Bis(μ-2,2′-biimidazole-κ²N³:N^3′)bis­[aqua­copper(I)] sulfate

In the structure of the title compound, [Cu₂(C₆H₆N₄)₂(H₂O)₂]SO₄, the asymmetric unit contains half each of two 2,2′-diimidazole ligands, one Cu⁺ cation, one water mol­ecule and half of a sulfate anion (2 symmetry). The dinuclear complex is completed through a twofold rotation axis, leading to a twisted ten-membered ring mol­ecule. The dihedral angle between the two symmetry-related 2,2′-diimidazole ligands is 23.6 (1)°. The copper centre is coordinated by two N atoms of two symmetry-related 2,2′-diimidazole ligands in an almost linear fashion. The water mol­ecule exhibits a weak coordination to Cu⁺ with a more remote distance of 2.591 (2) Å. The distance between the two copper centres is 2.5956 (6) Å. O—H...O and N—H...O hydrogen bonds between the complex cation, the water mol­ecule and the sulfate anion lead to the formation of a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 273 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.025
• wR factor = 0.073
• Data-to-parameter ratio = 11.0

checkCIF/PLATON results

No syntax errors found



Alert level B
PLAT232_ALERT_2_B Hirshfeld Test Diff (M-X)  Cu1    --  O1W     ..      10.25 su

Alert level C
PLAT195_ALERT_1_C Missing _cell_measurement_theta_max   datum ....          ?
PLAT196_ALERT_1_C Missing _cell_measurement_theta_min   datum ....          ?
PLAT244_ALERT_4_C Low   'Solvent' Ueq as Compared to Neighbors of          S1

Alert level G
PLAT199_ALERT_1_G Check the Reported _cell_measurement_temperature        273 K
PLAT200_ALERT_1_G Check the Reported   _diffrn_ambient_temperature        273 K

   0 ALERT level A = In general: serious problem
   1 ALERT level B = Potentially serious problem
   3 ALERT level C = Check and explain
   2 ALERT level G = General alerts; check

   4 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The design and synthesis of metal-organic frameworks (MOFs) has attracted continuous research interest not only because of their appealing structural and topological novelties, but also due to their optical, electronic, magnetic, and catalytic properties, as well as their potential medical applications (Lee et al. 2000). Here, we report the structure of the title compound.

As shown in Figure 1, the Cu⁺ cation is coordianted by two N atoms from two 2,2'-diimidazole molecules, showing an almost linear coordination to Cu(I), the Cu—N bond lengths being 1.8953 (18) and 1.9006 (18) Å, respectively. The separation between the two Cu⁺ cores is 2.5956 (6) Å. Moreover, the water molecule exhibits a weak coordination to Cu(I) with a more remote distance of 2.591 (2) Å. Each two Cu(I) ions and two 2,2'-diimidazole molecules form one ten-membered ring molecle via a twofold axis as symmetry element. The dihedral angle between two symmetry-related 2,2'-diimidazole molecules is 23.6 (1) °. In the voids of the packing, there is an intricate hydrogen bonding of the type O—H···O and N—H···O, as shown in Figure 2 and Table 2.

Related literature

For background to metal organic framework structures, see: Lee et al. (2000).

S2. Experimental

A mixture of 2,2'-diimidazole (1 mmol, 0.14 g), oxalic acid (1 mmol, 0.09 g), copper(II) sulfate pentahydrate (1 mmol, 0.25 g), and 10 ml H₂O was heated to 443 K for one day in an autoclave. Red crystals were obtained after cooling to room temperature with a yield of 82%. Elemental Analysis. Calc. for C₁₂H₁₆Cu₂N₈O₆S: C 27.30, H 3.03, N 21.23%; Found: C 27.15, H 2.95, N 21.11%. Under the given hydrothermal conditions, Cu(II) was apparently reduced to Cu(I), leading to the formation of the title complex.

S3. Refinement

All hydrogen atoms bound to carbon were refined using a riding model with C—H = 0.93 Å and U_iso(H) = 1.2Ueq(C). The H atoms of the water molecule were located from difference density maps and were refined with distance restraints of d(H–H) = 1.38 (2) Å, d(O–H) = 0.88 (2) Å, and with a fixed U_iso of 0.80 Ų. The H atoms on nitrogen atoms were located from difference density maps and were refined with distance restraints of d(N–H) = 0.97 (2) Å.

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. A view of the title compound with the unique atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. [Symmetry code: #I -x,y,-z + 3/2]
	Fig. 2. A view of the packing diagram of the title compound. Displacement ellipsoids are drawn at the 30% probability level.

Bis(µ-2,2'-biimidazole-κ²N³:N^3')bis[aquacopper(I)] sulfate

Crystal data

[Cu2(C6H6N4)2(H2O)2]SO4	F(000) = 1064
Mr = 527.50	Dx = 1.913 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 5587 reflections
a = 12.7597 (7) Å	θ = 0.0–0.0°
b = 14.8594 (7) Å	µ = 2.49 mm^−1
c = 10.6375 (5) Å	T = 273 K
β = 114.777 (3)°	Block, red
V = 1831.22 (16) Å^3	0.12 × 0.10 × 0.08 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer	1630 independent reflections
Radiation source: fine-focus sealed tube	1522 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ϕ and ω scans	θmax = 25.0°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Bruker, 2001)	h = −15→15
Tmin = 0.754, Tmax = 0.826	k = −17→17
9619 measured reflections	l = −12→12

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)] = 0.025	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.073	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ^2(Fo^2) + (0.047P)^2 + 2.1669P] where P = (Fo^2 + 2Fc^2)/3
1630 reflections	(Δ/σ)max = 0.008
148 parameters	Δρmax = 0.30 e Å^−3
0 restraints	Δρmin = −0.45 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	0.01189 (3)	0.265145 (18)	0.63467 (3)	0.04181 (14)
S1	1.0000	0.76744 (5)	0.7500	0.0392 (2)
C1	0.03743 (17)	0.45644 (13)	0.7144 (2)	0.0299 (4)
C2	0.14997 (19)	0.50798 (15)	0.6214 (2)	0.0379 (5)
H2	0.1923	0.5464	0.5913	0.045*
C3	0.1405 (2)	0.41751 (15)	0.6049 (2)	0.0400 (5)
H3	0.1766	0.3829	0.5616	0.048*
C4	−0.1342 (2)	0.12062 (16)	0.4636 (2)	0.0411 (5)
H4	−0.1675	0.1563	0.3848	0.049*
C5	−0.1485 (2)	0.03051 (16)	0.4682 (2)	0.0410 (5)
H5	−0.1917	−0.0068	0.3944	0.049*
C6	−0.03621 (17)	0.07952 (13)	0.6765 (2)	0.0302 (4)
N1	−0.08656 (15)	0.00532 (12)	0.6033 (2)	0.0352 (4)
N2	−0.06269 (16)	0.15125 (12)	0.59369 (19)	0.0356 (4)
N3	0.08523 (15)	0.53162 (11)	0.69092 (19)	0.0338 (4)
N4	0.06894 (16)	0.38469 (12)	0.66225 (19)	0.0350 (4)
O1	0.9542 (2)	0.71052 (14)	0.8273 (3)	0.0695 (6)
O2	0.90665 (16)	0.82506 (12)	0.6552 (2)	0.0561 (5)
O1W	0.1960 (2)	0.18900 (17)	0.6389 (3)	0.0708 (6)
H1W	0.169 (3)	0.191 (4)	0.5542 (3)	0.13 (2)*
H2W	0.2621 (13)	0.208 (3)	0.678 (3)	0.082 (12)*
H3A	0.069 (2)	0.5926 (7)	0.710 (3)	0.061 (8)*
H1A	−0.079 (2)	−0.0551 (7)	0.641 (3)	0.060 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cu1	0.0621 (2)	0.01984 (19)	0.0446 (2)	−0.00492 (11)	0.02347 (16)	−0.00188 (10)
S1	0.0481 (5)	0.0179 (4)	0.0512 (5)	0.000	0.0202 (4)	0.000
C1	0.0328 (10)	0.0188 (9)	0.0321 (10)	0.0000 (8)	0.0075 (8)	0.0009 (8)
C2	0.0378 (11)	0.0326 (11)	0.0440 (12)	−0.0024 (9)	0.0179 (10)	0.0032 (9)
C3	0.0457 (12)	0.0332 (12)	0.0448 (13)	0.0033 (10)	0.0227 (10)	0.0008 (10)
C4	0.0462 (12)	0.0379 (12)	0.0345 (11)	−0.0033 (10)	0.0122 (10)	0.0019 (10)
C5	0.0424 (12)	0.0387 (13)	0.0383 (12)	−0.0091 (10)	0.0133 (10)	−0.0073 (10)
C6	0.0317 (10)	0.0214 (10)	0.0384 (11)	−0.0013 (8)	0.0157 (8)	−0.0008 (8)
N1	0.0373 (9)	0.0235 (9)	0.0432 (10)	−0.0028 (7)	0.0153 (8)	−0.0024 (8)
N2	0.0438 (10)	0.0245 (9)	0.0368 (10)	−0.0024 (7)	0.0154 (8)	0.0006 (7)
N3	0.0350 (9)	0.0208 (9)	0.0417 (10)	−0.0009 (7)	0.0124 (8)	0.0009 (7)
N4	0.0436 (10)	0.0221 (9)	0.0391 (10)	0.0003 (7)	0.0173 (8)	−0.0002 (7)
O1	0.1064 (17)	0.0292 (9)	0.0917 (16)	−0.0109 (11)	0.0600 (14)	0.0037 (10)
O2	0.0531 (10)	0.0340 (9)	0.0671 (12)	0.0030 (8)	0.0113 (9)	0.0031 (8)
O1W	0.0653 (14)	0.0608 (14)	0.0795 (17)	−0.0082 (11)	0.0236 (12)	−0.0130 (12)

Geometric parameters (Å, º)

Cu1—N4	1.8953 (18)	C3—H3	0.9300
Cu1—N2	1.9006 (18)	C4—C5	1.355 (3)
Cu1—Cu1^i	2.5956 (6)	C4—N2	1.377 (3)
S1—O1	1.462 (2)	C4—H4	0.9300
S1—O1^ii	1.462 (2)	C5—N1	1.370 (3)
S1—O2^ii	1.4704 (18)	C5—H5	0.9300
S1—O2	1.4704 (18)	C6—N2	1.333 (3)
C1—N4	1.339 (3)	C6—N1	1.347 (3)
C1—N3	1.345 (3)	C6—C6^i	1.446 (4)
C1—C1^i	1.447 (4)	N1—H1A	0.972 (15)
C2—C3	1.355 (3)	N3—H3A	0.970 (14)
C2—N3	1.366 (3)	O1W—H1W	0.819 (6)
C2—H2	0.9300	O1W—H2W	0.82 (3)
C3—N4	1.383 (3)
N4—Cu1—N2	173.20 (8)	N2—C4—H4	125.3
N4—Cu1—Cu1^i	92.47 (6)	C4—C5—N1	106.3 (2)
N2—Cu1—Cu1^i	88.35 (6)	C4—C5—H5	126.9
O1—S1—O1^ii	109.29 (18)	N1—C5—H5	126.8
O1—S1—O2^ii	110.56 (13)	N2—C6—N1	110.22 (19)
O1^ii—S1—O2^ii	108.83 (13)	N2—C6—C6^i	125.81 (12)
O1—S1—O2	108.83 (13)	N1—C6—C6^i	123.98 (13)
O1^ii—S1—O2	110.56 (13)	C6—N1—C5	107.94 (18)
O2^ii—S1—O2	108.77 (15)	C6—N1—H1A	125.3 (18)
N4—C1—N3	110.28 (19)	C5—N1—H1A	126.8 (18)
N4—C1—C1^i	126.55 (12)	C6—N2—C4	106.10 (18)
N3—C1—C1^i	123.17 (12)	C6—N2—Cu1	126.64 (15)
C3—C2—N3	106.5 (2)	C4—N2—Cu1	125.59 (15)
C3—C2—H2	126.7	C1—N3—C2	108.11 (18)
N3—C2—H2	126.7	C1—N3—H3A	125.6 (17)
C2—C3—N4	109.4 (2)	C2—N3—H3A	125.9 (17)
C2—C3—H3	125.3	C1—N4—C3	105.68 (18)
N4—C3—H3	125.3	C1—N4—Cu1	130.40 (15)
C5—C4—N2	109.4 (2)	C3—N4—Cu1	122.96 (15)
C5—C4—H4	125.3	H1W—O1W—H2W	115 (4)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1W—H1W···O2^iii	0.82 (1)	2.04 (1)	2.848 (3)	170 (5)
O1W—H2W···O1^iv	0.82 (3)	2.29 (1)	3.072 (4)	159 (4)
N3—H3A···O1^v	0.97 (1)	1.79 (1)	2.697 (3)	153 (3)
N1—H1A···O2^vi	0.97 (2)	1.80 (1)	2.743 (3)	162 (3)

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