Poly[nickel(II)-di-μ-4,4′-bipyridyl-κ⁴N:N′-μ-dichromato-κ²O:O′] and poly[copper(II)-di-μ-4,4'-bipyridyl-κ⁴N:N′-μ-dichromato-κ²O:O′]

The novel title hybrid isomorphous organic–inorganic mixed-metal dichromates, [Ni(Cr₂O₇)(C₁₀H₈N₂)₂] and [Cu(Cr₂O₇)(C₁₀H₈N₂)₂], have been synthesized. A non-centrosymmetric three-dimensional (4,6)-net is formed from a linear chain of vertex-linked [Cr₂O]²⁻ and [MN₄O]²⁺ (M = Ni and Cu) units, which in turn are linked by the planar bidentate 4,4′-­bipyridine ligand through the four remaining vertices of the [MN₄O]²⁺ octahedra. There are two such three-dimensional nets that interpenetrate with inversion symmetry.

S1. Comment

Non-centrosymmetric solids, i.e. those without a center of inversion, may exhibit one or more interesting physical properties, such as ferroelectricity, pyroelectricity or piezoelectricity. A current approach to synthesizing non-centrosymmetric structures is to begin with asymmetric `building blocks' (Halasyamani & Poeppelmeier, 1998). One example of an asymmetric building block is the dichromate anion, Cr₂O₇²⁻, which is found in the compounds M(py)₄Cr₂O₇ (M = Cu²⁺ and Zn²⁺, and py is pyridine) (Norquist et al., 2001). These compounds consist of alternating vertex-linked CuN₄O₂ octahedra and Cr₂O₇²⁻ polyhedra that form linear chain structures. In contrast, the dichromate–containing Cu(2,2'–bpy)₂Cr₂O₇ (bpy is bipyridine) forms isolated molecular species rather than chains (Maggard et al., 2002). Both left- and right-handed enantiomers of isolated Cu(2,2'–bpy)₂Cr₂O₇ molecules pack with inversion symmetry between layers in space group P1. The structural difference between Cu(py)₄Cr₂O₇ and Cu(2,2'–bpy)₂Cr₂O₇ appears to be due to the modification evinced by the change of ligand. The different structures of the two compounds highlight the necessity of further studies to characterize the structure-directing features of organic mono- and bidentate ligands in relation to the dichromate anion. Presented here is continuing synthetic work employing the late transition metal oxides of nickel and copper with asymmetric dichromate species (also referred to as the anion) and the 4,4'–bipyridine (4,4'–bpy) ligand.

Ni(4,4'–bpy)₂Cr₂O₇, (I), and Cu(4,4'–bpy)₂Cr₂O₇, (II), are isostructural compounds. An ellipsoid plot is shown in Fig. 1. The bond lengths and angles of the dichromate anion in both (I) and (II) (Tables 1 and 2) are in good agreement with those reported for Na₂Cr₂O₇ (Panagiotopoulos & Brown, 1972). In both (I) and (II), a three-dimensional structure is generated from two bonding motifs, viz. a linear chain that consists of alternating late transition metal centered octahedra joined to Cr₂O₇²⁻ polyhedra, as shown in Fig. 2, and a two–dimensional square net of type (4,4) (Wells, 1977) composed of late transition metal cations coordinated by 4,4'–bpy ligands along the [200] plane (perpendicular to the chain; Fig. 3). The late transition metal cations are also bonded to O-atom vertices of the dichromate anions in a trans fashion. These opposing vertices are also designated as the axial positions of the octahedra. As expected, the Cu—O bonds in (II) are elongated owing to the Jahn–Teller distortion of the Cu²⁺ ion. The average bond length between Cu and N atoms is 2.05 Å, while the average bond length of the Cu–O bonds is 2.32 Å. In comparison, Ni²⁺ has on average longer M—N bonds (2.12 Å) and shorter M–O bonds (2.02 Å). A general feature of the M–N bonds in both structures is that one M–N bond, for example M—N1 (M = Ni, Cu) of a 4,4'–bpy, is longer than the second M—N bond (M—N4) of the same 4,4'–bpy (Fig. 1, and Tables 1 and 2). The difference between the two bonds is approximately 0.1 Å for both 4,4'–bipyridine ligands of (I) and (II). Similarly, for both (I) and (II), the shorter M—N bonds are trans to one another, as are the two longer M—N bonds. There are other examples of octahedrally coordinated Ni and Cu atoms having four bonds to N atoms and two bonds to O atoms exhibiting a similar trend (Prout et al., 1971; Kulynych & Shimizu, 2002; Fritsky et al., 2004]. A search of the Cambridge Structural Database revealed that for octahedrally coordinated M (M = Cu and Ni) with four N-containing heterocyclic ligands and two O-containing ligands there is a correlation between the ionic character of the M—O bond (carbonate or dichromate versus water for example) and the variation of length within the four M—N bonds (Allen, 2002). The differences in M—O and M—N bond lengths of the title compounds are also accompanied by other distortions, such as a small displacement of the 4,4'–bpy molecule with respect to the equatorial plane.

Both compounds have chain structures composed of a late transition metal and coordinated dichromates. The chains are parallel to one another in the [–100] direction. Along the 2₁ screw axis there is a 180° rotation of each dichromate anion as the chain propagates; thus the repeating segment in a chain is composed of two cations and two anions (Fig. 2).

The second bonding motif in M(bpy)₄Cr₂O₇ (M = Ni²⁺, Cu²⁺) is a two–dimensional (4,4)-net composed of the bridging ligands and the late transition metal atoms. Each Ni/Cu atom forms bonds to four 4,4'–bpy ligands in the equatorial positions. These ligands serve as linkers and bridge each Ni/Cu atom to four other Ni/Cu–centered octahedra (Fig. 3). The linking of octahedra creates a two–dimensional square net composed of Ni²⁺/Cu²⁺ cations and 4,4'–bpy ligands.

The combination of this square net with the linear chain motif results in a three-dimensional net where the points of connectivity for both motifs is the Ni²⁺/Cu²⁺-centered octahedra (n = 6) (Wells, 1977). The ligands act as spacers between the Ni²⁺/Cu²⁺-centered octahedra centers. Each three-dimensional net is non-centrosymmetric with large cavities (7.0 × 7.0 × 5.0 Å), owing to the physical size and rigidity of the linking ligands. When a single non-centrosymmetric three-dimensional net is considered, the net is compatible with the polar or chiral-polar space group Cc or C2, respectively. However, the title compounds crystallize in the centrosymmetric space group C2/c, which indicates that the structures are composed of more than one three-dimensional net.

Each parallel chain of late transition metal atoms and coordinated dichromate anions is surrounded by four other chains. These four surrounding chains are related to the central chain by an inversion center. The relationship between neighboring chains is shown in Fig. 4. Note that the Cr-centered tetrahedra have opposing facial directions. Additionally, the four closest neighboring chains are offset from the central chain by one-quater of the repeating segment along the chain propagation direction. The chains of the net are related to their neighbors by an inversion center and, in three dimensions, the entire non-centrosymmetric three-dimensional net is related to the second net by an inversion center. In addition, the second independent three-dimensional net effectively fills the cavities as it interpenetrates the first net (Fig. 5).

It is evident that the three-dimensional net is created from late transition metal cations with coordinated dichromate anions in one direction and, most importantly, the linking 4,4'-bipyridyl ligands in the other two directions. The rigidity and bidentate characteristics of 4,4'-bpy and dichromate bring about a stable three-dimensional net, while the length of the ligands affords enough space in the net to accommodate the interpenetration of an inversely related three-dimensional net.

S2. Experimental

Single crystals of Ni(4,4'–bipyridyl)₂Cr₂O₇ were synthesized by placing NiO (44.1 mg, Aldrich, 99.99%), (NH₄)₂Cr₂O₇ (291.6 mg, Aldrich, 99.5+%) and 4,4'–bipyridine (453.2 mg, Aldrich, 98%) into a Teflon (fluoroethylenepropylene) pouch (Harrison et al., 1993). To the pouch were added aqueous HF (885.9 mg, Aldrich, 49%, w/v) and deionized H₂O (55.1 mg). The pouches were heat sealed and placed in a 125 ml autoclave, which was back-filled with H₂O (45 ml). The autoclave was heated in a convection oven for 24 h at 423 K and cooled to room temperature at 6 K h⁻¹. The pouch was opened in air and (I) was recovered by filtration in a 39% yield based on Ni content. Single crystals of Cu(4,4'–dipyridyl)₂Cr₂O₇ were synthesized in a similar manner using Cu₂O (44.6 mg, Aldrich, 97%), (pyH)₂Cr₂O₇ (234.5 mg, Fluka, 98.0%), 4,4'–bipyridine (195.1 mg, Aldrich, 98%), aqueous HF (112.3 mg, Aldrich, 49%wv) and deionized H₂O (1111.5 mg). Compound (II) was recovered by filtration in a 75% yield based on Cu content. Crystals of (I) and (II) are isomorphous.

S3. Refinement

H atoms were included in the final refinement model as riding atoms in idealized positions using the default SHELXL settings at low temperature [C—H = 0.95 \%A and U_iso(H) = 1.2U_eq(C) or 1.5U_eq(C)].

Computing details

For both compounds, data collection: SMART-NT (Siemens, 1996); cell refinement: SAINT-Plus (Siemens, 1996); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1999); software used to prepare material for publication: program (reference)?.

Figures

	Fig. 1. A displacement ellipsoid plot (50% probability level) of (I). The superscripts refer to the following equivalent positions: i (x − 1/2, 1/2 − y, z − 1/2); ii (x, −y, 1/2 + z); iii (x, 1 − y, 1/2 + z); iv (x, −y, z − 1/2); v (x, 1 − y, z − 1/2); vi (1/2 + x, 1/2 − y, 1/2 + z).
	Fig. 2. Linear chains of dichromate anions bonded to metal cations. In the online version of the journal, Cr atoms are shown in green, O in red and Ni/Cu in pink. The 4,4'–bpy rings have been omitted for clarity.
	Fig. 3. A two-dimensional net of Ni^2+/Cu^2+-centered pseudo-octahedra and 4,4'–bpy ligands. In the online version of the journal, Ni^2+/Cu^2+-centered pseudo-octahedra are shown in pink, N in blue, O in red and C in black. The Cr2O7^2− anions bonded to the axial position of the pseudo-octahedra have been omitted for clarity, except for the O atom directly coordinated to the metal.
	Fig. 4. The overall structure of (I) and (II), including 4,4'–bpy ligands.
	Fig. 5. Two interpenetrating nets (differentiated in the online version of the journal as one formed from light pink octahedra and the other with dark pink octahedra). The ligand, as bars, of one net are darkened. The two corner-sharing tetrahedra (green online) make up one dichromate anion.

(I)

Crystal data

[Ni(C10H8N2)2(Cr2O7)]	F(000) = 2368
Mr = 587.08	Dx = 1.802 Mg m^−3 Dm = 1.784 (3) Mg m^−3 Dm measured by flotation pycnometry
Monoclinic, C_1_2/c_1	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 5184 reflections
a = 21.343 (7) Å	θ = 4–28°
b = 15.260 (5) Å	µ = 1.90 mm^−1
c = 16.658 (6) Å	T = 153 K
β = 127.094 (5)°	Columnar, blue
V = 4328 (3) Å^3	0.21 × 0.16 × 0.15 mm
Z = 8

Data collection

Bruker SMART AXS diffractometer	5184 independent reflections
Radiation source: fine-focus sealed tube	4364 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.083
ω–2θ scans	θmax = 28.3°, θmin = 1.8°
Absorption correction: analytical face-indexed (reference?)	h = −28→28
Tmin = 0.718, Tmax = 0.874	k = −20→20
19357 measured reflections	l = −21→22

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)] = 0.038	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.099	H-atom parameters constrained
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0448P)^2 + 7.5127P] where P = (Fo^2 + 2Fc^2)/3
5184 reflections	(Δ/σ)max = 0.001
307 parameters	Δρmax = 1.19 e Å^−3
0 restraints	Δρmin = −0.64 e Å^−3

Special details

Experimental. Stationary background counts were recorded at each end of the scan, and the scan time:background time ratio was 2:1.

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.

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

	x	y	z	Uiso*/Ueq
Ni	0.133935 (17)	0.251246 (17)	0.62064 (2)	0.01183 (9)
Cr1	0.33243 (2)	0.20390 (3)	0.77624 (3)	0.01774 (11)
Cr2	0.42678 (2)	0.26482 (3)	1.00533 (3)	0.01608 (10)
O1	0.25321 (10)	0.26572 (11)	0.70270 (13)	0.0187 (3)
O2	0.31487 (11)	0.10568 (13)	0.73330 (15)	0.0313 (4)
O3	0.40446 (11)	0.24397 (13)	0.78138 (15)	0.0281 (4)
O4	0.35578 (10)	0.19958 (12)	0.89870 (12)	0.0219 (4)
O5	0.40137 (12)	0.36647 (12)	0.98216 (16)	0.0315 (4)
O6	0.42760 (11)	0.23169 (13)	1.09782 (14)	0.0273 (4)
O7	0.51402 (10)	0.25213 (10)	1.03205 (13)	0.0175 (3)
N1	0.12171 (11)	0.35891 (13)	0.52794 (14)	0.0150 (4)
N2	0.13155 (11)	0.16338 (13)	0.52288 (14)	0.0146 (4)
N3	0.13357 (11)	−0.14412 (13)	0.20560 (14)	0.0156 (4)
N4	0.13908 (11)	0.65958 (12)	0.21796 (14)	0.0140 (4)
C1	0.15302 (14)	0.43888 (15)	0.56355 (17)	0.0170 (4)
H1	0.1735	0.4526	0.6309	0.020*
C2	0.15693 (14)	0.50248 (15)	0.50702 (17)	0.0168 (4)
H2	0.1775	0.5590	0.5344	0.020*
C3	0.13002 (13)	0.48201 (15)	0.40908 (17)	0.0153 (4)
C4	0.09568 (13)	0.39992 (15)	0.37108 (17)	0.0162 (4)
H4	0.0762	0.3837	0.3047	0.019*
C5	0.09025 (13)	0.34223 (15)	0.43078 (17)	0.0159 (4)
H5	0.0632	0.2885	0.4021	0.019*
C6	0.07940 (13)	0.60332 (14)	0.18138 (17)	0.0150 (4)
H6	0.0379	0.6037	0.1112	0.018*
C7	0.07586 (13)	0.54488 (15)	0.24163 (17)	0.0161 (4)
H7	0.0331	0.5051	0.2126	0.019*
C8	0.13481 (14)	0.54408 (15)	0.34481 (17)	0.0157 (4)
C9	0.19738 (14)	0.60186 (15)	0.38292 (17)	0.0177 (5)
H9	0.2393	0.6030	0.4529	0.021*
C10	0.19774 (14)	0.65782 (15)	0.31730 (17)	0.0177 (5)
H10	0.2411	0.6963	0.3437	0.021*
C11	0.18492 (13)	0.16913 (15)	0.50452 (17)	0.0159 (4)
H11	0.2261	0.2108	0.5412	0.019*
C12	0.18243 (14)	0.11706 (15)	0.43466 (17)	0.0171 (4)
H12	0.2194	0.1255	0.4211	0.021*
C13	0.12506 (14)	0.05208 (15)	0.38428 (17)	0.0158 (4)
C14	0.06953 (14)	0.04724 (15)	0.40277 (17)	0.0174 (5)
H14	0.0287	0.0049	0.3687	0.021*
C15	0.07394 (14)	0.10401 (15)	0.47052 (17)	0.0166 (4)
H15	0.0346	0.1009	0.4805	0.020*
C16	0.10397 (14)	−0.16031 (15)	0.25672 (17)	0.0175 (5)
H16	0.0842	−0.2173	0.2524	0.021*
C17	0.10103 (14)	−0.09849 (16)	0.31476 (18)	0.0182 (5)
H17	0.0821	−0.1140	0.3518	0.022*
C18	0.12610 (13)	−0.01273 (15)	0.31878 (16)	0.0158 (4)
C19	0.15314 (14)	0.00602 (16)	0.26246 (17)	0.0180 (5)
H19	0.1686	0.0639	0.2604	0.022*
C20	0.15720 (14)	−0.06155 (15)	0.20910 (17)	0.0170 (4)
H20	0.1778	−0.0485	0.1734	0.020*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ni	0.01557 (15)	0.01088 (15)	0.01136 (15)	0.00057 (10)	0.00934 (12)	0.00010 (10)
Cr1	0.01608 (19)	0.0201 (2)	0.01673 (19)	0.00120 (14)	0.00972 (16)	−0.00295 (15)
Cr2	0.01665 (19)	0.0174 (2)	0.01540 (19)	0.00174 (14)	0.01030 (16)	0.00025 (14)
O1	0.0188 (8)	0.0199 (8)	0.0168 (8)	0.0029 (7)	0.0105 (7)	−0.0008 (7)
O2	0.0307 (10)	0.0247 (10)	0.0315 (10)	0.0039 (8)	0.0151 (9)	−0.0086 (8)
O3	0.0203 (9)	0.0400 (12)	0.0267 (10)	0.0000 (8)	0.0156 (8)	−0.0007 (8)
O4	0.0204 (8)	0.0261 (9)	0.0165 (8)	−0.0027 (7)	0.0096 (7)	0.0002 (7)
O5	0.0362 (11)	0.0184 (9)	0.0390 (11)	0.0082 (8)	0.0222 (9)	0.0017 (8)
O6	0.0304 (10)	0.0353 (11)	0.0227 (9)	0.0005 (8)	0.0194 (8)	0.0009 (8)
O7	0.0174 (8)	0.0192 (8)	0.0171 (8)	−0.0008 (6)	0.0111 (7)	−0.0010 (6)
N1	0.0166 (9)	0.0145 (9)	0.0156 (9)	0.0014 (7)	0.0106 (8)	0.0034 (7)
N2	0.0190 (9)	0.0128 (9)	0.0134 (9)	0.0013 (7)	0.0104 (8)	0.0006 (7)
N3	0.0195 (9)	0.0157 (9)	0.0160 (9)	−0.0017 (7)	0.0130 (8)	−0.0023 (7)
N4	0.0185 (9)	0.0130 (9)	0.0153 (9)	0.0008 (7)	0.0126 (8)	0.0016 (7)
C1	0.0203 (11)	0.0162 (11)	0.0163 (10)	−0.0008 (9)	0.0120 (9)	−0.0001 (9)
C2	0.0195 (11)	0.0131 (10)	0.0191 (11)	−0.0011 (8)	0.0123 (9)	−0.0001 (9)
C3	0.0156 (10)	0.0143 (10)	0.0180 (11)	0.0028 (8)	0.0111 (9)	0.0044 (8)
C4	0.0187 (11)	0.0152 (11)	0.0149 (10)	0.0012 (9)	0.0104 (9)	0.0004 (8)
C5	0.0180 (11)	0.0115 (10)	0.0163 (10)	0.0008 (8)	0.0094 (9)	0.0011 (8)
C6	0.0180 (11)	0.0134 (10)	0.0153 (10)	0.0001 (8)	0.0110 (9)	−0.0009 (8)
C7	0.0179 (11)	0.0134 (10)	0.0180 (11)	−0.0004 (8)	0.0114 (9)	0.0011 (9)
C8	0.0212 (11)	0.0122 (10)	0.0181 (11)	0.0025 (8)	0.0142 (10)	0.0032 (8)
C9	0.0202 (11)	0.0183 (11)	0.0139 (10)	−0.0010 (9)	0.0099 (9)	0.0014 (9)
C10	0.0216 (11)	0.0156 (11)	0.0186 (11)	−0.0042 (9)	0.0136 (10)	−0.0009 (9)
C11	0.0187 (11)	0.0134 (10)	0.0171 (10)	−0.0025 (9)	0.0116 (9)	−0.0020 (8)
C12	0.0209 (11)	0.0161 (11)	0.0188 (11)	−0.0004 (9)	0.0143 (9)	−0.0011 (9)
C13	0.0193 (11)	0.0145 (10)	0.0145 (10)	0.0015 (8)	0.0107 (9)	−0.0008 (8)
C14	0.0196 (11)	0.0143 (11)	0.0195 (11)	−0.0024 (9)	0.0124 (10)	−0.0029 (9)
C15	0.0195 (11)	0.0143 (11)	0.0185 (11)	−0.0009 (9)	0.0127 (9)	0.0001 (9)
C16	0.0237 (12)	0.0126 (10)	0.0211 (11)	−0.0016 (9)	0.0161 (10)	−0.0019 (9)
C17	0.0226 (12)	0.0175 (11)	0.0199 (11)	−0.0007 (9)	0.0157 (10)	−0.0010 (9)
C18	0.0172 (10)	0.0156 (11)	0.0139 (10)	0.0000 (8)	0.0090 (9)	−0.0030 (8)
C19	0.0229 (12)	0.0148 (11)	0.0185 (11)	−0.0024 (9)	0.0135 (10)	−0.0019 (9)
C20	0.0210 (11)	0.0164 (11)	0.0180 (11)	−0.0023 (9)	0.0141 (10)	−0.0015 (9)

Geometric parameters (Å, º)

Ni—O1	2.0494 (19)	C3—C4	1.395 (3)
Ni—O7^i	2.0433 (19)	C3—C8	1.478 (3)
Ni—N1	2.160 (2)	C4—C5	1.384 (3)
Ni—N2	2.086 (2)	C4—H4	0.9500
Ni—N3^ii	2.165 (2)	C5—H5	0.9500
Ni—N4^iii	2.0683 (19)	C6—C7	1.378 (3)
Cr1—O1	1.6586 (18)	C6—H6	0.9500
Cr1—O2	1.605 (2)	C7—C8	1.389 (3)
Cr1—O3	1.608 (2)	C7—H7	0.9500
Cr1—O4	1.7854 (19)	C8—C9	1.393 (3)
Cr1—Cr2	3.1958 (13)	C9—C10	1.391 (3)
Cr2—O4	1.7877 (18)	C9—H9	0.9500
Cr2—O5	1.611 (2)	C10—H10	0.9500
Cr2—O6	1.6115 (19)	C11—C12	1.383 (3)
Cr2—O7	1.6440 (18)	C11—H11	0.9500
O7—Ni^iv	2.0433 (19)	C12—C13	1.396 (3)
N1—C1	1.345 (3)	C12—H12	0.9500
N1—C5	1.351 (3)	C13—C14	1.395 (3)
N2—C15	1.342 (3)	C13—C18	1.483 (3)
N2—C11	1.349 (3)	C14—C15	1.380 (3)
N3—C20	1.345 (3)	C14—H14	0.9500
N3—C16	1.354 (3)	C15—H15	0.9500
N3—Ni^v	2.165 (2)	C16—C17	1.379 (3)
N4—C6	1.340 (3)	C16—H16	0.9500
N4—C10	1.344 (3)	C17—C18	1.400 (3)
N4—Ni^vi	2.0683 (19)	C17—H17	0.9500
C1—C2	1.389 (3)	C18—C19	1.396 (3)
C1—H1	0.9500	C19—C20	1.398 (3)
C2—C3	1.400 (3)	C19—H19	0.9500
C2—H2	0.9500	C20—H20	0.9500
O7^i—Ni—O1	174.48 (7)	C3—C2—H2	120.5
Cr1—O1—Ni	137.24 (10)	C4—C3—C2	117.6 (2)
Cr2—O7—Ni^iv	156.82 (11)	C4—C3—C8	119.6 (2)
O7^i—Ni—N4^iii	91.94 (7)	C2—C3—C8	122.8 (2)
O1—Ni—N4^iii	87.07 (7)	C5—C4—C3	119.6 (2)
O7^i—Ni—N2	89.42 (7)	C5—C4—H4	120.2
O1—Ni—N2	91.47 (7)	C3—C4—H4	120.2
N4^iii—Ni—N2	178.23 (7)	N1—C5—C4	123.0 (2)
O7^i—Ni—N1	86.81 (7)	N1—C5—H5	118.5
O1—Ni—N1	87.75 (7)	C4—C5—H5	118.5
N4^iii—Ni—N1	89.22 (8)	N4—C6—C7	122.6 (2)
N2—Ni—N1	89.73 (8)	N4—C6—H6	118.7
O7^i—Ni—N3^ii	87.50 (7)	C7—C6—H6	118.7
O1—Ni—N3^ii	97.93 (7)	C6—C7—C8	120.0 (2)
N4^iii—Ni—N3^ii	90.22 (8)	C6—C7—H7	120.0
N2—Ni—N3^ii	90.97 (8)	C8—C7—H7	120.0
N1—Ni—N3^ii	174.25 (7)	C7—C8—C9	117.5 (2)
O2—Cr1—O3	109.74 (11)	C7—C8—C3	119.7 (2)
O2—Cr1—O1	110.00 (10)	C9—C8—C3	122.8 (2)
O3—Cr1—O1	109.82 (10)	C10—C9—C8	119.2 (2)
O2—Cr1—O4	107.70 (10)	C10—C9—H9	120.4
O3—Cr1—O4	110.74 (9)	C8—C9—H9	120.4
O1—Cr1—O4	108.82 (9)	N4—C10—C9	122.5 (2)
O2—Cr1—Cr2	127.84 (8)	N4—C10—H10	118.8
O3—Cr1—Cr2	86.11 (7)	C9—C10—H10	118.8
O1—Cr1—Cr2	110.12 (6)	N2—C11—C12	123.0 (2)
O4—Cr1—Cr2	26.59 (6)	N2—C11—H11	118.5
O5—Cr2—O6	109.82 (11)	C12—C11—H11	118.5
O5—Cr2—O7	109.93 (10)	C11—C12—C13	119.2 (2)
O6—Cr2—O7	110.28 (10)	C11—C12—H12	120.4
O5—Cr2—O4	109.69 (10)	C13—C12—H12	120.4
O6—Cr2—O4	106.81 (10)	C14—C13—C12	117.3 (2)
O7—Cr2—O4	110.26 (9)	C14—C13—C18	121.3 (2)
O5—Cr2—Cr1	96.62 (8)	C12—C13—C18	121.3 (2)
O6—Cr2—Cr1	133.32 (8)	C15—C14—C13	120.0 (2)
O7—Cr2—Cr1	94.83 (6)	C15—C14—H14	120.0
O4—Cr2—Cr1	26.55 (6)	C13—C14—H14	120.0
Cr1—O4—Cr2	126.86 (10)	N2—C15—C14	122.6 (2)
C1—N1—C5	117.07 (19)	N2—C15—H15	118.7
C1—N1—Ni	124.13 (15)	C14—C15—H15	118.7
C5—N1—Ni	118.14 (15)	N3—C16—C17	123.5 (2)
C15—N2—C11	117.69 (19)	N3—C16—H16	118.3
C15—N2—Ni	121.52 (15)	C17—C16—H16	118.3
C11—N2—Ni	120.59 (15)	C16—C17—C18	119.7 (2)
C20—N3—C16	116.64 (19)	C16—C17—H17	120.2
C20—N3—Ni^v	125.91 (15)	C18—C17—H17	120.2
C16—N3—Ni^v	117.40 (15)	C19—C18—C17	117.4 (2)
C6—N4—C10	118.12 (19)	C19—C18—C13	123.6 (2)
C6—N4—Ni^vi	118.60 (15)	C17—C18—C13	118.9 (2)
C10—N4—Ni^vi	123.21 (16)	C18—C19—C20	119.0 (2)
N1—C1—C2	123.5 (2)	C18—C19—H19	120.5
N1—C1—H1	118.3	C20—C19—H19	120.5
C2—C1—H1	118.3	N3—C20—C19	123.6 (2)
C1—C2—C3	118.9 (2)	N3—C20—H20	118.2
C1—C2—H2	120.5	C19—C20—H20	118.2

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

(II)

Crystal data

[Cu(C10H8N2)2(Cr2O7)]	F(000) = 2376
Mr = 591.91	Dx = 1.817 Mg m^−3 Dm = 1.828 (5) Mg m^−3 Dm measured by flotation pycnometry
Monoclinic, C_1_2/c_1	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 5221 reflections
a = 21.603 (3) Å	θ = 4–28°
b = 14.8505 (18) Å	µ = 2.01 mm^−1
c = 16.604 (2) Å	T = 153 K
β = 125.682 (2)°	Cube, green
V = 4326.8 (10) Å^3	0.15 × 0.15 × 0.14 mm
Z = 8

Data collection

Bruker SMART AXS diffractometer	5221 independent reflections
Radiation source: fine-focus sealed tube	4526 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.026
ω–2θ scans	θmax = 28.3°, θmin = 1.8°
Absorption correction: analytical face indexed	h = −28→27
Tmin = 0.769, Tmax = 0.816	k = −19→19
19193 measured reflections	l = −21→22

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) = 0.085	H-atom parameters constrained
S = 1.06	w = 1/[σ^2(Fo^2) + (0.047P)^2 + 7.1233P] where P = (Fo^2 + 2Fc^2)/3
5221 reflections	(Δ/σ)max = 0.001
307 parameters	Δρmax = 0.73 e Å^−3
0 restraints	Δρmin = −0.78 e Å^−3

Special details

Experimental. Stationary background counts were recorded at each end of the scan, and the scan time:background time ratio was 2:1.

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.

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

	x	y	z	Uiso*/Ueq
Cu	0.135200 (13)	0.251166 (14)	0.621092 (16)	0.01239 (8)
Cr1	0.335441 (18)	0.20572 (2)	0.77490 (2)	0.01886 (9)
Cr2	0.419807 (19)	0.26282 (2)	1.00090 (2)	0.01688 (9)
O1	0.26508 (8)	0.27596 (11)	0.70369 (11)	0.0210 (3)
O2	0.31226 (10)	0.10670 (12)	0.72644 (13)	0.0335 (4)
O3	0.41134 (9)	0.23950 (13)	0.78674 (13)	0.0312 (4)
O4	0.35066 (8)	0.19990 (11)	0.89264 (11)	0.0221 (3)
O5	0.39622 (11)	0.36783 (11)	0.98379 (14)	0.0362 (4)
O6	0.42047 (10)	0.22367 (12)	1.09203 (12)	0.0296 (4)
O7	0.50347 (9)	0.25031 (10)	1.02384 (12)	0.0211 (3)
N1	0.12198 (9)	0.35858 (11)	0.52904 (12)	0.0147 (3)
N2	0.13276 (9)	0.16381 (11)	0.52695 (12)	0.0140 (3)
N3	0.13121 (9)	−0.14545 (11)	0.20216 (12)	0.0147 (3)
N4	0.14071 (9)	0.66020 (11)	0.21516 (12)	0.0135 (3)
C1	0.15453 (11)	0.43983 (13)	0.56358 (14)	0.0167 (4)
H1	0.1763	0.4536	0.6310	0.020*
C2	0.15807 (11)	0.50457 (13)	0.50618 (14)	0.0170 (4)
H2	0.1796	0.5621	0.5329	0.020*
C3	0.12939 (11)	0.48343 (13)	0.40829 (14)	0.0156 (4)
C4	0.09333 (11)	0.40042 (13)	0.37136 (14)	0.0164 (4)
H4	0.0721	0.3843	0.3046	0.020*
C5	0.08864 (11)	0.34191 (13)	0.43209 (14)	0.0162 (4)
H5	0.0608	0.2876	0.4045	0.019*
C6	0.08085 (11)	0.60554 (13)	0.18120 (14)	0.0157 (4)
H6	0.0401	0.6070	0.1126	0.019*
C7	0.07645 (11)	0.54754 (13)	0.24207 (14)	0.0164 (4)
H7	0.0337	0.5089	0.2153	0.020*
C8	0.13493 (11)	0.54549 (13)	0.34331 (14)	0.0158 (4)
C9	0.19715 (11)	0.60211 (13)	0.37821 (14)	0.0177 (4)
H9	0.2383	0.6025	0.4466	0.021*
C10	0.19846 (11)	0.65783 (13)	0.31234 (14)	0.0169 (4)
H10	0.2415	0.6955	0.3365	0.020*
C11	0.18575 (11)	0.16864 (13)	0.50864 (14)	0.0167 (4)
H11	0.2268	0.2098	0.5459	0.020*
C12	0.18271 (11)	0.11611 (13)	0.43771 (15)	0.0171 (4)
H12	0.2198	0.1233	0.4247	0.021*
C13	0.12503 (11)	0.05265 (13)	0.38557 (14)	0.0159 (4)
C14	0.06949 (12)	0.04895 (14)	0.40375 (15)	0.0181 (4)
H14	0.0284	0.0076	0.3683	0.022*
C15	0.07463 (11)	0.10555 (13)	0.47342 (14)	0.0171 (4)
H15	0.0359	0.1033	0.4839	0.021*
C16	0.09949 (12)	−0.16223 (13)	0.25043 (15)	0.0177 (4)
H16	0.0779	−0.2200	0.2433	0.021*
C17	0.09685 (12)	−0.09950 (13)	0.30989 (14)	0.0180 (4)
H17	0.0761	−0.1154	0.3450	0.022*
C18	0.12486 (11)	−0.01267 (13)	0.31802 (14)	0.0159 (4)
C19	0.15445 (12)	0.00679 (13)	0.26421 (15)	0.0185 (4)
H19	0.1720	0.0657	0.2651	0.022*
C20	0.15771 (11)	−0.06132 (14)	0.20948 (14)	0.0178 (4)
H20	0.1798	−0.0480	0.1754	0.021*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu	0.01714 (13)	0.01155 (12)	0.01110 (12)	0.00053 (8)	0.00971 (11)	0.00007 (8)
Cr1	0.01455 (16)	0.02398 (18)	0.01634 (16)	0.00120 (12)	0.00804 (14)	−0.00423 (12)
Cr2	0.01653 (17)	0.01879 (17)	0.01471 (16)	0.00125 (12)	0.00876 (14)	0.00033 (11)
O1	0.0188 (7)	0.0258 (8)	0.0173 (7)	0.0022 (6)	0.0098 (6)	−0.0010 (6)
O2	0.0314 (9)	0.0280 (9)	0.0336 (9)	0.0045 (7)	0.0147 (8)	−0.0105 (7)
O3	0.0170 (8)	0.0529 (11)	0.0248 (9)	−0.0019 (7)	0.0128 (7)	−0.0042 (7)
O4	0.0182 (7)	0.0286 (8)	0.0169 (7)	−0.0041 (6)	0.0088 (6)	−0.0016 (6)
O5	0.0455 (11)	0.0219 (8)	0.0390 (10)	0.0113 (8)	0.0233 (9)	0.0017 (7)
O6	0.0318 (9)	0.0387 (9)	0.0231 (8)	−0.0023 (8)	0.0187 (7)	0.0005 (7)
O7	0.0146 (7)	0.0278 (8)	0.0180 (7)	−0.0015 (5)	0.0078 (6)	0.0012 (5)
N1	0.0151 (8)	0.0155 (8)	0.0138 (7)	0.0000 (6)	0.0085 (7)	0.0018 (6)
N2	0.0170 (8)	0.0128 (7)	0.0126 (7)	0.0019 (6)	0.0089 (6)	0.0007 (6)
N3	0.0167 (8)	0.0157 (8)	0.0135 (7)	−0.0010 (6)	0.0098 (7)	−0.0014 (6)
N4	0.0176 (8)	0.0122 (7)	0.0141 (7)	0.0007 (6)	0.0110 (7)	0.0004 (6)
C1	0.0191 (9)	0.0182 (9)	0.0141 (9)	−0.0009 (7)	0.0104 (8)	−0.0006 (7)
C2	0.0192 (9)	0.0147 (9)	0.0178 (9)	−0.0023 (7)	0.0112 (8)	−0.0003 (7)
C3	0.0148 (9)	0.0171 (9)	0.0165 (9)	0.0023 (7)	0.0099 (8)	0.0034 (7)
C4	0.0173 (9)	0.0174 (9)	0.0137 (9)	0.0014 (7)	0.0085 (8)	0.0003 (7)
C5	0.0168 (9)	0.0149 (9)	0.0151 (9)	0.0004 (7)	0.0083 (8)	0.0009 (7)
C6	0.0171 (9)	0.0163 (9)	0.0144 (9)	0.0008 (7)	0.0097 (8)	−0.0002 (7)
C7	0.0169 (9)	0.0168 (9)	0.0165 (9)	−0.0007 (7)	0.0103 (8)	0.0007 (7)
C8	0.0195 (9)	0.0147 (9)	0.0171 (9)	0.0020 (7)	0.0129 (8)	0.0022 (7)
C9	0.0194 (10)	0.0189 (9)	0.0125 (9)	−0.0008 (7)	0.0079 (8)	0.0011 (7)
C10	0.0180 (9)	0.0173 (9)	0.0157 (9)	−0.0036 (7)	0.0100 (8)	−0.0006 (7)
C11	0.0174 (9)	0.0171 (9)	0.0154 (9)	−0.0017 (7)	0.0093 (8)	−0.0020 (7)
C12	0.0186 (9)	0.0189 (9)	0.0177 (9)	0.0001 (7)	0.0127 (8)	−0.0013 (7)
C13	0.0186 (9)	0.0165 (9)	0.0128 (8)	0.0003 (7)	0.0092 (8)	−0.0010 (7)
C14	0.0196 (10)	0.0172 (9)	0.0184 (9)	−0.0020 (7)	0.0116 (8)	−0.0028 (7)
C15	0.0203 (10)	0.0164 (9)	0.0183 (9)	−0.0009 (7)	0.0133 (8)	−0.0002 (7)
C16	0.0206 (9)	0.0162 (9)	0.0190 (9)	−0.0017 (7)	0.0131 (8)	−0.0019 (7)
C17	0.0217 (10)	0.0181 (9)	0.0184 (9)	−0.0010 (8)	0.0141 (8)	−0.0016 (7)
C18	0.0167 (9)	0.0171 (9)	0.0136 (8)	0.0005 (7)	0.0086 (8)	−0.0014 (7)
C19	0.0224 (10)	0.0161 (9)	0.0184 (9)	−0.0033 (8)	0.0128 (8)	−0.0025 (7)
C20	0.0206 (10)	0.0195 (9)	0.0165 (9)	−0.0018 (7)	0.0126 (8)	−0.0015 (7)

Geometric parameters (Å, º)

Cu—O1	2.3238 (15)	C3—C8	1.476 (3)
Cu—O7^i	2.3120 (16)	C4—C5	1.379 (3)
Cu—N1	2.1102 (16)	C4—H4	0.95
Cu—N2	2.0082 (16)	C5—H5	0.95
Cu—N3^ii	2.1022 (16)	C6—C7	1.373 (3)
Cu—N4^iii	1.9923 (16)	C6—H6	0.95
Cr1—O1	1.6432 (15)	C7—C8	1.395 (3)
Cr1—O2	1.6095 (17)	C7—H7	0.95
Cr1—O3	1.6132 (17)	C8—C9	1.393 (3)
Cr1—O4	1.7855 (15)	C9—C10	1.385 (3)
Cr2—O4	1.7898 (15)	C9—H9	0.95
Cr2—O5	1.6135 (17)	C10—H10	0.95
Cr2—O6	1.6132 (16)	C11—C12	1.382 (3)
Cr2—O7	1.6258 (16)	C11—H11	0.95
O7—Cu^iv	2.3120 (16)	C12—C13	1.390 (3)
N1—C1	1.345 (3)	C12—H12	0.95
N1—C5	1.349 (2)	C13—C14	1.399 (3)
N2—C15	1.347 (3)	C13—C18	1.481 (3)
N2—C11	1.347 (2)	C14—C15	1.381 (3)
N3—C20	1.350 (3)	C14—H14	0.95
N3—C16	1.347 (2)	C15—H15	0.95
N3—Cu^v	2.1022 (16)	C16—C17	1.382 (3)
N4—C6	1.341 (2)	C16—H16	0.95
N4—C10	1.347 (2)	C17—C18	1.397 (3)
N4—Cu^vi	1.9923 (16)	C17—H17	0.95
C1—C2	1.387 (3)	C18—C19	1.399 (3)
C1—H1	0.95	C19—C20	1.389 (3)
C2—C3	1.396 (3)	C19—H19	0.95
C2—H2	0.95	C20—H20	0.95
C3—C4	1.395 (3)
O7^i—Cu—O1	169.82 (6)	C5—C4—C3	119.73 (18)
Cr1—O1—Cu	128.01 (9)	C5—C4—H4	120.1
Cr2—O7—Cu^iv	155.78 (9)	C3—C4—H4	120.1
N4^iii—Cu—N2	178.06 (7)	C4—C5—N1	122.78 (18)
N4^iii—Cu—N3^ii	89.85 (7)	C4—C5—H5	118.6
N2—Cu—N3^ii	91.36 (6)	N1—C5—H5	118.6
N4^iii—Cu—N1	89.39 (7)	C7—C6—N4	122.29 (18)
N2—Cu—N1	89.63 (6)	C7—C6—H6	118.9
N3^ii—Cu—N1	171.70 (6)	N4—C6—H6	118.9
N4^iii—Cu—O7^i	92.30 (6)	C6—C7—C8	119.86 (18)
N2—Cu—O7^i	89.28 (6)	C6—C7—H7	120.1
N3^ii—Cu—O7^i	86.94 (6)	C8—C7—H7	120.1
N1—Cu—O7^i	84.83 (6)	C9—C8—C7	117.66 (17)
N4^iii—Cu—O1	86.17 (6)	C9—C8—C3	122.86 (18)
N2—Cu—O1	92.08 (6)	C7—C8—C3	119.47 (18)
N3^ii—Cu—O1	103.11 (6)	C10—C9—C8	119.43 (18)
N1—Cu—O1	85.09 (6)	C10—C9—H9	120.3
O2—Cr1—O3	110.05 (9)	C8—C9—H9	120.3
O2—Cr1—O1	109.44 (8)	C9—C10—N4	122.04 (18)
O3—Cr1—O1	109.76 (9)	C9—C10—H10	119.0
O2—Cr1—O4	107.94 (9)	N4—C10—H10	119.0
O3—Cr1—O4	110.90 (8)	C12—C11—N2	122.56 (18)
O1—Cr1—O4	108.71 (7)	C12—C11—H11	118.7
O6—Cr2—O5	110.04 (10)	N2—C11—H11	118.7
O6—Cr2—O7	109.79 (8)	C11—C12—C13	119.55 (18)
O5—Cr2—O7	110.21 (9)	C11—C12—H12	120.2
O6—Cr2—O4	107.42 (8)	C13—C12—H12	120.2
O5—Cr2—O4	109.56 (9)	C12—C13—C14	117.55 (17)
O7—Cr2—O4	109.77 (7)	C12—C13—C18	121.39 (17)
Cr1—O4—Cr2	125.96 (9)	C14—C13—C18	120.94 (18)
C1—N1—C5	117.13 (16)	C15—C14—C13	119.80 (18)
C1—N1—Cu	123.58 (13)	C15—C14—H14	120.1
C5—N1—Cu	118.57 (13)	C13—C14—H14	120.1
C15—N2—C11	118.26 (16)	C14—C15—N2	122.16 (18)
C15—N2—Cu	121.31 (13)	C14—C15—H15	118.9
C11—N2—Cu	120.09 (13)	N2—C15—H15	118.9
C20—N3—C16	116.99 (17)	N3—C16—C17	123.18 (18)
C20—N3—Cu^v	125.11 (13)	N3—C16—H16	118.4
C16—N3—Cu^v	117.90 (13)	C17—C16—H16	118.4
C6—N4—C10	118.70 (16)	C16—C17—C18	119.67 (18)
C6—N4—Cu^vi	117.92 (13)	C16—C17—H17	120.2
C10—N4—Cu^vi	123.14 (13)	C18—C17—H17	120.2
N1—C1—C2	123.61 (18)	C17—C18—C19	117.55 (17)
N1—C1—H1	118.2	C17—C18—C13	119.16 (17)
C2—C1—H1	118.2	C19—C18—C13	123.24 (18)
C1—C2—C3	118.64 (18)	C20—C19—C18	118.95 (18)
C1—C2—H2	120.7	C20—C19—H19	120.5
C3—C2—H2	120.7	C18—C19—H19	120.5
C4—C3—C2	117.74 (17)	N3—C20—C19	123.52 (18)
C4—C3—C8	119.54 (18)	N3—C20—H20	118.2
C2—C3—C8	122.71 (18)	C19—C20—H20	118.2

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