research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

Bis(imidazo[1,2-a]pyridin-1-ium) tetra­chlorido­cuprate(II) dihydrate

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aLaboratoire de Matériaux et Cristallochimie, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Manar II Tunis, Tunisia
*Correspondence e-mail: habib.boughzala@ipein.rnu.tn

Edited by A. Van der Lee, Université de Montpellier II, France (Received 26 December 2016; accepted 10 January 2017; online 13 January 2017)

In the title salt, (C7H7N2)2[CuCl4]·2H2O, the Cu2+ cation is coordinated by four Cl atoms and adopts a distorted tetra­hedral geometry. Two mol­ecules of imidazo[1,2-a]pyridine are protonated ensuring electrical neutrality. O—H⋯Cl and N—H⋯O hydrogen bonds link the organic and the inorganic moieties, leading to a self-organized hydrated hybrid structure.

1. Chemical context

Copper halides have applications in biology as anti­fungal and anti­cancer agents (Creaven et al., 2010[Creaven, B. S., Duff, B., Egan, D. A., Kavanagh, K., Rosair, G., Thangella, V. R. & Walsh, M. (2010). Inorg. Chim. Acta, 363, 4048-4058.]; Santini et al., 2014[Santini, C., Pellei, M., Gandin, V., Porchia, M., Tisato, F. & Marzano, C. (2014). Chem. Rev. 114, 815-862.]) and are also good precursors for photovoltaic cells because of their optoelectronic and magnetic properties (Levitsky et al., 2004[Levitsky, I. A., Euler, W. B., Tokranova, N., Xu, B. & Castracane, J. (2004). Appl. Phys. Lett. 85, 6245-6247.]; Ahmadi et al., 2013[Ahmadi, R. A., Hasanvand, F., Bruno, G., Rudbari, H. A. & Saied, A. (2013). Inorg. Chem. pp. 1-7.]; Al-Far & Ali, 2009[Al-Far, R. H. & Ali, B. F. (2009). Acta Cryst. E65, m73-m74.]). For this reason, we have focused our research on copper-based hybrid materials using diverse organic moieties to balance the halide copper inorganic anions. We report in this paper the synthesis and structure determination using single crystal X-ray diffraction data of a tetrahedral tetrachloridocuprate(II) anion with imidazo[1,2-a]pyridin-1-ium organic cations and two lattice water molecules.

[Scheme 1]

2. Structural commentary

The structural unit (Fig. 1[link]) of the title compound comprises one [CuCl4]2− anion, two organic imidazo[1,2-a]pyridine ligands and two water mol­ecules.

[Figure 1]
Figure 1
ORTEP-style plot of the structural unit with displacement ellipsoids at the 50% probability level. [Symmetry code: (i) 1 − x, y, [{1\over 2}] − z.]

When coordinated by halide anions, copper can adopt several coordination geometries including tetra­hedral, square-pyramidal, square-planar and square-bipyramidal (Bhattacharya et al., 2004[Bhattacharya, R., Chanda, S., Bocelli, G., Cantoni, A. & Ghosh, A. (2004). J. Chem. Crystallogr. 34, 393-400.]; Yuan et al., 2004[Yuan, B.-L., Lan, H.-C., Chen, Y.-P. & Li, Y.-B. (2004). Acta Cryst. E60, m617-m619.]). A four-coordinate geometry is generally inter­mediate between square-planar and regular-tetra­hedral, as reported by Al-Far & Ali (2009[Al-Far, R. H. & Ali, B. F. (2009). Acta Cryst. E65, m73-m74.]). In our case and according to the angular values of the copper–chlorine bonds, summarized in Table 1[link], the tetra­hedral copper coordination seems to be slightly distorted. These distortions are a consequence of the lower mol­ecular symmetry.

Table 1
Selected geometric parameters (Å, °)

Cu—Cl2 2.2100 (11) Cu—Cl1 2.2499 (13)
       
Cl2—Cu—Cl2i 105.26 (7) Cl2—Cu—Cl1 121.58 (4)
Cl2—Cu—Cl1i 102.86 (5) Cl1i—Cu—Cl1 104.12 (7)
Symmetry code: (i) [-x+1, y, -z+{\script{1\over 2}}].

The (C7H7N2)+ cation adopts a quite planar conformation, as characterized by its low r.m.s deviation of 0.0064 Å. The maximum deviations are 0.010 (3) and −0.012 (2) Å for atoms C1 and N2, respectively.

The two water mol­ecules are located approximately in a common plane defined by the organic cations, directing their hydrogen atoms towards the anionic group [CuCl4]2− and leaving the oxygen free-electron pairs available for a hydrogen-bonding inter­action with the protonated nitro­gen site of the imidazo[1,2-a]pyridinum cation. In the anionic subnetwork, every [CuCl4]2− anion is linked to two water mol­ecules by hydrogen bonds via the Cl2 vertices, as shown in Fig. 2[link].

[Figure 2]
Figure 2
The [CuCl4]2− environment with hydrogen bonds shown as blue dashed lines. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry codes: (i) 1 − x, y, [{1\over 2}] − z; (ii) [{1\over 2}] + x, [{1\over 2}] + y, z; (iii) [{1\over 2}] − x, [{1\over 2}] + y, [{1\over 2}] − z.]

In spite of the single protonation of the organic mol­ecule on the aromatic nitro­gen site, every cation is linked to two water mol­ecules through bifurcated hydrogen-bonding inter­actions along [010], as shown in Fig. 3[link]. The organic cations are organized along (010), forming sheets parallel to the ab plane. A projection of the structural packing along the c axis, Fig. 4[link], reveals alternating empty elliptical channels delimited by the organic cations and inorganic tetra­hedra. The long and short dimensions of the elliptical sections are estimated to be, respectively, 6.1 (1) and 2.1 (1) Å for the largest ones and 4.3 (1) and 1.4 (1) Å for the narrowest. These voids are able to lodge several small solvent mol­ecules.

[Figure 3]
Figure 3
The environment around the (C7H7N2)+ cation showing the inter­actions with water mol­ecules through N1—H1A⋯OW and N1—H1A⋯OWi inter­actions. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry code: (i) 1 − x, y, [{1\over 2}] − z.]
[Figure 4]
Figure 4
Crystal packing along the c axis showing empty tunnels able to lodge small organic solvent mol­ecules. Displacement ellipsoids are displayed at the 50% probability level.

The water mol­ecules play a crucial role in the crystal-packing cohesion. Every water mol­ecule is linked to one [CuCl4] 2− tetra­hedron through O—H⋯Cl hydrogen bonds (Table 2[link]) and to two organic mol­ecules through O—H⋯N hydrogen bonds, as shown in Fig. 5[link]. The expected structural self-organization generally present in hybrid inorganic–organic compounds can also be found in the structure of the title salt. The alternating stacking of organic and inorganic sheets observed along the c axis (Fig. 6[link]) could possibly lead to luminescence properties.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
N1—H1A⋯OW 0.86 2.50 3.0723 125
N1—H1A⋯OWi 0.86 2.08 2.872 152 (1)
OW—HW2⋯Cl2ii 0.85 2.61 (1) 3.401 157 (1)
Symmetry codes: (i) [-x+1, y, -z+{\script{1\over 2}}]; (ii) [-x+{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}].
[Figure 5]
Figure 5
The environment around the water mol­ecule. Hydrogen bonds are indicated by blue dashed lines. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry codes: (i) 1 − x, y, [{1\over 2}] − z; (iii) [{1\over 2}] − x, −[{1\over 2}] + y, [{1\over 2}] − z.]
[Figure 6]
Figure 6
View of the packing showing the alternating stacking of the organic and inorganic layers connected through hydrogen bonds. The face-to-face ππ stacking between parallel organic mol­ecules is noteworthy with a centroid–centroid distance of 3.968 (3) Å. Displacement ellipsoids are displayed at the 50% probability level. [Symmetry code: (iii) [{1\over 2}] − x, −[{1\over 2}] + y, [{1\over 2}] − z.]

3. Supra­molecular features

The lowering of the symmetry of the copper coordination could also be due to halide–halide and intra- and intermol­ecular hydrogen-bonding inter­actions; these inter­actions are closely related to the shape and the size of the counter-cations (Bouacida et al., 2013[Bouacida, S., Bouchene, R., Khadri, A., Belhouas, R. & Merazig, H. (2013). Acta Cryst. E69, m610-m611.]; Parent et al., 2007[Parent, A. R., Landee, C. P. & Turnbull, M. M. (2007). Inorg. Chim. Acta, 360, 1943-1953.]; Haddad et al., 2006[Haddad, S. F., AlDamen, M. A. & Willett, R. D. (2006). Inorg. Chim. Acta, 359, 424-432.]; Marzotto et al., 2001[Marzotto, A., Clemente, D. A., Benetollo, F. & Valle, G. (2001). Polyhedron, 20, 171-177.]; Choi et al., 2002[Choi, S.-N., Lee, Y.-M., Lee, H.-W., Kang, S. K. & Kim, Y.-I. (2002). Acta Cryst. E58, m583-m585.]; Awwadi et al., 2007[Awwadi, F. F., Willett, R. D. & Twamley, B. (2007). Cryst. Growth Des. 7, 624-632.]). Non-covalent inter­actions such as hydrogen-bonding inter­actions and ππ stacking inter­actions represent the most important linkers in this kind of material. Moreover, these inter­actions are able to delimit not only the architecture, but also impact on the properties of metal–halide materials. The organic cations are linked to the water mol­ecule through N1—H1A⋯OW hydrogen bonds (Table 2[link]) and are connected through face-to-face ππ stacking [Cg1⋯Cg2([{3\over 2}] − x, [{1\over 2}] − y, 1 − z) = 3.968 (3) Å where Cg1 and Cg2 are the centroids of the N1/N3/C1–C3 and N2/C3–C7 rings, respectively]. The crystal packing can be described by alternating stacks of anions and cationic chains with the organic layers arranged parallel to the anionic stacks.

4. Database survey

Imidazo[1,2-a]-pyridyn-1-ium cations and several substituted forms have 53 entries in the Cambridge Structural Database (Groom et al., 2016[Groom, C. R., Bruno, I. J., Lightfoot, M. P. & Ward, S. C. (2016). Acta Cryst. B72, 171-179.]) without any hybrid compounds amongst them. To the best of our knowledge, this work is the first chemical and crystallographic identification of tetrachloridocuprate(II) combined with imidazo[1,2-a]-pyridyn-1-ium.

5. Synthesis and crystallization

The title salt was prepared by the reaction of imidazo[1,2-a]pyridine and Cu(NO3)2·2H2O (molar ratio 1:1) in an equal volume of water and ethanol (10 ml) mixed with 2 ml of hydro­chloric acid (37%). The solution was stirred for 1 h at 333 K. Prismatic yellow crystals suitable for X-ray diffraction were grown in one week by slow evaporation at room temperature.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 3[link]. H atoms were positioned geometrically and treated as riding on the parent atom with C—H = 0.93 Å and N—H = 0.86 Å. For HW1 and HW2, the restraints DFIX and DANG were used to stabilize the water mol­ecule.

Table 3
Experimental details

Crystal data
Chemical formula (C7H7N2)2[CuCl4]·2H2O
Mr 479.66
Crystal system, space group Monoclinic, C2/c
Temperature (K) 298
a, b, c (Å) 11.747 (8), 9.793 (2), 17.339 (4)
β (°) 102.48 (5)
V3) 1947.7 (15)
Z 4
Radiation type Mo Kα
μ (mm−1) 1.69
Crystal size (mm) 0.45 × 0.15 × 0.1
 
Data collection
Diffractometer Enraf–Nonius CAD-4
Absorption correction ψ scan (North et al., 1968[North, A. C. T., Phillips, D. C. & Mathews, F. S. (1968). Acta Cryst. A24, 351-359.]).
Tmin, Tmax 0.746, 0.845
No. of measured, independent and observed [I > 2σ(I)] reflections 3358, 2127, 1796
Rint 0.042
(sin θ/λ)max−1) 0.638
 
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.038, 0.108, 1.04
No. of reflections 2127
No. of parameters 120
No. of restraints 3
H-atom treatment H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3) 0.78, −0.49
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994[Enraf-Nonius (1994). CAD-4 EXPRESS. Enraf-Nonius, Delft, The Netherlands.]), XCAD4 (Harms & Wocadlo, 1995[Harms, K. & Wocadlo, S. (1995). XCAD4. University of Marburg, Germany.]), SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), SHELXL2014 (Sheldrick, 2015[Sheldrick, G. M. (2015). Acta Cryst. C71, 3-8.]), DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Bis(imidazo[1,2-a]pyridin-1-ium) tetrachloridocuprate(II) dihydrate top
Crystal data top
(C7H7N2)2[CuCl4]·2H2OF(000) = 972
Mr = 479.66Dx = 1.636 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
a = 11.747 (8) ÅCell parameters from 25 reflections
b = 9.793 (2) Åθ = 2–27°
c = 17.339 (4) ŵ = 1.69 mm1
β = 102.48 (5)°T = 298 K
V = 1947.7 (15) Å3Prism, yellow
Z = 40.45 × 0.15 × 0.1 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
Rint = 0.042
Radiation source: fine-focus sealed tubeθmax = 27.0°, θmin = 2.4°
non–profiled ω/2τ scansh = 144
Absorption correction: ψ scan
(North et al., 1968).
k = 112
Tmin = 0.746, Tmax = 0.845l = 2222
3358 measured reflections2 standard reflections every 120 min
2127 independent reflections intensity decay: 32%
1796 reflections with I > 2σ(I)
Refinement top
Refinement on F23 restraints
Least-squares matrix: fullHydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.038H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.108 w = 1/[σ2(Fo2) + (0.0535P)2 + 3.2027P]
where P = (Fo2 + 2Fc2)/3
S = 1.04(Δ/σ)max = 0.001
2127 reflectionsΔρmax = 0.78 e Å3
120 parametersΔρmin = 0.49 e Å3
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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 (Å2) top
xyzUiso*/Ueq
Cu0.50000.65843 (5)0.25000.03734 (16)
Cl10.64409 (8)0.79968 (10)0.30835 (5)0.0654 (3)
Cl20.41162 (7)0.52147 (11)0.31978 (6)0.0691 (3)
N10.5383 (2)0.1611 (3)0.39993 (14)0.0503 (6)
H1A0.54110.15550.35090.060*
N20.5837 (2)0.1477 (2)0.52756 (13)0.0407 (5)
C10.4463 (3)0.2105 (4)0.4280 (2)0.0564 (8)
H10.37700.24390.39730.068*
C20.4724 (3)0.2029 (3)0.50690 (19)0.0508 (7)
H20.42540.22940.54110.061*
C30.6232 (2)0.1228 (3)0.46046 (15)0.0411 (6)
C40.7339 (3)0.0682 (3)0.4645 (2)0.0522 (7)
H40.76150.05030.41910.063*
C50.8004 (3)0.0420 (4)0.5383 (2)0.0608 (8)
H50.87470.00560.54330.073*
C60.7581 (3)0.0691 (4)0.6061 (2)0.0614 (9)
H60.80470.05070.65560.074*
C70.6512 (3)0.1214 (3)0.60080 (17)0.0528 (7)
H70.62340.13940.64610.063*
OW0.3680 (2)0.1331 (5)0.23911 (17)0.0959 (12)
HW10.376 (5)0.2194 (15)0.244 (5)0.144*
HW20.2977 (19)0.114 (5)0.238 (4)0.144*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu0.0303 (2)0.0469 (3)0.0372 (2)0.0000.01252 (17)0.000
Cl10.0549 (5)0.0787 (6)0.0612 (5)0.0256 (4)0.0092 (4)0.0132 (4)
Cl20.0553 (5)0.0861 (6)0.0731 (5)0.0074 (4)0.0300 (4)0.0268 (5)
N10.0616 (15)0.0559 (15)0.0321 (11)0.0059 (12)0.0070 (11)0.0009 (10)
N20.0518 (13)0.0387 (12)0.0339 (10)0.0029 (10)0.0143 (10)0.0000 (9)
C10.0509 (17)0.0544 (18)0.0594 (19)0.0002 (14)0.0022 (14)0.0033 (15)
C20.0522 (17)0.0501 (16)0.0544 (17)0.0015 (13)0.0208 (14)0.0002 (14)
C30.0502 (15)0.0410 (13)0.0337 (12)0.0089 (11)0.0128 (11)0.0028 (11)
C40.0546 (17)0.0505 (16)0.0570 (17)0.0064 (13)0.0239 (14)0.0077 (14)
C50.0485 (17)0.0515 (18)0.079 (2)0.0010 (14)0.0060 (16)0.0004 (17)
C60.074 (2)0.0547 (18)0.0467 (17)0.0044 (16)0.0062 (16)0.0051 (15)
C70.074 (2)0.0523 (17)0.0312 (13)0.0027 (15)0.0085 (13)0.0015 (12)
OW0.0537 (15)0.186 (4)0.0483 (14)0.0107 (19)0.0127 (12)0.010 (2)
Geometric parameters (Å, º) top
Cu—Cl22.2100 (11)C2—H20.9300
Cu—Cl2i2.2100 (11)C3—C41.394 (4)
Cu—Cl1i2.2499 (13)C4—C51.372 (5)
Cu—Cl12.2499 (13)C4—H40.9300
N1—C31.336 (4)C5—C61.397 (6)
N1—C11.366 (5)C5—H50.9300
N1—H1A0.8600C6—C71.340 (5)
N2—C31.364 (3)C6—H60.9300
N2—C71.369 (4)C7—H70.9300
N2—C21.388 (4)OW—HW10.854 (10)
C1—C21.338 (5)OW—HW20.845 (10)
C1—H10.9300
Cl2—Cu—Cl2i105.26 (7)N2—C2—H2126.8
Cl2—Cu—Cl1i102.86 (5)N1—C3—N2106.6 (3)
Cl2i—Cu—Cl1i121.58 (4)N1—C3—C4132.6 (3)
Cl2—Cu—Cl1121.58 (4)N2—C3—C4120.7 (3)
Cl2i—Cu—Cl1102.86 (5)C5—C4—C3117.1 (3)
Cl1i—Cu—Cl1104.12 (7)C5—C4—H4121.5
C3—N1—C1109.5 (3)C3—C4—H4121.5
C3—N1—H1A125.3C4—C5—C6121.0 (3)
C1—N1—H1A125.3C4—C5—H5119.5
C3—N2—C7121.5 (3)C6—C5—H5119.5
C3—N2—C2108.9 (2)C7—C6—C5120.8 (3)
C7—N2—C2129.6 (3)C7—C6—H6119.6
C2—C1—N1108.7 (3)C5—C6—H6119.6
C2—C1—H1125.7C6—C7—N2118.9 (3)
N1—C1—H1125.7C6—C7—H7120.6
C1—C2—N2106.3 (3)N2—C7—H7120.6
C1—C2—H2126.8HW1—OW—HW2108 (3)
Symmetry code: (i) x+1, y, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···OW0.862.503.0723125
N1—H1A···OWi0.862.082.872152 (1)
OW—HW2···Cl2ii0.852.61 (1)3.401157 (1)
Symmetry codes: (i) x+1, y, z+1/2; (ii) x+1/2, y1/2, z+1/2.
 

Acknowledgements

We acknowledge the assistance of the staff of the Tunisian Laboratory of Materials and Crystallography during the data collection.

References

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