Zigzag hydrogen-bonded sheets in the structure of p-phenyl­azoaniline hydro­chloride

The structure of p-phenyl­azoanilinium chloride, C₁₂H₁₂N₃⁺·Cl⁻, consists of sheets each comprising organic cations and chloride anions linked by N—H...Cl and C—H...Cl hydrogen bonds. The p-phenyl­azoaniline mol­ecule is protonated at the azo site to form the azonium cation, while the amine group remains unchanged. The structure of the title compound has also been determined recently from powder diffraction data [Yatsenko et al. (2000). Acta Cryst. C56, 892–894].

Key indicators

• Single-crystal X-ray study
• T = 297 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.052
• wR factor = 0.150
• Data-to-parameter ratio = 11.9

checkCIF results

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S1. Comment

Azo compounds have not only been used in many chemical syntheses but they also constitute an important class of organic dyes with a wide range of industrial applications. Yatsenko et al. (2000) have recently reported the crystal structure of title compound, (I), from powder diffraction data where a constrained model of the organic cation and an isotropic refinement of non-H atoms, except for the chloride ion, were applied during structure refinement. Here we present a redetermination of this structure using single-crystal data from a Siemens SMART CCD diffractometer.

The crystal structure of (I) is shown in Fig. 1 and selected geometrical parameters are given in Table 1. The N═N bond distance of 1.291 (3) Å is significantly larger than the corresponding distances of 1.2493 (13) Å for p-phenylazoanilinium oxalate, and 1.246 (5) and 1.243 (5) Å for p-phenylazoanilinium phenylphosphonate (Mahmoudkhani & Langer, 2001a,b). In these compounds, the amine groups are protonated rather than the azo group. Furthermore, there is a shortening of the N2—C14 and N1—C11 bonds to 1.344 (3) and 1.324 (3) Å, respectively, compared to the C—N(H₃) distances of 1.4637 (12) and 1.458 (5) Å, and the (N═)N—-C distances of 1.4303 (14) and 1.427 (6) Å in the above-mentioned compounds. These differences can be attributed to a resonance hybrid of the organic cation, as shown in Scheme 2. The same feature has been reported by Moreiras et al. (1981). The structure exhibits both N—H···Cl and C—H···Cl hydrogen bonds. As shown in Fig. 2 (top), each organic cation is bonded to the chloride anions through hydrogen bonds via C13, C22 and N3. Each ion pair is then linked to another pair through the N1—H2···Cl hydrogen bond, thus forming a dimer. The dimers are connected to each other, in a zigzag fashion, via N1—H1···Cl hydrogen bonds to form sheets [see Fig. 2 (bottom)]. The sheets are stacked along the a axis (see Fig. 3), with chloride ions sandwiched between organic cations. The existence of C—H···Cl hydrogen bonds has recently been reviewed by Aakeröy et al. (1999), though they have not been invoked by Yatsenko et al. (2000).

S2. Experimental

The title compound was prepared by the reaction of a solution of p-phenylazoaniline in ethanol and HCl solution (37% in water) in a molar ratio of 1:1.5, at ambient temperature. Crystals suitable for X-ray diffraction analysis were obtained by very slow evaporation of the solution after several days.

S3. Refinement

The H atoms of the amine and azonium groups were located from difference Fourier maps and refined with a bond distance constrained to 0.85 Å. The other H atoms were constrained to idealized geometries using the appropriate riding model.

Computing details

Data collection: SMART (Siemens, 1995); cell refinement: SAINT (Siemens, 1995); data reduction: SAINT and SADABS (Sheldrick, 2001); program(s) used to solve structure: SHELXTL (Bruker, 2001); program(s) used to refine structure: SHELXTL; molecular graphics: DIAMOND (Brandenburg, 2000).

Figures

	Fig. 1. The molecular structure of (I). Displacement ellipsoids are shown at the 50% probability level.
	Fig. 2. Top: formation of a dimer by hydrogen bonds in the structure of (I). Bottom: representation of a hydrogen-bonded sheet.
	Fig. 3. Zigzag stacking of hydrogen-bonded sheets, shown by different colors.

p-Phenylazoaniline Hydrochloride

Crystal data

C12H12N3^+·Cl^−	F(000) = 488
Mr = 233.70	Dx = 1.375 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
a = 7.3718 (3) Å	Cell parameters from 2394 reflections
b = 18.5164 (7) Å	θ = 1–25°
c = 8.9123 (1) Å	µ = 0.31 mm^−1
β = 111.913 (1)°	T = 297 K
V = 1128.63 (6) Å^3	Needle, dark-red
Z = 4	0.60 × 0.20 × 0.20 mm

Data collection

Siemens SMART CCD diffractometer	1982 independent reflections
Radiation source: fine-focus sealed tube	1476 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.038
ω scans	θmax = 25.4°, θmin = 2.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	h = −8→8
Tmin = 0.835, Tmax = 0.940	k = −22→10
3608 measured reflections	l = −10→8

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)] = 0.052	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.150	H atoms treated by a mixture of independent and constrained refinement
S = 1.05	w = 1/[σ^2(Fo^2) + (0.0885P)^2 + 0.0439P] where P = (Fo^2 + 2Fc^2)/3
1982 reflections	(Δ/σ)max < 0.001
166 parameters	Δρmax = 0.40 e Å^−3
3 restraints	Δρmin = −0.32 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
Cl	0.25125 (11)	0.35094 (3)	0.25208 (7)	0.0583 (3)
N1	−0.1796 (3)	0.69262 (11)	0.1163 (3)	0.0450 (5)
H2	−0.227 (4)	0.6825 (15)	0.013 (2)	0.058 (9)*
H1	−0.212 (4)	0.7331 (11)	0.151 (3)	0.055 (8)*
N2	0.2890 (3)	0.51264 (9)	0.5880 (2)	0.0367 (5)
N3	0.3509 (3)	0.44960 (10)	0.5676 (2)	0.0363 (5)
H3	0.322 (4)	0.4275 (13)	0.474 (2)	0.053 (8)*
C11	−0.0719 (3)	0.64667 (11)	0.2278 (3)	0.0357 (6)
C12	−0.0222 (3)	0.57759 (12)	0.1830 (3)	0.0384 (6)
H12	−0.0707	0.5641	0.0747	0.041 (7)*
C13	0.0940 (3)	0.53167 (12)	0.2955 (3)	0.0379 (6)
H13	0.1252	0.4870	0.2640	0.042 (6)*
C14	0.1692 (3)	0.55117 (11)	0.4622 (3)	0.0344 (5)
C15	0.1147 (3)	0.61907 (12)	0.5067 (3)	0.0394 (6)
H15	0.1603	0.6321	0.6153	0.041 (7)*
C16	−0.0026 (3)	0.66536 (12)	0.3942 (3)	0.0386 (6)
H16	−0.0376	0.7093	0.4261	0.049 (7)*
C21	0.4736 (3)	0.41061 (12)	0.7048 (3)	0.0348 (5)
C22	0.5158 (4)	0.33944 (13)	0.6843 (3)	0.0435 (6)
H22	0.4691	0.3185	0.5821	0.038 (6)*
C23	0.6290 (4)	0.29977 (14)	0.8188 (3)	0.0516 (7)
H23	0.6572	0.2517	0.8069	0.059 (8)*
C24	0.7000 (4)	0.33110 (16)	0.9698 (3)	0.0555 (7)
H24	0.7746	0.3039	1.0594	0.078 (9)*
C25	0.6609 (4)	0.40211 (16)	0.9886 (3)	0.0562 (7)
H25	0.7110	0.4232	1.0907	0.071 (9)*
C26	0.5472 (4)	0.44282 (14)	0.8565 (3)	0.0466 (6)
H26	0.5206	0.4910	0.8692	0.055 (8)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl	0.0853 (6)	0.0381 (4)	0.0381 (4)	0.0054 (3)	0.0076 (4)	−0.0031 (2)
N1	0.0482 (13)	0.0401 (12)	0.0390 (14)	0.0084 (10)	0.0072 (10)	0.0050 (9)
N2	0.0323 (11)	0.0327 (10)	0.0384 (11)	−0.0019 (8)	0.0055 (8)	0.0013 (8)
N3	0.0349 (11)	0.0338 (10)	0.0322 (11)	0.0011 (8)	0.0031 (9)	0.0002 (8)
C11	0.0320 (12)	0.0340 (12)	0.0394 (13)	−0.0021 (9)	0.0114 (10)	0.0038 (9)
C12	0.0398 (13)	0.0365 (12)	0.0323 (13)	0.0010 (10)	0.0058 (10)	−0.0017 (9)
C13	0.0391 (13)	0.0321 (11)	0.0381 (14)	0.0004 (10)	0.0096 (10)	−0.0011 (9)
C14	0.0295 (12)	0.0311 (11)	0.0358 (13)	−0.0022 (9)	0.0042 (9)	0.0029 (9)
C15	0.0442 (14)	0.0361 (12)	0.0321 (13)	−0.0038 (10)	0.0078 (10)	−0.0032 (9)
C16	0.0400 (13)	0.0318 (11)	0.0403 (14)	0.0014 (10)	0.0104 (11)	−0.0018 (9)
C21	0.0259 (11)	0.0374 (12)	0.0351 (13)	0.0019 (9)	0.0046 (9)	0.0044 (9)
C22	0.0391 (13)	0.0411 (13)	0.0417 (15)	0.0018 (10)	0.0051 (11)	−0.0003 (10)
C23	0.0452 (15)	0.0427 (14)	0.0597 (18)	0.0116 (12)	0.0112 (12)	0.0065 (12)
C24	0.0503 (16)	0.0612 (17)	0.0478 (16)	0.0202 (13)	0.0100 (13)	0.0194 (13)
C25	0.0533 (17)	0.0669 (18)	0.0365 (15)	0.0169 (14)	0.0030 (12)	0.0010 (12)
C26	0.0459 (15)	0.0473 (14)	0.0378 (14)	0.0121 (11)	0.0056 (11)	−0.0001 (11)

Geometric parameters (Å, º)

N1—C11	1.324 (3)	C15—C16	1.356 (3)
N1—H2	0.878 (17)	C15—H15	0.9300
N1—H1	0.876 (17)	C16—H16	0.9300
N2—N3	1.291 (3)	C21—C22	1.382 (3)
N2—C14	1.344 (3)	C21—C26	1.389 (3)
N3—C21	1.418 (3)	C22—C23	1.388 (3)
N3—H3	0.879 (16)	C22—H22	0.9300
C11—C16	1.420 (3)	C23—C24	1.377 (4)
C11—C12	1.428 (3)	C23—H23	0.9300
C12—C13	1.350 (3)	C24—C25	1.370 (4)
C12—H12	0.9300	C24—H24	0.9300
C13—C14	1.425 (3)	C25—C26	1.386 (3)
C13—H13	0.9300	C25—H25	0.9300
C14—C15	1.421 (3)	C26—H26	0.9300
C11—N1—H2	123.0 (19)	C15—C16—C11	120.0 (2)
C11—N1—H1	117.0 (18)	C15—C16—H16	120.0
H2—N1—H1	120 (3)	C11—C16—H16	120.0
N3—N2—C14	121.29 (19)	C22—C21—C26	120.8 (2)
N2—N3—C21	118.97 (19)	C22—C21—N3	118.3 (2)
N2—N3—H3	125.5 (17)	C26—C21—N3	120.8 (2)
C21—N3—H3	115.6 (17)	C21—C22—C23	118.9 (2)
N1—C11—C16	120.6 (2)	C21—C22—H22	120.6
N1—C11—C12	120.7 (2)	C23—C22—H22	120.6
C16—C11—C12	118.73 (19)	C24—C23—C22	120.5 (2)
C13—C12—C11	121.0 (2)	C24—C23—H23	119.7
C13—C12—H12	119.5	C22—C23—H23	119.7
C11—C12—H12	119.5	C25—C24—C23	120.2 (2)
C12—C13—C14	120.5 (2)	C25—C24—H24	119.9
C12—C13—H13	119.8	C23—C24—H24	119.9
C14—C13—H13	119.8	C24—C25—C26	120.4 (3)
N2—C14—C15	113.79 (19)	C24—C25—H25	119.8
N2—C14—C13	127.9 (2)	C26—C25—H25	119.8
C15—C14—C13	118.3 (2)	C25—C26—C21	119.1 (2)
C16—C15—C14	121.4 (2)	C25—C26—H26	120.5
C16—C15—H15	119.3	C21—C26—H26	120.5
C14—C15—H15	119.3
N3—N2—C14—C13	−0.2 (4)	C21—N3—N2—C14	−178.7 (2)
N2—N3—C21—C26	−8.2 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···Cl^i	0.88 (2)	2.41 (2)	3.273 (2)	171 (2)
N1—H2···Cl^ii	0.88 (2)	2.38 (2)	3.227 (2)	162 (2)
N3—H3···Cl	0.88 (2)	2.33 (2)	3.200 (2)	170 (2)
C13—H13···Cl	0.93	2.70	3.609 (2)	166
C22—H22···Cl	0.93	2.84	3.617 (3)	142

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