). Within the chain units, Cu^I atoms make perfectly planar and slightly deformed penta­gons, which are further connected in a zigzag manner (Fig. 3). Closed-shell contacts between two Cu⁺ ions (d¹⁰ configuration) are quite frequent, well documented and usually discussed in term of cuprophilicity. Thus, Dinda & Samuelson (2012) showed that Cu^I···Cu^I inter­actions exist, but should be very weak, although involve some contribution of covalent bond. In this way, Cu^I···Cu^I inter­actions resemble features present in hydrogen bonds.

Related literature

For related literature, see: Andersson & Jagner (1988); Bondi (1964); Brown (1996); Chambreau et al. (2012); Chan et al. (1978); Chen & Wang (1996); Chen et al. (2011); Dinda & Samuelson (2012); Gao et al. (2010); Graham et al. (2000); Hammond et al. (2001); Hu et al. (2011); Ji et al. (2011); Karanović et al. (2011); Liu et al. (2014); Peng et al. (2010); Shao & Yu (2014); Subramanian & Hoffmann (1992); Wang et al. (2002); Wills (2010); Xin et al. (2013); Zeller et al. (2005); Zhang & Xiong (2012); Zhou et al. (2012).

Computing details

Data collection: COLLECT (Nonius, 2002); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski et al., 2003); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008) and WinGX (Farrugia, 2012); molecular graphics: Mercury (Macrae et al., 2006) and ATOMS (Dowty, 2000); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. (a) A view of the pentanuclear [Cu5Br7]^2- anion, (b) a polyhedral view of the same unit and (c) a displacement ellipsoid plot(50% probability level) of the emim cation showing the atomic numbering scheme. Dotted line in (a) indicate the position of the mirror plane and connects atoms in special positions. [Symmetry codes: (i) x, -y+1/2, z; (ii) x+1/2, -y+1/2, -z+1/2; (iii) x+1/2, y, -z+ 1/2.]
	Fig. 2. (a) The polymerization product of the [Cu5Br7]^2- anion, with Br atoms at the vertices of a very distorted pentagonal bipyramid and Cu atoms in distorted tetrahedral positions. (b) A topological view of the Cu···Cu contacts. Thick lines show Cu···Cu distances shorter than 3.9 Å, while dotted lines are used for longer distances.
	Fig. 3. Polyhedral representation of the {[Cu5Br7]^2-}n sinusoidal chains, projected approximately onto the (021) plane, showing short contacts between Br atoms and emim cations. For the sake of clarity, only some of the contacts are shown and only C and Br atoms involved in these contacts are labelled.

catena-Poly[bis(1-ethyl-3-methylimidazolium) [µ₅-bromido-tri-µ₃-bromido-tri-µ₂-bromido-pentacuprate(I)]]

Crystal data

(C6H11N2)2[Cu5Br7]	F(000) = 2048
Mr = 1099.41	Dx = 2.789 Mg m^−3
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
a = 12.736 (3) Å	µ = 14.69 mm^−1
b = 20.481 (4) Å	T = 293 K
c = 10.038 (2) Å	Prism, colorless
V = 2618.3 (9) Å^3	0.08 × 0.05 × 0.03 mm
Z = 4

Data collection

Nonius KappaCCD diffractometer	2307 reflections with I > 2σ(I)
Radiation source: Nonius KappaCCD	Rint = 0.055
ο and θ scans	θmax = 27.5°, θmin = 2.0°
Absorption correction: multi-scan (Otwinowski et al., 2003)	h = −16→15
Tmin = 0.418, Tmax = 0.644	k = −26→26
45708 measured reflections	l = −13→13
3085 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.032	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.069	H-atom parameters constrained
S = 1.02	w = 1/[σ^2(Fo^2) + (0.0229P)^2 + 9.4671P] where P = (Fo^2 + 2Fc^2)/3
3085 reflections	(Δ/σ)max = 0.001
133 parameters	Δρmax = 1.48 e Å^−3
0 restraints	Δρmin = −1.18 e Å^−3

Special details

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.82942 (8)	0.2500	0.26679 (10)	0.0514 (3)
Cu2	0.70539 (6)	0.17479 (4)	0.45799 (8)	0.0664 (2)
Cu3	0.50114 (6)	0.17821 (4)	0.33841 (9)	0.0655 (2)
Br1	0.89348 (5)	0.2500	0.01878 (7)	0.03839 (17)
Br2	0.63702 (5)	0.2500	0.21315 (7)	0.03377 (16)
Br3	0.70679 (6)	0.2500	0.63700 (7)	0.04681 (19)
Br4	0.88677 (4)	0.14820 (2)	0.36772 (5)	0.03742 (12)
Br5	0.58741 (4)	0.08417 (2)	0.42970 (5)	0.04333 (14)
N1	0.1721 (3)	0.4255 (2)	0.5215 (4)	0.0375 (9)
N2	0.0522 (3)	0.39696 (19)	0.6606 (4)	0.0381 (9)
C1	0.1105 (4)	0.3776 (2)	0.5599 (5)	0.0374 (11)
H1	0.1084	0.3363	0.5217	0.045*
C2	0.1533 (5)	0.4781 (3)	0.6006 (6)	0.0518 (14)
H2	0.1861	0.5186	0.5956	0.062*
C3	0.0782 (4)	0.4605 (3)	0.6875 (6)	0.0529 (15)
H3	0.0491	0.4866	0.7537	0.063*
C4	0.2476 (5)	0.4232 (3)	0.4112 (5)	0.0555 (15)
H4A	0.2827	0.4645	0.4039	0.083*
H4B	0.2112	0.4139	0.3296	0.083*
H4C	0.2983	0.3895	0.4279	0.083*
C5	−0.0265 (4)	0.3568 (3)	0.7296 (6)	0.0482 (13)
H5A	0.0024	0.3415	0.8134	0.058*
H5B	−0.0428	0.3189	0.6755	0.058*
C6	−0.1255 (4)	0.3946 (3)	0.7561 (7)	0.0652 (17)
H6A	−0.1752	0.3671	0.8008	0.098*
H6B	−0.1547	0.4093	0.6732	0.098*
H6C	−0.1097	0.4317	0.8112	0.098*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0529 (6)	0.0410 (5)	0.0602 (6)	0.000	−0.0027 (5)	0.000
Cu2	0.0635 (5)	0.0618 (5)	0.0739 (5)	−0.0127 (4)	0.0050 (4)	−0.0171 (4)
Cu3	0.0664 (5)	0.0577 (5)	0.0725 (5)	0.0162 (4)	0.0016 (4)	0.0098 (4)
Br1	0.0397 (4)	0.0418 (4)	0.0337 (4)	0.000	0.0018 (3)	0.000
Br2	0.0264 (3)	0.0341 (3)	0.0409 (4)	0.000	0.0006 (3)	0.000
Br3	0.0543 (5)	0.0449 (4)	0.0412 (4)	0.000	0.0002 (4)	0.000
Br4	0.0330 (2)	0.0374 (3)	0.0419 (3)	0.0012 (2)	0.0011 (2)	0.0088 (2)
Br5	0.0417 (3)	0.0343 (3)	0.0540 (3)	0.0001 (2)	0.0007 (2)	0.0038 (2)
N1	0.037 (2)	0.041 (2)	0.035 (2)	0.0030 (18)	0.0002 (17)	−0.0067 (19)
N2	0.041 (2)	0.035 (2)	0.038 (2)	−0.0013 (18)	0.0010 (18)	−0.0056 (18)
C1	0.040 (3)	0.032 (2)	0.039 (3)	0.001 (2)	−0.002 (2)	−0.007 (2)
C2	0.060 (4)	0.033 (3)	0.062 (4)	−0.006 (3)	0.014 (3)	−0.014 (3)
C3	0.062 (4)	0.039 (3)	0.058 (3)	−0.008 (3)	0.018 (3)	−0.023 (3)
C4	0.058 (4)	0.066 (4)	0.043 (3)	0.000 (3)	0.009 (3)	−0.006 (3)
C5	0.049 (3)	0.050 (3)	0.046 (3)	−0.009 (3)	0.003 (3)	0.006 (3)
C6	0.054 (4)	0.073 (4)	0.068 (4)	−0.010 (3)	0.017 (3)	−0.013 (4)

Geometric parameters (Å, º)

Cu1—Br4	2.4304 (8)	N1—C1	1.314 (6)
Cu1—Br4^i	2.4304 (8)	N1—C2	1.359 (6)
Cu1—Br2	2.5089 (13)	N1—C4	1.468 (6)
Cu1—Br1	2.6197 (13)	N2—C1	1.314 (6)
Cu1—Cu3^ii	2.8390 (12)	N2—C3	1.369 (6)
Cu1—Cu3^iii	2.8390 (12)	N2—C5	1.470 (6)
Cu1—Cu2^i	2.9243 (13)	C1—Br4^v	3.482 (5)
Cu1—Cu2	2.9243 (13)	C1—H1	0.9300
Cu2—Br3	2.3667 (10)	C2—C3	1.344 (8)
Cu2—Br5	2.4049 (10)	C2—Br4^vi	3.534 (5)
Cu2—Br4	2.5405 (10)	C2—H2	0.9300
Cu2—Br2	3.0283 (12)	C3—Br4^vi	3.910 (5)
Cu2—Cu3	2.8659 (12)	C3—Br5^vii	3.952 (6)
Cu2—Cu2^i	3.0805 (17)	C3—H3	0.9300
Cu3—Br5	2.3992 (9)	C4—Br4^viii	3.622 (5)
Cu3—Br1^iv	2.4692 (10)	C4—Cu3^i	3.908 (6)
Cu3—Br2	2.5958 (10)	C4—Br5^viii	3.987 (6)
Cu3—Br4^iv	2.6039 (10)	C4—H4A	0.9600
Cu3—Cu1^iv	2.8390 (12)	C4—H4B	0.9600
Cu3—Cu3^i	2.9407 (17)	C4—H4C	0.9600
Br1—Cu3^ii	2.4692 (10)	C5—C6	1.504 (8)
Br1—Cu3^iii	2.4692 (10)	C5—H5A	0.9700
Br2—Cu3^i	2.5958 (10)	C5—H5B	0.9700
Br2—Cu2^i	3.0283 (12)	C6—H6A	0.9600
Br3—Cu2^i	2.3667 (10)	C6—H6B	0.9600
Br4—Cu3^iii	2.6039 (10)	C6—H6C	0.9600
Br4—Cu1—Br4^i	118.15 (5)	Br2—Cu3—Br4^viii	62.06 (2)
Br4—Cu1—Br2	112.52 (3)	Br4^iv—Cu3—Br4^viii	68.21 (2)
Br4^i—Cu1—Br2	112.52 (3)	Cu2^i—Cu3—Br4^viii	75.86 (2)
Br4—Cu1—Br1	107.61 (3)	Br3—Cu3—Br4^viii	104.99 (2)
Br4^i—Cu1—Br1	107.61 (3)	Br5—Cu3—Br2^iv	135.71 (3)
Br2—Cu1—Br1	95.75 (4)	Br2—Cu3—Br2^iv	114.24 (3)
Br4—Cu1—Br2^iii	71.24 (3)	Br4^iv—Cu3—Br2^iv	57.09 (2)
Br4^i—Cu1—Br2^iii	71.24 (3)	Br3—Cu3—Br2^iv	123.76 (2)
Br2—Cu1—Br2^iii	170.55 (4)	Br4^viii—Cu3—Br2^iv	52.309 (11)
Br1—Cu1—Br2^iii	74.80 (3)	C1—N1—C2	108.4 (4)
Cu3^ii—Cu1—Br2^iii	41.39 (2)	C1—N1—C4	126.0 (4)
Cu3^iii—Cu1—Br2^iii	41.39 (2)	C2—N1—C4	125.6 (5)
Cu2^i—Cu1—Br2^iii	120.38 (3)	C1—N2—C3	107.5 (4)
Cu2—Cu1—Br2^iii	120.38 (3)	C1—N2—C5	125.3 (4)
Br3—Cu2—Br5	126.63 (4)	C3—N2—C5	127.1 (4)
Br3—Cu2—Br4	113.80 (4)	N1—C1—N2	109.7 (4)
Br5—Cu2—Br4	111.14 (4)	N1—C1—H1	125.1
Br3—Cu2—Br2	106.70 (4)	N2—C1—H1	125.1
Br5—Cu2—Br2	96.72 (3)	C3—C2—N1	106.9 (5)
Br4—Cu2—Br2	94.65 (3)	C3—C2—H2	126.5
Br3—Cu2—Br4^i	67.39 (3)	N1—C2—H2	126.5
Br5—Cu2—Br4^i	160.23 (4)	C2—C3—N2	107.4 (5)
Br4—Cu2—Br4^i	67.99 (3)	C2—C3—H3	126.3
Br2—Cu2—Br4^i	64.16 (2)	N2—C3—H3	126.3
Br5—Cu2—Br5^i	123.30 (3)	N1—C4—H4A	109.5
Br4—Cu2—Br5^i	116.72 (3)	N1—C4—H4B	109.5
Br2—Cu2—Br5^i	52.118 (17)	H4A—C4—H4B	109.5
Br1^iv—Cu2—Br5^i	52.230 (11)	N1—C4—H4C	109.5
Br4^i—Cu2—Br5^i	49.708 (16)	H4A—C4—H4C	109.5
Cu3^iii—Cu2—Br5^i	100.380 (19)	H4B—C4—H4C	109.5
Br3—Cu2—Br4^iv	123.18 (3)	N2—C5—C6	111.5 (4)
Br5—Cu2—Br4^iv	50.37 (2)	N2—C5—H5A	109.3
Br4—Cu2—Br4^iv	117.35 (3)	C6—C5—H5A	109.3
Br4^i—Cu2—Br4^iv	111.37 (2)	N2—C5—H5B	109.3
Br5^i—Cu2—Br4^iv	80.783 (16)	C6—C5—H5B	109.3
Br5—Cu3—Br2	109.53 (4)	H5A—C5—H5B	108.0
Br5—Cu3—Br4^iv	111.73 (4)	C5—C6—H6A	109.5
Br2—Cu3—Br4^iv	96.99 (4)	C5—C6—H6B	109.5
Br5—Cu3—Br3	74.08 (3)	H6A—C6—H6B	109.5
Br2—Cu3—Br3	74.59 (3)	C5—C6—H6C	109.5
Br4^iv—Cu3—Br3	171.24 (3)	H6A—C6—H6C	109.5
Br5—Cu3—Br4^viii	171.10 (3)	H6B—C6—H6C	109.5

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1···Br2^iv	0.93	2.97	3.803 (5)	150
C2—H2···Br4^vi	0.93	2.84	3.534 (5)	133
C4—H4B···Br5^viii	0.96	3.04	3.987 (6)	168
C5—H5A···Br1^ix	0.97	3.11	3.774 (5)	127
C6—H6A···Br3^x	0.96	3.27	3.842 (6)	120

Symmetry codes: (iv) x−1/2, y, −z+1/2; (vi) −x+1, y+1/2, −z+1; (viii) x−1/2, −y+1/2, −z+1/2; (ix) x−1, y, z+1; (x) x−1, y, z.