Copper(II) bromide and copper(II) acetate complexes of 4,4′-(p-phenyl­ene)bipyridazine

4,4′-(p-Phenyl­ene)bipyridazine, C₁₄H₁₀N₄, (I), and the coordination compounds catena-poly[[dibromidocopper(II)]-μ-4,4′-(p-phenyl­ene)bipyridazine-κ²N²:N^2′], [CuBr₂(C₁₄H₁₀N₄)]_n, (II), and catena-poly[[[tetra­kis(μ-acetato-κ²O:O′)­dicopper(II)]-μ-4,4′-(p-phenyl­ene)bipyridazine-κ²N¹:N^1′] chloro­form disolvate], {[Cu₂(C₂H₃O₂)₄(C₁₄H₁₀N₄)]·2CHCl₃}_n, (III), contain a new extended bitopic ligand. The combination of the p-phenyl­ene spacer and the electron-deficient pyridazine rings precludes C—H...π inter­actions between the lengthy aromatic mol­ecules, which could be suited for the synthesis of open-framework coordination polymers. In (I), the mol­ecules are situated across a center of inversion and display a set of very weak inter­molecular C—H...N hydrogen bonds [3.399 (3) and 3.608 (2) Å]. In (II) and (III), the ligand mol­ecules are situated across a center of inversion and act as N²,N^2′-bidentate [in (II)] and N¹,N^1′-bidentate [in (III)] long-distance bridges between the metal ions, leading to the formation of coordination chains [Cu—N = 2.005 (3) Å in (II) and 2.199 (2) Å in (III)]. In (II), the copper ion lies on a center of inversion and adopts CuN₂Br₄ (4+2)-coordination involving two long axial Cu—Br bonds [3.2421 (4) Å]. In (III), the copper ion has a tetra­gonal pyramidal CuO₄N environment. The uncoordinated pyridazine N atom and two acetate O atoms provide a multiple acceptor site for accommodation of a chloroform solvent mol­ecule by trifurcated hydrogen bonding [C—H...O(N) = 3.298 (5)–3.541 (4) Å].

S1. Comment

In coordination compounds, N¹,N²-bidentate pyridazine typically sustains short-distance bridges between metal ions and supports the generation of complicated polynuclear and polymeric metal–organic motifs (Otieno et al., 1995). Such arrays are interesting in view of strong magnetic coupling between the paramagnetic centers through pyridazine bridges (Carlucci et al., 1994) and also as coordination subtopologies for metal–organic frameworks (Domasevitch, Solntsev et al., 2007). In this way, multifunctional pyridazine N-atom donors offer a new potential for the designing of solid-state coordination architecture, as was revealed by examination of a simpler bitopic ligand 4,4'-bipyridazine (Domasevitch, Gural'skiy et al., 2007). The latter combines inherent ability for coordination of closely situated metal ions (3.2 Å) and long-distance bridging at ca 11 Å. Extension of the effective length of the ligand is relevant for the connection of even more distant metal ions and it is an essential prerequisite for the preparation of open metal–organic frameworks. These possibilities may be anticipated for a series of new extended ligands, which unite two pyridazine functions separated by a rigid covalent spacer, i.e. para-phenylene. Such species are readily accessible via the inverse electron demand Diels–Alder cycloaddition of 1,2,4,5-tetrazine (Sauer et al., 1998), and they may be viewed as new attractive `building blocks' for crystal design. We report here the structure of the hitherto unknown ligand 4,4'-(p-phenylene)bipyridazine, (I), and two new copper(II) complexes, (II) and (III), which feature two different bidentate coordination modes.

The asymmetric unit of structure (I) comprises a half-molecule of 4,4'-(p-phenylene)bipyridazine lying across a center of inversion (Fig. 1). The geometry of the heteroaromatic ring is consistent with the structure of pyridazine itself (Blake & Rankin, 1991). In the molecule of (I), the two pyridazine rings are coplanar, while exhibiting a significant twist angle of 43.15 (9)° with respect to the plane of the phenylene spacer. This suggests conformational flexibility of the molecule and a lack of conjugation between the hetero- and carbocyclic fragments, as is indicated also by the standard length of the C2—C5 [1.482 (2) Å]. The corresponding torsion angle [C1—C2—C5—C6 = -43.1 (3)°] appreciably exceeds the value for terphenyl (14.4°; Baudour et al., 1986), but it is consistent with a molecular geometry optimization (37.6°) performed using density function theory (DFT) with the 6–311(d,p) basis set and B3LYP hybrid functional defined in GAMESS (Schmidt et al., 1993).

In the crystal structure of (I), the molecules associate via a set of very weak interactions, namely C—H···N hydrogen bonding (Table 2) and π–π contacts. A pair of C4—H4···N1ⁱ bonds connects the molecules into centrosymmetric dimers, similar to those observed for unsubstituted pyridazine (Blake & Rankin, 1991), and C3—H3···N2ⁱⁱ interactions extend this motif along the a-axis direction with the formation of a layer parallel to the (021) plane [symmetry codes: (i) -x + 1, -y + 1, -z - 1; (ii) x + 1, y, z; Fig. 2]. Weak slipped π–π stacking occurs between a pair of antiparallel pyridazine rings related by inversion (symmetry code: -x + 1, -y + 1, -z). The parameters of this interaction [the interplanar and intercentroid distances are 3.4683 (11) and 3.564 (2) Å, respectively, and the slippage angle is 13.31 (8)°] are characteristic of weak π–π contacts of electron-deficient heteroaromatic rings (Janiak, 2000).

In the copper(II) complexes (II) and (III), the primary connectivity exists in the form of one-dimensional coordination chains supported by bridging of the ligand between the copper ions. In both structures, the molecules of the ligand are situated across a center of inversion, and therefore they adopt symmetric N,N'-bidentate bridging modes, while each of the pyridazine rings is coordinated in a monodentate manner. This is consistent with the coordination preferences of the simpler 4,4'-bipyridazine ligand, which is an efficient tetradentate linker towards silver(I) ions (Domasevitch, Solntsev et al., 2007) but is typically bidentate towards Cu²⁺ and Zn²⁺ ions (Domasevitch, Gural'skiy et al., 2007). The coordination modes in (II) and (III), however, are different, namely N²,N²'- and linear N¹,N¹'-coordinations, respectively. This may reflect the adaptability of the ligand to the demands of the crystal packing.

In the bromide (II), the copper ion is situated on a center of inversion and displays Jahn–Teller distorted octahedral (4+2)-coordination, with a trans-CuN₂Br₂ equatorial plane [Cu1—Br1 = 2.4151 (4) Å] (Fig. 3); the octahedron is completed by two very long axial contacts [Cu1···Br1ⁱ = 3.2421 (4) Å; symmetry code: (i) -x + 1, -y, -z]. These weak bonds connect linear Br—Cu—Br units into a chain of vertex-sharing Cu₂Br₂ rhombes running along the a-axis direction, and overall this generates coordination layers that lie parallel to the ab plane (Fig. 4). These features are analogous to the situation in dibromo-bis(pyridine)copper(II) (Cu—Br = 2.451 and 3.240 Å; Morosin, 1975), while shorter chloride bridges were essential for stabilization of the bidentate coordination of pyridazine in the copper(II) chloride complex (Fetzer et al., 1990). The axial Cu···Br contacts are accompanied also by weak C1—H1···Br1ⁱ hydrogen bonding [3.449 (4) Å; angle C—H···Br = 133°].

Structure of (III) is based on very characteristic dicopper(II)–tetracetate units, which are situated across a center of inversion [Cu1···Cu1ⁱ = 2.6332 (7) Å; symmetry code: (i) -x + 1, -y + 1, -z + 1; Fig. 5]. The ligands act as N¹,N¹'-bidentate linear bridges connecting these Cu₂(AcO)₄ units into rod-like linear chains, with a separation between the dinuclear unit centroids of 18.2164 (13) Å. This motif is similar to that found for a related 4,4'-bipyridazine complex (Domasevitch, Gural'skiy et al., 2007). The copper ions adopt tetragonal–pyramidal coordination, with four basal acetate O atoms [Cu—O = 1.960 (2)–1.975 (2) Å] and pyridazine atom N1 in at the apex [2.199 (2) Å]. The latter separation is consistent with the Cu—N bond length for the orthorhombic polymorph of tetracetato-bis(pyridine)dicopper(II) [2.191 (2) Å; Uekusa et al., 1989].

The uncoordinated N atoms (N2) are also functional as acceptors of hydrogen bonding and, together with two adjacent carboxylate atoms (O2 and O4), they provide three-center acceptor sites for the accommodation of chloroform molecules. The latter are held between the coordination chains (Fig. 6) and interact with them by means of weak trifurcated hydrogen bonding [C12—H12···O(N) = 3.298 (5)–3.541 (4) Å and 130–138°; Table 5 and Fig. 5]. Comparable trifurcated hydrogen bonding is known for chloroform solvates of molecular metal complexes such as tris(1-hydroxy-2-pyridinethionato-O,S)cobalt(III) (C—H···O = 3.07–3.39 Å; Manivannan et al., 1993). However, this supramolecular pattern is unprecedented for pyridazine and related polynitrogen heterocycles, and it may be relevant for functionalization of the metal–organic structure towards specific interactions with the guest species.

There are no π–π or C—H···π contacts in the structures (II) and (III), and no C—H···π bonding in (I). Thus the inherent electron deficiency of the pyridazine ring actually appears to preclude the formation of hydrogen bonds involving π acceptors. Such closely packed motifs supported by extensive C—H···π bonding are typical for lengthy aromatic ligands (Domasevitch et al., 2002), and they mitigate the formation of open structures. In this view, the combination of heterocyclic functions and carbocyclic spacer provided by 4,4'-(p-phenylene)bipyridazine could be especially favorable for the preparation of open metal–organic frameworks.

Related literature

For related literature, see: Baudour et al. (1986); Blake & Rankin (1991); Carlucci et al. (1994); Domasevitch et al. (2002); Domasevitch, Gural'skiy, Solntsev, Rusanov, Krautscheid, Howard & Chernega (2007); Domasevitch, Solntsev, Gural'skiy, Krautscheid, Rusanov, Chernega & Howard (2007); Fetzer et al. (1990); Janiak (2000); Manivannan et al. (1993); Morosin (1975); Otieno et al. (1995); Sauer et al. (1998); Schmidt et al. (1993); Uekusa et al. (1989).

S2. Experimental

The ligand was synthesized by reacting 1,2,4,5-tetrazine (2.30 g, 28 mmol) and 1,4-diethynylbenzene (1.76 g, 14 mmol) in 40 ml of dry 1,4-dioxane (24 h, 353 K). The yield of pure colorless crystalline product was 2.95 g (90%). For the synthesis of (II), CuBr₂ (11.1 mg, 0.05 mmol), (I) (11.7 mg, 0.05 mmol) and water (5 ml) were sealed in a Pyrex tube, heated at 443 K for 8 h and then cooled to room temperature over a period of 48 h. This afforded green prisms of (II) (yield 90%, 20.5 mg). Complex (III) was synthesized using the layering technique: a solution of Cu(AcO)₂.H₂O (16.0 mg, 0.08 mmol) in methanol (3 ml) was layered over a solution of (I) (9.4 mg, 0.04 mmol) in a mixture of methanol (2 ml) and chloroform (2 ml). Large green–blue prisms of (III) grew on the walls of the tube as the solutions interdiffused over a period of 15 d (yield 65%, 21.7 mg).

S3. Refinement

For (I), all the H atoms were found in intermediate difference Fourier maps and were refined fully with isotropic displacement parameters [C—H = 0.91 (2)–0.99 (2) Å]. For (II) and (III), the H atoms were treated as riding in geometrically idealized positions, with C—H (aromatic) distances of 0.93 Å, C—H (methyl) distances of 0.96 Å and C—H (chloroform) distances of 0.98 Å, and with U_iso(H) values of 1.2U_eq(C) and [1.5U_eq(C) for the methyl groups].

Computing details

For all compounds, data collection: SMART-NT (Bruker, 1998); cell refinement: SAINT-NT (Bruker, 1999); data reduction: SAINT-NT (Bruker, 1999); 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 (Version 1.70.01; Farrugia, 1999).

Figures

	Fig. 1. The structure of (I), showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 35% probability level, H atoms are shown as small spheres of arbitrary radii and N atoms are shaded gray. [Symmetry code: (iii) -x + 2, -y + 2, -z + 1.]
	Fig. 2. A projection of the structure of (I) on to the ac plane, showing weak C—H···N hydrogen-bonding interactions as dashed lines. N atoms are shaded gray. [Symmetry codes: (i) -x + 1, -y + 1, -z - 1; (ii) x + 1, y, z.]
	Fig. 3. The structure of (II), showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 40% probability level, H atoms are shown as small spheres of arbitrary radii and N atoms are shaded gray. [Symmetry codes: (i) -x + 1, -y, -z; (ii) -x, -y, -z; (iii) -x + 1, -y + 1, -z.]
	Fig. 4. Fragment of the structure of (II), showing weak coordination Cu···Br (open lines) and hydrogen-bonding C—H···Br (dashed lines) interactions between the metal–organic chains. N atoms are shaded gray. [Symmetry code: (i) -x + 1, -y, -z.]
	Fig. 5. The structure of (III), showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 40% probability level, H atoms are shown as small spheres of arbitrary radii and N atoms are shaded gray. Coordination bonds are shown with open lines and the trifurcated hydrogen bonding is indicated by dashed lines. [Symmetry codes: (i) -x + 1, -y + 1, -z + 1; (ii) -x - 1, -y, -z.]
	Fig. 6. A projection of the structure of (III) on to the bc plane, showing the mode of incorporation of hydrogen-bonded chloroform molecules between the coordination chains. N atoms are shaded gray and the coordination bonds are shown by open lines.

(I) 4,4'-(p-phenylene)bipyridazine

Crystal data

C14H10N4	Z = 1
Mr = 234.26	F(000) = 122
Triclinic, P1	Dx = 1.400 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.3588 (7) Å	Cell parameters from 2129 reflections
b = 6.9307 (9) Å	θ = 3.1–26.4°
c = 7.0681 (10) Å	µ = 0.09 mm^−1
α = 110.282 (3)°	T = 296 K
β = 90.823 (3)°	Prism, colorless
γ = 106.585 (2)°	0.26 × 0.23 × 0.20 mm
V = 277.80 (6) Å^3

Data collection

Siemens SMART CCD area-detector diffractometer	894 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.028
Graphite monochromator	θmax = 26.4°, θmin = 3.1°
ω scans	h = −7→7
2129 measured reflections	k = −8→7
1131 independent 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)] = 0.050	Hydrogen site location: difference Fourier map
wR(F^2) = 0.137	All H-atom parameters refined
S = 1.10	w = 1/[σ^2(Fo^2) + (0.0658P)^2 + 0.0624P] where P = (Fo^2 + 2Fc^2)/3
1131 reflections	(Δ/σ)max < 0.001
102 parameters	Δρmax = 0.30 e Å^−3
0 restraints	Δρmin = −0.18 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
N1	0.4490 (3)	0.6498 (3)	−0.2498 (2)	0.0457 (5)
N2	0.3692 (2)	0.7226 (3)	−0.0724 (2)	0.0454 (5)
C1	0.5050 (3)	0.8026 (3)	0.0994 (3)	0.0386 (5)
C2	0.7278 (3)	0.8157 (3)	0.1126 (3)	0.0321 (4)
C3	0.8067 (3)	0.7371 (3)	−0.0694 (3)	0.0382 (5)
C4	0.6601 (3)	0.6577 (3)	−0.2457 (3)	0.0426 (5)
C5	0.8672 (3)	0.9095 (3)	0.3121 (2)	0.0325 (4)
C6	0.8522 (3)	1.0984 (3)	0.4604 (3)	0.0375 (5)
C7	1.0161 (3)	0.8123 (3)	0.3538 (3)	0.0377 (5)
H1	0.438 (3)	0.851 (3)	0.223 (3)	0.045 (5)*
H3	0.956 (3)	0.736 (3)	−0.078 (3)	0.045 (5)*
H4	0.711 (3)	0.609 (4)	−0.368 (4)	0.052 (6)*
H6	0.756 (3)	1.170 (3)	0.431 (3)	0.046 (6)*
H7	1.026 (3)	0.677 (4)	0.249 (3)	0.057 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1	0.0480 (10)	0.0495 (10)	0.0332 (9)	0.0105 (8)	−0.0079 (7)	0.0115 (8)
N2	0.0385 (9)	0.0518 (11)	0.0404 (10)	0.0120 (7)	−0.0053 (7)	0.0122 (8)
C1	0.0370 (10)	0.0429 (11)	0.0320 (10)	0.0104 (8)	0.0008 (8)	0.0106 (8)
C2	0.0354 (9)	0.0330 (9)	0.0262 (9)	0.0076 (7)	0.0005 (7)	0.0112 (7)
C3	0.0368 (10)	0.0427 (11)	0.0311 (10)	0.0109 (8)	0.0007 (7)	0.0102 (8)
C4	0.0507 (11)	0.0458 (12)	0.0261 (10)	0.0127 (9)	0.0020 (8)	0.0089 (9)
C5	0.0303 (8)	0.0406 (10)	0.0254 (9)	0.0091 (7)	0.0011 (6)	0.0122 (8)
C6	0.0384 (9)	0.0424 (11)	0.0324 (10)	0.0177 (8)	−0.0018 (7)	0.0104 (8)
C7	0.0387 (9)	0.0404 (11)	0.0297 (10)	0.0141 (8)	−0.0001 (7)	0.0062 (8)

Geometric parameters (Å, º)

N1—C4	1.327 (3)	C3—H3	0.96 (2)
N1—N2	1.345 (2)	C4—H4	0.91 (2)
N2—C1	1.325 (2)	C5—C7	1.390 (3)
C1—C2	1.393 (3)	C5—C6	1.395 (3)
C1—H1	0.98 (2)	C6—C7^i	1.385 (2)
C2—C3	1.376 (3)	C6—H6	0.95 (2)
C2—C5	1.482 (2)	C7—C6^i	1.385 (2)
C3—C4	1.387 (2)	C7—H7	0.99 (2)
C4—N1—N2	118.61 (15)	N1—C4—H4	117.0 (13)
C1—N2—N1	118.85 (16)	C3—C4—H4	118.6 (13)
N2—C1—C2	124.98 (17)	C7—C5—C6	118.94 (16)
N2—C1—H1	115.2 (12)	C7—C5—C2	120.73 (16)
C2—C1—H1	119.8 (12)	C6—C5—C2	120.33 (16)
C3—C2—C1	115.71 (16)	C7^i—C6—C5	120.47 (17)
C3—C2—C5	123.19 (16)	C7^i—C6—H6	119.9 (13)
C1—C2—C5	121.10 (16)	C5—C6—H6	119.5 (13)
C2—C3—C4	117.48 (17)	C6^i—C7—C5	120.59 (17)
C2—C3—H3	122.8 (12)	C6^i—C7—H7	120.4 (12)
C4—C3—H3	119.7 (12)	C5—C7—H7	119.0 (12)
N1—C4—C3	124.35 (18)
C4—N1—N2—C1	1.1 (3)	C3—C2—C5—C7	−42.7 (3)
N1—N2—C1—C2	−0.9 (3)	C1—C2—C5—C7	137.45 (19)
N2—C1—C2—C3	−0.3 (3)	C3—C2—C5—C6	136.7 (2)
N2—C1—C2—C5	179.56 (17)	C1—C2—C5—C6	−43.1 (3)
C1—C2—C3—C4	1.2 (3)	C7—C5—C6—C7^i	0.1 (3)
C5—C2—C3—C4	−178.65 (17)	C2—C5—C6—C7^i	−179.34 (17)
N2—N1—C4—C3	−0.2 (3)	C6—C5—C7—C6^i	−0.1 (3)
C2—C3—C4—N1	−1.0 (3)	C2—C5—C7—C6^i	179.34 (17)

Symmetry code: (i) −x+2, −y+2, −z+1.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···N1^ii	0.91 (2)	2.66 (2)	3.399 (3)	139 (2)
C3—H3···N2^iii	0.96 (2)	2.65 (2)	3.608 (2)	175 (2)

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

(II) catena-poly[[dibromidocopper(II)]-µ₂-4,4'-(p-phenylene)bipyridazine- κ²N²:N^2']

Crystal data

[CuBr2(C14H10N4)]	F(000) = 442
Mr = 457.62	Dx = 2.169 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 4.1377 (2) Å	Cell parameters from 3750 reflections
b = 12.5407 (7) Å	θ = 2.2–26.3°
c = 13.5301 (8) Å	µ = 7.26 mm^−1
β = 93.786 (4)°	T = 296 K
V = 700.54 (7) Å^3	Prism, green
Z = 2	0.24 × 0.20 × 0.19 mm

Data collection

Siemens SMART CCD area-detector diffractometer	1415 independent reflections
Radiation source: fine-focus sealed tube	1099 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.031
ω scans	θmax = 26.3°, θmin = 2.2°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.203, Tmax = 0.251	k = −15→15
3750 measured reflections	l = −16→14

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) = 0.070	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.0308P)^2 + 0.206P] where P = (Fo^2 + 2Fc^2)/3
1415 reflections	(Δ/σ)max < 0.001
97 parameters	Δρmax = 0.54 e Å^−3
0 restraints	Δρmin = −0.37 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	0.0000	0.0000	0.0000	0.0350 (2)
Br1	0.38905 (9)	−0.07954 (3)	0.11892 (3)	0.03486 (15)
N1	−0.0773 (8)	0.1368 (3)	0.1682 (2)	0.0365 (8)
N2	0.0300 (7)	0.1365 (2)	0.0772 (2)	0.0314 (8)
C1	0.1530 (9)	0.2224 (3)	0.0389 (3)	0.0336 (9)
H1	0.2194	0.2182	−0.0253	0.040*
C2	0.1907 (8)	0.3205 (3)	0.0889 (3)	0.0262 (8)
C3	0.0708 (9)	0.3222 (3)	0.1811 (3)	0.0314 (9)
H3	0.0755	0.3843	0.2187	0.038*
C4	−0.0575 (10)	0.2285 (3)	0.2167 (3)	0.0371 (10)
H4	−0.1357	0.2304	0.2796	0.045*
C5	0.3470 (8)	0.4126 (3)	0.0428 (3)	0.0274 (8)
C6	0.4070 (10)	0.4144 (3)	−0.0570 (3)	0.0383 (10)
H6	0.3429	0.3565	−0.0965	0.046*
C7	0.4420 (10)	0.5009 (3)	0.0993 (3)	0.0383 (10)
H7	0.4034	0.5029	0.1662	0.046*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0549 (4)	0.0202 (4)	0.0286 (4)	0.0012 (3)	−0.0063 (3)	−0.0041 (3)
Br1	0.0412 (2)	0.0351 (3)	0.0283 (2)	0.00269 (19)	0.00236 (16)	0.00208 (18)
N1	0.0471 (19)	0.030 (2)	0.033 (2)	−0.0041 (16)	0.0073 (16)	−0.0023 (16)
N2	0.0450 (19)	0.0205 (18)	0.0282 (19)	−0.0005 (15)	−0.0004 (15)	−0.0034 (14)
C1	0.048 (2)	0.027 (2)	0.026 (2)	0.0024 (19)	0.0072 (18)	−0.0037 (18)
C2	0.0267 (18)	0.021 (2)	0.030 (2)	0.0029 (16)	−0.0030 (15)	−0.0035 (16)
C3	0.039 (2)	0.029 (2)	0.026 (2)	−0.0033 (18)	0.0005 (17)	−0.0075 (17)
C4	0.046 (2)	0.036 (3)	0.030 (2)	−0.0024 (19)	0.0058 (19)	−0.0085 (19)
C5	0.0299 (18)	0.021 (2)	0.031 (2)	0.0011 (16)	−0.0013 (16)	−0.0027 (17)
C6	0.057 (2)	0.026 (2)	0.032 (2)	−0.011 (2)	0.0042 (19)	−0.0124 (19)
C7	0.053 (3)	0.035 (3)	0.027 (2)	−0.006 (2)	0.0060 (19)	−0.0080 (18)

Geometric parameters (Å, º)

Cu1—N2^i	2.005 (3)	C2—C3	1.373 (5)
Cu1—N2	2.005 (3)	C2—C5	1.481 (5)
Cu1—Br1^i	2.4151 (4)	C3—C4	1.388 (5)
Cu1—Br1	2.4151 (4)	C3—H3	0.9300
Cu1—Br1^ii	3.2421 (4)	C4—H4	0.9300
N1—C4	1.325 (5)	C5—C7	1.388 (5)
N1—N2	1.336 (4)	C5—C6	1.390 (5)
N2—C1	1.312 (4)	C6—C7^iii	1.376 (5)
C1—C2	1.408 (5)	C6—H6	0.9300
C1—H1	0.9300	C7—H7	0.9300
N2^i—Cu1—N2	180.00 (17)	C1—C2—C5	121.1 (3)
N2^i—Cu1—Br1^i	89.43 (9)	C2—C3—C4	118.2 (4)
N2—Cu1—Br1^i	90.57 (9)	C2—C3—H3	120.9
N2^i—Cu1—Br1	90.57 (9)	C4—C3—H3	120.9
N2—Cu1—Br1	89.43 (9)	N1—C4—C3	125.1 (4)
Br1^i—Cu1—Br1	180.00 (3)	N1—C4—H4	117.5
N2—Cu1—Br1^ii	88.40 (9)	C3—C4—H4	117.5
Br1—Cu1—Br1^ii	87.158 (12)	C7—C5—C6	117.4 (3)
C4—N1—N2	116.5 (3)	C7—C5—C2	120.4 (3)
C1—N2—N1	121.5 (3)	C6—C5—C2	122.2 (3)
C1—N2—Cu1	120.5 (3)	C7^iii—C6—C5	122.2 (4)
N1—N2—Cu1	118.0 (2)	C7^iii—C6—H6	118.9
N2—C1—C2	124.1 (4)	C5—C6—H6	118.9
N2—C1—H1	117.9	C6^iii—C7—C5	120.4 (4)
C2—C1—H1	117.9	C6^iii—C7—H7	119.8
C3—C2—C1	114.5 (3)	C5—C7—H7	119.8
C3—C2—C5	124.4 (3)
C4—N1—N2—C1	1.0 (5)	C5—C2—C3—C4	−177.3 (3)
C4—N1—N2—Cu1	−179.2 (3)	N2—N1—C4—C3	−1.4 (6)
Br1^i—Cu1—N2—C1	−66.2 (3)	C2—C3—C4—N1	−0.8 (6)
Br1—Cu1—N2—C1	113.8 (3)	C3—C2—C5—C7	13.4 (5)
Br1^i—Cu1—N2—N1	114.1 (3)	C1—C2—C5—C7	−166.9 (4)
Br1—Cu1—N2—N1	−65.9 (3)	C3—C2—C5—C6	−167.1 (4)
N1—N2—C1—C2	1.5 (6)	C1—C2—C5—C6	12.6 (5)
Cu1—N2—C1—C2	−178.3 (3)	C7—C5—C6—C7^iii	0.8 (7)
N2—C1—C2—C3	−3.4 (6)	C2—C5—C6—C7^iii	−178.7 (4)
N2—C1—C2—C5	176.8 (3)	C6—C5—C7—C6^iii	−0.8 (7)
C1—C2—C3—C4	2.9 (5)	C2—C5—C7—C6^iii	178.7 (4)

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

(III) catena-poly[[[tetrakis(µ-acetato-κ²O:O')dicopper(II)]- µ₂-4,4'-(p-phenylene)bipyridazine-κ²N¹:N^1'] chloroform disolvate]

Crystal data

[Cu2(C2H3O2)4(C14H10N4)]·2CHCl3	Z = 1
Mr = 836.25	F(000) = 420
Triclinic, P1	Dx = 1.738 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.6349 (8) Å	Cell parameters from 8062 reflections
b = 8.0203 (8) Å	θ = 2.6–26.5°
c = 13.9312 (10) Å	µ = 1.88 mm^−1
α = 104.601 (2)°	T = 296 K
β = 103.993 (2)°	Prism, green-blue
γ = 90.123 (3)°	0.27 × 0.15 × 0.12 mm
V = 799.21 (13) Å^3

Data collection

Siemens SMART CCD area-detector diffractometer	3283 independent reflections
Radiation source: fine-focus sealed tube	2688 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.035
ω scans	θmax = 26.5°, θmin = 2.6°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −9→9
Tmin = 0.630, Tmax = 0.806	k = −10→10
8062 measured reflections	l = −17→16

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.090	H-atom parameters constrained
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0383P)^2 + 0.1918P] where P = (Fo^2 + 2Fc^2)/3
3283 reflections	(Δ/σ)max = 0.001
201 parameters	Δρmax = 0.35 e Å^−3
0 restraints	Δρmin = −0.41 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	0.37515 (4)	0.41141 (4)	0.42032 (3)	0.02542 (12)
O1	0.4749 (3)	0.7837 (3)	0.56696 (17)	0.0371 (5)
O2	0.2681 (3)	0.6361 (3)	0.42876 (17)	0.0394 (5)
O3	0.7298 (3)	0.6220 (3)	0.46891 (16)	0.0359 (5)
O4	0.5206 (3)	0.4719 (3)	0.33358 (15)	0.0365 (5)
N1	0.1314 (3)	0.2811 (3)	0.30510 (18)	0.0291 (6)
N2	0.1189 (3)	0.2746 (4)	0.20707 (19)	0.0380 (7)
C1	−0.0328 (4)	0.2105 (4)	0.1390 (2)	0.0368 (8)
H1	−0.0397	0.2086	0.0711	0.044*
C2	−0.1850 (4)	0.1446 (4)	0.1605 (2)	0.0289 (7)
C3	−0.1700 (4)	0.1586 (4)	0.2618 (2)	0.0369 (8)
H3	−0.2658	0.1219	0.2836	0.044*
C4	−0.0099 (4)	0.2280 (4)	0.3310 (2)	0.0367 (8)
H4	−0.0008	0.2382	0.4000	0.044*
C5	−0.3471 (4)	0.0707 (4)	0.0783 (2)	0.0293 (7)
C6	−0.5189 (4)	0.1108 (4)	0.0903 (2)	0.0362 (8)
H6	−0.5327	0.1853	0.1506	0.043*
C7	−0.3322 (4)	−0.0400 (4)	−0.0126 (2)	0.0396 (8)
H7	−0.2177	−0.0673	−0.0214	0.048*
C8	0.3332 (4)	0.7716 (4)	0.4966 (2)	0.0304 (7)
C9	0.2359 (5)	0.9324 (4)	0.4925 (3)	0.0416 (8)
H9A	0.2321	0.9944	0.5606	0.062*
H9B	0.1148	0.9022	0.4506	0.062*
H9C	0.2984	1.0038	0.4639	0.062*
C10	0.6657 (4)	0.5640 (4)	0.3743 (2)	0.0295 (7)
C11	0.7700 (5)	0.6105 (4)	0.3052 (3)	0.0423 (8)
H11A	0.7356	0.5291	0.2391	0.064*
H11B	0.8972	0.6076	0.3342	0.064*
H11C	0.7439	0.7244	0.2981	0.064*
C12	0.2578 (5)	0.6717 (5)	0.1792 (3)	0.0555 (10)
H12	0.2715	0.5881	0.2207	0.067*
Cl1	0.02744 (17)	0.69281 (19)	0.13244 (10)	0.0885 (4)
Cl2	0.35719 (18)	0.59579 (18)	0.07766 (9)	0.0910 (4)
Cl3	0.36454 (17)	0.87143 (14)	0.25682 (9)	0.0720 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.02236 (19)	0.0254 (2)	0.0242 (2)	−0.00199 (13)	−0.00009 (14)	0.00435 (14)
O1	0.0365 (12)	0.0291 (12)	0.0404 (13)	0.0034 (9)	0.0024 (10)	0.0066 (10)
O2	0.0329 (12)	0.0294 (12)	0.0485 (14)	0.0044 (9)	−0.0018 (10)	0.0086 (10)
O3	0.0332 (12)	0.0439 (13)	0.0275 (12)	−0.0073 (10)	0.0042 (9)	0.0069 (10)
O4	0.0371 (12)	0.0416 (13)	0.0267 (12)	−0.0075 (10)	0.0043 (10)	0.0053 (10)
N1	0.0246 (13)	0.0318 (14)	0.0264 (14)	−0.0018 (10)	−0.0001 (10)	0.0059 (11)
N2	0.0264 (14)	0.0558 (18)	0.0270 (15)	−0.0062 (12)	0.0020 (11)	0.0069 (13)
C1	0.0297 (17)	0.054 (2)	0.0215 (16)	−0.0035 (15)	0.0034 (13)	0.0038 (15)
C2	0.0221 (15)	0.0341 (17)	0.0232 (16)	−0.0020 (12)	−0.0006 (12)	0.0007 (13)
C3	0.0308 (17)	0.046 (2)	0.0292 (18)	−0.0116 (14)	0.0021 (13)	0.0075 (15)
C4	0.0338 (17)	0.049 (2)	0.0227 (16)	−0.0092 (15)	0.0001 (13)	0.0079 (14)
C5	0.0228 (15)	0.0358 (17)	0.0240 (16)	−0.0024 (12)	0.0011 (12)	0.0028 (13)
C6	0.0292 (16)	0.046 (2)	0.0252 (16)	0.0006 (14)	0.0052 (13)	−0.0036 (14)
C7	0.0215 (15)	0.055 (2)	0.0309 (18)	0.0008 (14)	0.0027 (13)	−0.0052 (15)
C8	0.0339 (17)	0.0263 (16)	0.0382 (19)	0.0046 (13)	0.0172 (15)	0.0133 (14)
C9	0.043 (2)	0.0316 (18)	0.055 (2)	0.0116 (15)	0.0168 (17)	0.0155 (16)
C10	0.0309 (16)	0.0267 (16)	0.0304 (17)	0.0053 (13)	0.0069 (13)	0.0073 (13)
C11	0.0421 (19)	0.050 (2)	0.039 (2)	−0.0011 (16)	0.0149 (16)	0.0135 (16)
C12	0.066 (3)	0.053 (2)	0.050 (2)	0.005 (2)	0.013 (2)	0.0212 (19)
Cl1	0.0641 (7)	0.1268 (12)	0.0844 (9)	0.0106 (7)	0.0168 (6)	0.0466 (8)
Cl2	0.0961 (10)	0.1107 (11)	0.0603 (8)	0.0354 (8)	0.0234 (7)	0.0074 (7)
Cl3	0.0962 (9)	0.0542 (6)	0.0657 (7)	−0.0054 (6)	0.0237 (6)	0.0126 (5)

Geometric parameters (Å, º)

Cu1—O1^i	1.960 (2)	C4—H4	0.9300
Cu1—O4	1.967 (2)	C5—C7	1.382 (4)
Cu1—O2	1.969 (2)	C5—C6	1.390 (4)
Cu1—O3^i	1.975 (2)	C6—C7^ii	1.370 (4)
Cu1—N1	2.199 (2)	C6—H6	0.9300
Cu1—Cu1^i	2.6332 (7)	C7—H7	0.9300
O1—C8	1.257 (4)	C8—C9	1.496 (4)
O2—C8	1.254 (4)	C9—H9A	0.9600
O3—C10	1.253 (4)	C9—H9B	0.9600
O4—C10	1.255 (3)	C9—H9C	0.9600
N1—C4	1.318 (4)	C10—C11	1.500 (4)
N1—N2	1.334 (3)	C11—H11A	0.9600
N2—C1	1.314 (4)	C11—H11B	0.9600
C1—C2	1.402 (4)	C11—H11C	0.9600
C1—H1	0.9300	C12—Cl2	1.743 (4)
C2—C3	1.364 (4)	C12—Cl1	1.746 (4)
C2—C5	1.471 (4)	C12—Cl3	1.759 (4)
C3—C4	1.374 (4)	C12—H12	0.9800
C3—H3	0.9300
O1^i—Cu1—O4	88.70 (9)	C3—C4—H4	118.1
O1^i—Cu1—O2	168.03 (9)	C7—C5—C6	118.5 (3)
O4—Cu1—O2	88.73 (9)	C7—C5—C2	120.8 (2)
O1^i—Cu1—O3^i	89.99 (9)	C6—C5—C2	120.8 (3)
O4—Cu1—O3^i	168.07 (8)	C7^ii—C6—C5	119.6 (3)
O2—Cu1—O3^i	90.12 (9)	C7^ii—C6—H6	120.2
O1^i—Cu1—N1	101.31 (9)	C5—C6—H6	120.2
O4—Cu1—N1	101.53 (9)	C6^ii—C7—C5	121.9 (3)
O2—Cu1—N1	90.66 (9)	C6^ii—C7—H7	119.1
O3^i—Cu1—N1	90.35 (9)	C5—C7—H7	119.1
O1^i—Cu1—Cu1^i	84.77 (7)	O2—C8—O1	125.3 (3)
O4—Cu1—Cu1^i	87.34 (6)	O2—C8—C9	117.4 (3)
O2—Cu1—Cu1^i	83.44 (6)	O1—C8—C9	117.3 (3)
O3^i—Cu1—Cu1^i	80.74 (6)	C8—C9—H9A	109.5
N1—Cu1—Cu1^i	169.26 (6)	C8—C9—H9B	109.5
C8—O1—Cu1^i	122.62 (19)	H9A—C9—H9B	109.5
C8—O2—Cu1	123.8 (2)	C8—C9—H9C	109.5
C10—O3—Cu1^i	127.26 (19)	H9A—C9—H9C	109.5
C10—O4—Cu1	119.78 (19)	H9B—C9—H9C	109.5
C4—N1—N2	119.2 (2)	O3—C10—O4	124.9 (3)
C4—N1—Cu1	122.0 (2)	O3—C10—C11	117.1 (3)
N2—N1—Cu1	118.30 (18)	O4—C10—C11	118.0 (3)
C1—N2—N1	118.6 (2)	C10—C11—H11A	109.5
N2—C1—C2	125.2 (3)	C10—C11—H11B	109.5
N2—C1—H1	117.4	H11A—C11—H11B	109.5
C2—C1—H1	117.4	C10—C11—H11C	109.5
C3—C2—C1	114.7 (3)	H11A—C11—H11C	109.5
C3—C2—C5	124.2 (3)	H11B—C11—H11C	109.5
C1—C2—C5	121.1 (3)	Cl2—C12—Cl1	110.0 (2)
C2—C3—C4	118.4 (3)	Cl2—C12—Cl3	110.4 (2)
C2—C3—H3	120.8	Cl1—C12—Cl3	110.1 (2)
C4—C3—H3	120.8	Cl2—C12—H12	108.8
N1—C4—C3	123.8 (3)	Cl1—C12—H12	108.8
N1—C4—H4	118.1	Cl3—C12—H12	108.8
O1^i—Cu1—O2—C8	−12.1 (6)	N2—C1—C2—C3	3.1 (5)
O4—Cu1—O2—C8	−89.7 (2)	N2—C1—C2—C5	−178.2 (3)
O3^i—Cu1—O2—C8	78.4 (2)	C1—C2—C3—C4	−2.2 (5)
N1—Cu1—O2—C8	168.8 (2)	C5—C2—C3—C4	179.1 (3)
Cu1^i—Cu1—O2—C8	−2.2 (2)	N2—N1—C4—C3	2.8 (5)
O1^i—Cu1—O4—C10	−85.3 (2)	Cu1—N1—C4—C3	174.6 (3)
O2—Cu1—O4—C10	83.0 (2)	C2—C3—C4—N1	−0.5 (5)
O3^i—Cu1—O4—C10	−1.6 (6)	C3—C2—C5—C7	−137.3 (3)
N1—Cu1—O4—C10	173.4 (2)	C1—C2—C5—C7	44.1 (5)
Cu1^i—Cu1—O4—C10	−0.5 (2)	C3—C2—C5—C6	42.8 (5)
O1^i—Cu1—N1—C4	93.5 (2)	C1—C2—C5—C6	−135.8 (3)
O4—Cu1—N1—C4	−175.5 (2)	C7—C5—C6—C7^ii	0.2 (6)
O2—Cu1—N1—C4	−86.7 (2)	C2—C5—C6—C7^ii	−179.9 (3)
O3^i—Cu1—N1—C4	3.4 (2)	C6—C5—C7—C6^ii	−0.2 (6)
Cu1^i—Cu1—N1—C4	−30.2 (5)	C2—C5—C7—C6^ii	179.9 (3)
O1^i—Cu1—N1—N2	−94.6 (2)	Cu1—O2—C8—O1	0.9 (4)
O4—Cu1—N1—N2	−3.6 (2)	Cu1—O2—C8—C9	179.95 (19)
O2—Cu1—N1—N2	85.2 (2)	Cu1^i—O1—C8—O2	1.9 (4)
O3^i—Cu1—N1—N2	175.3 (2)	Cu1^i—O1—C8—C9	−177.10 (19)
Cu1^i—Cu1—N1—N2	141.6 (3)	Cu1^i—O3—C10—O4	−0.4 (4)
C4—N1—N2—C1	−2.0 (4)	Cu1^i—O3—C10—C11	178.9 (2)
Cu1—N1—N2—C1	−174.1 (2)	Cu1—O4—C10—O3	0.7 (4)
N1—N2—C1—C2	−1.0 (5)	Cu1—O4—C10—C11	−178.6 (2)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C12—H12···O2	0.98	2.83	3.541 (4)	130
C12—H12···O4	0.98	2.50	3.298 (5)	138
C12—H12···N2	0.98	2.71	3.496 (5)	137