Two novel organic-inorganic hybrid materials from tetra­chlorido­metallate(II) salts and 4-[(E)-2-(pyri­din-1-ium-2-yl)ethenyl]pyridinium

Two organic-inorganic hybrid compounds have been prepared by the combination of the 4-[(E)-2-(pyridin-1-ium-2-yl)ethen­yl]pyridinium cation with perhalometallate anions to give 4-[(E)-2-(pyridin-1-ium-2-yl)ethen­yl]pyridinium tetra­chlo­r­ido­cobaltate(II), (C₁₂H₁₂N₂)[CoCl₄], (I), and 4-[(E)-2-(pyri­din-1-ium-2-yl)ethen­yl]pyridinium tetra­chlorido­zincate(II), (C₁₂H₁₂N₂)[ZnCl₄], (II). The compounds have been structurally characterized by single-crystal X-ray diffraction analysis, showing the formation of a three-dimensional network through X-H...Cl_nM^- (X = C, N⁺; n = 1, 2; M = Co^II, Zn^II) hydrogen-bonding inter­actions and [pi]-[pi] stacking inter­actions. The title compounds were also characterized by FT-IR spectroscopy and thermogravimetric analysis (TGA).

S1. Introduction

Hydrogen-bond-based organic–inorganic hybrid materials have gained widespread inter­est because of their structural, magnetic, optical and electrical properties (Weng et al., 2011; Pardo et al., 2011; Sanchez et al., 2014). The use of hydrogen-bonding inter­actions with metal salts to control the crystal structure of the product has also recently received attention (Felloni et al., 2004; Boldog et al., 2009; Al-Ktaifani & Rukiah, 2012). Many research groups have contributed to this area, utilizing supra­molecular synthons, such as charge-assisted N—H···Cl hydrogen bonds, to form organic–inorganic hybrid crystalline solids containing organic cations and anionic metal complexes (Podesta & Orpen, 2005; Kumar et al., 2006; Deifel & Cahill, 2009; Vitorica-Yrezabal et al., 2011). In these assemblies, the cations are usually protonated nitro­gen bases with peripheral functional groups, such as bipyridinium groups, and the anionic metal complexes generally refer to the primary coordination sphere of metal ions containing halogens. Typical bond acceptors are, for example, [MCl₄]^2- and [MCl₆]^2-. Deliberate efforts have been made to construct intriguing supra­molecular assemblies using metal–halide-based hydrogen bonds formed between organic molecules containing protonated ring N atoms (either aromatic or alicyclic) and inorganic perhalometallate salts (MX₄; M = transition metal, X = halogen, mainly Cl) (Zordan et al., 2005; Rademeyer et al., 2011).

In this context, we reported recently the synthesis and molecular structure characterization of the complex salts (C₁₈H₁₆N₅)[CuCl₄]Cl, (C₁₈H₁₆N₅)₂[MCl₄]·4H₂O (M = Pd or Pt; Enríquez et al., 2012), (C₁₂H₁₆N₃O)₂[PdCl₄]₃ and (C₁₂H₁₆N₃O)[PtCl₄]Cl (Campos-Gaxiola, Almaral Sánchez et al., 2013; Campos-Gaxiola, Báez-Castro et al., 2013).

In the present article, the synthesis of 4-[(E)-2-(pyridin-1-ium-2-yl)ethenyl]pyridinium tetra­chloridocobaltate(II), (I), and 4-[(E)-2-(pyridin-1-ium-2-yl)ethenyl]pyridinium tetra­chloridozincate(II), (II), is presented, together with their structural characterization by single-crystal X-ray diffraction analysis.

S2. Experimental

The chemicals and solvents used in this work were of analytical grade, commercially available and used without further purification. FT–IR spectra were recorded as KBr pellets in the range 4000–400 cm^-1 on a Bruker Alpha Tensor 27 spectrophotometer. Thermogravimetric analyses (TGA) were performed under nitro­gen (50 ml min^-1) in the temperature range 303–1073 K (283 K min^-1 [Should this be 10 K min^-1?]) using a TA SDT Q600 apparatus.

S2.1. Synthesis and crystallization

For the synthesis of (I), a mixture of cobalt(II) chloride (0.23 g) and 4-[(E)-2-(pyridin-2-yl)vinyl]­pyridine (0.30 g) (1:1 molar ratio) was dissolved in an aqueous solution of hydro­chloric acid [Volume? Concentration or pH?]. The mixture was stirred for 1 h and then kept at room temperature. After two weeks, green crystals of (I) had formed (yield 53%). IR (KBr, ν, cm^-1): 3242–3102 (⁺N—H_py), 3055–2933 (C—H_py + ═C—H_vinyl), 1616 (C═N), 1535–1458 (C═C_vinyl + C═C_py). TGA analysis, calculated for 2HCl: 18.9%, found: 17.9% (368–629 K); calculated for C₇H₇N: 27.9%, found: 27.3% (629–742 K); calculated for C₅H₅N: 20.3%, found: 20.7% (742–1004 K).

For the synthesis of (II), a mixture of zinc(II) chloride (0.22 g) and 4-[(E)-2-(pyridin-2-yl)vinyl]­pyridine (0.30 g) (1:1 molar ratio) was dissolved in an aqueous solution of hydro­chloric acid [Volume? Concentration or pH?]. The mixture was stirred for 30 min and then kept at room temperature. After three weeks, amber crystals of (II) had formed (yield 60%). IR (KBr, cm^-1): 3242–3104 (⁺N—H_py), 3056–2934 (C—_py + ═C—H_vinyl), 1615 (C═N), 1535–1457 (C═C_vinyl + C═C_py). TGA analysis, calculated for 2HCl: 18.6%, found: 17.0% (306–607 K); calculated for C₇H₇N: 26.6%, found: 27.5% (607–723 K); calculated for C₅H₅N+2HCl: 38.6%, found: 36.7% (723–925 K).

S2.2. Refinement

C-bound H atoms were positioned geometrically and constrained using the riding-model approximation, with vinyl and aryl C—H = 0.95 Å, and with U_iso(H) = 1.2U_eq(C). N-bound H atoms were located in difference Fourier maps. Their distances were fixed at N—H = 0.840 (1) Å (pyridinium), with U_iso(H) = 1.5U_eq(N), and the coordinates were refined with this restraint.

S3. Results and discussion

X-ray crystallographic study of (I) and (II) reveals that both structures crystallize in a monoclinic crystal system with the space group P2₁/c. The compounds are isostructural. Each asymmetric unit contains one [MCl₄]^2- dianion and one 4-[(E)-2-(pyridin-1-ium-2-yl)ethenyl]pyridinium dication (Fig. 1). The [CoCl₄]^2- anions in (I) and the [ZnCl₄]^2- anions in (II) have distorted tetra­hedral coordination environments, with Co—Cl bond lengths in the range 2.2519 (6)–2.2953 (6) Å and Cl—Co—Cl bond angles in the range 107.01 (2)–111.65 (2)° in (I) (Table 2). For (II), the Zn—Cl bond lengths are in the range 2.2470 (7)–2.3024 (6) Å and the Cl—Zn—Cl bond angles vary from 107.37 (2) to 111.80 (2)° (Table 3). Regarding the organic cations in the two crystal structures, the pyridinium rings attached to the central vinyl­ene fragment adopt an anti conformation, as indicated by the central C3—C6—C7—C8 torsion angles of 177.48 (17) and 177.4 (2)° in (I) and (II), respectively. The planes of the pyridine rings in each ligand are inclined to one another, by 17.18 (10)° in (I) and 17.02 (11)° in (II).

In the crystal structures of (I) and (II), the [MCl₄]^2- anions operate as linking building blocks between the dipyridinium cations to give, in the first instance, one-dimensional chains along b (Fig. 2a). Within these chains, the [MCl₄]^2- and dipyridinium ions are connected through strong inter­molecular N⁺—H···Cl^- hydrogen-bonding inter­actions, with N1···Cl3 and N2···Cl4 separations of 3.109 (2) and 3.145 (2) Å, respectively, for (I), and 3.111 (2) and 3..149 (3) Å, respectively, for (II). These distances are similar to previously reported values (Brammer et al., 2001; Valdés-Martínez et al., 2007). Adjacent one-dimensional chains are further inter­connected through a C—H···Cl^- contact [C6···Cl2 = 3.659 (2) Å in (I) and 3.660 (3) Å in (II)] and two crystallographically independent π–π inter­actions involving inversion-related pyridinium rings [for (I): Cg···Cgⁱ = 3.465 (1) Å, inter­planar distance = 3.285 Å; Cg'···Cg'ⁱⁱ = 4.376 (2) Å, inter­planar distance = 3.409 Å; for (II): Cg···Cgⁱ = 3.466 (1) Å, inter­planar distance = 3.285 Å; Cg'···Cg'ⁱⁱ = 4.389 (2) Å, inter­planar distance = 3.418 Å; Cg and Cg' are the centroids of the N1/C1–C5 ring [If they refer to the same ring, can just Cg be used for both and the primed one omitted, as in the next paragraph?]; symmetry codes: (i) -x, -y + 1, -z; (ii) -x, -y + 2, -z] to form double chains running parallel to the b axis (Figs. 2b and 3a).

In the remaining directions of the crystal structure, these double chains are inter­connected through additional C—H···Cl^- [C4···Cl4 = 3.502 (2) and 3.509 (3) Å; C5···Cl1 = 3.691 (2) and 3.702 (3) Å; C11···Cl1 = 3.533 (2) and 3.540 (2) Å for (I) and (II), respectively] and π–π contacts [for (I): Cg···Cgⁱ = 4.728 (2) Å, inter­planar distance = 3.274 Å; for (II): Cg···Cgⁱ = 4.732 (2) Å, inter­planar distance = 3.289 Å; Cg is the centroid of the N1/C1–C5 ring; symmetry code: (i) -x + 1, -y + 2, -z] to form an overall three-dimensional supra­molecular network structure (Fig. 3b).

In the C—H···Cl contacts, both C—H groups of the vinyl­ene and the pyridinium groups are involved (meta position). All hydrogen-bonding distances summarized in Tables 4 and 5 are within the range found for pyridinium perhalometallates (Brammer et al., 2001; Valdés-Martínez et al., 2007).

The IR spectra for (I) and (II) are in good agreement with the results of the X-ray structural analyses and are shown in Fig. 4. They show characteristic absorption bands resulting from: (i) the skeletal vibrations of the vinyl group and the aromatic rings in the 1535–1458 cm^-1 region; (ii) the stretching vibration of the C═N_imino functions at 1616 and 1615 cm^-1, respectively, and (iii) the pyridinium⁺ N—H stretching vibrations in the range 3242–3104 cm^-1. The vibration bands in the region of 1000 and 500 cm^-1 are attributed to out-of-plane bending modes for C—H, C—C and C—N (Paciorek et al., 2013; Al-Ota­ibi & Al-Wabli, 2015).

To examine the thermal stability of (I) and (II), thermogravimetric analyses (TGA) were performed under an N₂ atmosphere for crystalline samples with a heating rate of 283 K min^-1 [Should this be 10 K min^-1?] from ambient temperature up to 1073 K. The TGA curve of (I) reveals three main regions of weight loss (see Fig. 5). The first initiates at 368 K with completeness at 629 K, and corresponds to the elimination of two HCl molecules. The observed weight loss of 17.9% is close to the calculated value (18.9%). The second step, in the temperature range 629–742 K, corresponds to the loss of one vinyl­pyridine (C₇H₇N) equivalent. The observed weight loss of 27.3% is in good agreement with the calculated value of 27.9%. Finally, a third step (found 20.7%; theoretical 20.3%), in the range 742–1004 K, is attributed to the loss of one equivalent of pyridine (C₅H₅N). As shown in Fig. 4, the TGA curve of (II) also reveals three main weight loss steps. The first, starting at 306 K with completeness at 607 K, corresponds to the elimination of two HCl molecules (found 17.0%; theoretical 18.6%). The second step, in the range 607–723 K, corresponds to the loss of one vinyl­pyridine (C₇H₇N) equivalent (found 27.5%; theoretical 26.6%). However, in the third step (found 36.7%; theoretical 38.0%), in the range 723–925 K, there is a larger weight loss that might correspond to the loss of one pyridine and two additional equivalents of HCl.

S4. Conclusions

The analysis of the crystal structures described herein has shown that the dipyridinium cation is a suitable ionic tecton for the crystal engineering of higher-dimensional networks when combined with perhalometallates. This is because the pyridinium and vinyl­ene groups can form charge-assisted N⁺—H···Cl^- and C—H···Cl^- hydrogen bonds, as well as π–π contacts, to stabilize the supra­molecular networks.

Related literature

For related literature, see: Al-Ktaifani & Rukiah (2012); Al-Otaibi & Al-Wabli (2015); Boldog et al. (2009); Brammer et al. (2001); Deifel & Cahill (2009); Enríquez et al. (2012); Felloni et al. (2004); Kumar et al. (2006); Paciorek et al. (2013); Pardo et al. (2011); Podesta & Orpen (2005); Rademeyer et al. (2011); Sanchez et al. (2014); Valdés-Martínez, Toscano & Germán-Acacio (2007); Vitorica-Yrezabal, Sullivan, Purver, Curfs, Tang & Brammer (2011); Weng et al. (2011); Zordan et al. (2005).

Computing details

For both compounds, data collection: SMART (Bruker, 2000); cell refinement: SAINT-Plus NT (Bruker 2001); data reduction: SAINT-Plus NT (Bruker 2001); program(s) used to solve structure: SHELXTL-NT (Sheldrick, 2008); program(s) used to refine structure: SHELXTL-NT (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. The molecular structures of the asymmetric units of (a) (I) and (b) (II), showing the atom-labelling schemes. Displacement ellipsoids are drawn at the 50% probability level. [Please supply a revision with the labels not touching the atoms]
	Fig. 2. Hydrogen-bonding motifs found in the crystal structures of (I) and (II), showing (a) the formation of one-dimensional single chains and (b) the formation of one-dimensional double chains along b.
	Fig. 3. (a) A perspective view of the one-dimensional hydrogen-bonded double chains running parallel to the b axis of (I) and (II), and (b) the packing in three-dimensional space. [Where is the origin? Please also supply the missing part]
	Fig. 4. The IR spectra of (I) and (II).
	Fig. 5. Thermograms of salts (I) and (II).

(I) 4-[(E)-2-(Pyridin-1-ium-2-yl)ethenyl]pyridinium tetrachloridocobaltate(II)

Crystal data

(C12H12N2)[CoCl4]	F(000) = 772
Mr = 384.97	Dx = 1.713 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.6971 (11) Å	Cell parameters from 5346 reflections
b = 12.4656 (18) Å	θ = 2.6–28.3°
c = 15.915 (2) Å	µ = 1.85 mm^−1
β = 102.171 (2)°	T = 100 K
V = 1492.7 (4) Å^3	Block, blue
Z = 4	0.50 × 0.44 × 0.41 mm

Data collection

Bruker SMART CCD area-detector diffractometer	2632 independent reflections
Radiation source: fine-focus sealed tube	2617 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.022
ϕ and ω scans	θmax = 25.0°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −9→8
Tmin = 0.46, Tmax = 0.52	k = −14→14
11172 measured reflections	l = −18→18

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)] = 0.022	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.049	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0104P)^2 + 1.9738P] where P = (Fo^2 + 2Fc^2)/3
2632 reflections	(Δ/σ)max = 0.001
178 parameters	Δρmax = 0.29 e Å^−3
2 restraints	Δρmin = −0.29 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
Co1	0.31255 (3)	0.30215 (2)	0.264095 (16)	0.01246 (8)
Cl1	0.43900 (6)	0.22524 (4)	0.39020 (3)	0.01845 (11)
Cl2	0.05993 (6)	0.21481 (4)	0.19900 (3)	0.01601 (11)
Cl3	0.51384 (6)	0.29302 (4)	0.17648 (3)	0.01642 (11)
Cl4	0.23596 (7)	0.47555 (4)	0.28215 (3)	0.02002 (12)
N1	0.3614 (2)	1.07680 (14)	0.09541 (11)	0.0183 (4)
H1'	0.413 (3)	1.1358 (10)	0.1076 (15)	0.027*
N2	−0.0683 (2)	0.55033 (13)	0.12896 (10)	0.0137 (3)
H2'	−0.001 (2)	0.5576 (18)	0.1775 (6)	0.021*
C1	0.3301 (3)	1.01655 (16)	0.16037 (13)	0.0184 (4)
H1	0.3723	1.0390	0.2181	0.022*
C2	0.2374 (3)	0.92271 (16)	0.14346 (13)	0.0163 (4)
H2	0.2154	0.8797	0.1894	0.020*
C3	0.1751 (2)	0.89039 (15)	0.05831 (12)	0.0135 (4)
C4	0.2114 (3)	0.95548 (16)	−0.00735 (13)	0.0165 (4)
H4	0.1714	0.9351	−0.0657	0.020*
C5	0.3052 (3)	1.04911 (16)	0.01272 (13)	0.0185 (4)
H5	0.3300	1.0939	−0.0316	0.022*
C6	0.0710 (3)	0.79290 (15)	0.03567 (12)	0.0143 (4)
H6	0.0193	0.7815	−0.0233	0.017*
C7	0.0430 (3)	0.71857 (15)	0.09150 (12)	0.0141 (4)
H7	0.0981	0.7277	0.1504	0.017*
C8	−0.0677 (2)	0.62398 (15)	0.06720 (12)	0.0127 (4)
C9	−0.1728 (3)	0.60398 (15)	−0.01367 (12)	0.0142 (4)
H9	−0.1746	0.6535	−0.0592	0.017*
C10	−0.2743 (3)	0.51220 (16)	−0.02762 (12)	0.0155 (4)
H10	−0.3463	0.4988	−0.0829	0.019*
C11	−0.2724 (3)	0.43905 (16)	0.03836 (12)	0.0156 (4)
H11	−0.3436	0.3761	0.0292	0.019*
C12	−0.1654 (3)	0.45980 (15)	0.11695 (12)	0.0150 (4)
H12	−0.1598	0.4104	0.1629	0.018*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Co1	0.01372 (14)	0.01341 (14)	0.00992 (14)	−0.00001 (10)	0.00177 (10)	0.00069 (10)
Cl1	0.0156 (2)	0.0226 (3)	0.0160 (2)	−0.00006 (19)	0.00055 (18)	0.00790 (19)
Cl2	0.0156 (2)	0.0188 (2)	0.0128 (2)	−0.00303 (18)	0.00119 (18)	0.00045 (18)
Cl3	0.0174 (2)	0.0188 (2)	0.0142 (2)	−0.00533 (18)	0.00578 (18)	−0.00266 (18)
Cl4	0.0223 (3)	0.0174 (2)	0.0171 (2)	0.0057 (2)	−0.00304 (19)	−0.00318 (19)
N1	0.0140 (9)	0.0132 (8)	0.0276 (10)	−0.0008 (7)	0.0041 (7)	−0.0027 (7)
N2	0.0135 (8)	0.0176 (8)	0.0097 (8)	−0.0003 (7)	0.0016 (6)	0.0002 (7)
C1	0.0172 (10)	0.0183 (10)	0.0184 (10)	0.0034 (8)	0.0011 (8)	−0.0026 (8)
C2	0.0172 (10)	0.0158 (10)	0.0151 (10)	0.0021 (8)	0.0015 (8)	−0.0001 (8)
C3	0.0102 (9)	0.0140 (10)	0.0156 (9)	0.0034 (7)	0.0014 (7)	0.0002 (7)
C4	0.0157 (10)	0.0185 (10)	0.0151 (10)	0.0021 (8)	0.0026 (8)	0.0010 (8)
C5	0.0162 (11)	0.0181 (10)	0.0219 (11)	0.0016 (8)	0.0052 (8)	0.0037 (8)
C6	0.0139 (10)	0.0161 (10)	0.0119 (9)	0.0007 (8)	0.0004 (8)	−0.0018 (7)
C7	0.0144 (10)	0.0164 (10)	0.0113 (9)	0.0017 (8)	0.0027 (7)	−0.0019 (8)
C8	0.0108 (9)	0.0154 (9)	0.0130 (9)	0.0033 (7)	0.0051 (7)	0.0003 (7)
C9	0.0143 (10)	0.0161 (10)	0.0125 (9)	0.0030 (8)	0.0034 (7)	0.0016 (7)
C10	0.0130 (10)	0.0190 (10)	0.0143 (10)	0.0017 (8)	0.0025 (8)	−0.0039 (8)
C11	0.0127 (10)	0.0151 (10)	0.0204 (10)	−0.0010 (8)	0.0067 (8)	−0.0029 (8)
C12	0.0162 (10)	0.0142 (9)	0.0162 (10)	0.0000 (8)	0.0071 (8)	0.0025 (8)

Geometric parameters (Å, º)

Co1—Cl1	2.2519 (6)	C4—C5	1.374 (3)
Co1—Cl4	2.2745 (6)	C4—H4	0.9500
Co1—Cl2	2.2782 (6)	C5—H5	0.9500
Co1—Cl3	2.2953 (6)	C6—C7	1.332 (3)
N1—C1	1.340 (3)	C6—H6	0.9500
N1—C5	1.341 (3)	C7—C8	1.458 (3)
N1—H1'	0.8400 (11)	C7—H7	0.9500
N2—C12	1.345 (3)	C8—C9	1.391 (3)
N2—C8	1.346 (2)	C9—C10	1.377 (3)
N2—H2'	0.8400 (10)	C9—H9	0.9500
C1—C2	1.367 (3)	C10—C11	1.388 (3)
C1—H1	0.9500	C10—H10	0.9500
C2—C3	1.398 (3)	C11—C12	1.369 (3)
C2—H2	0.9500	C11—H11	0.9500
C3—C4	1.397 (3)	C12—H12	0.9500
C3—C6	1.458 (3)
Cl1—Co1—Cl4	111.52 (2)	N1—C5—C4	119.45 (19)
Cl1—Co1—Cl2	111.65 (2)	N1—C5—H5	120.3
Cl4—Co1—Cl2	107.01 (2)	C4—C5—H5	120.3
Cl1—Co1—Cl3	107.46 (2)	C7—C6—C3	124.92 (18)
Cl4—Co1—Cl3	110.49 (2)	C7—C6—H6	117.5
Cl2—Co1—Cl3	108.71 (2)	C3—C6—H6	117.5
C1—N1—C5	122.65 (18)	C6—C7—C8	123.57 (18)
C1—N1—H1'	117.8 (17)	C6—C7—H7	118.2
C5—N1—H1'	119.5 (17)	C8—C7—H7	118.2
C12—N2—C8	123.80 (17)	N2—C8—C9	117.55 (17)
C12—N2—H2'	116.0 (16)	N2—C8—C7	116.74 (17)
C8—N2—H2'	120.1 (16)	C9—C8—C7	125.71 (17)
N1—C1—C2	119.93 (19)	C10—C9—C8	119.86 (18)
N1—C1—H1	120.0	C10—C9—H9	120.1
C2—C1—H1	120.0	C8—C9—H9	120.1
C1—C2—C3	119.70 (19)	C9—C10—C11	120.57 (18)
C1—C2—H2	120.1	C9—C10—H10	119.7
C3—C2—H2	120.1	C11—C10—H10	119.7
C4—C3—C2	118.41 (18)	C12—C11—C10	118.37 (18)
C4—C3—C6	119.04 (17)	C12—C11—H11	120.8
C2—C3—C6	122.54 (18)	C10—C11—H11	120.8
C5—C4—C3	119.85 (19)	N2—C12—C11	119.83 (18)
C5—C4—H4	120.1	N2—C12—H12	120.1
C3—C4—H4	120.1	C11—C12—H12	120.1
C5—N1—C1—C2	0.0 (3)	C12—N2—C8—C9	−0.6 (3)
N1—C1—C2—C3	−0.3 (3)	C12—N2—C8—C7	178.96 (17)
C1—C2—C3—C4	0.5 (3)	C6—C7—C8—N2	173.12 (18)
C1—C2—C3—C6	−178.18 (18)	C6—C7—C8—C9	−7.4 (3)
C2—C3—C4—C5	−0.5 (3)	N2—C8—C9—C10	0.9 (3)
C6—C3—C4—C5	178.25 (17)	C7—C8—C9—C10	−178.58 (18)
C1—N1—C5—C4	0.1 (3)	C8—C9—C10—C11	−0.2 (3)
C3—C4—C5—N1	0.2 (3)	C9—C10—C11—C12	−0.9 (3)
C4—C3—C6—C7	172.60 (19)	C8—N2—C12—C11	−0.5 (3)
C2—C3—C6—C7	−8.7 (3)	C10—C11—C12—N2	1.3 (3)
C3—C6—C7—C8	177.48 (17)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2′···Cl4	0.84	2.42	3.145 (2)	145
N1—H1′···Cl3^i	0.84	2.30	3.109 (2)	162
C4—H4···Cl4^ii	0.95	2.80	3.502 (2)	131
C5—H5···Cl1^ii	0.95	2.79	3.691 (2)	159
C6—H6···Cl2^iii	0.95	2.73	3.659 (2)	165
C11—H11···Cl1^iv	0.95	2.78	3.533 (2)	137

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

(II) 4-[(E)-2-(Pyridin-1-ium-2-yl)ethenyl]pyridinium tetrachloridozincate(II)

Crystal data

(C12H12N2)[ZnCl4]	F(000) = 784
Mr = 391.41	Dx = 1.737 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.7074 (7) Å	Cell parameters from 9787 reflections
b = 12.4680 (11) Å	θ = 2.6–28.3°
c = 15.9344 (14) Å	µ = 2.34 mm^−1
β = 102.173 (1)°	T = 100 K
V = 1496.8 (2) Å^3	Block, brown
Z = 4	0.49 × 0.43 × 0.42 mm

Data collection

Bruker SMART CCD area-detector diffractometer	2549 independent reflections
Radiation source: fine-focus sealed tube	2442 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.025
ϕ and ω scans	θmax = 25.0°, θmin = 2.1°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −6→9
Tmin = 0.39, Tmax = 0.44	k = −14→14
7110 measured reflections	l = −18→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)] = 0.026	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.064	H atoms treated by a mixture of independent and constrained refinement
S = 1.09	w = 1/[σ^2(Fo^2) + (0.0279P)^2 + 1.2017P] where P = (Fo^2 + 2Fc^2)/3
2549 reflections	(Δ/σ)max < 0.001
178 parameters	Δρmax = 0.43 e Å^−3
2 restraints	Δρmin = −0.48 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
Zn1	0.31141 (4)	0.30176 (2)	0.264259 (17)	0.01287 (10)
Cl1	0.43838 (8)	0.22471 (5)	0.38967 (4)	0.01838 (14)
Cl2	0.05976 (8)	0.21417 (4)	0.19880 (4)	0.01610 (14)
Cl3	0.51252 (8)	0.29376 (4)	0.17615 (4)	0.01638 (14)
Cl4	0.23619 (8)	0.47508 (4)	0.28222 (4)	0.02006 (15)
N1	0.3613 (3)	1.07702 (16)	0.09563 (14)	0.0184 (5)
H1'	0.418 (3)	1.1344 (12)	0.1089 (18)	0.028*
N2	−0.0678 (3)	0.55020 (15)	0.12901 (12)	0.0138 (4)
H2'	−0.003 (3)	0.560 (2)	0.1778 (7)	0.021*
C1	0.3306 (3)	1.01641 (19)	0.16039 (17)	0.0191 (5)
H1	0.3730	1.0387	0.2181	0.023*
C2	0.2386 (3)	0.92263 (18)	0.14344 (16)	0.0165 (5)
H2	0.2172	0.8794	0.1893	0.020*
C3	0.1758 (3)	0.89017 (18)	0.05846 (15)	0.0136 (5)
C4	0.2121 (3)	0.95564 (18)	−0.00707 (16)	0.0164 (5)
H4	0.1726	0.9352	−0.0654	0.020*
C5	0.3047 (3)	1.04935 (19)	0.01292 (16)	0.0183 (5)
H5	0.3287	1.0943	−0.0314	0.022*
C6	0.0716 (3)	0.79282 (17)	0.03569 (16)	0.0150 (5)
H6	0.0197	0.7815	−0.0232	0.018*
C7	0.0438 (3)	0.71859 (18)	0.09158 (15)	0.0141 (5)
H7	0.0991	0.7275	0.1503	0.017*
C8	−0.0675 (3)	0.62423 (18)	0.06699 (15)	0.0134 (5)
C9	−0.1719 (3)	0.60408 (18)	−0.01343 (15)	0.0142 (5)
H9	−0.1733	0.6536	−0.0589	0.017*
C10	−0.2742 (3)	0.51214 (19)	−0.02776 (16)	0.0159 (5)
H10	−0.3460	0.4988	−0.0830	0.019*
C11	−0.2725 (3)	0.43912 (18)	0.03841 (16)	0.0164 (5)
H11	−0.3437	0.3763	0.0294	0.020*
C12	−0.1657 (3)	0.46004 (18)	0.11672 (15)	0.0155 (5)
H12	−0.1607	0.4107	0.1626	0.019*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.01101 (17)	0.01667 (15)	0.01050 (17)	−0.00008 (10)	0.00128 (13)	0.00070 (10)
Cl1	0.0132 (3)	0.0250 (3)	0.0159 (3)	0.0000 (2)	0.0005 (3)	0.0075 (2)
Cl2	0.0128 (3)	0.0219 (3)	0.0129 (3)	−0.0033 (2)	0.0010 (3)	0.0005 (2)
Cl3	0.0146 (3)	0.0213 (3)	0.0141 (3)	−0.0053 (2)	0.0050 (3)	−0.0023 (2)
Cl4	0.0194 (3)	0.0201 (3)	0.0176 (3)	0.0056 (2)	−0.0030 (3)	−0.0031 (2)
N1	0.0118 (11)	0.0164 (10)	0.0266 (13)	−0.0010 (8)	0.0032 (10)	−0.0028 (9)
N2	0.0108 (11)	0.0209 (10)	0.0090 (10)	0.0002 (8)	0.0002 (9)	0.0001 (8)
C1	0.0141 (13)	0.0231 (12)	0.0187 (14)	0.0032 (10)	0.0001 (11)	−0.0029 (10)
C2	0.0145 (13)	0.0193 (12)	0.0147 (13)	0.0037 (10)	0.0008 (11)	0.0014 (9)
C3	0.0074 (12)	0.0176 (11)	0.0151 (13)	0.0044 (9)	0.0007 (10)	0.0009 (9)
C4	0.0120 (12)	0.0214 (12)	0.0149 (13)	0.0019 (10)	0.0008 (11)	−0.0001 (10)
C5	0.0133 (13)	0.0219 (12)	0.0199 (14)	0.0025 (10)	0.0040 (11)	0.0033 (10)
C6	0.0116 (12)	0.0203 (12)	0.0121 (13)	0.0006 (9)	0.0000 (11)	−0.0018 (9)
C7	0.0116 (12)	0.0204 (11)	0.0096 (12)	0.0012 (9)	0.0009 (10)	−0.0013 (9)
C8	0.0084 (12)	0.0195 (11)	0.0135 (13)	0.0033 (9)	0.0050 (10)	0.0002 (9)
C9	0.0105 (12)	0.0194 (11)	0.0129 (13)	0.0024 (9)	0.0028 (11)	0.0018 (9)
C10	0.0091 (12)	0.0225 (12)	0.0154 (13)	0.0015 (10)	0.0011 (10)	−0.0044 (10)
C11	0.0123 (12)	0.0186 (11)	0.0196 (14)	−0.0011 (9)	0.0062 (11)	−0.0022 (10)
C12	0.0127 (13)	0.0189 (11)	0.0168 (14)	0.0000 (10)	0.0078 (11)	0.0033 (9)

Geometric parameters (Å, º)

Zn1—Cl1	2.2470 (7)	C4—C5	1.371 (3)
Zn1—Cl4	2.2710 (6)	C4—H4	0.9500
Zn1—Cl2	2.2780 (7)	C5—H5	0.9500
Zn1—Cl3	2.3024 (6)	C6—C7	1.333 (3)
N1—C1	1.340 (3)	C6—H6	0.9500
N1—C5	1.343 (3)	C7—C8	1.460 (3)
N1—H1'	0.8400 (11)	C7—H7	0.9500
N2—C12	1.345 (3)	C8—C9	1.385 (3)
N2—C8	1.353 (3)	C9—C10	1.383 (3)
N2—H2'	0.8400 (10)	C9—H9	0.9500
C1—C2	1.365 (3)	C10—C11	1.391 (3)
C1—H1	0.9500	C10—H10	0.9500
C2—C3	1.398 (3)	C11—C12	1.367 (4)
C2—H2	0.9500	C11—H11	0.9500
C3—C4	1.399 (3)	C12—H12	0.9500
C3—C6	1.459 (3)
Cl1—Zn1—Cl4	111.69 (2)	N1—C5—C4	119.5 (2)
Cl1—Zn1—Cl2	111.80 (2)	N1—C5—H5	120.3
Cl4—Zn1—Cl2	107.37 (2)	C4—C5—H5	120.3
Cl1—Zn1—Cl3	107.50 (2)	C7—C6—C3	124.7 (2)
Cl4—Zn1—Cl3	109.92 (2)	C7—C6—H6	117.6
Cl2—Zn1—Cl3	108.52 (2)	C3—C6—H6	117.6
C1—N1—C5	122.5 (2)	C6—C7—C8	123.2 (2)
C1—N1—H1'	117 (2)	C6—C7—H7	118.4
C5—N1—H1'	121 (2)	C8—C7—H7	118.4
C12—N2—C8	123.4 (2)	N2—C8—C9	117.5 (2)
C12—N2—H2'	117.4 (19)	N2—C8—C7	116.4 (2)
C8—N2—H2'	119.1 (19)	C9—C8—C7	126.1 (2)
N1—C1—C2	120.0 (2)	C10—C9—C8	120.2 (2)
N1—C1—H1	120.0	C10—C9—H9	119.9
C2—C1—H1	120.0	C8—C9—H9	119.9
C1—C2—C3	119.9 (2)	C9—C10—C11	120.2 (2)
C1—C2—H2	120.0	C9—C10—H10	119.9
C3—C2—H2	120.0	C11—C10—H10	119.9
C4—C3—C2	118.1 (2)	C12—C11—C10	118.3 (2)
C4—C3—C6	119.1 (2)	C12—C11—H11	120.8
C2—C3—C6	122.8 (2)	C10—C11—H11	120.8
C5—C4—C3	120.0 (2)	N2—C12—C11	120.2 (2)
C5—C4—H4	120.0	N2—C12—H12	119.9
C3—C4—H4	120.0	C11—C12—H12	119.9
C5—N1—C1—C2	−0.1 (3)	C12—N2—C8—C9	−1.1 (3)
N1—C1—C2—C3	−0.2 (3)	C12—N2—C8—C7	178.8 (2)
C1—C2—C3—C4	0.7 (3)	C6—C7—C8—N2	173.0 (2)
C1—C2—C3—C6	−177.9 (2)	C6—C7—C8—C9	−7.0 (4)
C2—C3—C4—C5	−0.9 (3)	N2—C8—C9—C10	1.2 (3)
C6—C3—C4—C5	177.8 (2)	C7—C8—C9—C10	−178.7 (2)
C1—N1—C5—C4	−0.1 (3)	C8—C9—C10—C11	−0.2 (3)
C3—C4—C5—N1	0.6 (3)	C9—C10—C11—C12	−1.0 (3)
C4—C3—C6—C7	172.7 (2)	C8—N2—C12—C11	−0.1 (3)
C2—C3—C6—C7	−8.7 (4)	C10—C11—C12—N2	1.1 (3)
C3—C6—C7—C8	177.4 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2′···Cl4	0.84	2.45	3.149 (2)	142
N1—H1′···Cl3^i	0.84	2.30	3.111 (2)	162
C4—H4···Cl4^ii	0.95	2.81	3.509 (3)	131
C5—H5···Cl1^ii	0.95	2.80	3.702 (3)	159
C6—H6···Cl2^iii	0.95	2.74	3.660 (3)	165
C11—H11···Cl1^iv	0.95	2.79	3.540 (2)	136

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