Anion...π inter­actions in copper(I) chloride and bromide coordination polymers bearing 1,4-bis(pyridazin-4-yl)benzene ligands

In poly[[μ₄-1,4-bis­(pyridazin-4-yl)benzene-1:2:3:4κ⁴N¹:N²:N^1′:N^2′]di-μ₂-chlorido-dicopper(I)], [Cu₂Cl₂(C₁₄H₁₀N₄)]_n, (I), and its isomorphous bromide analogue, [Cu₂Br₂(C₁₄H₁₀N₄)]_n, (II), the organic ligand is situated across a centre of inversion. The Cu^I cations adopt a distorted tetra­hedral [CuN₂X₂] [X = Cl in (I) or Br in (II)] environment [Cu—N = 2.0183 (14)–2.0936 (14) Å; Cu—Cl = 2.2686 (6) and 2.4241 (5) Å; Cu—Br = 2.4002 (6) and 2.5284 (5) Å] and the primary coordination motif consists of cuprohalogenide chains accommodating μ-pyridazine groups. The organic ligands are tetra­dentate and link the inorganic chains into corrugated layers. Their packing is influenced by inter­layer anion...π inter­actions [Cl...π = 3.540 (2) Å and Br...π = 3.593 (2) Å] with the electron-deficient pyridazine rings. This kind of inter­action precludes the characteristic slipped π–π stacking and close parallel alignment of the organic tectons; it may be involved as a structure-defining factor for coordination layers based upon lengthy polyaromatic linkers.

S1. Introduction

Non-covalent inter­actions involving anions and π-acidic aromatic ligands are important factors for the structure and functional properties of coordination polymers (Frontera, 2013). In this way, complexes based upon geometrically rigid polyaromatic ligands reveal an ability for selective binding of anions (Schottel et al., 2006; Wenzel et al., 2010). Multiple anion···π inter­actions are also possible in the case of condensed π-acidic heteroaromatic receptors (Gural'skiy et al., 2006). Although different kinds of electron-deficient hetero­aryl rings are applicable in this area (for example, 1,3,5-triazines and 1,2,4,5-tetra­zines), a special potential for generating coordination polymers and sustaining anion···π inter­actions could be postulated for pyridazine species. They combine such inputs as π-acidity of the hetero­aryl frame and a relatively good donor ability towards metal ions. Pyridazines act as acceptors of d-orbital electron density in metal–ligand backbonding due to the relatively low energy of π^* orbitals, and thereby possess an enhanced affinity for d¹⁰ cations such as Cu⁺ and Ag⁺ (Munakata et al., 1999). Secondly, unlike 1,3,5-triazine ligands, the 1,2-diazine structure of pyridazines is suited to connecting closely separated metal ions, and such pyridazine bridges may be complementary with a variety of short-distance anionic inorganic links (µ-halogenide or µ-hydroxide bridges, etc.) for the construction of neutral coordination frameworks. The ability of pyridazines to take part in anion···π inter­actions is also prominent (Domasevitch, Gural'skiy et al., 2007 or Domasevitch, Solntsev et al., 2007 ?).

Within crystal structures, these forces commonly influence the orientation of non-coordinated counteranions, but they may also be important when considering inter­actions between integral parts of the framework. In particular, anion···π inter­actions between pyridazine and coordinated halogenide anions may contribute significantly to the packing of coordination layers, which could be anti­cipated for the copper(I) halogenide series. In this context, we have prepared two new complexes with the extended polyaromatic N-donor tetra­dentate ligand 1,4-di(pyridazin-4-yl)benzene, namely the copper(I) chloride compound, (I), and the copper(I) bromide compound, (II), and report their structures here.

Multifaceted inorganic substructures of Cu^I halogenide coordination polymers exist as various Cu₂X₂ dimers, Cu₄X₄ tetra­mers and (CuX)_n polymers that attract considerable attention for extending the framework by means of organic ligands (Peng et al., 2010). They are important for obtaining new types of thermally stable solid-state materials, which possess fascinating electroluminescent properties (Jeß et al., 2007; Pospíšil et al., 2011), and this adds an extra strand of inter­est to the present work. [Added text OK? Was this aspect tested for these compounds?]

S2. Experimental

S2.1. Synthesis and crystallization

The 1,4-bi(pyridazin-4-yl)benzene ligand was prepared according to the reported procedure (Degtyarenko et al., 2008). For the synthesis of (I), a solution of CuCl (9.95 mg, 0.10 mmol) in dry aceto­nitrile (2 ml) was layered over a solution of the ligand (11.7 mg, 0.05 mmol) in chloro­form (2 ml). A mixture of aceto­nitrile and chloro­form (1:1 v/v; 6 ml) was introduced as an inter­mediate layer. Dark-red crystals of complex (I) grew on the walls of the tube as the solutions slowly inter­diffused in a period of 9 d (yield 80%). Complex (II) (dark-red prisms, yield 80%) was prepared similarly, starting with CuBr (14.4 mg, 0.10 mmol) and the ligand (11.7 mg, 0.05 mmol).

Elemental analysis, calculated for (I): C 38.90, H 2.33, N 12.97%; found: C 38.75, H 2.27, N 13.11%. Elemental analysis, calculated for (II): C 32.26, H 1.93, N 10.75%; found: C 32.41, H 1.97, N 10.97%.

S2.2. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. All H atoms were located from difference maps and then refined as riding, with the angles constrained, C—H distances constrained to 0.94 Å and U_iso(H) = 1.2U_eq(parent C atom).

S3. Results and discussion

In the isomorphous complexes (I) and (II), the organic ligands reside across a centre of inversion (Fig. 1). The Cu^I cations adopt a distorted tetra­hedral coordination that is completed by two pyridazine N atoms [Cu—N = 2.0183 (14)–2.0936 (14) Å] and two chloride (bromide) anions. Alternatively, the polyhedra might be regarded as distorted trigonal pyramids, with the relatively distal N1 atom (Tables 2 and 3) at the apex. However, the deviations of the Cu^I cations from the basal planes of such pyramids are significant [(I): 0.5415 (6) Å; (II): 0.6215 (10) Å]. The distortions of the coordination polyhedra may be best evaluated by considering the parameters of tetra­hedral character [THC, developed for triorganoboron compounds; Toyota & Öki, 1992], which are 57.0 and 68.9 for (I) and (II), respectively, nearly inter­mediate between the values of 100 for tetra­hedral and 0 for trigonal pyramidal geometries. The recently introduced four-coordinate geometry index, τ₄ (Yang et al., 2007), is less applicable in the present case, although it does actually indicate ideal trigonal pyramidal geometries for both compounds [0.86 for (I); 0.88 for (II)].

The chloride (bromide) bridges link the Cu^I anions, thus producing inorganic cuprohalogenide chains running along the c direction, in which each pair of adjacent metal ions is additionally bridged by pyridazine (Fig. 2). This results in very similar Cu···Cu separations along the chain [(I): 3.3863 (4) Å; (II): 3.4245 (3) Å], despite the fact that the Cu—Br distances [2.4002 (6) and 2.5284 (5) Å] are longer than the Cu—Cl ones [2.2686 (6) and 2.4241 (5) Å].

The bipyridazine ligands are tetra­dentate and connect two cuprohalogenide chains. Thus, the common motif of the structures comprises one-dimensional inorganic (CuX)_n subtopologies inter­linked by the organic tectons. These extend the structure in a second dimension, giving rise to corrugated layers which are parallel to the bc plane (Fig. 2). This morphology is similar to that adopted by the Cu^I chloride and bromide complexes with the simpler ligand 4,4'-bipyridazine (Domasevitch, Gural'skiy et al., 2007) and the compounds actually represent an isoreticular series. However, the related complexes of the parent unsubstituted pyridazine are completely different, while incorporating discrete rhombus (CuX)₂ cores linked by double organic bridges (Näther & Jeß, 2003). Comparable chain-like (CuX)_n (X = Cl, Br or I) motifs are common for complexes of polycondensed pyridazines (Solntsev et al., 2004; Domasevitch et al., 2012), which feature rather a 4₁ helical alignment of the ligands coordinated along the inorganic chains. In the present cases, the configuration of the chains is different and the repeat unit of the motif in (I) and (II) comprises only two [Cu₂X(pyridazine)] fragments (sharing Cu vertices). This results in the formation of two-dimensional networks, instead of the tetra­gonal framework structures reported by Solntsev et al. (2004). That the halogenide anions of the single inorganic chain are situated on the same side of the layer suggests their accessibility to secondary non-covalent inter­actions, which occur between the successive layers of the present complexes (Table 4).

In this way, each coordinated halogenide anion establishes contacts with the C and N atoms of the pyridazine ring in the adjacent layer [shortest distances X···C2^iv = 3.4058 (17) Å (I); 3.458 (3) Å (II); symmetry code: 1 + x, 1/2 - y, 1/2 + z], namely the anion···π inter­action (Fig. 3). In spite of the relatively distant location of the negatively polarized ions from the π-systems, these bonding contacts may be considered as relatively directional. Thus, atom Cl1 is situated nearly above the pyridazine ring centroid (Cg), with an angle between the Cl1···Cg^iv axis and the plane of the ring of 72.90 (2)° (Table 4). It is not surprising that the present Cl1···π contacts are slightly longer than those found for the most electron-deficient hetero­aryl rings of 1,2,4,5-tetra­zine [3.300 (2) Å; Gural'skiy et al., 2009] and 1,3,5-triazine [3.200 (2) Å; Mascal et al., 2002]. The corresponding parameters for the structure of (II) (Table 4) are consistent with the values for Br···π inter­actions recently reported in the literature, with the Br1···Cg^iv separation [3.593 (2) Å] approaching the mean Br···π separation for bromide–pyridine systems [3.561 (3) Å; Mooibroek et al., 2008]. However, documented cases of such bonding with the soft Br atom are very rare (Mooibroek et al., 2008).

The present examples provide the first observation of an obvious anion···π bonding among the complexes with the 1,4-di(pyridazin-4-yl)benzene ligand, although this type of inter­action is typical for the simpler 4,4'-bipyridazine ligand (Domasevitch, Solntsev et al., 2007). This may be attributed to a greater ability for slipped aromatic π–π inter­actions (Janiak, 2000), which dominate the parallel packing of lengthy polyaromatic species. Such characteristic alignment (either double or triple π–π inter­actions are possible between adjacent molecules) makes the pyridazine-π sites inaccessible for weak inter­actions with anions, as occurs in coordination compounds of 1,4-di(pyridazin-4-yl)benzene (Degtyarenko et al., 2008; Degtyarenko & Domasevitch, 2013). Notably in the present cases, these close aromatic π–π inter­actions are eliminated completely, in favour of anion···π stacking. This suggests a comparable significance of both types of inter­action as competitive non-covalent weak forces for structures with extended polyaromatic ligands.

As a result, these close anion···π contacts facilitate the holding together of adjacent layers, with the formation of a three-dimensional array (Fig. 4). Additional inter­actions involve very weak inter­layer C7—H7···Cl1^v (Br1^v) hydrogen bonds [symmetry code: (v) -x, -1/2 + y, 1/2 - z], with angles at the H atoms of 142° in (I) and 141° in (II) (Table 4). There are no such inter­actions utilizing pyridazine CH groups (as the most polarized and acidic), while those noted above are observed for phenyl­ene rings only. Such a bonding scheme is slightly unusual. It is likely influenced by the mode of packing of the coordination layers, which is favorable for generating close inter­layer anion···π inter­actions.

In brief, the 1,4-bi(pyridazin-4-yl)benzene tecton may be regarded as an efficient tetra­dentate ligand for Cu^I cations, with a special potential for different kinds of secondary supra­molecular inter­action. Weak anion···π stackings could be relevant for the structures of these coordination polymers, while mediating close inter­layer inter­actions and controlling the alignment of the extended polyaromatic ligands.

Related literature

For related literature, see: Degtyarenko & Domasevitch (2013); Degtyarenko et al. (2008); Domasevitch et al. (2012); Domasevitch, Gural'skiy, Solntsev, Rusanov, Krautscheid, Howard & Chernega (2007); Domasevitch, Solntsev, Gural'skiy, Krautscheid, Rusanov, Chernega & Howard (2007); Frontera (2013); Gural'skiy, Escudero, Frontera, Solntsev, Rusanov, Chernega, Krautscheid & Domasevitch (2009); Gural'skiy, Solntsev, Krautscheid & Domasevitch (2006); Janiak (2000); Jeß, Taborsky, Pospíšil & Näther (2007); Mascal et al. (2002); Mooibroek et al. (2008); Munakata et al. (1999); Näther & Jeß (2003); Peng et al. (2010); Pospíšil et al. (2011); Schottel et al. (2006); Solntsev et al. (2004); Toyota & Öki (1992); Wenzel et al. (2010); Yang et al. (2007).

Computing details

For both compounds, data collection: IPDS Software (Stoe & Cie, 2000); cell refinement: IPDS Software (Stoe & Cie, 2000); data reduction: IPDS Software (Stoe & Cie, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

Fig. 1. The structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. N and Cl atoms are shaded grey. In the isomorphous bromide analogue, (II), the atom-labelling scheme is identical, with atom Br1 instead of Cl1. [Symmetry codes: (i) -1 - x, -y, -1 - z; (ii) x, 1/2 - y, -1/2 + z; (iii) x, 1/2 - y, 1/2 + z.]

Fig. 2. The coordination layer formed by the cuprochloride chains (indicated by grey strips) and tetradentate organic linkers of (I). H atoms have been omitted for clarity and N and Cl atoms are shaded grey. [Symmetry code: (iii) x, 1/2 - y, 1/2 + z.]

Fig. 3. A fragment of the structure of (I), showing anion···π interactions (indicated by dashed lines) between adjacent [CuCl(pyridazine)] chains. H atoms have been omitted for clarity. [Symmetry code: (ii) x, 1/2 - y, -1/2 + z.]

Fig. 4. A projection of the structure of (I) on the ab plane, showing the tight packing of the coordination layers (which are orthogonal to the drawing plane) dominated by anion···π interactions. The complementary weak C—H···Cl hydrogen bond is also shown, and N and Cl atoms are shaded grey.

(I) poly[di-µ-chlorido-µ₄-[1,4-bis(pyridazin-4-yl)benzene- -1:2:3:4κ⁴N¹:N²:N^1':N^2']dicopper(I)]

Crystal data

[Cu2Cl2(C14H10N4)]	F(000) = 428
Mr = 432.24	Dx = 1.965 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.0696 (8) Å	Cell parameters from 8000 reflections
b = 17.2872 (16) Å	θ = 2.4–27.9°
c = 6.6046 (7) Å	µ = 3.28 mm^−1
β = 115.198 (10)°	T = 213 K
V = 730.36 (13) Å^3	Prism, red
Z = 2	0.24 × 0.20 × 0.17 mm

Data collection

Stoe IPDS diffractometer	1753 independent reflections
Radiation source: fine-focus sealed tube	1440 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
φ oscillation scans	θmax = 27.9°, θmin = 2.4°
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)]	h = −9→9
Tmin = 0.507, Tmax = 0.606	k = −20→22
6296 measured reflections	l = −8→8

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)] = 0.023	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.053	H-atom parameters constrained
S = 0.92	w = 1/[σ^2(Fo^2) + (0.0362P)^2] where P = (Fo^2 + 2Fc^2)/3
1753 reflections	(Δ/σ)max = 0.001
100 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.38 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	0.16852 (4)	0.271681 (12)	0.06728 (3)	0.03023 (8)
Cl1	0.36545 (8)	0.30907 (3)	0.42540 (7)	0.03873 (13)
N1	−0.0301 (2)	0.18754 (8)	0.0991 (2)	0.0272 (3)
N2	0.0013 (2)	0.16009 (8)	0.3033 (2)	0.0240 (3)
C1	−0.1505 (3)	0.14859 (10)	−0.0833 (3)	0.0286 (4)
H1	−0.1740	0.1704	−0.2224	0.034*
C2	−0.2459 (3)	0.07678 (9)	−0.0845 (3)	0.0235 (3)
C3	−0.2049 (3)	0.04779 (10)	0.1263 (3)	0.0272 (4)
H3	−0.2576	−0.0006	0.1425	0.033*
C4	−0.0841 (3)	0.09196 (10)	0.3128 (3)	0.0279 (4)
H4	−0.0610	0.0727	0.4545	0.033*
C5	−0.4882 (3)	0.08052 (9)	−0.4929 (3)	0.0270 (4)
H5	−0.4810	0.1348	−0.4886	0.032*
C6	−0.3763 (3)	0.03783 (9)	−0.2977 (3)	0.0233 (3)
C7	−0.3907 (3)	−0.04332 (9)	−0.3076 (3)	0.0264 (3)
H7	−0.3174	−0.0727	−0.1777	0.032*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.03694 (15)	0.02870 (12)	0.02224 (12)	−0.00349 (9)	0.00990 (10)	0.00161 (8)
Cl1	0.0461 (3)	0.0450 (3)	0.0262 (2)	−0.0212 (2)	0.0164 (2)	−0.01082 (19)
N1	0.0308 (8)	0.0263 (7)	0.0210 (7)	−0.0040 (6)	0.0078 (7)	0.0005 (6)
N2	0.0260 (8)	0.0233 (6)	0.0205 (7)	−0.0001 (5)	0.0077 (6)	−0.0008 (5)
C1	0.0335 (11)	0.0288 (8)	0.0211 (8)	−0.0073 (7)	0.0093 (8)	−0.0001 (7)
C2	0.0219 (9)	0.0237 (8)	0.0236 (8)	0.0000 (6)	0.0083 (8)	−0.0015 (6)
C3	0.0298 (10)	0.0232 (8)	0.0275 (8)	−0.0036 (7)	0.0111 (8)	0.0006 (6)
C4	0.0328 (11)	0.0273 (8)	0.0238 (8)	−0.0009 (7)	0.0124 (8)	0.0026 (7)
C5	0.0279 (10)	0.0204 (7)	0.0291 (9)	−0.0013 (7)	0.0086 (8)	−0.0010 (6)
C6	0.0210 (9)	0.0220 (7)	0.0260 (8)	−0.0019 (6)	0.0092 (7)	−0.0023 (6)
C7	0.0271 (10)	0.0220 (7)	0.0253 (8)	0.0003 (7)	0.0067 (8)	0.0021 (6)

Geometric parameters (Å, º)

Cu1—N2^i	2.0183 (14)	C2—C6	1.477 (2)
Cu1—N1	2.0936 (14)	C3—C4	1.391 (3)
Cu1—Cl1	2.2686 (6)	C3—H3	0.9400
Cu1—Cl1^i	2.4241 (5)	C4—H4	0.9400
N1—C1	1.325 (2)	C5—C7^ii	1.386 (2)
N1—N2	1.3557 (19)	C5—C6	1.402 (2)
N2—C4	1.337 (2)	C5—H5	0.9400
C1—C2	1.411 (2)	C6—C7	1.406 (2)
C1—H1	0.9400	C7—C5^ii	1.386 (2)
C2—C3	1.389 (2)	C7—H7	0.9400
N2^i—Cu1—N1	108.75 (6)	C3—C2—C6	124.77 (15)
N2^i—Cu1—Cl1	127.44 (4)	C1—C2—C6	120.60 (14)
N1—Cu1—Cl1	103.49 (4)	C2—C3—C4	118.48 (15)
N2^i—Cu1—Cl1^i	102.96 (4)	C2—C3—H3	120.8
N1—Cu1—Cl1^i	99.14 (4)	C4—C3—H3	120.8
Cl1—Cu1—Cl1^i	111.63 (3)	N2—C4—C3	124.16 (15)
Cu1—Cl1—Cu1^iii	92.316 (19)	N2—C4—H4	117.9
C1—N1—N2	119.76 (14)	C3—C4—H4	117.9
C1—N1—Cu1	117.38 (10)	C7^ii—C5—C6	120.55 (14)
N2—N1—Cu1	120.70 (11)	C7^ii—C5—H5	119.7
C4—N2—N1	117.98 (14)	C6—C5—H5	119.7
C4—N2—Cu1^iii	125.77 (11)	C5—C6—C7	118.76 (15)
N1—N2—Cu1^iii	116.24 (10)	C5—C6—C2	121.06 (14)
N1—C1—C2	124.89 (15)	C7—C6—C2	120.18 (15)
N1—C1—H1	117.6	C5^ii—C7—C6	120.68 (16)
C2—C1—H1	117.6	C5^ii—C7—H7	119.7
C3—C2—C1	114.63 (15)	C6—C7—H7	119.7
N2^i—Cu1—Cl1—Cu1^iii	122.32 (5)	N1—C1—C2—C3	0.0 (3)
N1—Cu1—Cl1—Cu1^iii	−4.55 (5)	N1—C1—C2—C6	−179.57 (16)
Cl1^i—Cu1—Cl1—Cu1^iii	−110.27 (3)	C1—C2—C3—C4	2.3 (2)
N2^i—Cu1—N1—C1	49.18 (15)	C6—C2—C3—C4	−178.12 (16)
Cl1—Cu1—N1—C1	−172.95 (13)	N1—N2—C4—C3	−0.7 (3)
Cl1^i—Cu1—N1—C1	−57.96 (14)	Cu1^iii—N2—C4—C3	177.57 (13)
N2^i—Cu1—N1—N2	−147.56 (12)	C2—C3—C4—N2	−2.1 (3)
Cl1—Cu1—N1—N2	−9.69 (13)	C7^ii—C5—C6—C7	−0.5 (3)
Cl1^i—Cu1—N1—N2	105.31 (12)	C7^ii—C5—C6—C2	179.68 (15)
C1—N1—N2—C4	3.1 (2)	C3—C2—C6—C5	150.60 (17)
Cu1—N1—N2—C4	−159.80 (12)	C1—C2—C6—C5	−29.8 (2)
C1—N1—N2—Cu1^iii	−175.36 (13)	C3—C2—C6—C7	−29.2 (2)
Cu1—N1—N2—Cu1^iii	21.77 (16)	C1—C2—C6—C7	150.37 (17)
N2—N1—C1—C2	−2.8 (3)	C5—C6—C7—C5^ii	0.5 (3)
Cu1—N1—C1—C2	160.60 (14)	C2—C6—C7—C5^ii	−179.68 (15)

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

(II) poly[di-µ-bromido-µ₄-[1,4-bis(pyridazin-4-yl)benzene- -1:2:3:4κ⁴N¹:N²:N^1':N^2']dicopper(I)]

Crystal data

[Cu2Br2(C14H10N4)]	F(000) = 500
Mr = 521.16	Dx = 2.241 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.1998 (6) Å	Cell parameters from 8000 reflections
b = 17.7305 (13) Å	θ = 3.1–27.9°
c = 6.7135 (6) Å	µ = 7.92 mm^−1
β = 115.668 (9)°	T = 213 K
V = 772.45 (11) Å^3	Prism, red
Z = 2	0.22 × 0.20 × 0.18 mm

Data collection

Stoe IPDS diffractometer	1838 independent reflections
Radiation source: fine-focus sealed tube	1511 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.040
φ oscillation scans	θmax = 27.9°, θmin = 3.1°
Absorption correction: numerical [X-RED (Stoe & Cie, 2001) and X-SHAPE (Stoe & Cie, 1999)]	h = −9→9
Tmin = 0.275, Tmax = 0.330	k = −23→23
6771 measured reflections	l = −8→8

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)] = 0.031	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.074	H-atom parameters constrained
S = 0.93	w = 1/[σ^2(Fo^2) + (0.0503P)^2] where P = (Fo^2 + 2Fc^2)/3
1838 reflections	(Δ/σ)max = 0.001
100 parameters	Δρmax = 0.71 e Å^−3
0 restraints	Δρmin = −0.91 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	0.14544 (6)	0.26912 (2)	0.04410 (6)	0.03144 (12)
Br1	0.35289 (6)	0.31465 (2)	0.41093 (6)	0.04184 (12)
N1	−0.0435 (4)	0.18719 (13)	0.0823 (4)	0.0285 (5)
N2	−0.0104 (4)	0.16187 (13)	0.2847 (4)	0.0261 (5)
C1	−0.1593 (5)	0.14781 (17)	−0.0962 (5)	0.0310 (6)
H1	−0.1835	0.1683	−0.2344	0.037*
C2	−0.2491 (5)	0.07730 (15)	−0.0935 (5)	0.0267 (6)
C3	−0.2059 (5)	0.05016 (16)	0.1161 (5)	0.0312 (6)
H3	−0.2545	0.0026	0.1340	0.037*
C4	−0.0894 (5)	0.09447 (16)	0.2994 (5)	0.0314 (6)
H4	−0.0649	0.0764	0.4403	0.038*
C5	−0.4949 (5)	0.07840 (15)	−0.4945 (5)	0.0307 (6)
H5	−0.4922	0.1314	−0.4919	0.037*
C6	−0.3775 (5)	0.03817 (15)	−0.3015 (5)	0.0275 (6)
C7	−0.3848 (5)	−0.04119 (16)	−0.3107 (5)	0.0299 (6)
H7	−0.3069	−0.0693	−0.1826	0.036*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0378 (2)	0.02572 (19)	0.0306 (2)	−0.00262 (15)	0.01458 (17)	0.00155 (14)
Br1	0.0489 (2)	0.0454 (2)	0.0357 (2)	−0.02296 (15)	0.02256 (17)	−0.01230 (14)
N1	0.0325 (15)	0.0238 (12)	0.0293 (13)	−0.0060 (10)	0.0135 (11)	−0.0011 (9)
N2	0.0276 (13)	0.0229 (11)	0.0276 (12)	−0.0007 (9)	0.0117 (10)	−0.0017 (9)
C1	0.0350 (18)	0.0273 (14)	0.0297 (15)	−0.0065 (12)	0.0130 (13)	0.0008 (12)
C2	0.0235 (15)	0.0224 (12)	0.0355 (16)	−0.0003 (11)	0.0140 (13)	−0.0029 (11)
C3	0.0314 (17)	0.0253 (13)	0.0365 (17)	−0.0041 (12)	0.0142 (14)	−0.0014 (12)
C4	0.0376 (18)	0.0267 (14)	0.0299 (16)	−0.0018 (12)	0.0145 (14)	0.0033 (11)
C5	0.0338 (17)	0.0180 (12)	0.0397 (17)	−0.0008 (11)	0.0153 (14)	−0.0019 (12)
C6	0.0279 (16)	0.0230 (13)	0.0336 (16)	−0.0023 (11)	0.0153 (13)	−0.0037 (11)
C7	0.0300 (17)	0.0222 (13)	0.0343 (16)	−0.0002 (11)	0.0109 (13)	0.0003 (11)

Geometric parameters (Å, º)

Cu1—N2^i	2.024 (3)	C2—C6	1.473 (4)
Cu1—N1	2.080 (2)	C3—C4	1.393 (4)
Cu1—Br1	2.4002 (6)	C3—H3	0.9400
Cu1—Br1^i	2.5284 (5)	C4—H4	0.9400
N1—C1	1.324 (4)	C5—C7^ii	1.384 (4)
N1—N2	1.351 (3)	C5—C6	1.397 (4)
N2—C4	1.346 (4)	C5—H5	0.9400
C1—C2	1.411 (4)	C6—C7	1.408 (4)
C1—H1	0.9400	C7—C5^ii	1.384 (4)
C2—C3	1.389 (4)	C7—H7	0.9400
N2^i—Cu1—N1	112.32 (11)	C3—C2—C6	124.8 (3)
N2^i—Cu1—Br1	123.11 (7)	C1—C2—C6	120.5 (3)
N1—Cu1—Br1	104.95 (7)	C2—C3—C4	119.0 (3)
N2^i—Cu1—Br1^i	104.07 (7)	C2—C3—H3	120.5
N1—Cu1—Br1^i	98.70 (7)	C4—C3—H3	120.5
Br1—Cu1—Br1^i	111.10 (2)	N2—C4—C3	123.2 (3)
Cu1—Br1—Cu1^iii	87.985 (16)	N2—C4—H4	118.4
C1—N1—N2	120.2 (2)	C3—C4—H4	118.4
C1—N1—Cu1	116.50 (19)	C7^ii—C5—C6	120.8 (3)
N2—N1—Cu1	121.1 (2)	C7^ii—C5—H5	119.6
C4—N2—N1	118.2 (2)	C6—C5—H5	119.6
C4—N2—Cu1^iii	124.6 (2)	C5—C6—C7	118.3 (3)
N1—N2—Cu1^iii	117.08 (18)	C5—C6—C2	121.2 (2)
N1—C1—C2	124.6 (3)	C7—C6—C2	120.6 (3)
N1—C1—H1	117.7	C5^ii—C7—C6	120.9 (3)
C2—C1—H1	117.7	C5^ii—C7—H7	119.5
C3—C2—C1	114.7 (3)	C6—C7—H7	119.5
N2^i—Cu1—Br1—Cu1^iii	125.52 (8)	N1—C1—C2—C3	−0.5 (5)
N1—Cu1—Br1—Cu1^iii	−4.53 (8)	N1—C1—C2—C6	179.4 (3)
Br1^i—Cu1—Br1—Cu1^iii	−110.24 (3)	C1—C2—C3—C4	2.7 (4)
N2^i—Cu1—N1—C1	50.5 (3)	C6—C2—C3—C4	−177.2 (3)
Br1—Cu1—N1—C1	−173.4 (2)	N1—N2—C4—C3	−0.9 (5)
Br1^i—Cu1—N1—C1	−58.7 (2)	Cu1^iii—N2—C4—C3	176.3 (2)
N2^i—Cu1—N1—N2	−146.5 (2)	C2—C3—C4—N2	−2.1 (5)
Br1—Cu1—N1—N2	−10.4 (2)	C7^ii—C5—C6—C7	0.0 (5)
Br1^i—Cu1—N1—N2	104.3 (2)	C7^ii—C5—C6—C2	180.0 (3)
C1—N1—N2—C4	3.2 (4)	C3—C2—C6—C5	148.8 (3)
Cu1—N1—N2—C4	−159.1 (2)	C1—C2—C6—C5	−31.1 (4)
C1—N1—N2—Cu1^iii	−174.2 (2)	C3—C2—C6—C7	−31.3 (4)
Cu1—N1—N2—Cu1^iii	23.5 (3)	C1—C2—C6—C7	148.9 (3)
N2—N1—C1—C2	−2.6 (5)	C5—C6—C7—C5^ii	0.0 (5)
Cu1—N1—C1—C2	160.5 (2)	C2—C6—C7—C5^ii	−180.0 (3)

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