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

Mokaddem, S.; Boughzala, H.

doi:10.1107/S2056989017000482

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Volume 73| Part 2| February 2017| Pages 196-199

https://doi.org/10.1107/S2056989017000482

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

Sonia Mokaddem ^a and Habib Boughzala ^a ^*

^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.

Keywords: crystal structure; copper(II); organic–inorganic hybrid.

CCDC reference: 1526513

1. Chemical context

Copper halides have applications in biology as antifungal and anticancer agents (Creaven et al., 2010 ; Santini et al., 2014 ) and are also good precursors for photovoltaic cells because of their optoelectronic and magnetic properties (Levitsky et al., 2004 ; Ahmadi et al., 2013 ; Al-Far & Ali, 2009 ). 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.

2. Structural commentary

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

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 ; Yuan et al., 2004 ). A four-coordinate geometry is generally intermediate between square-planar and regular-tetrahedral, as reported by Al-Far & Ali (2009). In our case and according to the angular values of the copper–chlorine bonds, summarized in Table 1, 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.

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. 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, 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
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
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) and to two organic molecules through O—H⋯N hydrogen bonds, as shown in Fig. 5. 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) could possibly lead to luminescence properties.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	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
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
View of the packing showing the alternating stacking of the organic and inorganic layers connected through hydrogen bonds. The face-to-face π–π 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 ; Parent et al., 2007 ; Haddad et al., 2006 ; Marzotto et al., 2001 ; Choi et al., 2002 ; Awwadi et al., 2007 ). Non-covalent interactions such as hydrogen-bonding interactions and π–π 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) and are connected through face-to-face π–π 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 ) 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. 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
M_r	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)
V (Å³)	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 ).
T_min, T_max	0.746, 0.845
No. of measured, independent and observed [I > 2σ(I)] reflections	3358, 2127, 1796
R_int	0.042
(sin θ/λ)_max (Å⁻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
Δρ_max, Δρ_min (e Å⁻³)	0.78, −0.49
Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994 ), XCAD4 (Harms & Wocadlo, 1995 ), SHELXS97 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ), DIAMOND (Brandenburg, 2006 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1526513

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989017000482/vn2122sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017000482/vn2122Isup2.hkl

checkCIF report

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]·2H₂O	F(000) = 972
M_r = 479.66	D_x = 1.636 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 11.747 (8) Å	Cell parameters from 25 reflections
b = 9.793 (2) Å	θ = 2–27°
c = 17.339 (4) Å	µ = 1.69 mm⁻¹
β = 102.48 (5)°	T = 298 K
V = 1947.7 (15) Å³	Prism, yellow
Z = 4	0.45 × 0.15 × 0.1 mm

Data collection top

Enraf–Nonius CAD-4 diffractometer	R_int = 0.042
Radiation source: fine-focus sealed tube	θ_max = 27.0°, θ_min = 2.4°
non–profiled ω/2τ scans	h = −14→4
Absorption correction: ψ scan (North et al., 1968).	k = −1→12
T_min = 0.746, T_max = 0.845	l = −22→22
3358 measured reflections	2 standard reflections every 120 min
2127 independent reflections	intensity decay: 32%
1796 reflections with I > 2σ(I)

Refinement top

Refinement on F²	3 restraints
Least-squares matrix: full	Hydrogen site location: mixed
R[F² > 2σ(F²)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F²) = 0.108	w = 1/[σ²(F_o²) + (0.0535P)² + 3.2027P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = 0.001
2127 reflections	Δρ_max = 0.78 e Å⁻³
120 parameters	Δρ_min = −0.49 e Å⁻³

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

	x	y	z	U_iso*/U_eq
Cu	0.5000	0.65843 (5)	0.2500	0.03734 (16)
Cl1	0.64409 (8)	0.79968 (10)	0.30835 (5)	0.0654 (3)
Cl2	0.41162 (7)	0.52147 (11)	0.31978 (6)	0.0691 (3)
N1	0.5383 (2)	0.1611 (3)	0.39993 (14)	0.0503 (6)
H1A	0.5411	0.1555	0.3509	0.060*
N2	0.5837 (2)	0.1477 (2)	0.52756 (13)	0.0407 (5)
C1	0.4463 (3)	0.2105 (4)	0.4280 (2)	0.0564 (8)
H1	0.3770	0.2439	0.3973	0.068*
C2	0.4724 (3)	0.2029 (3)	0.50690 (19)	0.0508 (7)
H2	0.4254	0.2294	0.5411	0.061*
C3	0.6232 (2)	0.1228 (3)	0.46046 (15)	0.0411 (6)
C4	0.7339 (3)	0.0682 (3)	0.4645 (2)	0.0522 (7)
H4	0.7615	0.0503	0.4191	0.063*
C5	0.8004 (3)	0.0420 (4)	0.5383 (2)	0.0608 (8)
H5	0.8747	0.0056	0.5433	0.073*
C6	0.7581 (3)	0.0691 (4)	0.6061 (2)	0.0614 (9)
H6	0.8047	0.0507	0.6556	0.074*
C7	0.6512 (3)	0.1214 (3)	0.60080 (17)	0.0528 (7)
H7	0.6234	0.1394	0.6461	0.063*
OW	0.3680 (2)	0.1331 (5)	0.23911 (17)	0.0959 (12)
HW1	0.376 (5)	0.2194 (15)	0.244 (5)	0.144*
HW2	0.2977 (19)	0.114 (5)	0.238 (4)	0.144*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu	0.0303 (2)	0.0469 (3)	0.0372 (2)	0.000	0.01252 (17)	0.000
Cl1	0.0549 (5)	0.0787 (6)	0.0612 (5)	−0.0256 (4)	0.0092 (4)	−0.0132 (4)
Cl2	0.0553 (5)	0.0861 (6)	0.0731 (5)	−0.0074 (4)	0.0300 (4)	0.0268 (5)
N1	0.0616 (15)	0.0559 (15)	0.0321 (11)	−0.0059 (12)	0.0070 (11)	0.0009 (10)
N2	0.0518 (13)	0.0387 (12)	0.0339 (10)	−0.0029 (10)	0.0143 (10)	0.0000 (9)
C1	0.0509 (17)	0.0544 (18)	0.0594 (19)	−0.0002 (14)	0.0022 (14)	0.0033 (15)
C2	0.0522 (17)	0.0501 (16)	0.0544 (17)	0.0015 (13)	0.0208 (14)	0.0002 (14)
C3	0.0502 (15)	0.0410 (13)	0.0337 (12)	−0.0089 (11)	0.0128 (11)	−0.0028 (11)
C4	0.0546 (17)	0.0505 (16)	0.0570 (17)	−0.0064 (13)	0.0239 (14)	−0.0077 (14)
C5	0.0485 (17)	0.0515 (18)	0.079 (2)	−0.0010 (14)	0.0060 (16)	−0.0004 (17)
C6	0.074 (2)	0.0547 (18)	0.0467 (17)	−0.0044 (16)	−0.0062 (16)	0.0051 (15)
C7	0.074 (2)	0.0523 (17)	0.0312 (13)	−0.0027 (15)	0.0085 (13)	0.0015 (12)
OW	0.0537 (15)	0.186 (4)	0.0483 (14)	−0.0107 (19)	0.0127 (12)	0.010 (2)

Geometric parameters (Å, º) top

Cu—Cl2	2.2100 (11)	C2—H2	0.9300
Cu—Cl2ⁱ	2.2100 (11)	C3—C4	1.394 (4)
Cu—Cl1ⁱ	2.2499 (13)	C4—C5	1.372 (5)
Cu—Cl1	2.2499 (13)	C4—H4	0.9300
N1—C3	1.336 (4)	C5—C6	1.397 (6)
N1—C1	1.366 (5)	C5—H5	0.9300
N1—H1A	0.8600	C6—C7	1.340 (5)
N2—C3	1.364 (3)	C6—H6	0.9300
N2—C7	1.369 (4)	C7—H7	0.9300
N2—C2	1.388 (4)	OW—HW1	0.854 (10)
C1—C2	1.338 (5)	OW—HW2	0.845 (10)
C1—H1	0.9300

Cl2—Cu—Cl2ⁱ	105.26 (7)	N2—C2—H2	126.8
Cl2—Cu—Cl1ⁱ	102.86 (5)	N1—C3—N2	106.6 (3)
Cl2ⁱ—Cu—Cl1ⁱ	121.58 (4)	N1—C3—C4	132.6 (3)
Cl2—Cu—Cl1	121.58 (4)	N2—C3—C4	120.7 (3)
Cl2ⁱ—Cu—Cl1	102.86 (5)	C5—C4—C3	117.1 (3)
Cl1ⁱ—Cu—Cl1	104.12 (7)	C5—C4—H4	121.5
C3—N1—C1	109.5 (3)	C3—C4—H4	121.5
C3—N1—H1A	125.3	C4—C5—C6	121.0 (3)
C1—N1—H1A	125.3	C4—C5—H5	119.5
C3—N2—C7	121.5 (3)	C6—C5—H5	119.5
C3—N2—C2	108.9 (2)	C7—C6—C5	120.8 (3)
C7—N2—C2	129.6 (3)	C7—C6—H6	119.6
C2—C1—N1	108.7 (3)	C5—C6—H6	119.6
C2—C1—H1	125.7	C6—C7—N2	118.9 (3)
N1—C1—H1	125.7	C6—C7—H7	120.6
C1—C2—N2	106.3 (3)	N2—C7—H7	120.6
C1—C2—H2	126.8	HW1—OW—HW2	108 (3)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	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+1/2; (ii) −x+1/2, y−1/2, −z+1/2.

Acknowledgements

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

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